Mehryoon Shah M[1]

Analysis and Comparison of Power Loss and Voltage Drop of 15 kV and 20 kV Medium

Voltage Levels in the North Substation of the Kabul Power Distribution System by

CYMDIST

A thesis presented to

the faculty of

the Russ College of Engineering and Technology of Ohio University

In partial fulfillment

of the requirements for the degree

Master of Science

Shah M. Mehryoon

November 2009

© 2009 Shah M. Mehryoon. All Rights Reserved.

2

This thesis titled

Analysis and Comparison of Power Loss and Voltage Drop of 15 kV and 20 kV Medium


CYMDIST

by

SHAH M. MEHRYOON

has been approved for

the School of Electrical Engineering and Computer Science

and the Russ College of Engineering and Technology by

Jeffrey J. Giesey

Associate Professor of Electrical Engineering and Computer Science

Dennis Irwin

Dean, Russ College of Engineering and Technology

3

ABSTRACT MEHRYOON, SHAH M., M.S., November 2009, Electrical Engineering Analysis and Comparison of Power Loss and Voltage Drop of 15 kV and 20 kV Medium


CYMDIST (102 pp)

Director of Thesis: Jeffrey J. Giesey

This thesis analyzes and compares the performances of two levels of medium

voltages (15 kV and 20 kV) in the North substation of the Kabul power distribution

system. Although performance of a power distribution system contains numerous

important factors such as harmonics, voltage sags, short circuits, outages, and so forth

this thesis focuses only on two factors that are more important for the Kabul power

distribution system. The two factors are power loss and voltage drop. The analysis of the

two medium voltage (MV) levels is done by a software (CYMDIST) simulation. At the

end, 20 kV is recommended as MV level for the Kabul power distribution system.

Key terms: Power distribution, power loss, voltage drop, under-voltage.

Approved: _____________________________________________________________

Jeffrey J. Giesey

Associate Professor of Electrical Engineering and Computer Science

4

ACKNOWLEDGMENTS

This thesis is a work on a part of the Kabul power distribution system by

CYMDIST software (software is introduced in Section 2.4.1) that needed the software

package and skills to use it. Dr. Jeffery J. Giesey, my advisor, prepared the package of

the software for the project and taught me how to use it for the project analysis.

Meanwhile, he was always answering my questions and helping me to find the materials

for the research project. On the other hand, this research work has been conducted on a

project (the Kabul power distribution system) that was not physically accessible. I was

able to conduct the work with the assistances of friends by means of sending required

data from the Kabul city.

Hereby I sincerely thank Dr. Jeffery J. Giesey for his friendly assistance and kind

advices that made me able to complete the thesis. I also appreciate the assistances of my

graduation committee members, Dr. Savas Kaya, Dr. Wojciech M. Jadwisienczak, and

Dr. Martin J. Mohlenkamp Graduate Chair of Mathematics Department of College of Art

and Science, and thank them for their time to read the thesis and give comments on. I

give special thanks to Najib Rahman Sabory Deputy Dean of the Engineering School of

the Kabul University because of his friendly assistances (collecting the data and sending

the technical reports about MV and LV of the Kabul distribution system). Finally, I thank

those staffs of the Ministry of Energy and Water, Da Afghanistan Breshna Moassessa

(DABM), and US Agency for International Developments (USAID) that have played

indirect role for completion of this thesis; I thank them because of their assistances in

regard to preparing the required data for simulation of the research project.

5

PREFACE

In the twenty-first century, it is hard to imagine life without electricity in

developed countries. Yet, in developing countries, not all the people have access to

electric power. In Afghanistan, for example, less than 15% of the whole population has

access to electricity; while in residential areas, electric power is used only for lighting

purposes; a few people are using it for electronic devices such as television, radio, and

computer. Meaning that, they cannot use electric power for cooking, heating, and air-

conditioning. It is worth mentioning that, in most residential areas, the power provided is

not running 24 hours a day. The people are using electric power 2-4 hours a day

periodically. In Kabul city, the capital of the country, with almost 3.5 million people,

supplied peak electric power was 130 MW in (2006) [1]. On the other hand, because of

the economic growth, the demand for electric power increases day by day. Thus, lack of

electric power is one of the biggest challenges for the government of Afghanistan and

electrical engineers.

Despite growing demand for electric power, the people of Afghanistan are faced

with a lack of resources. For instance, the actual peak capacity of four electric power

generation stations (three hydro power plants and one thermal power plant) providing

power for Kabul city and its surrounding areas was 211 MW in 2007 [2]. The efficiency

of the system is terribly low because of the transmission and distribution system’s low

quality and poor material condition. Now, in order to have a good power system,

involved people must pay full attention to the system losses, reliability of the system,

power quality, and affordability of the electric power. Although all the factors mentioned

above are extremely important for a standard power system, in Afghanistan, priority must

be given to the loss reduction because we have a very low electric power generation kWh

(per capita). That is why the consumers use the electric power only for lighting purposes

and electronic devices, in residential areas.

As was already mentioned, electric power is, mostly, used for lighting purposes

and electronic devices – and the people have access to the city power every other night

periodically, or every other two nights. This is not, of course, the only problem with the

6 Kabul city power system. Voltage drop in the distribution system, especially in low

voltage, is another significant problem affecting the quality of the electric power. In some

cases the voltage drop in low voltage reaches to 30%; while it is six times the worst case

according to standards, for example national electric code (NEC). Therefore, it is crucial

to take care of voltage drops in medium voltage and low voltage in the distribution

system because voltage drop affects the lighting quality and electronic devices

functionality and causes increases in reactive load. This means that, when the people are

using electronic devices, they have to use small single phase transformers in order to

compensate the voltage drop. As a result, inductive load goes up and causes a low power

factor and more voltage drop. Considering the above explanation, power generation

capacity, in the Kabul power system, is not sufficient to satisfy the demand. On the other

hand, the Kabul power system is not an efficient system; hence, it needs to be upgraded

in order to reduce system’s losses and improve its efficiency.

7

TABLE OF CONTENTS

Abstract………………………………………………………………………………….3

Acknowledgments…………………………………………………………………….....4

Preface ………………………………………………….………………………………..5

List of Figures……………………………………………………………………………9

List of Tables ……………………………………………………………………………11

1. Chapter 1: Background .................................................................................................... 12

1.1 Introduction ....................................................................................................... 12

1.2 Parts of a Power System ................................................................................... 13

1.2.1 Power Generation .......................................................................................... 13

1.2.2 Power Transmission ...................................................................................... 13

1.2.3 Power Distribution ........................................................................................ 14

1.3 Background ....................................................................................................... 14

1.3.1 Historical Background .................................................................................. 14

1.3.2 Current Situation of the Kabul Electrical Power System .............................. 18

1.3.3 Over Loaded Transformers ........................................................................... 23

1.3.4 Future Growth and Anticipation ................................................................... 24

1.4 Power Loss Minimization and Power Reliability and Quality Maximization .. 27

1.5 Voltage Drop and Voltage Sag ......................................................................... 28

1.6 Medium Voltage in Power Distribution Systems ............................................. 29

1.7 The Kabul Power System Voltage Configuration ............................................ 29

2 Chapter 2: Methodology .................................................................................................. 32

2.1 Consumer Classification ................................................................................... 32

2.2 Research Project Selection ................................................................................ 33

2.3 Data Used for Network Simulation ................................................................... 33

2.3.1 Transmission Lines ....................................................................................... 33

2.3.2 Loads ............................................................................................................. 34

2.4 Simulation Tool and Network Simulation Data ................................................ 47

2.4.1 Simulation Tool (CYMDIST Software) ....................................................... 47

8

2.4.2 Network Elements ......................................................................................... 47

2.4.3 Load Modeling for the Network Simulation ................................................. 49

2.4.4 Load Allocation for the North Substation Simulation .................................. 50

2.4.5 Simulation Settings and Accuracy ................................................................ 51

3 Chapter 3: Results ............................................................................................................ 52

3.1 Simulation Results with 15 kV MV .................................................................. 52

3.1.1 Levels of Under Voltage ............................................................................... 52

3.1.2 Overloaded Feeders ...................................................................................... 58

3.1.3 Losses, Under-voltage, and Overload Summary .......................................... 62

3.1.4 Abnormal Conditions with 50 MVA ............................................................ 64

3.2 Simulation Results with 20 kV MV .................................................................. 65

3.2.1 Levels of Under Voltage ............................................................................... 65

3.2.2 Overloaded Feeders ...................................................................................... 69

3.2.3 Losses, Under-voltage, and Overload Summary .......................................... 71

3.2.4 Abnormal Conditions with 50 MVA ............................................................ 73

4 Chapter 4: Discussions ..................................................................................................... 74

4.1 Criteria for MV Application ............................................................................. 74

4.1.1 Technological Feasibility .............................................................................. 74

4.1.2 Economical Justification ............................................................................... 75

4.1.3 Technical Advantages ................................................................................... 76

4.2 Analysis of Voltage Drop in the North Substation ........................................... 76

4.2.1 Analysis of 15 kV MV .................................................................................. 77

4.2.2 Analysis of 20 kV MV .................................................................................. 81

4.2.3 Summary of the Discussion .......................................................................... 85

5 Chapter 5: Conclusions ..................................................................................................... 88

5.1 Conclusions ....................................................................................................... 88

5.2 Future Works .................................................................................................... 89

References …………………………………………………………………………….…92

Appendix - A: Abnormal Conditions in 15 kV Scenario………………………….……..94

Appendix - B: Abnormal Conditions in 20 kV Scenario ….…………………….………99

9

LIST OF TABLES

Table 1-1 The Compact Information about the Kabul Power System Transmission Lines

[2]. ..................................................................................................................................... 16

Table 2-1 Outgoing Feeders of the North Substation and its Associated Junction Stations.

........................................................................................................................................... 34

Table 2-2 Combination of nominal Loads in the North Substation. ................................ 35

Table 2-3 Conductors Specifications Used for Overhead Lines in the North Substation.

........................................................................................................................................... 48

Table 2-4 Under-ground Cable Conductors Specifications Used in the North Substation.

........................................................................................................................................... 49

Table 3-1 Feeders Having Under-voltage Conditions (15 kV MV). ............................... 55

Table 3-2 Overhead Lines Sections Having Under-voltage Conditions (15 kV MV). .... 56

Table 3-3 Underground Cables Sections Having Under-voltage Conditions (15 kV MV) .

........................................................................................................................................... 57

Table 3-4 Overloaded Feeder Sections in the North Substation. ..................................... 62

Table 3-5 Load and Losses Summary of the North Substation with 15 kV MV. ............ 64

Table 3-6 Summary of Extreme Abnormal Condition in the North Substation with 15 kV

MV. ................................................................................................................................... 64

Table 3-7 Feeder Having Under-voltage Conditions (20 kV MV). ................................. 67

Table 3-8 Overhead Lines Sections Having Under-voltage Conditions (20 kV MV). .... 68

Table 3-9 Underground Cable Sections Having Under-voltage Conditions (20 kV MV).

........................................................................................................................................... 68

Table 3-10 Overloaded Feeder Sections in the North Substation. ................................... 71

Table 3-11 Load and Losses Summary of the North Substation with 20 kV MV. .......... 72

Table 3-12 Summary of Extreme Abnormal Condition in the North Substation with 20

kV MV. ............................................................................................................................. 73

Table 4-1 Slope of the Voltage Profiles in sample feeders (513 and 516). ..................... 86

10

LIST OF FIGURES

Figure 1-1 The Kabul Power System General Layout [2]. .............................................. 17

Figure 1-2 The Kabul Power Distribution System General Layout [2]. .......................... 19

Figure 1-3 The Breshna Kot Power Substation Layout [2]. ............................................. 21

Figure 1-4 The North-west Substation Layout [2]. .......................................................... 21

Figure 1-5 The East Substation Layout [2]. ..................................................................... 22

Figure 1-6 The North Substation Layout [2]. .................................................................. 23

Figure 1-7 A Destroyed Transformer House in the Kabul Power Distribution System [2].

........................................................................................................................................... 25

Figure 1-8 A Piece of Secondary Distribution Underground Cable in the Kabul

Distribution System [2]. .................................................................................................... 26

Figure 1-9 The Kabul Power Distribution System Voltage Arrangement. ...................... 30

Figure 2-1 Layout of the Feeder 512 with 20 Loads. ...................................................... 36

Figure 2-2 the Layout of Feeder 528 with 13 Loads. ...................................................... 37

Figure 2-3 Layout of the Feeder 513 with 18 Loads. ...................................................... 38

Figure 2-4 The Layout of the Feeders 519 and 520 with their Associated Loads. .......... 39

Figure 2-5 The Layout of Feeder 529 and the Feeders Connected to the Junction Station

Five. .................................................................................................................................. 40

Figure 2-6 The Layout of the Feeder 518 and its Associated Feeders Connected to the

Junction Station Two. ....................................................................................................... 42

Figure 2-7 The Layout of the Feeder 515 and its Associated Feeders Connected to the

Junction Station Two. ....................................................................................................... 43

Figure 2-8 The Layout of the Feeder 514 with its Associated Loads. ............................. 44

Figure 2-9 The Layout of the Feeder 516 with its Associated Loads. ............................. 45

Figure 2-10 The Layout of the Feeder 517 with its Associated Loads. ........................... 46

Figure 2-11 The Layout of the Feeder 527, Connected to the Junction Station Ten, with

its Associated Loads. ........................................................................................................ 46

Figure 3-1 The North Substation Map with 15 KV Simulation Results. ......................... 63

Figure 3-2 The North Substation Map with 20 kV Simulation Results. .......................... 72

11 Figure 4-1 Histogram of Overhead Lines Sections under Under-voltage Conditions (15

kV). ................................................................................................................................... 77

Figure 4-2 Histogram of Underground Cable Sections under Under-voltage Conditions

(15 kV). ............................................................................................................................. 78

Figure 4-3 Voltage Profile along the Feeder 513 in case of 15 kV MV. ......................... 79


Figure 4-5 Histogram of Overhead Lines Sections under Under-voltage Conditions (20

kV). ................................................................................................................................... 81

Figure 4-6 Histogram of Underground Cable Sections under Under-voltage Conditions

(20 kV). ............................................................................................................................. 82



Figure 4-9 Graph of the Voltage Profile along the Feeder 513. ...................................... 85

Figure 4-10 Graph of the Voltage Profile along the Feeder 516. .................................... 86

12

1. CHAPTER 1: BACKGROUND

1.1 Introduction

Power loss and voltage drop minimization, in medium voltage (MV) and low voltage

(LV), is the first priority in the Kabul city power distribution system because it seriously

affects the lighting quality and causes an increase of reactive power. In other words,

lighting quality is directly proportional to the voltage quality, and reactive power is

inversely proportional to the voltage quality. However, reliability of power is highly

important [3] in governmental office buildings and commercial loads because of the

usage of the digital electronics devices, the power loss and voltage drop are serious

concerns in the Kabul city power distribution condition. Therefore, this thesis focuses

mainly on how to reduce the losses and voltage drop in medium voltage (MV) in the

Kabul city power distribution system. In this thesis, two levels of voltages (15 kV and 20

kV) will be analyzed mainly in regard to power loss and voltage drop, for the Kabul city

power distribution system at the medium voltage levels.

This thesis contains three main parts: background of electric power and preventing

problems in the Kabul city power distribution system, problem analysis, and results. In

order to have a general view of electric power in Afghanistan, the historical background

of the Kabul city electrical power distribution system is explained in the first part of the

thesis. In historical background we see that when the power network was established and

how it has grown in Kabul. In addition, preventing problems of further growth of the

system are evaluated. Also the current situation of the system, after the civil war, will be

discussed. In the second part, 15 kV vs. 20 kV will be analyzed at the medium voltage

level. The evaluation method is such that we will divide consumers in three parts:

industrial, commercial, and residential loads. Then we will make some assumptions

considering the local culture and the social conditions and simulate the system with

(CYMDIST) software. Finally, the results for 15 kV and 20 kV are compared and the

best result is recommended to implement in the Kabul electrical distribution system

reconstruction.

13

1.2 Parts of a Power System

1.2.1 Power Generation

Electrical energy is obtained by means of changing another type of energy existed

in the nature, such as mechanical, thermal, and light. Considering that power is energy

consumption during a period of time ( / , power is used instead of energy in the

rest of this discussion.

There are seven common types of power plants (sources) for bulk electric power

generation: hydro, nuclear, coal, oil, gas, wind, and solar. Of course, there are some other

sources such as biomass, geothermal, waste, and tide as well. In hydro power plants and

wind power plants, electric power is generated in one step; mechanical power is

transformed to electrical power. Yet, in coal power plants and nuclear power plants,

electrical power is generated in two steps; first generated thermal power is transformed to

mechanical power, and then the mechanical power is transformed to electrical power.

There are two ways to generate electric power by using solar power. Solar panels (PV)

generate electric power in one step process; while light concentrators generate electric

power in a two step process. First, light is concentrated to produce heat and the heat is

used to operate electrical power generator.

1.2.2 Power Transmission

Transmission of electric power is highly crucial because power is, generally,

generated far from the consumption area, in centralized (large scale) systems. Electric

power is transmitted by means of transmission lines. On the other hand, since

transmission of low voltage (voltages usable for electrical appliances) causes

unacceptable real power losses based on , the voltage for transmission is

stepped up. Higher voltage reduces the current I based on and as a result power

loss is reduced, in transmission lines. Transmission voltage is called high voltage and it is

the voltage in transmission lines connecting a power generation plant to a power

substation. It should be mentioned that different countries have their own standards for

transmission voltages. The transmission voltage level is in the range of 110 kV – 765 kV;

14 in the future it may become higher. We should notice that transmission voltage in the

Kabul power distribution system, for four power plants located in the Kabul city, is 110

kV; and recently, 220 kV transmission lines have been installed to transmit power from

Uzbekistan to the Kabul city.

1.2.3 Power Distribution

Power distribution in a power system is composed of medium voltage (MV) part

and low voltage (LV) part. Medium voltage part starts from substation and continues to

distribution transformers. The level of the voltage in (MV) is in the range of 7.2 kV – 110

kV [4], [5] according to the different standards and applications. Medium voltage in the

Kabul power distribution system is 10 kV, 15 kV, and 20 kV.

Low voltage in an electric power system contains transmission lines with low

voltages connecting the distribution transformers to consumers. The voltage in this part

of a power system is also different; it is in the range of 110 V – 600 V. The usual low

voltage in the Kabul electric power system is 220 V line to neutral (LN) and 380 V phase

to phase (LL).

1.3 Background

1.3.1 Historical Background

1.3.1.1 Starting Point of Electric Power

Although discoveries in electricity had a rapidly increasing rate in the 1800s, the first

practical generator and motor was developed by Zenobe Theophile Gramme, a Belgian

born engineer in 1873, and in 1879, the first incandescent lamp was perfected by Thomas

Alva Edison. At the same time, the first electric company started working in San

Francisco California. Thomas Edison established his DC electric network in Manhattan

New York in 1882 to serve several incandescent lamps. This network was the first

commercial electric system which served customers by 100V DC voltage [6]. By 1900,

there were 3000 electrical stations in the United States [7]; this indicates an extremely

rapid increase in electric power usage.

15

1.3.1.2 Electric Power Generation in the Kabul Power System

The first electric power network was established in the Kabul city in 1957 [2] (75 years

after Edison’s first power distribution station), with the capacity of 22 MVA. This

network was fed by the first power generation station, the Surobi hydro power plant,

which was built in 1957 by Germany. This power plant has a rated peak capacity of 22

MVA with two turbines. The Surobi hydro power plant was built along the Kabul and

Panjsher rivers. The Mahipar hydro power plant was built in 1967 by Germany along the

Kabul and Logar rivers. This power plant does not have a dam (water reservoir). It works

with the flowing water, which is why it is not functioning 12 months a year. The Mahipar

power generation station has three turbines with a total rated peak capacity of 66 MVA.

In 1967, the Naghlu hydro power plant was built by the USSR along the Panjsher River.

Naghlu power plant has a water reservoir and it has four turbines with a total peak rated

capacity of 100 MVA. This power plant is the largest power plant in the Kabul power

system so far. The last power plant built in Kabul is the North-West Kabul thermal power

plant, which was built by Switzerland in 1985. This power plant has two turbines with a

total peak capacity of 45 MVA.

1.3.1.3 Electric Power Transmission in the Kabul Power System

In 1985 the Kabul electric power system had contained eight transmission lines [2]

carrying electric power from power plants to the Kabul city with 110 kV voltage level.

Transmission line 121, with a length of 12 km, connected the Naghlu power plant to the

Surobi power plant. Transmission lines 111 and 112, with a length of 66 km, were

transmitting the power from Surobi power plant to the Breshna Kot substation.

Transmission lines 141 and 142, with a length of 54.5 km, were transmitting the power

from Naghlu power plant to the East substation. Transmission line 144, with a length of

16 km, had connected the East substation to the Breshna Kot substation. Transmission

line 143, with a length of 27 km, had connected the East substations to the North

substation. Transmission line 145, with a length of 9 km, had connected the North

16 substation to the North-west substation. Table 1-1 contains the compact information

about the Kabul power system transmission lines.

Table 1-1 The Compact Information about the Kabul Power System Transmission Lines [2]

Number Lines Name From- To Distance 1 121 Naghlu to Surobi 12 km 2 111 & 112 Surobi to Breshna Kot 66 km 3 141 & 142 Naghlu to East 54.5 km 4 144 East to Breshna Kot 16 km 5 143 East to North 27 km 6 145 North to North-west 9 km

1.3.1.4 Electric Power Distribution in the Kabul Power System

In the late 1980s, the Kabul power distribution system was composed of six

power substations: 1) Breshna Kot, 2) North-west, 3) North, 4) East, 5) Pul-e-charkhi,

and 6) Butkhak. The Breshna Kot substation had two 25 MVA power transformers [2].

The North-west substation had two 25 MVA and one 20 MVA power transformers. The

North substation had two 40 MVA power transformers. The East substation had one 25

MVA power transformers. The Pul-e-Charkhi substation had two 6.3 MVA power

transformers. The Butkhak substation had one 4 MVA power transformer.

Figure 1-1 illustrates the Kabul power systems layout containing generation

stations, power transmission lines and power distribution substations. After 1985, the

Kabul power system did not have a significant improvement until 2007. Of course,

because of increasing power demand, some privately owned small generators have fed

the system, but the power generation, transmission, and distribution system have

seriously suffered from bad maintenance, long wars and conflicts.

17

Figure 1-1 The Kabul Power System General Layout [2].

18

1.3.2 Current Situation of the Kabul Electrical Power System

The Kabul electrical power system has not upgraded since 1985; it has been affected and

damaged during the three decades of wars and conflicts. Particularly, the power

distribution system has been seriously affected during the civil war in the Kabul city in

early 1990s. Even though there is no reliable data showing the percentage of the people

who have access to the electric power, according to the director general of Da

Afghanistan Breshna Moassesa (DABM), it is estimated that the power coverage is over

70% in urban areas and less than 7% in rural areas. This power coverage contains

privately owned small generators and even batteries [1]. Meaning that, some of the

people mentioned do not have access to reliable electric power. On the other hand, since

the people usually use electric power only for lighting, the coverage mentioned means

that 70% of the urban people have access to electric power for a few hours a day. In some

cities, for example Herat, the situation is better, and the people in Herat city are using

electric power for a longer time.

The Kabul electric power system is served by three hydro power plants: Naghlu,

Mahipar, Surobi, and one thermal power plant located in the North-West of the Kabul

city. The rated capacities of the plants are 100 MVA, 66 MVA, 22 MVA, and 45 MVA,

and the actual capacities of the plants are 100 MVA, 44 MVA, 22 MVA, and 45 MVA

respectively. The capacities are peak capacities and the stations can only work at their

peak capacities when the water and diesel are available. On the other hand, all four

generation stations need rehabilitation. From the four generation stations, only two

turbines of the three in Mahipar station have been rehabilitated so far [2].

However, the 110 kV transmission lines, carrying power from generation stations

to the Kabul city, are operational and in a better condition compared to generation and

distribution systems, but still they need upgrading and rehabilitation. Figure 1-2 shows a

general layout of Kabul power distribution system containing four power distribution

substations and 11 junction stations (For AutoCAD drawing see attachments of [2]). This

layout does not contain Pule Charkhi substation which is in island mode. An important

achievement in transmission line is the transmission line installed from Hairatan

19 (Northern border of the country), to Kabul to carry 100 MVA power from Uzbekistan to

Kabul with 220 kV voltage level.

Figure 1-2 The Kabul Power Distribution System General Layout [2].

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20 According to [2], the Kabul power distribution system is composed of five

distribution substations, 11 junction stations, and 717 distribution transformers in 2007.

The Butkhak substation (sixth substation) and one junction station (nine), in Paghmaan

district, have been destroyed to the ground during the wars in 1991 to 1993. The existing

part of the Kabul distribution system has three different medium voltages, 20 kV, 15 kV,

and 10 kV.

The Breshna Kot substation has two 25 MVA power transformers. They have two

different output voltages, 15 kV and 20 kV. Eight outgoing feeders with four additional

spare feeders1 have been connected to this power substation. The Breshna Kot substation

and its associated junction stations feed 156 distribution transformers with 20 kV/0.4kV

and 15 kV/ 0.4kV voltages. The total capacity of the distribution transformers is 89.5

MVA [2]. Figure 1-3 shows the layout of the Breshna Kot substation.

The north-west substation has two 25 MVA transformers with output voltages of 15 kV

and one 20 MVA transformer with 15 kV output. There are nine feeders connected to this

power substation and also it has three spare feeders. The north-west substation and its

associated junction stations feed 207 distribution transformers with 15 kV/0.4 kV

voltages. The capacity of the transformers fed by the north-west substation is 108.7 MVA

[2]. Figure 1-4 shows the layout of the north-west substation.

The east substation has one transformer with 25 MVA capacity and its output

voltages are 15 kV and 20 kV. This power substation has six operational feeders and one

spare feeder. The east substation and its associated junction stations feed 133 distribution

transformers with 20 kV/ 0.4kV and 15 kV/0.4 kV. The total capacity of the distribution

transformers is 68.3 MVA [2]. Figure 1-5 shows the layout of the east substation.

1 Reserve (spare) feeders are additional installed feeders that are not in use. In case of necessity, they are used.

21

Figure 1-3 The Breshna Kot Power Substation Layout [2].

Figure 1-4 The North-west Substation Layout [2].

Breshna Kot Substation

Junction # 6

Junction # 3

Junction # 1

North-WestSubstation

Junction # 4

Junction # 8

Junction # 11

101.57 %

101.90 %

101.76 %N W-514- Borj_2_Par wan she

22

Figure 1-5 The East Substation Layout [2].

Pul-e-Charkhi substation has two 6.3 MVA transformers. This substation is in

island mode and feeds the Kabul Radio Station and villages near the station. The output

voltage of this substation is 10 kV [2]. Map for the Pul-e-Charkhi substation was not

found.

The north substation has two power transformers. Each of the transformers in the

north substation has 40 MVA capacity and the output voltages of these transformers are

15 kV. There have been connected 12 outgoing feeders to this power substation and there

exist nine spare feeders. One of these outgoing feeders has been installed for transformers

repairing shop which is located inside the substation offices building. The North

substation and its associated junction stations feed 221 operational distribution

transformers with 15 kV/0.4 kV voltage. The total capacity of these distribution

transformers is 130 MVA [2]. Figure 1-6 illustrates the layout of the North substation.

EastSubstation

Junction # 7

23

Figure 1-6 The North Substation Layout [2].

Finally, the total capacity of the five substations is 237.6 MVA, which does not

satisfy the Kabul city power demand. Hence, the Kabul city power distribution system

needs upgrading and expanding to meet the increasing demand.

1.3.3 Over Loaded Transformers

One of the important concerns in the Kabul power distribution system is

inappropriate load conditions of the distribution transformers. There are a total of 96 over

loaded distribution transformers in the Kabul distribution system in 2007 [2], which are

13.4% of the transformers. Unfortunately, the number of overloaded distribution

transformers goes up increasing population and demands. The over loaded transformers

are distributed in the four substations as the following. The Breshna Kot substation and

its associated junction stations feed 19 over loaded transformers. A total of 44 over

loaded transformers are connected to the North substation and its associated junction

NorthSubstation

Junction # 2

Junction # 5

Junction # 5

Junction # 10

Junction # 11

Junction # 12

24 stations. The North-west substation and its associated junction stations feed a total of 24

over loaded transformers. A total of nine over loaded transformers are connected to the

East substation and its associated junction stations. We should remember that the number

of overloaded transformers is increasing because more customers are connected to the

existing transformers.

1.3.4 Future Growth and Anticipation

Although the whole system of electrical power in Afghanistan is in a very bad condition,

the distribution system is the worst. During the early 1990s wars and conflicts in the

Kabul city the distribution system was seriously affected. For example, Butkhak power

distribution substation was damaged to the ground and it does not exist now. A

considerable part of the underground feeders and overhead lines of the distribution

system were also destroyed. On the other side, the system has not been upgraded since

1985. Furthermore, the weakness of the distribution system causes constraints and it

limits power supply seriously. Therefore, the main focus in power system rehabilitation

has been expansion and rehabilitation of the distribution system [1]. Figure 1-7 illustrates

a war hit distribution transformer house. We should remember that some transformer

houses have been destroyed to the ground. Figure 1-8 exhibits a piece of secondary

distribution cable showing the conditions of the power distribution system.

It is proposed that over 90% of the Kabul population, as capital of the country,

will have access to affordable electric power by 2013. Also over 50% of the population in

small towns and villages will have access to electric power by then. As electric power

production growth has a direct co-relation with Gross Domestic Product (GDP), it will

help eliminate extreme poverty in the country. Therefore, it is anticipated that the

operating capacity should be increased from 464 MVA in 2007 to 850 MVA by the end

of 2010, in the whole country. This will provide electric power for, at least, 65% of the

dwellings in major urban areas. Of course, the installed capacity is much higher than

operating capacity. The current installed capacity is estimated to be 769 MVA, while the

operating capacity is estimated to be less than 448 MVA [1]. It is estimated that, the

power losses can be reduced as much as 285 MVA in urban areas and 80 MVA in rural

25 areas by 2020 by system improvement. The power availability increase needs the power

distribution system to be enhanced and improved to meet the requirements [1].

Figure 1-7 A Destroyed Transformer House in the Kabul Power Distribution System [2].

Especially in the Kabul city because of significant population growth, the power

demand will exceed 500 MVA by 2013, while the total installed capacity, including small

generators, is estimated to be 205 MVA in 2007. This implies that in the next five years

the power demand will increase more than two times. Therefore, improving the capacity

of the distribution system to an adequate level and upgrading the medium voltage from

10 kV and 15 kV to 20 kV in order to reduce losses of the system are considered

necessary.

26

Figure 1-8 A Piece of Secondary Distribution Underground Cable in the Kabul Distribution

System [2].

As mentioned in section 1.2.2, the Kabul distribution system has five substations

that all need upgrading to meet the increasing demand for power. Therefore, there are

plans to upgrade the capacity of the five distribution substations, and also to establish an

additional substation in south part of the Kabul city [2]. Due to upgrading plan of the

Kabul power distribution system, two 25 MVA transformers with their associated

equipment have been added to the Breshna Kot substation. The capacity of this substation

has been increased from 50 MVA to 100 MVA. The capacity of the East substation has

been increased from 25 MVA to 65 MVA by adding a 40 MVA power transformer and

its associated equipment. The North substation has capacity of 80 MVA. A 40 MVA

power transformer will be added in this substation to increase the capacity from 80 MVA

to 120 MVA. The existing capacity of the North-west substation is 70 MVA which is

27 composed of two 25 MVA transformers and one 20 MVA transformer. These

transformers will be replaced by three 40 MVA transformers. The Pul-e-Charkhi

substation (island mode), at the present time, has two 6.3 MVA transformers. They will

be replaced by two 16 MVA transformers. The total capacity in this substation will be

increased from 12.6 MVA to 32 MVA. Based on this upgrading plan, the total capacity of

the Kabul power distribution substations will be 437 MVA [2].

Although the current plans to upgrade the Kabul power distribution substations may be

considered as a big change, they will not be adequate to meet the increasing power

demand. Therefore, the Kabul city distribution system needs at least one more substation

to serve minimum power demand in next five years. The distribution system’s losses, on

the other hand, are another important problem to have an optimized power distribution

system. Theoretically, one of the efficient factors to reduce the losses is upgrading the

medium voltage from 10 kV and 15 kV to 20 kV; which is part of the subject of this

thesis. At the present time, the Kabul power distribution system has three medium

voltage levels, 10 kV, 15 kV, and 20 kV. It has been planned that the 10 kV and 15 kV

voltage levels should be upgraded to 20 kV. In this way the losses will be reduced;

meanwhile the capacity of feeders will be increased as well.

1.4 Power Loss Minimization and Power Reliability and Quality Maximization

Minimization of power loss and maximization of power reliability and quality are

the three fundamental aspects in power distribution systems, which have drawn serious

attention of researchers and designers. Therefore, many ways have been proposed to

minimize power losses and maximize power reliability and quality. One of the common

approaches to the power loss minimization is reconfiguration of a system [8]. One should

know that a power network normally contains different types of loads such as industrial,

commercial, residential, and lighting loads. On the other hand, the peak load occurs in

different times of the days. Hence, by switching loads from one feeder to another, it is

possible to minimize the power losses in the network [8], [9]. Also, this type of

reconfiguration allows making the peak load more smooth [9], which consequently

results more reliability of the power network.

28

Reconfiguration of a power network is performed to minimize power losses and

make the network more balanced [8]; however, in the Kabul power distribution system

efficient reconfiguration of the network seems difficult because of the improper modeling

of the system. Whereas, proper modeling of a power network is one of the considerations

in the power network reconfiguration [8].

1.5 Voltage Drop and Voltage Sag

From supply quality point of view, voltage level at the load point is one of the most

important parameters [10]. To keep the voltage level in a certain range, voltage

regulations is usually applied to a standard power distribution system. One knows that the

slope of voltage profile is determined by type of a transmission line, its cross-section, and

the power flowing through it [10], [11]. Although the Kabul power distribution system is

not well equipped according to a high standard (for example American standards) it is

possible to compensate the voltage drop by changing MV/LV transformers tap; and by

placing shunt capacitor banks in the network [11], reactive power can be compensated;

which causes a decrease in voltage drop. But this voltage regulation and reactive power

compensation does not help sufficiently to minimize power loss and voltage drop in the

MV level of the Kabul power distribution system, because it does not deal with primary

feeders and medium voltage level.

Another severe power quality disturbing factor, propagating in a network, is

voltage sag2 [12]. The severity of this phenomenon is because it occurs numerous times

per year; also, it affects businesses very seriously. For instance, very short (10 ms)

voltage sag can cause an industry or laboratory to be inoperable for hours [12]. Even it

can cause loose of data and so forth. According to [12], voltage sag is characterized by its

duration3 and magnitude4 (for details, see [12]). Usually a voltage sage lasts for 10ms to

one minute. It is worth keeping in mind that there is a type of voltage sag that cannot be

2 Voltage sag is a momentary decrease in RMS value of voltage in a range of 10% - 90% of nominal voltage [12]. 3 The duration time of a voltage sag starts from the instant that voltage sag crosses the threshold (90% of nominal voltage) and ends when voltage sag arrives back to the threshold [12]. 4 Magnitude of a sag is defined as minimum RMS value of voltage during the voltage sag occurrence [12]

29 defined by it duration and magnitude; also it cannot be characterized with respect to its

duration because the wave form of it decreases linearly to a minimum value (e.g. 33%)

and then increases linearly to its nominal voltage level [3]. In other words, this type of

voltage sag does not have a “single definitive value”.

Even though, voltage sag is considered a severe disturbance in power distribution

network from power quality point of view, but it is not big concern in this thesis work.

Because this research work does not deal with highly sensitive consumers and big

industries; rather it deals more with residential consumer and some commercial, hospital,

and governmental consumers.

1.6 Medium Voltage in Power Distribution Systems

Medium voltage functions as a bridge between high voltage (110 kV and 220 kV

in our case) and usable (low) voltage (0.4 kV in our case). Therefore, medium voltage has

key role in power distribution system. In order for a system to be considered efficient, it

must have an efficient medium voltage [4], besides other elements of the system such as

generation, transmission, and low voltage system. Meaning that, the medium voltage part

of a power system should have minimum power loss and voltage drop and it should

satisfy required criteria of an optimum system (for criteria, see section 4.1.).

1.7 The Kabul Power System Voltage Configuration

Kabul power distribution system is composed of substations, junction stations,

and distribution transformers. There are three voltage configurations in Kabul power

system, 110 kV/10 kV/0.4 kV, 110 kV/15 kV /0.4 KV, and 110 kV/20 kV /0.4 kV. High

voltage, in Kabul distribution system, is 110 kV, which comes from generation stations to

the distribution substations. The outputs of substations, medium voltages (MV), are 10

kV, 15 kV, and 20 kV, which go to junction stations5 or directly to distribution

5 Junction station is a place where the several feeders are connected together. Junction stations have one to three incoming feeders and several outgoing feeders.

30 transformers6. Figure 1-9 illustrates the Kabul power distribution system’s voltage

arrangement.

Figure 1-9 The Kabul Power Distribution System Voltage Arrangement.

Although the Kabul power distribution system has three level voltage

configurations the levels of the medium voltages are not the same in all substations. The

Breshna Kot and the East substations have two voltage arrangements, 110 kV/15 kV

/0.4KV and 110 kV/20 kV /0.4kV; but the North-west and the North substations have

only one voltage arrangement, 110 kV/15 kV /0.4KV. The Pule-charkhi substation

(island mode substation) has also a three level voltage configuration, which is 110 kV/10

kV/0.4kV arrangement. However, these voltage arrangements have the least voltage

levels and distribution stages, but still 15 kV and 10 kV medium voltages have some

disadvantages [4] to be considered. The criteria for MV application are discussed in

section 4.1.

In reference [4], three voltage configurations – 220 kV/110 kV/10 kV, 220 kV/110

kV/20, and 220 kV/20 kV – have been experimented with different load densities (1.0

6 In (2007), there have been 4 substations, 12 junction stations, and 717 distribution transformers in Kabul power distribution transformers [2].

31 MW/km2 – 60.0 MW/km2), for overhead lines and underground cables. The results of the

research in [4] show that the cost of unit load in all three projects decreases if the load

density increases. In other words, the cost of unit load has inverse (may not be linear)

correlation with load density. Likewise, the radius of power supply would also decrease if

load density increases.

In case of overhead lines, for load densities lower than 10 MW/km2,

220kV/110kV/20 kV is the best arrangement if the cost of unit load is concerned [4];

considering reliability, the voltage arrangement 220 kV/110 kV/10 kV is the best in all

three cases that are studied in [4]. For underground cables, 220 kV/110 kV/20 kV

configuration is better than 220 kV/110 kV/10 kV taking the cost of unit load into

account. Even though, as result of the research, 20 kV has been recommended in [4] as

medium voltage for the area assuming the load density more than 10 MW/km2, compared

to 10 kV medium voltage; in the project in hand, two voltage arrangements 110 kV/15

kV and 110 kV/20 kV are studied for load density lower than 10 MW/ km2 in the Kabul

power distribution system.

32

2 CHAPTER 2: METHODOLOGY

2.1 Consumer Classification

In general, consumers of electric power are divided into three main groups (types)

which have some different characteristics [6]. The three groups are: 1) industrial, 2)

commercial, and 3) residential consumers. The main requirements of the three types of

consumers can be determined as: total amount of electrical energy consumed over a

period of time (the period of time can be annually or monthly), the rate of change of the

consumption, the required voltage level (for different operation purposes), the reliability

requirement of the system serving the consumption area, and power quality requirements.

The quality includes, mainly, continuity of power supply and the level of the voltage and

the frequency of the voltage wave [13].

The consumers are divided into two main groups in this research work, residential

consumers and commercial consumers. There are two other categories of consumers,

governmental7 and hospital that have similar characteristics to commercial consumers;

therefore, they are considered as commercial consumers. There is no industrial consumer

connected to the North substation, which is studied in this research work.

Based upon the customers characteristics and their power demands a power

distribution system is designed and implemented. Commercial, industrial, hospitals, and

governmental (in our case) power customers need more reliable power with higher

quality. Therefore, economy is not the first priority for commercial, industrial, hospital,

and governmental customers. Yet, for residential customers the priority is given to

economy. Meaning that, for residential customers cheaper systems are designed and

applied. One should notice that the optimization of the system according to the

requirements of the customers is highly important.

7 Governmental consumers are referred to governmental office buildings. This type of consumers has similar characteristics to the commercial consumers.

33

2.2 Research Project Selection

As was mentioned in earlier sections, currently the Kabul power distribution

system has five substations with different output voltage levels. The Breshna Kot

substation and the East substations have two output voltages with 15 kV and 20 kV

voltage levels. The North and North-west substations have one 15 kV output voltage

level. The Pul-e-charkhi substation has also one output voltage level but it is 10 kV.

For the present research work, the North substation is chosen based upon the

following reasons. The North substation has the best location in the Kabul power

distribution system, and it covers mostly the central part of the Kabul city. It is located in

a central location of the Kabul city; thus it covers an area, which have higher load density

and it serves more customers compared to the other substations. Also it serves a relatively

good combination of the consumers’ types in the Kabul power distribution system. This

substation has the highest capacity and serves a great number of residential customers

and governmental customers. The North substation has not been rehabilitated yet; hence,

it worth examining and upgrading the level of the output voltage.

2.3 Data Used for Network Simulation

The data for the network simulation are taken from the results of a survey

conducted by Advanced Engineering Associates International (AEAI), funded by the US

Agency for International Development (USAID), with approval of Da Afghanistan

Breshna Moassessa (DABM) in 2007 [2]. The results of the survey have been reported as

a technical report to the DABM.

2.3.1 Transmission Lines

According to the report prepared based on the survey, the North substation has 12

outgoing feeders, from which 11 feeders serve distribution transformers and junction

stations and one feeder serves the workshop of distribution transformer repairing located

inside of the North substation office building. This substation also has nine reserve

(spare) feeders which are not considered in this research work. A list of the North

34 substation and its associated junction stations outgoing feeders and their conductors’

sizes is shown in Table 2-1. It should be remembered that the size of the feeders are not

the same from the beginning to the end of the feeders. The sizes in the table are the sizes

of the first portion of the feeders going out of the substation and junction stations.

Table 2-1 Outgoing Feeders of the North Substation and its Associated Junction Stations

North S/S Junction # 2 Junction # 5 Junction # 10

Feeder Name

Size (mm2) & Type

Feeder Name

Size (mm2) & Type

Feeder Name

Size (mm2) & Type

Feeder Name

Size (mm2) & Type

512 120 – Al 531 50 – Cu B-2-5 95 – Cu 527 185 – Al 528 185 – Al 517 50 – Cu F-3-5 50 – Cu J-10 95 – Cu 513 185 – Al D-2-7 50 – Cu MO 50 – Cu MA 70 – Cu 520 185 – Al E-1-2 50 – Cu AU 95 – Cu EL 35 – Cu 519 185 – Al B-1-2 35 – Cu F-4-5 95 – Cu 529 185 – Al A-1-2 50 – Cu 518 185 – Al B-2-5 50 – Cu 515 185 – Al 515 185 – Al 511 185 – Al 516 185 – Al 517 185 – Al

2.3.2 Loads

The North substation and its associated junction stations serve a total of 229

distribution transformers that are considered as spot loads for the network simulation

(including some of the inactive distribution transformers). As was mentioned in the first

section of this chapter, the loads are composed of four types: residential loads,

governmental loads, hospital loads, and commercial loads. There are no industrial loads

connected to the North substation; however, some of the distribution transformers serve

some small technical workshops having small electrical motors. In order to have an easy

view of the network loads, they are categorized into feeders and types; but before that,

see Table 2-2 for the combination of nominal loads served by the North substation. It

should be noted that the table contains some inactive transformers also.

35

Table 2-2 Combination of nominal Loads in the North Substation

Feeder ID

Load Type Total Number/MVAResidential Governmental Hospital Commercial

Number MVA Number MVA Number MVA Number MVA 512 11 7.520 5 1.840 4 3.630 0 0.000 20 12.990 528 13 8.900 0 0.000 0 0.000 0 0.000 13 8.900 513 12 7.090 6 4.260 0 0.000 0 0.000 18 13.160 520 12 8.240 0 0.000 0 0.000 0 0.000 12 8.240 519 Connects J/S #10 to the North S/S 529 1 0.800 Connects J/S #5 1 0.160 2 0.960 518 1 0.160 Connects J/S #2 0 0.000 1 0.160 515 Connects J/S #2 to the North S/S 514 12 7.780 0 0.000 0 0.000 0 0.000 12 7.780 511 1 Unknown 1 516 15 10.030 9 5.350 0 0.000 0 0.000 24 15.380 517 13 8.730 4 1.760 0 0.000 0 0.000 17 10.490 527 13 7.690 0 0.000 0 0.000 1 0.250 14 7.940 EL 0 0.000 0 0.000 0 0.000 1 0.250 1 0.250 MA 0 0.000 0 0.000 0 0.000 1 0.400 1 0.400 D2-7 0 0.000 5 2.140 0 0.000 0 0.000 5 2.140 531 1 0.400 3 1.200 0 0.000 0 0.000 4 1.600 517 2 1.260 10 4.440 0 0.000 0 0.000 12 5.700 E2-1 1 0.630 13 7.690 2 1.400 0 0.000 16 9.720 B2-1 3 1.770 7 2.100 0 0.000 0 0.000 10 3.870 A2-1 6 3.050 3 1.000 0 0.000 2 1.250 11 5.300 B2-5 5 2.690 2 0.880 0 0.000 2 2.500 9 6.070 B5-2 6 3.770 2 0.600 2 1.030 2 0.410 12 5.810 F5-3 3 2.060 0 0.000 0 0.000 0 0.000 3 2.060 F5-4 5 3.460 2 0.800 0 0.000 2 1.600 9 5.860 MOK 2 1.260 0 0.000 0 0.000 0 0.000 2 1.260 Aux 1 0.630 0 0.000 0 0.000 0 0.000 1 0.630 Total 138 82.608 79 40.120 0 0.000 12 6.820 229 129.548

Feeder 512 serves 11 residential loads with a total nominal power of 7.52 MVA,

five governmental loads with a total nominal power of 2.07 MVA, four hospital loads

with a total nominal power of 3.63 MVA. No commercial load is served by this feeder.

Feeder 511 serves the repairing workshop for distribution transformers in the North

substation area. The power of the load for this feeder is unknown. The layout of the

feeders 512, 511, and connected loads to them is shown in Figure 2-1 (for AutoCAD

drawings see attachments of [2]).

36

Figure 2-1 Layout of the Feeder 512 with 20 Loads.

Feeder 528 serves 13 residential loads with a total nominal power of 8.9 MVA.

This feeder does not serve any commercial load and governmental load. See Figure 2-2

for a layout of feeder 528 and connected loads to it.

120sqmm 70sqmm

50sqmm

70sqmm

70sqmm

70sqmm70sqmm

50sqmm

95sqmmUG Cable

50sqmmUGC

185sqmmUG Cable

70sqmm

95sqmm50sqmm

95sqmm35sqmm70sqmm

50sqmmUGC

50sqmmUGC

50sqmm UGC

50sqmmUGC

F-512

F-511

A

A

-0.35 MW N-512-Lawaye Amniat

N-512-Chamandi-0.35 MW

-0.35 MW-0.35 MW

-0.55 MW-0.14 MW

-0.70 MW -0.55 MW

-0.35 MW-0.55 MW

-0.87 MW

-0.87 MW

-0.22 MW-0.87 MW

-0.87 MW

-0.87 MW-0.55 MW

-0.55 MW

N-512-Abrasani

N-512-Blak hay HawaeeN-512-Hawa Shenasi

N-512-Qaloi Wakil

N-512-Qalai KhwajaN-512-Qalai Khater

N-512-Moqabele Bibi MahroN-512-Nowabad Bibi Mahro

2 x ︵-0.87 ︶MWN-512-400 Bester 1&2

N-512-T#3 Wzir Akber Khan

N-512-Tr/S 12

N-512-Ministry of Public Health



N-512-Sehate Tefl

N-512- Wzir Akber Khan Hospital

N-512- Nursing

North Substation

Junction # 2

37

Figure 2-2 the Layout of Feeder 528 with 13 Loads.

Feeder 513 serves 12 residential loads with a total nominal power of 7.09 MVA

and six governmental loads with a total nominal power of 4.26 MVA. This feeder does

not serve any commercial load. See Figure 2-3 for a layout of feeder 513 and connected

loads to it.

-0.55 MWN-528- Taqiatee Chmandi

-0.87 MWN-528- Chmandi Hawaee

-0.55 MW-0.55 MWN-528- Syed Nezam #1&2

-0.70 MW

N-528-Mohammadya#2

-0.55 MWN-528-Mohammadya#1

-0.70 MWN-528-Taqwiatee Wazir Abad

-0.55 MWN-528- Wazir Abad

-0.55 MWN-528- Borje Tahire

-0.55 MW-0.55 MW

N-528- Char Qala Wazir Abad #1&2

-0.55 MWN-528- Now Abad Qala Mosa

-0.55 MWN-528- No-3- Qala Mosa

North Substation

F-528185sqmmUCG

38

Figure 2-3 Layout of the Feeder 513 with 18 Loads.

Feeder 520 serves 12 residential loads with a total power of 8.24 MVA. No

governmental and commercial loads are connected to this feeder. Feeder 519 connects the

junction station 10 to the North substation. The layout of the feeders 519, 520 and

connected loads to them is shown in Figure 2-4. Feeder Mastora serves one 400 kVA

commercial load. Feeder Elham serves one 250 kVA commercial load.

N-513-No-1 Khaja Bughra #1&2-0.70 MW-0.55 MW

-0.55 MWN-513-No-2 Hawaee Khaja Bughra-0.70 MW

N-513-No-3 Zaminee Khaja Bughra-0.70 MW

N-513-No-60Khaja Bughra

-0.35 MW

N-513-No-59 Khaja Bughra-A-0.35 MW N-513-No-62 Hawaee Khaja Bughra-A

-0.35 MW

N-513-No-59 Khaja Bughra-B

-0.70 MW

N-513-No-59 TaqwiateeKhaja Bughra

-0.55 MW A

A

N-513-Reyasat-e-logistic-0.35 MW

N-513-Gaurd Milli #1&2-0.70 MW-0.70 MW

-0.55 MWN-513-Technic wa Asleha

N-513-Taharokat Transport-0.87 MW

-0.55 MWN-513-Tasadee Kamaz

-0.35 MWN-513-Regration

-0.35 MWN-513-Mamr-e-Wazarate Transport

F-513

150sqmm

185sqmmUGC

N-513-No-1 Taqwiatee Khaja Bughra

North Substation

39

Figure 2-4 The Layout of the Feeders 519 and 520 with their Associated Loads.

Feeder 529 serves one residential load with a total nominal power of 800 kVA

and one commercial load with a total power of 160 kVA. This feeder does not serve any

governmental load; but it connects junction station five to the North substation. Whereas,

the junction station five feeds the following loads:

Feeder B-5-2 serves six residential loads with a total nominal power of 3.77

MVA, two governmental loads with a total power of 630 kVA, two hospitals with a total

load of 1.03 MVA, and two commercial loads with a total nominal power of 410 kVA.

Feeder F-5-3 serves only three residential loads with a total nominal power of 2.06 MVA.

Feeder Mohammad Omar Khan (MOK) serves two residential loads with a total nominal

power of 1.26 MVA. This feeder does not serve any governmental and commercial loads.

The Feeder Auxiliary serves only one 630 kVA residential load. No governmental loads

and commercial loads are connected to this feeder. Feeder F-5-4 serves five residential

loads with a total nominal power of 3.46 MVA, two governmental loads with a total

nominal power of 800 kVA, and two commercial loads with a total power of 1.6 MVA.

-0.70 MWN-520- No-11- Zamini #1&2

-0.55 MWN-520- No-11- Hawaee

-0.55 MW

-0.35 MW-0.22 MW N-J/S 10 Bland Manzel Mastora #1&2

N-520- Sarwar-e-Kaynat-0.55 MW

N-520- No-12 Taqwiatee-0.55 MW

-0.70 MW -0.55 MWN-520- No-12 Zamini #1&2

-0.70 MW-0.55 MW

N-520- 8 Jeem #1&2

-0.55 MW-0.55 MW

N-520- Borj Sera Mena #1&2

-0.70 MW-0.55 MW

N-520- No-13 Zamini #1&2

Junction # 10

North Substation

F-519

185sqmmUGC

F-520

40 Figure 2-5 shows the layout of the feeder 529 and the feeders distributed from the

junction station five.

Figure 2-5 The Layout of Feeder 529 and the Feeders Connected to the Junction Station Five.

Feeder 518 serves a water-pump load with a nominal power of 160 kVA and

connects junction station 2 to the North substation. This feeder does not serve any other

load. However, the other loads connected to the junction station two are served by feeder

518. Meanwhile, the feeder 515 connects the junction station 2 to the North substation. In

-0.17 MW

N-529-JS5-B-2-5Technic wa Asleha Amneiat

N-529-JS5-B-2-5Malalay Hospital

-0.55 MW -0.35 MWN-529-JS5-B-2-5Zamini Qwai Markaz

N-529-JS5-B-2-5Market Najib Aarab

-0.14 MW

N-529-JS5-B-2-5Borj Zamini Market Kohna

-0.30 MW

-0.35 MWN-529-JS5-B-2-5Amniat Hospital

-0.35 MWN-529-JS5-B-2-5No-2- Karte Aryana

-0.70 MWN-529-JS5-B-2-5No-1- Karte Aryana

-0.55 MWN-529-JS5-B-2-5Sarak Awal Baharistan

-0.70 MWN-529-JS5-B-2-5Hesa Awal Karte Parwan

N-529-Bland Manzel Gulzad-0.14 MW

N-529-JS5-B-2-5Noor TV StationN-529-JS5-B-2-5

Borj Bagh Bala #1&2

-0.22 MW-0.55 MW -0.55 MW

N-529-JS5-B-4-5Borj Awal Karte Mamoreen

-0.70 MW

-0.35 MWN-529-JS5-B-4-5Borj Dowom Karte Mamoreen

N-529-JS5-B-4-5Borj Siloy Markaz

-0.87 MW

-0.70 MW-0.70 MW

-0.35 MW-0.35 MW

N-529-JS5-B-4-5Borj Politechnic #1&2

N-529-JS5-B-4-5Borj Intercontinental #1&2

-0.55 MW-0.55 MW

N-529-JS5-B-4-5M. Omar Khan #1&2

-1.29 MWN-JS5-Milli Bus

N-529-JS5-B-2-5UK Embassy-0.35 MW

N-529-JS5-B-4-5Auxiliary-0.55 MW

N-529-Borj 5 Chamani Babrak-0.55 MW

Junction # 5

A

A

North SubstationF-529

185sqmmUGC

41 Figure 2-6 the layout of feeders 518 is shown and the layout of feeder 515 is illustrated in

Figure 2-7. The loads, connected to the junction station two, are as the following:

Feeder D-2-7 serves only five governmental loads with a total nominal power of

2.14 MVA. Neither residential nor commercial loads are served by this feeder. Feeder

531 serves one 400 kVA residential load and three governmental loads with a total

nominal power 1.2 MVA. No commercial load is connected to this feeder. Feeder 517

serves two residential loads with a total nominal power of 1.26 MVA and 10

governmental loads with a total nominal power 4.44 MVA. There is no commercial load

connected to this feeder. Feeder E-2-1 serves one 630 kVA residential load, two hospitals

with a total connected power of 1.4 MVA, and 13 governmental loads with a total

nominal power of 7.69 MVA. This feeder serves no commercial load. Feeder B-2-1

serves three residential loads with a total power of 1.77 MVA and seven governmental

loads with a total power of 2.1 MVA. This feeder does not serve any commercial load.

Feeder A-2-1serves six residential loads with a total power of 3.05 MVA, three

governmental loads with a total power of 1000 kVA, and two commercial loads with a

total power of 1.25 MVA. Feeder B-2-5 serves five residential loads with a total power of

2.69 MVA, two governmental loads with a total power of 880 kVA, and two commercial

loads with a total power of 2.5 MVA. One can see the layout of the junction feeders and

connected loads to them in the loads associated with feeder 518 and 515.

42

Figure 2-6 The Layout of the Feeder 518 and its Associated Feeders Connected to the Junction

Station Two.

34

-0.35 MW

N-518-JS2-E-1-2Edara Omoor

-0.55 MWN-518-JS2-E-1-2Wezarat DefaaN-518-JS2-E-1-2

Wezarat Mokhaberat2 ︵-0.87 MW ︶

5

N-518-JS2-E-1-2- Kartografi

︵-0.17 MW ︶

5

-0.55 MWN-518-JS2-E-1-2Wezarat Madan

-0.35 MW N-518-JS2-B-1-2Wezarat Malya

N-518-JS2-E-1-2Pashtonistan Waat

-0.55 MW-0.17 MW

N-518-JS2-E-1-2Post Telephone Telegram

-0.22 MWN-518-JS2-B-1-2Spenzar Hotel

N-518-JS2-B-1-2-Wezarat Etelaat

N-518-JS2-B-1-2-Pashtani Bank

-0.35 MW-0.17 MW 7 6

N-518-JS2-E-1-2- Rabia Balkhi Hospital

︵-0.87 MW ︶

6

N-518-JS2-E-1-2- Stomatology

︵-0.35 MW ︶

7

B

B

Junction # 2

A

A

North Substation

F-518

185sqmmUGC

N-518- A-1-2Qalai Fathullah #1-0.55 MW-0.14 MW

-0.55 MW

N-518- A-1-2Naqlia Sheerpoor

-0.14 MW

N-518- AbrasaniWazir Abad

-0.55 MW-0.135 MW

N-518-JS2-Radio Afghnistan #1&2

-0.22 MWN-518-JS2-517-Hawanawardi

-0.55 MW-0.35 MW

N-518-JS2-517-AfghnistanNational TV #1&2

-0.35 MWN-518-JS2-517-Afghan Film-0.35 MW

N-518-JS2-517-Lessee Amani

-0.17 MWN-518-JS2-517Sefarat Alman

-0.22 MWN-518-JS2-517Sefarat Turkia

-0.22 MW

N-EmegencyHospital-0.55 MW

N-518-JS2-B-2-5Gulkhani Park

-0.22 MWN-518-JS2-A-1-2Bland Manzel Ansar

-0.55 MW-0.17 MW

N-518-JS2-A-1-2Haji Yaqoob #1&2

N-518-JS2-A-1-2 Omarzia-0.87 MW

-0.55 MW

N-518-JS2-B-2-5Konj Park Shahr Now

2 ︵-1.09 MW ︶

N-518-JS2-B-2-5-KabulCity Center #1&2

-0.35 MWN-518-JS2-B-2-5-Tank Teel Shar Now

-0.35 MWN-518-JS2-A-1-2-Wezarat Dakhela -0.17 MWN-518-JS2-A-1-2-Mokhabrat Share Now

N-518-JS2-E-1-2-Jamhooriat Hospital

-0.87 MW-0.70 MW

N-518-JS2-A-1-2-Moqabel Wezarat Dakhela

N-518-JS2-B-2-5-Moqabe Markaz Lesan

-0.55 MW -0.55 MW-0.22 MW

-0.35 MW

N-518-JS2-E-1-2-Borj-2-Sedarat

-0.55 MW

N-518-JS2-E-1-2-Borj-1-Sedarat

-0.35 MW

N-518-JS2-E-1-2-Wezarat Eqtesad

-0.70 MWN-518-JS2-B-1-2-Sedarat-0.70 MWN-518-JS2-B-1-2-Wezarat Khareja

-0.3 MW

N-518-JS2-B-1-2Arge Jamhoori

N-518-JS2-E-1-2- Lesse Esteqlal

1

︵-0.35 MW ︶

1

N-518-JS2-B-1-2- Guard Milli︵-0.17 MW ︶

2

N-518-JS2-E-1-2- Da Aghanistan Bank

︵-0.70 MW ︶

3

N-518-JS2-B-1-2- Bank Milli

︵-0.22 MW ︶4

2

43

Figure 2-7 The Layout of the Feeder 515 and its Associated Feeders Connected to the Junction

Station Two.

Feeder 514 serves only 12 residential loads with a total nominal power of 7.78

MVA. No governmental and commercial loads are served by this feeder. A simple layout

of the feeder 514 and connected loads to it is shown in Figure 2-8.

-0.55 MWN-515-JS2-D-2-7-Edara Computer

185sqmmUGC

-0.55 MW -0.55 MWN-515-JS2-D-2-7-Ehsaye Markazi #1&2-0.35 MWN-515-JS2-531- Ariana Hotel-0.35 MW

N-515-JS2-531- Matbea Urdo

-0.35 MW

-0.35 MWN-515-JS2-531- Qasr Delkosha #1&2

A

A

North Substation

F-515

Junction # 2

44

Figure 2-8 The Layout of the Feeder 514 with its Associated Loads.

Feeder 516 serves 15 residential loads with a total power of 10.03 MVA and nine

governmental loads with a total nominal power of 5.35 MVA. No commercial load is

connected to this feeder. A simple layout of the feeder 516 and connected loads to it can

be seen in Figure 2-9.


and four governmental loads with a total nominal power of 1.76 MVA. This feeder does

not serve any commercial load. Figure 2-10 shows a simple layout of feeder 517 and the

loads connected to it.


and one 250 kVA commercial load. No governmental load is served by this feeder. One

can see the layout of the feeder 527 in Figure 2-11.

-0.63 MWN-514-No-6-ProjaWazir Abad #1&2

-0.50 MW

-0.37 MW-0.24 MW

N-514-No-2-ProjaWazir Abad #1&2

-0.31 MWN-514-Salim Karwan-0.63 MW

-0.63 MW N-514-No-3-ProjaWazir Abad #1&2

-0.50 MW-0.50 MW


-0.50 MW-0.63 MW


-0.50 MWN-514-No-4-Proja Wazir Abad

North Substation

F-514

185sqmmUGC

45


-0.70 MWN-516-40 Metra Wazir Abad

BB

-0.55 MWN-516-No-1- Qwai Hawaye

-0.55 MWN-516-No-2- Qwai Hawaye

-0.87 MWN-516-Academey Nezame

-0.70 MWN-516-T/S Markazi Blak Hawaye #1

-0.35 MW

N-516-T/S RiasatAmniat Kabul

-0.87 MW

N-516-No-11Macroryan

N-516-No-MacroryanComunication

N-516-No-9-Macroryan

-0.70 MW-0.35 MWN-516-Stara Mahkama

-0.22 MW

N-516-No-12- Macrorayan

︵-0.87 MW ︶

1

2

3

4

12


︵-0.55 MW ︶


︵-0.70 MW ︶

34


︵-0.55 MW ︶

-0.70 MW-0.55 MW

N-516-No-15-Macroryan #1&2

-0.55 MW N-516-No-14-Macroryan-0.55 MW

N-516-No-14-Macroryan-0.55 MW-0.55 MW

N-516-Matbea #1&2-0.35 MWN-516-Emalat Khana Urdo

-0.35 MWN-516-Garnizion

-0.55 MWN-516-Ryasat Aamniat #16

-0.55 MWN-516-Shash Drak

Junction # 12

Junction # 2

North Substation

F-516185sqmmUNG

A

A

46


Figure 2-11 The Layout of the Feeder 527, Connected to the Junction Station Ten, with its

Associated Loads.

N-517- Taleem Wa Tarbia-0.09 MW -0.35 MW

N-517- Hawa Shenasee-0.55 MWN-517- Do SarakaMaidan Hawaee

-0.55 MWN-517- Qala Wakil Jadeed

-0.55 MWN-517-No-23-Macrorayan



-0.55 MWN-517-No-21-Macrorayan #1&2

-0.87 MW



-0.55 MW

-0.55 MW -0.55 MWN-517-No-18-Macrorayan

N-517-No-17-Macrorayan N-517-No-16-Macrorayan #1&2

-0.55 MW -0.55 MWN-517-Bukhar Khana Macrorayan #1&2

Junction # 12

A

ANorth Substation

F-517185sqmmUGC

N-527-No-10 Zamini #1&2

-0.55 MW

-0.55 MW-0.35 MWN-527-Qala Najarha

N-527-No-22 Zamini

-0.70 MWN-527-No-25-Hawaee

-0.35 MWN-527-No-25-Hawaee #1&2

-0.35 MW

A

A

-0.35 MWN-527-No-10 Hawaee

-0.22 MWN-527-Hotel Shame Paris

-0.70 MWN-527-Shahrak Police

-0.70 MW

N-527-No-9 Zamini #1&2-0.55 MW

-0.70 MW

Junction # 10

F-527

47

2.4 Simulation Tool and Network Simulation Data

2.4.1 Simulation Tool (CYMDIST Software)

For the network simulation, well known and powerful software is used. The

software is named CYMDIST (version 4.7 revision 11), which has been designed for

power distribution system modeling and analysis by CYME International Inc. This

software has been used for distribution systems’ simulation and design, fault analysis,

and reliability analysis worldwide. As an example, CYMDIST – RAM has been used for

reliability analysis of the distribution system in New York (the area served by Niagara

Mohawk Power Corporation), by Niagara Mohawk Power Corporation [16]. Another

example, CYMDIST has been used to prove numerical accuracy of a proposed load flow

method in [17]. In fact, this software needs a very detailed and specific data according to

the type, complexity, advancement, types of equipment, and devices used in a network.

Although the software is able to analyze very specific issues regarding to a power

distribution system there are two main features of analysis in CYMDIST8. One is

network analysis based on voltage drop and the other one is analysis of the system based

on short circuit. The software analyzes the system base on power flow theory ladder

iterative technique (for power flow analysis and ladder iterative technique, see [5]). In

this research work, the network is analyzed based on voltage drop analysis. On the other

hand, since the system power losses and voltage drop are the first priority in this research,

more attention is paid on the factors causing power loss and voltage drop.

2.4.2 Network Elements

This research project has a situation that obtaining the specific detail, for

CYMDIST, is very difficult. Because the project is located in the Kabul city and there are

no complete data available for the Kabul power distribution system and equipment even

in DABM. Therefore, the distribution transformers are not included in the simulation of

8 For more information about CYMDIST, one can see http://www.cyme.com/software/cymdist/CYMDIST.pdf

48 the network. Also, some devices such as, fuses, re-closers, circuit breakers, switches, and

etc are not included in the network simulation. Since the main point of the research is

system’s power loss and voltage drop in the MV level, the ignorance of the distribution

transformers and protection devices do not have significant effect on the system

simulation results.

For the feeders, as main factor causing power loss and voltage drop in the system,

the zero sequence and negative sequence impedances and admittances and size of the

conductors, used in CYMDIST, are collected for the system simulation. Table 2-3 shows

bare conductors sizes used in the North substation electric network for overhead MV

transmission lines. Similarly, Table 2-4 contains specifications9 of the under-ground

cables used in the North substation. Note that the spacing of the overhead lines is the

default values in CYMDIST with a geometric mean distance (GMD) of 1.3m because the

exact spacing for overhead lines was not available.

Table 2-3 Conductors Specifications Used for Overhead Lines in the North Substation

Material Size (mm2)

Z1 (Ω/km) Z0(Ω/km) B1 (μS/km)

B0 (μS/km)

RatingsR1 X1 R0 X0

ACSR 35 0.8579 0.4022 1.006 1.57 9.05 4.43 165 ACSR 50 0.6108 0.3915 0.7588 1.5593 9.31 4.49 200 ACSR 70 0.4219 0.3791 0.57 1.5468 9.63 4.56 270 ACSR 95 0.3125 0.3696 0.461 1.5374 9.89 4.62 330 ACSR 120 0.2602 0.3678 0.4083 1.5376 9.94 4.63 365 ACSR 150 0.2069 0.3602 0.355 1.528 10.16 4.68 425 ACSR 185 0.1676 0.3538 0.3157 1.5216 10.35 4.78 490

9 Z1and B1 are positive sequence impedance and susceptance respectively, Z0 and B0 are zero sequence impedance and susceptance respectively.

49

Table 2-4 Under-ground Cable Conductors Specifications Used in the North Substation

Material Size (mm2)

Z1 (Ω/km) Z0(Ω/km) B1 (μS/km)

B0 (μS/km)

RatingsR1 X1 R0 X0

Cu 35 0.527 0.153 1.38074 0.5661 159 159 189 Cu 50 0.39 0.146 1.2441 0.56064 175 175 222 Cu 70 0.271 0.138 1.12194 0.55338 196 196 271 Cu 95 0.196 0.132 1.045 0.54912 216 216 323 Cu 120 0.167 0.127 0.96526 0.5461 235 235 354 Cu 150 0.129 0.122 0.76497 0.29646 254 254 409 Cu 185 0.104 0.118 0.73944 0.29382 273 273 461 Cu 240 0.081 0.133 0.71523 0.29154 304 304 532 Al 50 0.644 0.146 1.50052 0.56064 175 175 172 Al 70 0.446 0.138 1.29786 0.55338 196 196 210 Al 95 0.323 0.132 1.172 0.54912 216 216 251 Al 120 0.256 0.127 1.10336 0.5461 235 235 285 Al 150 0.209 0.122 0.9422 0.29646 254 254 340 Al 185 0.169 0.118 0.804 0.29382 273 273 361

2.4.3 Load Modeling for the Network Simulation

As was mentioned in the previous sections, there are no real industrial loads

connected to the network under study of this research work. Thus, considering the load

characteristics, four types of loads are specified in the network: residential loads,

commercial loads, governmental loads, and hospital loads. Governmental loads, and

hospital loads, introduced in the earlier sections, have similar characteristics to the

commercial loads. Therefore, they are considered similar to the commercial loads in the

simulation of the system. In order to model the loads for the system simulation, the

following assumptions are made.

Although, for residential consumers with low income constant current is used in

[14] because it is not an exact model and it gives a higher loss and voltage regulation, the

residential loads are considered 20% constant power and 80% constant impedance

according to [3]. Likewise, commercial loads, in developing countries, are proposed 20%

constant power and 80% constant impedance in [3] it is assumed that 30% constant

power and 70% constant impedance is more convenient for commercial loads because of

computers and other electronic devices

50

2.4.4 Load Allocation for the North Substation Simulation

For analysis of a power distribution system, loads must be allocated properly,

either in transformer level or feeder level. On the other hand, load allocation needs

specific data of customer’s consumption. If sufficient data are available, load demand

curve can be obtained by statistical method, for example regression. This type of load

allocation is done when sufficient power is available for consumers. In this project, it is

not possible to allocate the load based upon the consumers needs, because of two

obstacles; 1) power supplied from the source (the North substation) is limited (80 MVA

that does not satisfy the consumers’ needs), 2) there are no specific and sufficient data

available for customers energy consumption served by the North substation.

It is obvious that for lower allocated loads the performance of the North

substations is better; fewer numbers of feeders’ sections are overloaded, and/or have

under-voltage conditions (see results sections 3.1.4 and 3.2.4 in next chapter). This is not

a good assumption for the North substation in the Kabul power distribution system;

because not only the total nominal power of the transformers connected to the substation

is high (130 MVA), but also the transformers are working under the loads that are,

mostly, near their nominal capacities. Even 44 transformers connected to the North

substation have been overloaded in 2007 [2]. Therefore, loads are allocated for each load

points (transformers) based upon their connected capacity and the nominal capacity of the

North substation; because it is more realistic and safe. According to the CYMDIST load

allocation option, loads allocated for each load points are 52.328% of connected capacity

of the loads. Note that in either case, loads are allocated based on nominal capacity of the

substation or loads allocated based on 50 MVA of the capacity of the substation, 20 kV

gives better results. The system simulation shows that if the loads allocated for load

points are decreased the performance of the network becomes better; meaning that power

loss and voltage drop decrease (see sections 3.1.4 and 3.2.4). We should remember that

because of the North substation’s load condition 50% load is not a realistic assumption as

it was explained before.

51

2.4.5 Simulation Settings and Accuracy

While running the voltage drop function of the software (CYMDIST), the number

of iteration and percentage of voltage clamp level do not have noticeable impact on the

results of the network simulation, as long as the number of iterations and percentage of

voltage clamp level are sufficient to satisfy the error tolerance (higher number of

iterations for the system simulation might need little longer time if more complex

network is simulated). For the present network simulation, at least 12 iterations are

needed to achieve results with an error less than 1% for voltage level calculation;

whereas, if a higher number of iteration (e.g. 5000) is chosen, the simulation results and

simulation times are still the same. The time of simulation, in any case is less than one

second. However, the least level of voltage clamp is 85% in 15 kV scenario; while it is

92% in 20 kV scenario. As was mentioned, because the number of iterations and

percentage of voltage clamp level do not have noticeable effect on the results of the

system simulation, conservatively, the number of iteration is chosen 40 and the voltage

clamp level is chosen 80% for both cases, 15 kV and 20 kV.

52

3 CHAPTER 3: RESULTS

3.1 Simulation Results with 15 kV MV

3.1.1 Levels of Under Voltage

3.1.1.1 At Feeder

Simulation results of the North substation in the Kabul power distribution system

with 15 kV MV shows that 172 loads (transformers) out of 229 loads have under-voltage

conditions and 57 loads have normal conditions, considering 230 V base voltage10.

Meaning that, 75% of the loads, based on number of loads, have under-voltage

conditions. This under-voltage occurs in the range of 87.39% to 96.88% of the base

voltage. Under-voltage condition is the condition in which the level of the input voltage

of equipment (transformer for example) drops below 97% of the base voltage.

Eight out of 11 main feeders with their associated sub-feeders have under-voltage

conditions. In some feeders all the connected loads have under-voltage conditions; in

some feeders a number of loads have under-voltage conditions. Clearly, under-voltage

happens on those loads that are located at the far end of the feeders. The loads served in

under-voltage conditions are as the following:

Feeder 512 and its associated sub-feeders serve 11 residential loads, four

governmental loads, and four hospital loads in under-voltage conditions (see Figure 2-1

for feeder 512 and loads attached to it). Only one load (Lewa-e-Amniat)11 closed to the

North substation, has normal conditions. The lowest level of the voltage, at loads served

by this feeder is 92.1% of the base voltage, which occurs at the transformer of the

ministry of public health. The total connected load served in under-voltage condition is

12.86 MVA (more details in the next chapter).

Seven residential loads, at the far end of the feeder 528, have under-voltage

conditions. The lowest voltage level occurs at a residential load in Qala-e-Musa, which is

96.57% of the base voltage (230 V). The total connected load with under-voltage

10 Low voltage in the Kabul distribution system is 400V line to line, and 230 V line to ground. The base voltage 230 V is line to ground voltage in secondary feeders (low voltage). 11 Name of the load is an indicator for location of the load.

53 conditions, attached to the feeder 528 is 1.43 MVA. The rest of loads attached to this

feeder have normal conditions (see Figure 2-2 for the feeder 528 and loads attached to it).

Ten loads, connected to the feeder 513, have the condition of the under-voltage.

The lowest under-voltage in this feeder occurs at the transformer of ministry of transport

located at the far end of the feeder. The level of the voltage at this load is 95.61% of the

base voltage. The remaining eight residential loads, connected to this feeder, have normal

conditions from voltage drop perspective. The total connected load under under-voltage

conditions attached to the feeder 513 is 6.09 MVA (for the loads attached to the feeder

513, see Figure 2-3).

All of the loads attached to the feeder 529 and its associated sub-feeders have

under-voltage conditions. The combination of the loads, served by feeder 529, is as the

following: 18 residential loads, four governmental loads, two hospital loads, and four

commercial loads. The lowest level of the voltage occurs at a residential load (Siloy

Markaz transformer); which is 94.39% of the base voltage (230 V). While the highest

level of the voltage, at loads attached to the feeder 529 is 96.65% of the base voltage. The

connected load attached to this feeder, that have under-voltage conditions, is 16.55 MVA

(for the load details, see Figure 2-5).

Similar to the feeder 529, all of the loads attached to the feeder 518 and its

associated sub-feeders have under-voltage conditions. Feeder 518 and its associated sub-

feeders feed 17 residential loads, 40 governmental loads, and two hospital loads. Ministry

of communication has the lowest level of the voltage; level of the voltage at this load is

89.35% of the base voltage. The highest level of the voltage at the loads attached to the

feeder 518 and its associated sub-feeders is 94.74% of the base voltage. The total

connected load attached to the feeder 518, in under-voltage condition is 29.67 MVA (for

load details, see Figure 2-6).

All of the loads attached to the feeder 515 have under-voltage conditions. Loads

served by the feeder 515 are composed of three residential loads and four governmental

loads. The lowest level of the voltage occurs at the governmental load (Matbah Urdu);

which is 92.04% of the base voltage (230 V). While the highest level of the voltage, at

loads attached to the feeder 515 is 92.22% of the base voltage. The connected load

54 attached to this feeder that have under-voltage conditions is 3.49 MVA (for the load

details, see Figure 2-7).

From voltage drop perspective, feeder 516 has similar conditions to the feeder

512. Only one load, closed to the North substation, is under normal conditions with

98.61% of the base voltage. The rest of the loads have under-voltage conditions; from

which 15 loads are residential and four loads are governmental. The lowest level of the

voltage (the lowest level of the voltage in the North substation) occurs at a residential

load (Shash Darak) attached to a sub-feeder associated with the feeder 516. This lowest

level of the voltage is 87.39% of the base voltage (230 V). The total connected load

attached to the feeder 516 and its associated sub-feeders, with under-voltage conditions,

is 15.38 MVA (see Figure 2-9, for loads locations and details).

Finally, all of the loads attached to the feeder 517 and its associated sub-feeders

have under-voltage conditions. The feeder 517 and its associated sub-feeders feed 13

residential loads and four governmental loads. Two transformers (16-1&2) in

Macrorayon have the lowest voltage level, which is 91.3% of the base voltage; while the

highest level of the voltage at the loads attached to the feeder 517 and its associated sub-

feeders is 93.18% of the base voltage. The total connected load attached to the feeder 517

and its associated sub-feeders having under-voltage conditions is 10.49 MVA (for loads

locations and details, see Figure 2-10).

For a compact description of feeders having under-voltage conditions in the

North substation, one can see Table 3-1. Notice that this table does not contain feeders

511, 519, 520, 514, 526, and their associated sub-feeders, because the loads attached to

them have normal conditions (The levels of the voltages at the loads attached to the

mentioned feeders are over 97% of the base voltage).

55

Table 3-1 Feeders Having Under-voltage Conditions (15 kV MV)

Number Feeder Load type

Number of Loads (out of)

Lowest Voltage Level (%)

Connected Load (kVA) (out of)

1 512 Residential Governmental Hospital

11 (11) 4 (5) 4 (4)

-- 92.1 --

12,860 (13,220)

2 528 Residential 7 (13) 96.57 1,430 (8,900)

3 513 Residential Governmental

3 (12) 6 (6)

-- --

6,090 (11,350)

4 529 Residential Governmental Hospital Commercial

18 (18) 4 (4) 2 (2) 4 (4)

94.39 -- -- --

16,550 (16,550)


17 (17) 40 (40) 2 (2)

-- 89.35 --

29,670 (29,670)


3 (3) 4 (4)

92.17 --

3,490 (3,490)


15 (15) 9 (9)

87.39 --

15,380 (15,380)


13 (13) 4 (4)

91.3 --

10,490 (10,490)

Total 8 171 95,960 3.1.1.2 At Sections

Considering a base voltage of 230 V line to neutral and 15 kV medium voltage for

the North substation, 194 out of 279 sections of the feeders and sub-feeders have under-

voltage conditions. From these sections, 63 out of 122 sections are overhead lines and

remaining 131 out of 157 sections are underground cables sections. As was mentioned in

earlier section, the level of the voltage, in under-voltage sections, differs from 87.39% of

the base voltage to 96.88% of the base voltage. The voltage level over 97% of the base

voltage is considered normal conditions. Compact details of the sections that have under-

voltage conditions are illustrated in Table 3-2 and Table 3-3.

56

Table 3-2 Overhead Lines Sections Having Under-voltage Conditions (15 kV MV)

Section Number

Conductor Size and ID

Voltage (%)

Section Number


Voltage (%)

N132 OHL_120 91.52 N125 OHL_95 91.47 N129 OHL_95 91.44 N131 OHL_95 91.44 N133 OHL_95 91.46 N134 OHL_120 90.26 N135 OHL_95 90.17 N136 OHL_95 90.17 N147 OHL_120 89.38 N148 OHL_120 88.01 N165 OHL_50 87.42 N166 OHL_95 87.44 N23 OHL_70 96.93 N24 OHL_35 96.88 N26 OHL_70 96.64 N27 OHL_70 96.62 N29 OHL_70 96.47 N30 OHL_70 96.43 N35 OHL_50 96.10 N36 OHL_50 96.04 N38 OHL_50 96.06 N41 OHL_50 95.81 N42 OHL_50 95.77 N43 OHL_50 95.76 N44 OHL_50 95.67 N45 OHL_70 95.63 N48 OHL_50 95.76 N49 OHL_50 95.73 N186 OHL_120 93.17 N187 OHL_120 93.16 N188 OHL_95 93.15 N189 OHL_120 93.08 N190 OHL_120 93.04 N196 OHL_150 91.58 N229 OHL_70 96.89 N230 OHL_50 96.76 N231 OHL_50 96.69 N232 OHL_50 96.75 N233 OHL_50 96.58 N234 OHL_50 96.56 N235 OHL_50 96.56 N255 OHL_150 96.71 N256 OHL_95 96.15 N501 OHL_50 95.20 N529 OHL_150 95.20 N258 OHL_50 96.13 N259 OHL_70 96.67 N325 OHL_70 94.12 N265 OHL_70 95.72 N266 OHL_50 95.70 N269 OHL_70 95.23 N270 OHL_70 95.21 N271 OHL_70 94.42 N272 OHL_95 94.37 N277 OHL_95 93.32 N278 OHL_95 93.27 N279 OHL_50 93.25 N563 OHL_95 93.12 N564 OHL_70 92.50 N565 OHL_70 92.40 N322 OHL_150 94.74 N327 OHL_150 94.74

57

Table 3-3 Underground Cables Sections Having Under-voltage Conditions (15 kV MV)

Section Number


Voltage (%)

Section Number


Voltage (%)

N130 UC_120_CU 91.44 N137 UC_95 90.17 N150 UC_185_AL 87.99 N257 UC_95_CU 96.12 N153 UC_185 87.86 N490 UC_95_AL 96.12 N154 UC_185 87.76 N492 UC_95_AL 96.08 N155 UC_185 87.65 N493 UC_95_AL 95.88 N156 UC_185 87.63 N494 UC_95_AL 95.87 N158 UC_185 87.62 N495 UC_95_AL 95.75 N157 UC_185 87.56 N496 UC_95_AL 95.61 N159 UC_185 87.49 N497 UC_50_CU 95.33 N160 UC_185 87.49 N498 UC_35_CU 95.32 N161 UC_185 87.45 N499 UC_50_CU 95.23 N162 UC_185 87.44 N500 UC_50_CU 95.23 N163 UC_185 87.43 N502 UC_35_CU 95.19 N164 UC_185 87.43 N506 UC_95_AL 95.27 N167 UC_185_AL 87.42 N507 UC_95_AL 95.26 N168 UC_185_AL 87.41 N508 UC_95_AL 95.25 N169 UC_185_AL 87.39 N509 UC_95_AL 95.24 N31 UC_35_CU 96.42 N519 UC_50_CU 96.07 N39 UC_95_CU 96.05 N522 UC_50_CU 96.00 N191 UC_95 93.08 N523 UC_50_CU 95.90 N197 UC_185_AL 91.50 N524 UC_50_CU 95.89 N198 UC_185_AL 91.49 N528 UC_95_CU 96.04 N199 UC_185 91.49 N530 UC_95_AL 94.78 N200 UC_185 91.46 N531 UC_95_AL 94.49 N201 UC_95 91.44 N532 UC_95_AL 94.48 N202 UC_185 91.43 N533 UC_95_AL 94.39 N210 UC_185 91.44 N537 UC_70_CU 94.44 N211 UC_185 91.40 N273 UC_185_AL 93.63 N212 UC_185 91.37 N275 UC_95_CU 93.60 N213 UC_185 91.34 N276 UC_95_AL 93.43 N214 UC_185 91.31 N492 UC_95_AL 96.08 N424 UC_50 89.28 N493 UC_95_AL 95.88 N281 UC_95_CU 93.12 N425 UC_50 89.24 N282 UC_35_CU 93.11 N426 UC_50 89.22 N326 UC_150_CU 92.39 N427 UC_50 89.14 N323 UC_150_CU 92.39 N406 UC_50 89.45 N295 UC_50_CU 92.26 N407 UC_50 89.45 N294 UC_50_CU 92.22 N408 UC_50 89.38 N293 UC_50_CU 92.24 N409 UC_50 89.38 N292 UC_50_CU 92.40 N410 UC_50 89.35 N300 UC_50_CU 92.17 N432 UC_35 91.59

(Continued)

58

Section Number


Voltage (%)

Section Number


Voltage (%)

N301 UC_50_CU 92.08 N433 UC_35 91.58 N297 UC_50 92.13 N434 UC_35_CU 91.37 N298 UC_50 92.10 N435 UC_50_CU 91.32 N291 UC_50 92.08 N436 UC_50_CU 91.29 N566 UC_50_CU 91.99 N437 UC_50_CU 91.29 N367 UC_50 92.00 N438 UC_35_CU 91.25 N368 UC_35 91.81 N446 UC_35_CU 91.31 N369 UC_50 91.79 N447 UC_35_CU 91.31 N370 UC_50 91.69 N448 UC_35_CU 91.31 N371 UC_35 91.67 N452 UC_50_AL 92.38 N372 UC_35_CU 91.66 N453 UC_50_CU 91.86 N373 UC_50_CU 92.03 N454 UC_35_CU 91.85 N374 UC_50_CU 92.02 N455 UC_35_CU 91.85 N375 UC_50_CU 92.25 N456 UC_50_CU 91.50 N387 UC_50 92.24 N457 UC_50_CU 91.42 N388 UC_35 92.18 N458 UC_50_CU 91.36 N392 UC_50 92.17 N459 UC_95_CU 91.34 N393 UC_50 89.79 N474 UC_35_CU 91.42 N394 UC_50 89.77 N475 UC_35_CU 91.38 N395 UC_50 89.56 N476 UC_35_CU 91.36 N401 UC_50 89.47 N469 UC_50_CU 92.30 N402 UC_50 89.41 N470 UC_50_CU 91.94 N403 UC_50 89.40 N471 UC_50_CU 91.81 N404 UC_50 93.12 N472 UC_50_CU 91.80 N405 UC_50 93.11 N483 UC_50_CU 91.81

3.1.2 Overloaded Feeders

Simulation results of the North substation in the Kabul power distribution system

with 15 kV medium voltage shows that six out 11 main feeders have overloaded

conditions. One should remember that this over load conditions happens at some parts of

the mentioned feeders. Since the feeders are composed of several pieces with different

sizes and lengths, the results are noted separately for each section of the feeders. Notice

that overload condition is a condition in which the amount of current flowing through a

conductor exceeds its capacity. For example, a conductor has 100 A capacity; when the

current flowing through this conductor exceeds 100 A, it is considered to be overloaded.

It is worth mentioning that because of higher current density in overloaded feeders’

sections they are heated up and temperature of the sections go up; as a consequence of

higher temperature, the resistance of conductor in the feeders’ sections increases and

59 causes more voltage drop in that sections. Even high temperature can burn the insulators

of underground cables and can break overhead lines and cause outages.

Assuming a balanced load, feeder 512 carries 217.5 A current; therefore, the first

portion of this feeder (section connected to the North substation) is under normal

conditions, because this section is 185 mm2 aluminum conductor underground cable with

270 A capacity12. The length of this section is 80m. Second section of the feeder 512 is

70 mm2 ACSR conductor overhead lines, which has 4400 m length and 162 A capacity.

This section of the feeder 512 is under overloaded conditions. Four other sections of this

feeder are also under overloaded conditions because they have the same conductor as the

second section of the feeder. The severest overloaded condition in the feeder 512 is

134.26% of the conductor capacity and it occurs at the second section of the feeder. The

least overloaded condition is 119% of the conductor capacity and it occurs at the fifth

section of the feeder 512.

Magnitude of current flowing through feeder 516 is 341.4 A at the beginning end

of it. While the first section of this feeder is 185 mm2 aluminum conductor underground

cable, which has 80m length and 270 A capacity. Second section of the feeder 516 is 150

mm2 ACSR conductor overhead lines, which has 950 m length and 255 A capacity. Third

section of this feeder is 120 mm2 ACSR conductor overhead lines and it has 4700 m

length and 219 A capacity. Fourth section of the feeder 516 has the same characteristics

as the third section, but it has 1000 m length. Magnitude of current flowing through this

section is 275.6 A. The last overloaded section in this feeder is 120 mm2 ACSR

conductor. It has 2050 m length and 219 A capacity. The current flowing through this

section has 240 A magnitude.

Considering the flowing currents through different parts of the feeder 516, the

highest abnormality, from overload perspective, is 148.5% of the conductor capacity and

it occurs at the second section of the feeder. The lowest abnormality is 109.59% of the

conductor capacity and it occurs at the fifth section of the feeder 516.

12 Capacity of the conductors has been calculated by CYMDIST, which is 60% of the capacity noted in earlier sections for conductors.

60

Feeder 517, connecting the North substation to the junction station 12, has four

sections, which have over load conditions. The first section of this feeder is 185mm2

aluminum conductor underground cable. It has 100m length and 270 A capacity. Second

section of the feeder 517 is 120 mm2 ACSR conductor overhead lines. It has 5650 m

length and 219 A capacity. Third section of this feeder is 150 mm2 ACSR conductor

overhead lines, which has 1800m length and 255A capacity. Magnitude of current

flowing from first and second section of the feeder 517 is 259.3 A.

Considering the description of this feeder, only the second section of it is under

overload conditions. The level of the abnormality in the feeder 517 is 118.4% of the

conductor capacity.

One of the two feeders connecting the North substation to the junction station two

is feeder 515. This feeder is composed of three sections from which the first and second

sections have overload conditions. The first section (connected to the North substation) is

aluminum conductor 185 mm2 underground cable. This cable has 150 m length and 270

A capacity. Second section of the feeder 515 is 70 mm2 ACSR conductor overhead lines,

which has 2700 m length and 162 A capacity. The last section of this feeder is 150 mm2

copper conductor underground cable. This section of the feeder 515 has 2630m length

and 360 A capacity. Magnitude of current passing through this feeder is 353.4 A.

Based upon the description above, the first section of the feeder 515 is under

overload conditions with a level of 130.85% of the conductor capacity. Likewise, the

second section of the feeder is under overload conditions with the level of 218.15% of the

conductor capacity. It is worth mentioning that 218.15% overload is the highest overload

level in the North substation in case of 15 kV MV.

Second feeder connecting the North substation to the junction station two is

feeder 518. This feeder is composed of three sections that have overload conditions.

Besides, one sub-feeder associated with this feeder is under overload conditions. Similar

to the feeder 515, the first section of the feeder 518 is 185mm2 aluminum conductor

underground cable, which has 150m length and 270 A capacity. Second section of this

feeder is 150 mm2 ACSR conductor overhead lines, which has 2700 m length and 255 A

capacity. Third section of the feeder 518 is 150mm2 copper conductor underground cable.

61 This cable has 2630 m length and 368 A capacity. The overloaded sub-feeder is 50mm2

copper conductor underground cable, which has 2500 m length and 199.8 A capacity.

Magnitude of current in the first and second section of the feeder 518 is 448.5 A and

magnitude of current in the overloaded sub-feeder is 215.4 A.

Based upon the feeder 518 and its load description, the highest level of overload

condition is 179.3% of the conductor capacity. This abnormality occurs at the second

section of the feeder. The lowest level of the overload condition is 110.0% of the

conductor capacity and it occurs at the sub-feeder associated with the feeder 518.

Finally, feeder 529 that connects the North substation to the junction station five

is also under overload conditions. This feeder is composed of four different sections. The

first section of the feeder 529 is 185 mm2 aluminum underground cable, which has 80 m

length and 270 A capacity. Second section of this feeder is 150 mm2 ACSR conductor

overhead lines, which has 2450 m length and 255 A capacity. Third section of the feeder

529 is 95 mm2 ACSR conductor overhead lines. This section has 350 m length and 198 A

capacity. The last section of the feeder 529 is 95 mm2 copper conductor underground

cable, which has 50 m length and 290.7 A capacity. Magnitude of current passing

through this feeder is 337.9 A in the first and second sections. Magnitude of current in the

third section and fourth section are 321.4 A and 318 A respectively.

Considering the description of the feeder 529, the highest overload level is

162.32% of the conductor capacity, which occurs at the third section of the feeder. The

lowest level of the overload is 109.39% of the conductor capacity, which occurs at the

last overloaded section of the feeder 529.

Detailed information about overloaded feeders, in the North substation, is

illustrated in Table 3-4. This table does not show the feeder sections that have normal

conditions, from overload conditions perspective. One should note that, 29990 m13 of

feeders is overloaded in 15 kV MV scenario. The highest value of the overload is

218.15% of the conductor’s capacity.

13 This length is just to compare with the length of the overloaded feeders in 20 kV scenario. The total length of the feeders in the North substation has not been calculated.

62

Table 3-4 Overloaded Feeder Sections in the North Substation

Feeder Section Number

Conductor Type

Line Type

Length (m)

Size (mm2)

Capacity (Amp)

Current (Amp)

Over Load (%)

512 2nd 3rd 4th 5th

ACSR ACSR ACSR ACSR

OH OH OH OH

1100 2300 400 700

70 70 70 70

162 162 162 162

217.5 209.4 201.1 192.8

134.26 129.26 118.99 114.10

516 1st 2nd 3rd 4th 5th 6th

Al ACSR ACSR ACSR ACSR ACSR

UG OH OH OH OH OH

80 950 4700 1000 800 1300

185 150 120 120 120 120

270 255 219 219 219 219

341.4 341.5 325.2 275.6 240.0 240.0

126.44 133.88 148.49 125.86 109.59 109.59

517 2nd ACSR OH 5650 120 219 259.3 118.40 515 1st

2nd Al ACSR

UG OH

100 2700

185 70

270 162

353.3 353.3

130.85 218.15

518 1st 2nd 3rd 4th

Al ACSR Cu Cu

UG OH UG UG

100 2700 2630 2500

185 150 150 50

270 255 368 199.8

448.5 448.5 445.2 215.5

166.11 175.88 120.98 107.86

529 1st 2nd 3rd 4th

Al ACSR ACSR Cu

UG OH OH UG

100 2500 350 30

185 150 95 95

270 255 198 290.7

337.9 337.9 321.4 318.0

125.15 132.51 162.32 109.39

3.1.3 Losses, Under-voltage, and Overload Summary

Considering 15 kV MV, the North substation in the Kabul power distribution

system can supply 74550.70 kVA with 89.41% PF. Therefore, real power and reactive

power are 66656.81 kW and 33386.76 kVA respectively. On the other hand, capacitance

of the conductors is 2029.10 kVAR. Used load in the North substation, according to the

CYMDIST simulation is 70773.50 kVA with 89.48 PF, which results 63329.05 kW real

power and 31596.20 kVAR reactive power in the network. Taking capacitance of the

conductors into account, the total loss of the network is 5065.89 kVA with 65.69% PF,

which results 3327.71 kW real power loss and 3819.63 kVAR reactive power loss. Figure

3-1 shows a map of the North substation with the results of the system simulation in case

of 15 kV MV. Notice that in color print, the dark green lines (in black and white print

63 dark thick lines) show overloaded feeders’ sections, orange lines (in black and white print

light thick lines) show sections having under-voltage conditions, and light green lines (in

black and white print light thin lines) show sections having normal conditions. Table 3-5

shows a brief description of the network power loss.

For cost calculation of the distribution system power loss, exact energy

consumption for a period of time is needed. Therefore, because there is not such a data

available (see section 5.2 for details), cost of power loss has been calculated based on the

possible maximum annual energy consumption in the North substation by the software.

Cost of the loss – based upon an average of $0.12/kWh cost for electricity, for the North

substation with 15 kV MV – is $3,497,150/year14. Although this is not actual value of

the loss and its cost this cost can be an indicator for comparison of the loss in 15 kV and

20 kV MVs scenarios.

Figure 3-1 The North Substation Map with 15 KV Simulation Results.

14 This annual loss cost is simply a multiplication of total power loss and number of hours in one year period.

64

Table 3-5 Load and Losses Summary of the North Substation with 15 kV MV

Type Real Power (kW)

Reactive Power (kVA)

Apparent Power (kVA)

PF (%)

Power from Source 66656.81 33386.76 74550.70 89.41 Load Used 63329.05 31596.20 70773.50 89.48 Conductor Capacitance -- 2029.10 -- -90 Losses 3327.71 3819.63 5065.89 65.69

From abnormal conditions perspective, there are 721 feeder sections, spot loads,

and nodes that have under-voltage conditions, from which 194 are feeder sections

including overhead lines and underground cables. In the severest case, the level of the

voltage is 87.39% of the base voltage (230 V). Beside the under-voltage conditions, there

are 21 feeder sections that have overloaded conditions. With 15 kV MV, there is no over-

voltage case in the network. Summary of extreme abnormal conditions, assuming

balanced system, is show in Table 3-6 (for more details, see Table 3-1 and Table 3-4).

Table 3-6 Summary of Extreme Abnormal Condition in the North Substation with 15 kV MV

Phase Section ID In CYMDIST

Overload %

Section ID In CYMDIST

Under-voltage %

A N325 218.14 N169 87.39 B N325 218.14 N169 87.39 C N325 218.14 N169 87.39

3.1.4 Abnormal Conditions with 50 MVA

Applying 50 MVA for the North substation simulation, four feeders’ sections

remains overloaded with the highest amount of 144.2% of conductor’s capacity. While in

case of loads allocated based on the North substation nominal capacity, 21 feeders’

sections are overloaded with the highest amount of 218.15% of the conductor capacity.

With 50 MVA allocated source load, 137 out of 229 loads have under-voltage conditions

with the lowest level of 91.74% of the base voltage. From feeder section perspective, 33

overhead lines sections and 117 underground cable sections have under-voltage

conditions with 50 MVA allocated loads. Yet, 62 overhead lines sections and 132

underground cables sections have under-voltage conditions with loads allocated based on

65 nominal capacity of the North substation. Power loss in the MV transmission lines is

3.3% of the supplied power by the North substation if 50 MVA is allocated for the load,

which is 64.1% of the power loss in case of loads allocated based on the substation

nominal capacity.

3.2 Simulation Results with 20 kV MV

3.2.1 Levels of Under Voltage

3.2.1.1 At Feeders

Considering 230 V base voltage line to the ground, simulation results of the North

substation in the Kabul distribution system with 20 kV MV shows that 120 loads

(transformers), out of 229, have under-voltage conditions and 141 loads, out of 229, have

normal conditions. When voltage level, at a load or a section drops below 97% of the

base voltage, it is considered under-voltage conditions.

From voltage drop perspective, only two main feeders have under-voltage

conditions in case of 20 kV MV. Beside these two feeders, some other loads attached to

the far ends of three other feeders have under-voltage conditions. One should note that

under-voltage occurs mostly at loads attached to the outgoing feeders of the junction

station two, in case of 20 kV MV.

Eight residential loads, three governmental loads, and four hospital loads,

attached to the feeder 512, have under-voltage conditions (see Figure 2-1 for feeder 512

and loads attached to it). The lowest level of the voltage occurs at the transformer of

Ministry of health, which is 95.91% of the base voltage. The highest level of the voltage,

at loads that have under-voltage conditions, is 96.7% of the base voltage (230 V). The

total connected load served in under-voltage conditions by feeder 512 is 10.76 MVA.

Among loads attached to the feeder 518, only one load, having shorter distance to

the North substation, is under normal conditions. The remaining loads attached to the

feeder 518 and its associated sub-feeders have under-voltage conditions. Feeder 518 and

its associated sub-feeders feed 17 residential loads, 39 governmental loads, and three

hospital loads in under-voltage conditions. Ministry of communication has the lowest

66 level of the voltage; level of the voltage at this load is 94.48% of the base voltage. The

highest level of the voltage at the loads attached to the feeder 518 and its associated sub-

feeders is 96.04% of the base voltage. The total connected load attached to the feeder

518, in under-voltage condition is 29.51 MVA (For load details, see Figure 2-6).

All of the loads attached to the feeder 515 have under-voltage conditions. Loads

served by this feeder are composed of three residential loads and four governmental load.

The lowest level of the voltage occurs at the governmental load (Matbah Urdu); which is

95.96% of the base voltage (230 V). While the highest level of the voltage, at loads

attached to the feeder 515 is 96.00% of the base voltage. The connected loads, having

under-voltage conditions, attached to this feeder is 3.49 MVA (For the load details, see

Figure 2-7).

Among the loads attached to the feeder 516, only one residential load, closed to

the North substation, is under normal conditions with 99.26% of the base voltage. The

rest of the loads have under-voltage conditions; from which 15 loads are residential and

nine loads are governmental. The highest level of the voltage, in under-voltage conditions

in this feeder is 95.57% of the base voltage; while the lowest level of the voltage (the

lowest level of the voltage in the North substation) occurs at a residential load (Shash

Darak) attached to a sub-feeder associated with the feeder 516. This lowest level of the

voltage is 93.48% of the base voltage (230 V). The total connected load attached to the

feeder 516 and its associated sub-feeders, with under-voltage conditions, is 15.38 MVA

(See Figure 2-9, for loads locations and details).

As in 15 kV MV, all of the loads attached to the feeder 517 and its associated sub-

feeders have under-voltage conditions; but the levels of under-voltage are different. The

feeder 517 and its associated sub-feeders feed 13 residential loads and four governmental

loads. Two residential transformers (#16 1 & 2) in Macrorayon have the lowest voltage

level, which is 95.43% of the base voltage; while the highest level of the voltage at the

loads attached to the feeder 517 and its associated sub-feeders is 96.35% of the base

voltage. The total under-voltage connected load attached to the feeder 517 and its

associated sub-feeders is 10.49 MVA (for loads locations and details, see Figure 2-10).

67 Table 3-7 contains compact description of feeders having under-voltage

conditions in the North substation in case of 20 kV MV. Notice that this table does not

contain feeders 511, 513, 519, 520, 514, 526, 528, 529, and their associated sub-feeders,

because the loads attached to them have normal conditions (the levels of the voltages at

the loads attached to the mentioned feeders are over 97% of the base voltage).

Table 3-7 Feeder Having Under-voltage Conditions (20 kV MV)

Number Feeder Load type

Number of Loads (out of)

Lowest Voltage Level (%)

Connected Load (KVA) (out of)


8 (11) 3 (5) 4(4)

-- 95.91 --

10,760 (13,220)


17 (17) 39 (40) 2 (2)

-- 94.48 --

29,510 (29,670)


3 (3) 4 (3)

-- 95.87

3,490 (3,490)


14 (15) 9 (9)

93.48 --

14,580 (15,380)


13 (13) 4 (4)

95.39 10,490 (10,490)

Total 5 120 68,830 3.2.1.2 At Sections

The network simulation results, considering a base voltage of 230 V line to

neutral and 20 kV medium voltage, show that 128 sections of the feeders and sub-feeders

have under-voltage conditions. From these sections, 25 sections are overhead lines and

remaining 103 sections are underground cables sections. With 20 kV MV, the level of the

voltage, in under-voltage sections, differs from 93.47% of the base voltage to 96.7% of

the base voltage. Again, the voltage level over 97% of the base voltage is considered

normal conditions. Table 3-8 and Table 3-9 show compact detail of the sections that have

under-voltage conditions.

68

Table 3-8 Overhead Lines Sections Having Under-voltage Conditions (20 kV MV)

Section Number


Voltage (%)

Section Number


Voltage (%)

N132 OHL_120 95.62 N125 OHL_95 95.62 N129 OHL_95 95.57 N131 OHL_95 95.57 N133 OHL_95 95.59 N134 OHL_120 94.96 N135 OHL_95 94.92 N136 OHL_95 94.91 N147 OHL_120 94.51 N148 OHL_120 93.80 N165 OHL_50 93.49 N166 OHL_95 93.50 N186 OHL_120 96.37 N187 OHL_120 96.36 N188 OHL_95 96.36 N189 OHL_120 96.32 N190 OHL_120 96.30 N196 OHL_150 95.52 N277 OHL_95 96.54 N278 OHL_95 96.51 N279 OHL_50 96.50 N563 OHL_95 96.44 N564 OHL_70 96.12 N565 OHL_70 96.07 N325 OHL_70 96.96

Table 3-9 Underground Cable Sections Having Under-voltage Conditions (20 kV MV)

Section Number


Voltage (%)

Section Number


Voltage (%)

N130 UC_120_CU 95.57 N137 UC_95 94.92 N150 UC_185_AL 93.79 N257 UC_95_CU 96.12 N153 UC_185 93.73 N154 UC_185 93.67 N155 UC_185 93.61 N156 UC_185 93.60 N158 UC_185 93.60 N197 UC_185_AL 95.48 N157 UC_185 93.57 N198 UC_185_AL 95.47 N159 UC_185 93.53 N199 UC_185 95.47 N160 UC_185 93.53 N200 UC_185 95.46 N161 UC_185 93.51 N201 UC_95 95.44 N162 UC_185 93.50 N202 UC_185 95.44 N163 UC_185 93.50 N210 UC_185 95.45 N164 UC_185 93.50 N211 UC_185 95.43 N167 UC_185_AL 93.49 N212 UC_185 95.41 N168 UC_185_AL 93.49 N213 UC_185 95.39 N169 UC_185_AL 93.48 N214 UC_185 95.38 N191 UC_95 96.32 N273 UC_185_AL 96.70 N275 UC_95_CU 96.69 N281 UC_95_CU 96.43 N276 UC_35_AL 96.60 N282 UC_35_CU 96.43 N323 UC_150_CU 96.07 N406 UC_50 94.52 N326 UC_150_CU 96.07 N407 UC_50 94.52 N295 UC_50_CU 96.00 N408 UC_50 94.48 N294 UC_50_CU 95.97 N409 UC_50 94.48 N293 UC_50_CU 95.98 N410 UC_50 94.46 N292 UC_50_CU 96.07 N432 UC_35 95.64

(Continued)

69

Section Number


Voltage (%)

Section Number


Voltage (%)

N300 UC_50_CU 95.94 N433 UC_35 95.64 N301 UC_50_CU 95.90 N434 UC_35_CU 95.53 N297 UC_50 95.92 N435 UC_50_CU 95.50 N298 UC_50 95.90 N436 UC_50_CU 95.49 N291 UC_50 95.90 N437 UC_50_CU 95.49 N566 UC_50_CU 95.90 N438 UC_35_CU 95.46 N367 UC_50 95.86 N446 UC_35_CU 95.50 N368 UC_35 95.85 N447 UC_35_CU 95.50 N369 UC_50 95.86 N448 UC_35_CU 95.49 N370 UC_50 95.76 N452 UC_50_AL 96.06 N371 UC_35 95.76 N453 UC_50_CU 95.78 N372 UC_35_CU 95.75 N454 UC_35_CU 95.78 N373 UC_50_CU 95.70 N455 UC_35_CU 95.78 N374 UC_50_CU 95.68 N456 UC_50_CU 95.59 N375 UC_50_CU 95.68 N457 UC_50_CU 95.55 N387 UC_50 95.88 N458 UC_50_CU 95.52 N388 UC_35 95.78 N459 UC_95_CU 95.51 N392 UC_50 96.00 N474 UC_35_CU 95.55 N393 UC_50 95.99 N475 UC_35_CU 95.53 N394 UC_50 95.95 N476 UC_35_CU 95.52 N395 UC_50 95.95 N469 UC_50_CU 96.02 N401 UC_50 94.70 N470 UC_50_CU 95.83 N402 UC_50 94.69 N471 UC_50_CU 95.76 N403 UC_50 94.58 N472 UC_50_CU 95.75 N404 UC_50 94.53 N483 UC_50_CU 95.76 N405 UC_50 94.50 N425 UC_50 94.41 N411 UC_50 94.49 N426 UC_50 94.40 N424 UC_50 94.43 N427 UC_50 94.35

3.2.2 Overloaded Feeders

In case of applying 20 kV MV, results of simulation of the North substation in the

Kabul power distribution system show that five sections of main feeders, 516, 515, 518,

and 529 have overloaded conditions. These overload conditions occur only at one section

of the feeders 515, 516, and 529. In addition, two sections of the feeder 518 have

overload conditions. The rest of the feeder sections in the network have normal

conditions. Remember that, when the amount of current flowing through a conductor

exceeds its capacity, the conductor is considered overloaded.

At the beginning end of the feeder 516, magnitude of current flowing through it is

240A. Considering the characteristics of the feeder 516 in section 4.1.2, and the flowing

70 currents through different parts of it, from overload perspective, only the third section of

this feeder is overloaded. Magnitude of current at the first and second sections is 240 A

and it is 227.9 A in third section. Since third section of the feeder 516 is 120 mm2 ACSR

conductor, which has 4700 m length and 219 A capacity, it is overloaded. The level of

this overload conditions is 104.41% of the rated capacity of conductor. The remaining

parts of the feeder 516 have normal conditions.

Considering characteristics of the feeder 515 (see section 4.1.2 for details), only

second section of this feeder is under overloaded conditions. Magnitude of current

passing through first three sections of this feeder is 248.9 A. While the second section of

the feeder is 70 mm2 ACSR conductor overhead line, which has 162 A capacity and 2700

m length. Therefore, the second section of the feeder 515 is overloaded with a level of

153.62% of the conductor capacity. The rest of the feeder sections have normal

conditions.

The first two sections of the feeder 518 are also overloaded. Magnitude of current

flowing through first and second sections of the feeder 518 is 315.9 A. While capacity of

the first and second sections conductors are 270 A and 255 A respectively (for more

details, see section 4.1.2). Thus, based upon the feeder 518 and its load descriptions, the

level of overload condition is 117.00% and 124% of the conductor capacity. Remaining

sections of this feeder and its associated sub-feeders have normal conditions.

Ultimately, third section of the feeder 529 has also overload conditions. This

section is 95 mm2 ACSR conductor overhead line, which has 350m length and 198 A

capacity (see section 4.1.2, for details of the feeder 529). Magnitude of current passing

through the overloaded section is 230.9 A; therefore, the level of overload is 116.62% of

the conductor capacity. Remaining sections of the feeder 529 and its associated sub-

feeders have normal conditions.

Table 3-10 shows overloaded feeder sections in the North substation. The feeder

sections that have normal conditions are not included in this table. In 20 kV MV scenario,

10600 m feeders are in overloaded conditions; but the highest overload value is 153.62%

of the conductor’s capacity that is 70% of highest overload value in 15 kV scenario.

71

Table 3-10 Overloaded Feeder Sections in the North Substation

Feeder Section Number

Conductor Type

Line Type

Length (m)

Size (mm2)

Capacity (Amp)

Current (Amp)

Over Load (%)

516 3rd ACSR OH 4700 120 219 227.9 104.07 515 2nd ACSR OH 2700 70 162 248.9 153.62 518 1st

2nd AL ACSR

UC OH

150 2700

185 150

270 255

315.8 315.8

116.96 123.86

529 3rd ACSR OH 350 95 198 230.9 116.62

3.2.3 Losses, Under-voltage, and Overload Summary

If 20 kV is applied as MV in the North substation, the source supplies 71451.80

kVA with 90.98% power factor. Of course this apparent power and power factor results

65008.62 kW real power and 29651.97 kVAR reactive power. CYMDIST simulation

results show 70773.60 kVA apparent power with 89.48% PF used power, which results

633329.18 kW real power and 31596.16 kVAR reactive power. Considering 3869.98

kVA conductors’ capacitance, the total loss of the network is 1679.44 kW. Power factor

of the loss is 65.73%, which results 1925.77 kVAR reactive power loss and 2555.21 kVA

apparent power loss. Figure 3-2 illustrates abnormal conditions and the area where

abnormal conditions happen in the North substation in 20 kV scenario; again, in color

print, the dark green lines (in black and white print dark thick lines) show overloaded

feeders’ sections, orange lines (in black and white print light thick lines) show sections

having under-voltage conditions, and light green lines (in black and white print light thin

lines) show sections having normal conditions. Also one can see the description of

supplied power from the source and losses of the network in Table 3-11. Cost of the loss

– considering an average of $0.12/kWh, is $1,765,120/year for the North substation of

the Kabul power distribution system. As mentioned in section 3.1.3, it is not actual value

of the cost of the annual loss of the North substation. It is the maximum possible value of

the loss in 20 kV MV case calculated by the software. CYMDIST assumes that the

system is operated at its maximum capacity during the year. One should remember that

the cost is obtained only in order to compare the loss in 15 kV and 20 kV MVs scenarios.

72

Figure 3-2 The North Substation Map with 20 kV Simulation Results.

Table 3-11 Load and Losses Summary of the North Substation with 20 kV MV

Type Real Power (kW)

Reactive Power (kVA)

Apparent Power (kVA)

PF (%)

Power from Source 65008.62 29651.97 71451.80 90.98 Load Used 63329.18 31596.16 70773.60 89.48 Conductor Capacitance -- 3878.88 -- -90 Losses 1679.44 1925.77 2555.21 65.73

CYMDIST table for abnormal conditions shows that there are a total number of

five feeders sections that have overload conditions. Meanwhile, the table shows that 491

spot loads, and feeder sections have under-voltage conditions, from which 128 are feeder

and sub-feeders sections (for more details, see section 4.2.1.2). Similar to 15 kV MV,

there are no over-voltages in the network with 20 kV MV. Table 3-12 illustrates a

summary of extreme overload and under-voltage conditions, while the network has been

simulated with 20 kV MV considering balanced system.

73

Table 3-12 Summary of Extreme Abnormal Condition in the North Substation with 20 kV MV

Phase Section ID In CYMDIST

Overload %

Section ID In CYMDIST

Under-voltage %

A N325 153.62 N169 93.48 B N325 153.62 N169 93.48 C N325 153.62 N169 93.48

3.2.4 Abnormal Conditions with 50 MVA

Allocating 50 MVA for loads in the North substation, only one feeder’s section

remains overloaded with 106.1% of conductor’s capacity. While in case of loads

allocated based on the North substation nominal capacity, 7 feeders’ sections are

overloaded. In case of 50 MVA allocated load, 45 loads have under-voltage conditions.

Considering feeder’s sections, 13 overhead lines sections and 62 underground cable

sections have under-voltage conditions with allocating 50 MVA for loads. Yet, 27

overhead lines sections and 107 underground cables sections have under-voltage

conditions with loads allocated based on nominal capacity of the North substation. Power

loss in the MV transmission lines is 1.8% of the supplied power by the North substation

if 50 MVA is allocated for the loads; the loss is 2.8% of the supplied load in case of loads

allocated based on the substation nominal capacity. Comparing the results of 15 kV and

20 kV MVs levels, we can see that the power loss, in 20 kV scenario, is less than 55% of

the power loss in 15 kV scenario.

74

4 CHAPTER 4: DISCUSSIONS

4.1 Criteria for MV Application

A voltage level, in an electric power system, is considered applicable if it satisfies

the following criteria. 1) The voltage level application must be, technologically, feasible

[4]. 2) Its application must be economically acceptable [4]. 3) From quality point of view,

the system, with that level of the voltage, must have sufficient advantages. Meaning that,

the system losses, voltage quality, and system reliability must be optimum. Based upon

the above criteria, the existing MV (15 kV) in the North substation of the Kabul power

distribution system and 20 kV are evaluated as medium voltage level for the Kabul power

distribution system, and the results are discussed and compared. The 10 kV MV is not

evaluated in this research work because only one small substation (Pul-e-charkhi) in the

Kabul power distribution system serves with this voltage level. The Pul-e-charkhi

substation has 12.6 MVA capacity and covers a small portion of the Kabul power

distribution system containing the Kabul radio station and some villages near to it.

4.1.1 Technological Feasibility

Feasibility is a fundamental criterion for every technological aspect, which

depends on development of technology related to that aspect. Applying 20 kV as medium

distribution voltage was not feasible in the past; because manufacturing of electrical

equipment was challenging and expensive. Despite 20 kV, 15 kV and 10 kV were

applicable for medium voltage; thus the two levels of MV (15 kV and 10 kV) had been

applied in the Kabul power distribution system. Now, there is sufficient electrical

equipment available in the market for 20 kV [4]. It is also worth mentioning that 20 kV

has been applied, partially, in Breshna Kot and East substations as medium voltage in the

Kabul power distribution system [2]. However, there is no manufacturer of electrical

equipment for 15 kV and 20 kV MVs in Afghanistan, but the equipment can be imported

from neighboring countries. From the operation point of view, 20 kV is not extremely

different from 15 kV. Thus, it is possible to enhance the qualification of the technicians,

by short term training classes, to handle proper operation of the system with 20 kV. This

75 is achievable because capacity building of the staff (including technical and non-

technical) is one of the priority of the Ministry of Water and Power and DABM [1].

4.1.2 Economical Justification

In [4], it has been shown that 220 kV /110 kV/10 kV system is more expensive

than 220 kV /110 kV/20 kV, in the cases of overhead lines and underground cables15.

This result has been achieved by analysis based on minimal cost (for more details see

[4]). Although the Kabul power distribution system is a two stage system (considering

transmission level and feeder level) and it is not completely similar to the systems

evaluated in [4] still 110 kV/20 kV is economically justifiable for the following reasons:

The cost of the equipment for 20 kV is not much different (higher) than the cost of the

equipment for 15 kV. There is no difference between skilled and ordinary labor cost for

15 kV and 20 kV16. Based on the rehabilitation plan of the Kabul power distribution

system [1], the North substation needs to be upgraded. Remember that the present project

is not implemented in new areas; the feeders have been installed. Only some parts of the

medium voltage transmission lines need to be replaced and/or upgraded. According to

[4], the price of 20 kV equipments is in the range of 110% - 120% of 10 kV equipments;

while the cost of annual loss of 15 kV, in the North substation, is 198.125% of 20 kV cost

regardless of the load amount and conditions. Relying on the results obtained in

literature, one can infer that there will not be much difference between 15 kV and 20 kV

setting costs.

15 The costs of transmission lines are calculated based upon a unit length [3] (for example

$20000/km). Assuming same conditions (size and length of conductors, poles, topology of the area, and so forth), because with higher voltage level more power is transmitted, the cost of the power transmitted decreases. Therefore, the cost of transmission line is considered justifiable. Even for different conditions, power transmission is cheaper with higher voltage level, if the voltage is technologically applicable. However, the cost of transmission linens per unit length increases. For example, the cost of a low cost sub-transmission line with wooden pole and 46 kV voltage level carrying 50MVA is perhaps $30000/km; in this case, the cost of unit power is $0.60 per kVA-km [3]. Yet, it can be a double circuit 500 kV transmission lines carrying 2000 MVA with $600000/km cost; in this case, the cost of unit power decreases to $0.30 per kVA-km. 16 Even though there are some differences between skilled labors cost according to the standards it is not considered in the Kabul work market.

76

4.1.3 Technical Advantages

The advantages of 20 kV medium voltage are as the followings: 1) Voltage drop

is reduced [4], which is the biggest problem in Kabul power distribution system. The

voltage drop reduction will be 75% in the case of raising the voltage from 10 kV to 20

kV, if the load is not changed. Due to this, we can show that if the voltage is raised from

15 kV to 20 kV, voltage drop decreases by 48.3%. 2) Since, current density is inversely

proportional to voltage level, the capability of the lines for power transfer gets higher [4].

As it has been shown in sections 3.1.3 and 3.2.3, maximum overload decreases to 70.40%

in case of 20 kV MV; meaning that the power transfer capacity of the conductors

increases by 30%. 3) If the voltage is kept constant, the radius of supplied power in

medium voltage will be increased, significantly. 4) Power loss reduction is also an

obvious consequence of higher voltage [4], because power is lost based on (I2R); while

current (I) is inversely proportional to voltage. 5) No-load losses of transformers, also,

decrease in the case of 20 kV compared to 10 kV and 15 kV. If an equivalent circuit

model of a transformer is studied, it will be seen that for higher voltage (if power is kept

constant) “excitation admittance” [15] decreases, which results higher “excitation

impedance” and therefore, no-load current is lowered. Again, based on (I2R), the lower

the current is the smaller the power losses will be. To find the no-load losses of a

transformer, one can conduct an open-circuit test [15] on a transformer (for details of

open-circuit test, see [15] chapter 2).

4.2 Analysis of Voltage Drop in the North Substation

In the following sections the effects of MV level, on the North substations, is

analyzed and discussed. Although power density in the North substation is not constant, it

may not exceed from 10 MW/km2. In any case, the reliability, power quality, and voltage

level will be affected by the level of medium voltage [4]. Therefore, two MV levels, 15

kV and 20 kV, are evaluated for the North substation of the Kabul power distribution

system.

77

4.2.1 Analysis of 15 kV MV

4.2.1.1 Voltage Drop

It has been shown in section 4.1.1.2 that 131 underground cable sections and 62

overhead line sections have under-voltage conditions when 15 kV MV is applied in the

North substation of the Kabul power distribution system. These sections are parts of eight

feeders and their associated sub-feeders, which feed 171 loads in the network. As it is

seen, considering 229 loads served by the North substation, 75.66% of the loads (based

on number of loads) in the network have under-voltage conditions. Taking amount of the

total allocated loads into account, 50.2145 MVA allocated loads in the network have

under-voltage conditions, which is 67.381% of the total load supplied from the North

substation. Figure 4-1 illustrates a histogram of the level of under-voltage conditions for

overhead line sections in the North substation with 15 kV MV, and Figure 4-2 shows a

histogram of the level of under-voltage conditions for underground cable sections.

Figure 4-1 Histogram of Overhead Lines Sections under Under-voltage Conditions (15 kV).

87 88 89 90 91 92 93 94 95 96 970

2

4

6

8

10

12

14

16

18

20Histogram of Under-voltage Overhead Lines' Sections (15kV)

Voltage Level (%)

Num

ber o

f Sec

tions

78

Figure 4-2 Histogram of Underground Cable Sections under Under-voltage Conditions (15 kV).

4.2.1.2 Voltage Profile

In general, the voltage profile along the feeders, in case of 15 kV MV has faster

rate of decrease; therefore, along feeders more voltage drop happens depending on

feeders’ length, size, current passing through it, and type of conductor. Since, the voltage

profile happens in similar manner at all feeders with either level of MVs (15 kV & 20

kV) regardless of appearance of the profile, only two feeders are chosen in order to

analyze the voltage profile at them. One should remember that these voltage profiles are

not the profile for feeders’ branches; rather they are the profile of the voltages along a

single path starting from the North substations and ending at the far end of the feeder.

87 88 89 90 91 92 93 94 95 96 970

5

10

15

20

25

30

35

40Histogram of Under-voltage Underground Cables' Sections (15)

Num

ber o

f Sec

tions

Voltage Level (%)

79

Figure 4-3 Voltage Profile along the Feeder 513 in case of 15 kV MV.

Along the feeder 513, the voltage profile has a voltage drop rate of 2.62 V/km for

the first 1.03 km distance. The rate of voltage drop decreases to 1.67 V/km for the next

0.4 km distance; for next 2.85 km the rate of voltage drop is, approximately 1.6 V/km; for

next 0.8 km the rate of voltage drop is 1.12 V/km; for the next 1.25 km the rate of voltage

drop is, approximately, 0.51 V/km; and for the last 2.1 km distance the rate of voltage

drop is, approximately, 0.09 V/km. Figure 4-3 illustrates the voltage drop at the feeder

513 along a single path starting from the North substation and ending at the Ministry of

Transportation.

Along the feeder 516, the voltage drop has, approximately, 3.25 V/km rate of

decrease for the first 5.7 km distance. For next 3.35 km distance, the rate of voltage drop

is 2.81 V/km for the last 2.1 km distance, the rate of voltage drop is 0.48 V/km. Figure

4-4 shows rates of the voltage drop along the feeder 516, starting from the North

substation and ending at the Shash Darak residential transformer.

0 1000 2000 3000 4000 5000 6000 7000 8000 9000218

220

222

224

226

228

230Voltage Profile along the Feeder 513

Distance from the Source (m)

Vol

tage

Lev

el (V

)

15 kV

80


4.2.1.3 Power Losses

Based upon the simulation results by CYMDIST, the North substation, as source,

supplies 74550.70 kVA with 89.41% PF. Difference between magnitude of supplied

power and used power in the network is 3750.02 kVA, which is lost in the network. On

the other hand, due to smaller line capacitance, supplied power from the source has

smaller power factor. In addition, real power losses in the network is 3327.71 kW, which

makes 5.25% and apparent power losses is 5065.89 kVA that is 7.16% of the total used

power. It is worth mentioning that these losses are not including transformers’, protection

devices’, and secondary feeders’ losses. Because sum of secondary feeders’, protection

devices’, and distribution transformers’ losses is, usually, more than MV transmission

lines’ losses, the network power losses will exceed 10% of the used power, in case of 15

kV MV.

0 2000 4000 6000 8000 10000 12000200

205

210

215

220

225



Vol

tage

Lev

el (V

)

15 kV

81

4.2.2 Analysis of 20 kV MV

The results of CYMDIST simulation in section 4.2.1.2 shows that 25 overhead

line sections and 103 underground cable sections have under-voltage conditions if 20 kV

MV is applied in the North substation. Considering number of loads in the network, 120

loads have under-voltage conditions that make 53.10% of the total loads (229 loads).

From amount perspective, 39.43 MVA (52.95%) of the total load supplied by the North

substation has under-voltage conditions. Beside these, the range of the voltage drop is not

wide (3.52%), considering 97% of the nominal base voltage as normal conditions. Notice

that the lowest level of the voltage level, in case of 20 kV MV is 93.48% of the base

voltage. Figure 4-5 and Figure 4-6 illustrate the histograms of overhead lines and

underground cables sections having under-voltage conditions, with 20 kV MV,

respectively.

Figure 4-5 Histogram of Overhead Lines Sections under Under-voltage Conditions (20 kV).

93 93.5 94 94.5 95 95.5 96 96.5 970

1

2

3

4

5

6

7

8

9

Voltage Level (%)

Num

ber o

f Sec

tions

Histogram of Under-voltage Overhead Lines' Sections (20kV)

82

Figure 4-6 Histogram of Underground Cable Sections under Under-voltage Conditions (20 kV).

4.2.2.1 Voltage Profile

Although the voltage profile along the feeder, with 20 kV MV, has similar shape

to the voltage profile in case of 15 kV MV, it has slower rate of decrease in case of 20 kV

MV. Because of the slower rate of decrease of voltage profile, amount of voltage drop

along the feeders is less than the same figure obtained in 15 kV scenario. In order to

analyze voltage profile in the North substation with 20 kV MV and compare them with

the profiles analyzed in case of 15 kV MV again feeder 513 and 516 are chosen.

Along the feeder 513, the voltage profile has a voltage drop rate of 1.111 V/km

for the first 1.03 km distance. For next 0.4 km the rate of voltage drop is 0.938 V/km; for

next 2.85 km the rate of voltage drop is 0.8 V/km; for next 0.8 km the rate of voltage

drop is 0.6 V/km; for next 1.25 km the rate of voltage drop is 0.3 V/km. for the last

2.1km distance, the rate of voltage drop is 0.05 V/km. for the voltage drop rate and

voltage profile along the feeder 513, starting the North substation and ending the Ministry

of Transportation, one can see Figure 4-7.

93 93.5 94 94.5 95 95.5 96 96.5 970

5

10

15

20

25

30

Voltage Level (%)

Num

ber o

f Sec

tions

Histogram of Under-voltage Underground Cables' Sections (20kV)

83


Along the feeder 516, starting from the North substations and ending the Shash

Darak residential transformer, the voltage profile has the following characteristics: For

the first 5.7 km distance, the voltage profile has a voltage drop rate of, approximately,

1.75 V/km. the rate of voltage drop for the next 3.35 km is 1.32 V/km. for the last 2.7 km

distance the rate voltage drop is, approximately, 0.25 V/km. Figure 4-8 illustrates the

voltage profile and the rate of voltage drops along the feeder 516, in case of 20 kV MV.

0 1000 2000 3000 4000 5000 6000 7000 8000 9000224

225

226

227

228

229



Vol

tage

Lev

el (V

)

20 kV

84


4.2.2.2 Power Losses

Simulation results of the North substation show that the North substation supplies

71451.08 kVA with 90.98% power factor. Yet, the used apparent power has almost the

same magnitude as it had in case of 15 kV MV. The used power in the network is

70773.60 kVA with 89.48% PF. In this case, the source supplies 4.1% lighter load than in

case of 15 kV MV, if 76000.00 kVA nominal power is considered for the North

substation. The network has slightly greater PF, because, the line capacitance, in case of

20 kV MV. Medium voltage transmission lines’ loss is 2555.21 kVA in magnitude with

65.73% PF that is 3.61% of the used apparent power in the network. Real power loss of

the lines is 1679.44 kW that is 2.65% of the real power used in the network. If it is

assumed that the sum of transformers and secondary feeders’ loss is 150% of the MV

transmission lines, still the total losses will be 6.625%.

0 2000 4000 6000 8000 10000 12000214

216

218

220

222

224

226

228



Vol

tage

Lev

el (V

)

20 kV

85

4.2.3 Summary of the Discussion

Studying the results of the simulation of the system by CYMDIST, in case of 15

kV MV, not only the number of loads having under-voltage conditions is large, but also

the lowest level of the voltage is very low compared to the same figures evaluated for 20

kV MV. The lowest level of the voltage with 20 kV MV is 93.48% of the base voltage;

while it is 87.39% in 15 kV MV scenario. Also if the level of the voltage is studied at

load points, the amount of voltage drop with 20 kV MV decreases to 51.70% of the

voltage drop level with 15 kV MV.

The voltage profiles along the feeders have faster rate of decrease (slope) in case

of 15 kV compared to the voltage profile in case of 20 kV; meaning that the slope of

voltage profile along the feeders with 15 kV MV is more than 150% of the slope with 20

kV MV (depending onto amount of the current flowing through the feeder). One can see

Figure 4-9 and Figure 4-10 for graphs of the voltage profile, and Table 4-1 for the slope of

voltage profiles along the sample feeders (513 and 516).

Figure 4-9 Graph of the Voltage Profile along the Feeder 513.

0 1000 2000 3000 4000 5000 6000 7000 8000 9000218

220

222

224

226

228



Vol

tage

Lev

el (V

)

15 kV20 kV

86

Figure 4-10 Graph of the Voltage Profile along the Feeder 516.

Table 4-1 Slope of the Voltage Profiles in sample feeders (513 and 516)

Feeder 15 kV MV 20 kV MV Section Number

Slope (V/km)

Section Number

Slope (V/km)

513 1st 2nd 3rd 4th 5th

6th

2.62 1.67 1.6 1.12 0.51 0.09

1st 2nd 3rd 4th 5th

6th

1.11 0.938 0.80 0.60 0.3 0.05

516 1st 2nd 3rd

3.25 2.81 0.48

1st 2nd 3rd

1.75 1.32 0.25

In addition, more feeders’ sections are overloaded in case of 15 kV MV compared

to 20 kV MV; meaning that conductors’ have higher capability of power transfer with 20

kV MV. With 15 kV MV, 24450 m overhead line feeders and 5540 m underground cable

0 2000 4000 6000 8000 10000 12000200

205

210

215

220

225



Vol

tage

Lev

el (V

)

15 kV20 kV

87 feeders are overloaded; the highest overload value is 218.15% of the conductor’s

capacity. While, in case of 20 kV MV, 10450 m overhead line feeders and 150 m

underground cable feeders are overloaded. The highest overloaded value, in this scenario,

is 153.62% of the conductor’s capacity. Besides the decreasing of the overloaded feeders,

in 20 kV scenario, power loss decreases to 50.1% of the power loss in case of 15 kV MV.

Results of simulation in case of 50 MVA allocated load for the North substation

shows that, in 15 kV MV scenario four feeders’ sections are overloaded. The worst

overloaded condition is 144.2% of the conductor’s capacity. In 20 kV MV only one

feeder section remains overloaded with 106.1% of the conductor’s capacity. Likewise,

with 15 KV MV, 150 overhead and underground feeders’ sections have under-voltage

conditions. The lowest under-voltage is 91.74% of the base voltage (230 V). Whereas,

with 20 kV MV 75 overhead lines and underground cable sections have under-voltage

conditions with the lowest level of 95.65% of the base voltage. Power loss in MV

transmission lines is 3.3% of the supplied power from the source in 15 kV scenario; while

it is 1.8% of the supplied power in case of 20 kV medium voltage.

As the results of the simulation of the North substation by CYMDIST show,

compared to 20 kV medium voltage, 15 kV medium voltage has three main

disadvantages. 1) Capability of power transfer of the feeders with 15 kV MV is

significantly low. 2) Power loss (I2R) in the system with 15 kV MV is high. 3) Voltage

quality, the most important factor in the Kabul distribution system, is low and the voltage

drop is high; the rate of change of voltage profile with respect to distance is large.

88

5 CHAPTER 5: CONCLUSIONS

5.1 Conclusions

Power loss and voltage drop are two major concerns in the Kabul power system

that have been analyzed in the North substation with 15 kV and 20 kV MV levels by

CYMDIST software. The results of the studies conducted in this research show that the

Kabul power system not only has not had sufficient improvement since 1985, it has

suffered from bad maintenance and war conditions. In the Kabul power system,

distribution part of it has been affected more seriously compared to generation and

transmission parts. In addition, the demand for electric power has a rapid increasing rate

because of significant economic and population growth in the Kabul city. Based on this

increasing rate, the demand for electric power will exceed more than 200% in 2013

according to prediction of ministry of Energy and Water [1]. Hence, due to these

constraints and limitations, the Kabul power system, especially, distribution system does

not satisfy the increasing demands for electric power.

Although poor conditions of the distribution system causes low voltage quality and

higher power loss, in the Kabul distribution system, the level of the medium voltage also

has significant effects on the voltage quality and power loss. Therefore, in the North

substation with the existing MV (15 kV) a big part of the network (67.38%) have under-

voltage conditions with the lowest level of 87.39% of the base voltage; also a large

number of feeders’ sections are overloaded. As an effective factor to reduce the power

loss and voltage drop in the Kabul distribution system, 20 kV has been applied in the

North substation as MV and analyzed by CYMDIST software.

From the results of the system simulation with 15 kV MV and 20 kV MV by

CYMDIST, it is concluded that in case of 20 kV MV the North substation has lower

power loss and less voltage drop. In addition, the total loss, in MV transmission lines, is

5.25% of the total used real power with 15 kV; while the power loss is 2.65% of the total

used real power in the network in 20 kV scenario. Furthermore, the source supplies

74523.7 kVA in case of 15 kV; and supplied power in case of 20 kV is 71435.68 kVA,

89 which is 3088.02 kVA lighter17 than supplied power in case of 15 kV MV. It is worth

mentioning that in both cases, 15 kV and 20 kV, second section of the feeder 515

(overhead lines 70 mm2 ACSR conductor) is highly overloaded; therefore, the first

priority is thought to be upgrading of this section.

Applying 20 kV as medium voltage helps to decrease the power loss and voltage

drop in the medium voltage transmission lines. Hence, in order to enhance the efficiency

of the Kabul power distribution system, 20 kV is recommended for medium voltage;

because upgrading the MV level from 15 kV to 20 kV is highly effective and applicable

to achieve the goal of optimization of the power loss and voltage drop in the MV

transmission lines of the Kabul power distribution system.

Even though the research project in hand has been completed successfully there

were numerous limitations and obstacles in regard to measurements and data collecting

procedure. Because the project is located in the Kabul city, it was not physically

accessible to measure the exact location of the transformers. Meanwhile, the data sources

were not easily accessible. Thus, to collect the required data, several institutions and

individuals were contacted by electronic messages, which were a time consuming

process. In the other side, there was not a single source having all the required data.

5.2 Future Works

Due to improvements of life style and more usage of digital electronic devices, the

demand, for high quality power, has an increasing rate in the Kabul city. Hence, not only

power loss and voltage drop at the medium voltage level have been major problems but

also harmonics, short circuits, voltage sags, and outages are other crucial concerns for the

Kabul power distributions system; because digital electronic devices need high quality

power. On the other hand, they are causing more harmonics in the network. Besides

theses disturbance factors, serious attentions must be paid to power loss and voltage drop

at low voltage (LV) level in the Kabul power distribution system. In the reason that

17 The source supplies 4.1% smaller power in case of 20 kV MV; while the used power in the network is the same in either scenarios

90 present power distribution system has high power loss and voltage drop because of long

transmission lines at low voltage.

Taking the above considerations into account, for the future – short circuits,

harmonics, voltage sags, and other disturbance factors to the power quality must be

analyzed to achieve an optimum case for the Kabul power distribution system to meet the

demand for high quality power. In order for power loss and voltage drop optimization at

low voltage level, the performance of pole mount smaller size18 distributions transformer

system versus pad mount distribution transformer system should be studied. Besides pole

mount transformers system, placing capacitor banks in the Kabul power distribution

system should be studied for reactive power compensation. Although the analysis could

be conducted by means of different software; CYMDIST could be a better option for this

purpose because it has variety of features for the distribution system simulation.

CYMDIST has been designed for distribution systems simulation purposes.

Economic analysis of the Kabul power distribution system is another important

research project for the future work. For the present project it was not possible to conduct

economic analysis for the network because of the following obstacles and preventing

limitations: economic analysis of the network needs very specific and detailed data, such

as equipment cost, transportation cost, labor cost, operating and maintaining cost, and so

on; whereas, mentioned data are not available. In addition the network has suffered from

civil war and significant parts of the network have been affected, and some of equipments

need to be replaced; therefore, specific survey is needed. At the present time, the project

is not accessible for required survey; hopefully it will be possible in the future.

Ultimately, to satisfy the demand for high quality power, the performance of the

Kabul power distribution system must be enhanced. Yet, to achieve this goal, power

quality disturbances such as harmonics, voltage sags, and outages must be studied and

analyzed and optimum case must be acquired. Also for power loss and voltage drop

minimization, the low voltage system with small size pole-mount transformers must be

evaluated. Besides the disturbance factors optimization and power loss and voltage drop

18 Distribution transformer with 60 kVA – 200 kVA

91 minimization, precise economical analyzes will be required in order to have an

advantageous power distribution system.

92

REFERENCES

[1] Mir M. Sediq and R. Naeem, “Power Sector Strategy for the Afghanistan National

Development Strategy,” Ministry of Energy and Water, Kabul, Afghanistan,

Tech. Rep. (Draft), April 15, 2007.

[2] Advanced Engineering Associates, Inc. “Kabul city medium voltage (MV) and low

voltage (LV) distribution system assessment study,” AEAI Inc., Washington, DC

20036, USA, Tech. Rep., October 2007.

[3] H. L. Willis, Power distribution system planning reference book. CRC press,

Taylor & Francis Group, Boca Raton, FL 33487-2742, 2004.

[4] H. Liu, S. Ge, and X. Jiang, “Research on voltage level configuration in medium

voltage network of new area,” IEEE International Conference on Electric Utility

Deregulation, Restructuring, and Power Technology, pp. 1359-1364, April 2008.

[5] W. H. Kersting, Power distribution system modeling and analysis. CRC press,

Taylor & Francis Group, 2007.

[6] A. J. Pansini, Power transmission and distribution. Fairmount Press Inc: 700

Indian Trails, Lilburn, GA 30047, 2005.

[7] L. M. Faulkenberry and W. Coffer, Electrical power distribution and

transmission. United States of America: Prentice-Hall Inc, 1996.

[8] D. P. Bernardon et al., “Electric distribution network reconfiguration based on a

fuzzy multi-criteria decision making algorithm,” Electrical Power Systems

Research, 79 (2009), pp. 1400-1407.

[9] M. W. Siti et al., “ Reconfiguration and load balancing in the LV and MV

distribution networks for optimal performance,” IEEE Transactions on Power

Delivery, vol. 22, No. 4, pp. 2534-2540, Oct. 2007.

[10] F. Bignucolo et al., “Radial MV networks regulation with distribution

management system coordinated controller,” Electric Power System Research, 78

(2008) pp. 634-645.

93 [11] A. Augugliaro et al., “Voltage regulation and power losses minimization in

automated distribution networks by an evolutionary multiobjective approach,”

IEEE Transactions on Power System, vol. 19, No. 3, pp. 1516-1527, August 2004.

[12] A. Khoravi et al., “Classification of sags gathered in distribution substations based

on multiway principal component analysis,” Electric Power System Research, 79

(2009) pp. 144-151.

[13] J. I. Garcia-Roman et al., “Method of assessment of the state of chare and voltage

level in the electric power distribution network. Implementation in the

improvement of supply quality,” Electrical Power & Energy Systems, 28 (2006),

pp. 496-502.

[14] S. W. Heunis and R. Herman, “A probabilistic model for residential consumer

loads,” IEEE Transactions on Power System, vol. 17, No. 3, pp. 621-625, August

2002.

[15] S. J. Chapman, “Transformers,” in Electric Machinery Fundamentals, 4th Ed.

McGraw-Hill Companies Inc. New York, NY 10020, 2005, chap. 2, pp 65-143.

[16] R. Arora and T. McMahon, (2001). A case study on reliability improvement of 10

worst performing feeders in Niagara Mohawk Power Corporation (NMPC)

service territory. IEEE PES Transmission and Distribution [Online]. Available:

http://www.edist.ca/2003/presentations/Tom_McMahon-extra1-IEEE.pdf

[17] J. A. Peralta et al., “Unbalanced multiphase load-flow using a positive sequence

load-flow program,” IEEE Transactions on Power System, vol. 23, No. 2, pp.

469-476, May 2008.

94

APPENDIX-A: ABNORMAL CONDITIONS IN 15 kV SCENARIO

Detailed information of abnormal conditions in the North substations (15 kV MV) Section Number

Conductor ID

Line Type

Loading (%)

Thru Real Power/ph

Thru Reactive Power/ph

Voltage (%)

N123 UC_185 Underground Cable 126.5 2581.4 1442.2 99.94 N124 OHL_150 Overhead Lines 133.9 2579.9 1441.9 98.61 N132 OHL_120 Overhead Lines 148.5 2432.1 1340.4 91.52 N125 OHL_95 Overhead Lines 25.1 353.0 175.2 91.47 N129 OHL_95 Overhead Lines 14.0 196.7 97.3 91.44 N130 UC_120_CU Underground Cable 4.3 98.3 48.3 91.44 N131 OHL_95 Overhead Lines 7.0 98.3 49.0 91.44 N133 OHL_95 Overhead Lines 11.1 156.1 77.8 91.46 N134 OHL_120 Overhead Lines 125.9 1949.8 985.6 90.26 N135 OHL_95 Overhead Lines 18.0 249.9 124.1 90.17 N136 OHL_95 Overhead Lines 13.5 187.3 93.4 90.17 N137 UC_95 Underground Cable 4.3 62.4 30.7 90.17 N147 OHL_120 Overhead Lines 109.6 1680.1 834.1 89.38 N148 OHL_120 Overhead Lines 109.6 1668.1 817.7 88.01 N150 UC_185_AL Underground Cable 73.9 1649.3 791.9 87.99 N153 UC_185 Underground Cable 76.8 1425.9 680.9 87.86 N154 UC_185 Underground Cable 71.5 1325.5 632.0 87.76 N155 UC_185 Underground Cable 66.1 1225.7 583.2 87.65 N156 UC_185 Underground Cable 11.8 218.6 105.8 87.63 N158 UC_185 Underground Cable 3.4 62.4 29.3 87.62 N157 UC_185 Underground Cable 47.5 880.7 415.5 87.56 N159 UC_185 Underground Cable 42.2 781.4 367.4 87.49 N160 UC_185 Underground Cable 2.1 39.0 18.6 87.49 N161 UC_185 Underground Cable 33.3 617.0 287.3 87.45 N162 UC_185 Underground Cable 10.7 196.7 97.6 87.44 N163 UC_185 Underground Cable 6.8 124.9 60.6 87.43 N164 UC_185 Underground Cable 3.4 62.4 30.8 87.43 N165 OHL_50 Overhead Lines 7.7 62.4 31.0 87.42 N166 OHL_95 Overhead Lines 14.2 196.8 80.9 87.44 N167 UC_185_AL Underground Cable 8.6 196.7 81.0 87.42 N168 UC_185_AL Underground Cable 8.7 196.7 86.4 87.41 N169 UC_185_AL Underground Cable 4.3 98.4 38.1 87.39 N23 OHL_70 Overhead Lines 78.4 966.4 478.4 96.93 N24 OHL_35 Overhead Lines 13.2 98.4 48.9 96.88 N26 OHL_70 Overhead Lines 70.3 858.4 422.0 96.64 N27 OHL_70 Overhead Lines 5.1 62.4 31.0 96.62 N29 OHL_70 Overhead Lines 65.2 793.8 389.3 96.47 N30 OHL_70 Overhead Lines 25.8 312.3 155.2 96.43 N31 UC_35_CU Underground Cable 19.6 249.8 124.0 96.42 N35 OHL_50 Overhead Lines 53.3 480.3 233.2 96.10

(Continued)

95 Section Number

Conductor ID

Line Type

Loading (%)

Thru Real Power/ph


Voltage (%)

N36 OHL_50 Overhead Lines 11.0 98.4 48.7 96.04 N38 OHL_50 Overhead Lines 42.3 380.2 183.8 96.06 N39 UC_95_CU Underground Cable 7.2 156.1 74.9 96.05 N41 OHL_50 Overhead Lines 24.9 224.0 108.9 95.81 N42 OHL_50 Overhead Lines 18.0 160.9 78.8 95.77 N43 OHL_50 Overhead Lines 11.0 98.3 49.0 95.76 N44 OHL_50 Overhead Lines 7.0 62.5 29.8 95.67 N45 OHL_70 Overhead Lines 5.2 62.5 30.7 95.63 N48 OHL_50 Overhead Lines 7.0 62.5 30.4 95.76 N49 OHL_50 Overhead Lines 7.0 62.5 30.8 95.73 N186 OHL_120 Overhead Lines 118.4 1970.6 1075.1 93.17 N187 OHL_120 Overhead Lines 17.3 274.9 135.8 93.16 N188 OHL_95 Overhead Lines 1.1 15.6 7.5 93.15 N189 OHL_120 Overhead Lines 10.2 160.9 79.2 93.08 N190 OHL_120 Overhead Lines 6.2 98.4 48.7 93.04 N191 UC_95 Underground Cable 4.2 62.4 30.9 93.08 N196 OHL_150 Overhead Lines 86.9 1596.8 803.5 91.58 N197 UC_185_AL Underground Cable 68.2 1578.5 772.8 91.50 N198 UC_185_AL Underground Cable 8.5 196.7 94.7 91.49 N199 UC_185 Underground Cable 5.1 98.3 48.0 91.49 N200 UC_185 Underground Cable 23.5 451.3 221.9 91.46 N201 UC_95 Underground Cable 13.4 196.7 96.2 91.44 N202 UC_185 Underground Cable 5.1 98.3 48.2 91.43 N210 UC_185 Underground Cable 43.3 830.9 409.9 91.44 N211 UC_185 Underground Cable 38.2 732.1 361.6 91.40 N212 UC_185 Underground Cable 31.7 606.9 300.0 91.37 N213 UC_185 Underground Cable 26.6 508.3 251.7 91.34 N214 UC_185 Underground Cable 21.4 409.8 203.4 91.31 N229 OHL_70 Overhead Lines 32.3 394.0 195.8 96.89 N230 OHL_50 Overhead Lines 21.8 197.0 97.5 96.76 N231 OHL_50 Overhead Lines 10.9 98.4 48.7 96.69 N232 OHL_50 Overhead Lines 35.7 322.7 160.1 96.75 N233 OHL_50 Overhead Lines 24.8 223.6 111.0 96.58 N234 OHL_50 Overhead Lines 10.9 98.3 49.0 96.56 N235 OHL_50 Overhead Lines 13.9 124.9 62.2 96.56 N254 UC_185 Underground Cable 125.1 2647.6 1245.8 99.94 N255 OHL_150 Overhead Lines 132.5 2646.2 1245.5 96.71 N256 OHL_95 Overhead Lines 162.3 2463.4 1084.4 96.15 N257 UC_95_CU Underground Cable 109.4 2427.1 1059.4 96.12 N490 UC_95_AL Underground Cable 5.8 98.3 46.8 96.12 N492 UC_95_AL Underground Cable 51.1 883.5 379.2 96.08 N493 UC_95_AL Underground Cable 47.5 820.6 349.4 95.88 N494 UC_95_AL Underground Cable 2.2 39.0 13.5 95.87

(Continued)

96 Section Number

Conductor ID

Line Type

Loading (%)

Thru Real Power/ph


Voltage (%)

N495 UC_95_AL Underground Cable 45.4 779.9 341.9 95.75 N496 UC_95_AL Underground Cable 38.1 653.9 283.9 95.61 N497 UC_50_CU Underground Cable 36.5 554.7 240.4 95.33 N498 UC_35_CU Underground Cable 1.9 25.0 9.2 95.32 N499 UC_50_CU Underground Cable 14.6 218.8 99.0 95.23 N500 UC_50_CU Underground Cable 4.2 62.5 29.3 95.23 N501 OHL_50 Overhead Lines 7.0 62.5 30.2 95.20 N502 UC_35_CU Underground Cable 5.0 62.4 30.5 95.19 N506 UC_95_AL Underground Cable 15.0 254.6 113.9 95.27 N507 UC_95_AL Underground Cable 11.4 192.0 88.9 95.26 N508 UC_95_AL Underground Cable 7.7 129.6 59.9 95.25 N509 UC_95_AL Underground Cable 1.8 31.2 12.8 95.24 N519 UC_50_CU Underground Cable 13.1 196.8 93.3 96.07 N522 UC_50_CU Underground Cable 21.2 322.2 144.0 96.00 N523 UC_50_CU Underground Cable 14.8 223.4 102.3 95.90 N524 UC_50_CU Underground Cable 8.4 124.9 61.6 95.89 N528 UC_95_CU Underground Cable 41.6 925.7 396.1 96.04 N529 OHL_150 Overhead Lines 47.5 925.0 399.6 95.20 N530 UC_95_AL Underground Cable 41.9 722.8 293.2 94.78 N531 UC_95_AL Underground Cable 27.2 469.9 183.4 94.49 N532 UC_95_AL Underground Cable 3.7 62.4 26.1 94.48 N533 UC_95_AL Underground Cable 9.1 156.2 60.6 94.39 N537 UC_70_CU Underground Cable 6.8 124.9 50.5 94.44 N258 OHL_50 Overhead Lines 2.8 25.0 11.9 96.13 N259 OHL_70 Overhead Lines 10.3 124.9 62.1 96.67 N263 OHL_70 Overhead Lines 134.3 1762.9 661.7 98.57 N265 OHL_70 Overhead Lines 129.3 1679.5 612.6 95.72 N266 OHL_50 Overhead Lines 7.0 62.4 31.1 95.70 N269 OHL_70 Overhead Lines 124.2 1575.4 545.6 95.23 N270 OHL_70 Overhead Lines 5.2 62.4 30.9 95.21 N271 OHL_70 Overhead Lines 119.0 1506.2 508.8 94.42 N272 OHL_95 Overhead Lines 90.7 1396.9 450.4 94.37 N273 UC_185_AL Underground Cable 55.2 1396.2 449.7 93.63 N275 UC_95_CU Underground Cable 59.2 1323.9 444.2 93.60 N276 UC_95_AL Underground Cable 76.3 1323.7 444.7 93.43 N277 OHL_95 Overhead Lines 80.3 1222.9 398.2 93.32 N278 OHL_95 Overhead Lines 10.5 149.9 74.2 93.27 N279 OHL_50 Overhead Lines 2.9 25.0 12.2 93.25 N563 OHL_95 Overhead Lines 70.0 1071.8 322.7 93.12 N281 UC_95_CU Underground Cable 4.6 98.3 45.7 93.12 N282 UC_35_CU Underground Cable 8.0 98.3 48.5 93.11 N564 OHL_70 Overhead Lines 77.3 971.7 275.1 92.50 N565 OHL_70 Overhead Lines 77.3 966.1 270.5 92.40

(Continued)

97 Section Number

Conductor ID

Line Type

Loading (%)

Thru Real Power/ph


Voltage (%)

N321 UC_185 Underground Cable 166.1 3268.7 2097.5 99.86 N322 OHL_150 Overhead Lines 175.9 3263.9 2095.8 94.74 N323 UC_150_CU Underground Cable 121.0 3126.5 1889.6 92.39 N295 UC_50_CU Underground Cable 28.0 308.6 324.0 92.26 N294 UC_50_CU Underground Cable 18.4 151.9 251.5 92.22 N293 UC_50_CU Underground Cable 21.6 343.7 12.8 92.24 N292 UC_50_CU Underground Cable 56.0 865.4 223.6 92.40 N300 UC_50_CU Underground Cable 25.0 365.6 159.6 92.17 N301 UC_50_CU Underground Cable 18.2 267.0 113.8 92.08 N297 UC_50 Underground Cable 23.6 339.3 164.1 92.13 N298 UC_50 Underground Cable 12.8 182.9 90.6 92.10 N291 UC_50 Underground Cable 2.6 39.0 12.8 92.08 N566 UC_50_CU Underground Cable 3.5 45.5 32.1 92.08 N367 UC_50 Underground Cable 67.2 971.9 456.5 92.00 N368 UC_35 Underground Cable 3.1 39.0 16.4 91.99 N369 UC_50 Underground Cable 2.1 31.2 13.9 92.00 N370 UC_50 Underground Cable 55.6 799.1 382.2 91.81 N371 UC_35 Underground Cable 5.1 62.4 30.1 91.81 N372 UC_35_CU Underground Cable 5.0 62.4 27.4 91.79 N373 UC_50_CU Underground Cable 25.2 361.1 172.5 91.69 N374 UC_50_CU Underground Cable 22.6 321.6 158.2 91.67 N375 UC_50_CU Underground Cable 11.3 160.8 79.1 91.66 N387 UC_50 Underground Cable 20.1 296.2 126.3 92.03 N388 UC_35 Underground Cable 8.1 98.3 47.8 92.02 N392 UC_50 Underground Cable 17.0 250.2 105.2 92.25 N393 UC_50 Underground Cable 17.2 249.9 114.0 92.24 N394 UC_50 Underground Cable 8.5 125.0 52.8 92.18 N395 UC_50 Underground Cable 4.3 62.4 30.0 92.17 N401 UC_50 Underground Cable 107.9 1569.8 713.1 89.79 N402 UC_50 Underground Cable 7.0 98.4 45.9 89.77 N403 UC_50 Underground Cable 97.1 1363.5 646.2 89.56 N404 UC_50 Underground Cable 94.9 1328.6 631.9 89.47 N405 UC_50 Underground Cable 40.4 567.9 261.7 89.41 N411 UC_50 Underground Cable 4.4 62.4 28.0 89.40 N424 UC_50 Underground Cable 27.0 380.2 172.8 89.28 N425 UC_50 Underground Cable 22.6 317.2 146.7 89.24 N426 UC_50 Underground Cable 18.2 254.6 117.6 89.22 N427 UC_50 Underground Cable 11.1 156.2 69.6 89.14 N406 UC_50 Underground Cable 9.2 129.6 61.0 89.45 N407 UC_50 Underground Cable 2.2 31.2 14.0 89.45 N408 UC_50 Underground Cable 38.2 531.4 260.7 89.38 N409 UC_50 Underground Cable 11.3 156.1 77.8 89.38 N410 UC_50 Underground Cable 22.5 312.3 154.2 89.35

(Continued)

98 Section Number

Conductor ID

Line Type

Loading (%)

Thru Real Power/ph


Voltage (%)

N432 UC_35 Underground Cable 49.5 620.4 262.4 91.59 N433 UC_35 Underground Cable 5.1 62.4 30.1 91.58 N434 UC_35_CU Underground Cable 34.5 427.5 183.4 91.37 N435 UC_50_CU Underground Cable 13.4 195.3 80.7 91.32 N436 UC_50_CU Underground Cable 9.1 132.7 53.9 91.29 N437 UC_50_CU Underground Cable 2.2 31.2 13.9 91.29 N438 UC_35_CU Underground Cable 5.0 62.5 23.2 91.25 N446 UC_35_CU Underground Cable 10.8 132.8 59.4 91.31 N447 UC_35_CU Underground Cable 2.6 31.2 14.4 91.31 N448 UC_35_CU Underground Cable 5.1 62.4 30.0 91.31 N452 UC_50_AL Underground Cable 3.4 39.0 17.0 92.38 N453 UC_50_CU Underground Cable 78.9 1141.7 537.6 91.86 N454 UC_35_CU Underground Cable 3.2 39.0 17.5 91.85 N455 UC_35_CU Underground Cable 8.1 98.3 48.5 91.85 N456 UC_50_CU Underground Cable 62.7 899.2 427.8 91.50 N457 UC_50_CU Underground Cable 38.8 551.8 269.1 91.42 N458 UC_50_CU Underground Cable 31.9 453.0 222.1 91.36 N459 UC_95_CU Underground Cable 18.9 390.3 193.0 91.34 N474 UC_35_CU Underground Cable 23.1 281.3 132.8 91.42 N475 UC_35_CU Underground Cable 12.8 156.2 73.4 91.38 N476 UC_35_CU Underground Cable 10.3 124.9 60.8 91.36 N469 UC_50_CU Underground Cable 37.7 549.1 249.1 92.30 N470 UC_50_CU Underground Cable 30.9 450.3 202.7 91.94 N471 UC_50_CU Underground Cable 22.6 325.1 153.9 91.81 N472 UC_50_CU Underground Cable 11.0 156.1 76.8 91.80 N483 UC_50_CU Underground Cable 2.7 39.0 18.9 91.81 N327 OHL_150 Conductor 1.3 25.0 12.4 94.74 N324 UC_185 Underground Cable 130.9 2876.0 1045.3 99.89 N325 OHL_70 Conductor 218.1 2873.0 1044.5 94.12 N326 UC_150_CU Underground Cable 96.0 2730.8 918.5 92.39

99

APPENDIX-B: ABNORMAL CONDITIONS IN 20 kV SCENARIO

Detailed information of abnormal conditions in the North substations (20 kV MV) Section Number

Conductor ID

Line Type

Loading (%)

Thru Real Power/ph


Voltage (%)

N132 OHL_120 Overhead Lines 104.1 2336.4 1170.1 95.62 N125 OHL_95 Overhead Lines 18.0 352.9 174.1 95.59 N129 OHL_95 Overhead Lines 10.0 196.7 96.4 95.57 N131 OHL_95 Overhead Lines 5.0 98.3 49.0 95.57 N133 OHL_95 Overhead Lines 8.0 156.1 77.8 95.59 N134 OHL_120 Overhead Lines 87.9 1919.9 912.1 94.96 N135 OHL_95 Overhead Lines 12.8 249.8 123.3 94.92 N136 OHL_95 Overhead Lines 9.6 187.3 93.4 94.91 N147 OHL_120 Overhead Lines 76.3 1660.4 776.3 94.51 N148 OHL_120 Overhead Lines 76.3 1654.6 769.1 93.80 N165 OHL_50 Overhead Lines 5.4 196.7 30.9 93.49 N166 OHL_95 Overhead Lines 9.7 62.4 63.1 93.50 N186 OHL_120 Overhead Lines 84.8 1912.0 970.9 96.37 N187 OHL_120 Overhead Lines 12.6 274.8 134.4 96.36 N188 OHL_95 Overhead Lines 0.8 15.6 7.2 96.36 N189 OHL_120 Overhead Lines 7.3 98.3 78.1 96.32 N190 OHL_120 Overhead Lines 4.5 160.8 48.3 96.30 N256 OHL_95 Overhead Lines 62.2 1586.5 772.0 95.52 N196 OHL_150 Overhead Lines 116.6 2448.8 933.9 98.00 N277 OHL_95 Overhead Lines 56.6 1200.4 346.0 96.54 N278 OHL_95 Overhead Lines 7.6 149.9 73.6 96.51 N279 OHL_50 Overhead Lines 2.1 25.0 11.9 96.50 N563 OHL_95 Overhead Lines 49.1 1049.9 271.9 96.44 N564 OHL_70 Overhead Lines 54.2 950.7 228.5 96.12 N565 OHL_70 Overhead Lines 54.2 947.9 227.0 96.07 N322 OHL_150 Overhead Lines 123.9 3176.0 1787.5 97.30 N325 OHL_70 Overhead Lines 153.6 2751.7 822.6 95.62 N132 OHL_120 Overhead Lines 104.1 2336.4 1170.1 96.97 N130 UC_120_CU Underground Cable 3.1 98.3 47.6 95.57 N137 UC_95 Underground Cable 3.1 62.4 30.4 94.92 N150 UC_185_AL Underground Cable 51.5 1645.5 757.7 93.79 N153 UC_185 Underground Cable 53.4 1422.2 647.2 93.73 N154 UC_185 Underground Cable 49.7 1322.9 600.2 93.67 N155 UC_185 Underground Cable 46.0 1223.8 552.8 93.61 N156 UC_185 Underground Cable 8.3 218.5 102.5 93.60 N158 UC_185 Underground Cable 2.3 62.4 27.4 93.60 N157 UC_185 Underground Cable 33.0 879.7 390.2 93.57 N159 UC_185 Underground Cable 29.2 780.9 343.9 93.53 N160 UC_185 Underground Cable 1.5 39.0 17.8 93.53 N161 UC_185 Underground Cable 23.0 616.7 266.0 93.51

(Continued)

100 Section Number

Conductor ID

Line Type

Loading (%)

Thru Real Power/ph


Voltage (%)

N162 UC_185 Underground Cable 7.5 196.7 97.1 93.50 N163 UC_185 Underground Cable 4.7 124.9 58.7 93.50 N164 UC_185 Underground Cable 2.4 62.4 30.5 93.50 N167 UC_185_AL Underground Cable 5.9 196.7 63.1 93.49 N168 UC_185_AL Underground Cable 6.0 196.7 74.3 93.49 N169 UC_185_AL Underground Cable 2.9 98.3 26.8 93.48 N191 UC_95 Underground Cable 3.0 62.4 30.7 96.32 N197 UC_185_AL Underground Cable 48.8 1577.1 758.0 95.48 N198 UC_185_AL Underground Cable 6.1 196.7 91.5 95.47 N199 UC_185 Underground Cable 3.7 98.3 47.0 95.47 N200 UC_185 Underground Cable 9.6 196.7 94.5 95.46 N201 UC_95 Underground Cable 16.8 451.2 218.8 95.44 N202 UC_185 Underground Cable 3.7 98.3 47.3 95.44 N210 UC_185 Underground Cable 31.0 830.2 405.2 95.45 N211 UC_185 Underground Cable 27.4 731.7 358.0 95.43 N212 UC_185 Underground Cable 22.7 606.6 297.2 95.41 N213 UC_185 Underground Cable 15.4 409.8 202.4 95.39 N214 UC_185 Underground Cable 19.0 508.2 249.9 95.38 N273 UC_185_AL Underground Cable 38.8 1367.4 360.7 96.70 N275 UC_95_CU Underground Cable 41.8 1300.0 387.6 96.69 N276 UC_95_AL Underground Cable 53.8 1299.9 388.9 96.60 N281 UC_95_CU Underground Cable 3.3 98.3 42.7 96.43 N282 UC_35_CU Underground Cable 5.8 98.3 48.1 96.43 N321 UC_185 Underground Cable 117.0 3178.4 1787.4 99.93 N323 UC_150_CU Underground Cable 85.2 3095.3 1681.6 96.07 N295 UC_50_CU Underground Cable 20.8 324.7 328.2 96.00 N294 UC_50_CU Underground Cable 14.0 168.3 261.0 95.97 N293 UC_50_CU Underground Cable 14.9 327.8 37.8 95.98 N292 UC_50_CU Underground Cable 39.2 848.4 183.9 96.07 N300 UC_50_CU Underground Cable 17.7 364.5 146.0 95.94 N301 UC_50_CU Underground Cable 12.9 266.0 103.4 95.90 N297 UC_50 Underground Cable 16.8 339.9 151.7 95.92 N298 UC_50 Underground Cable 9.1 183.7 82.3 95.90 N291 UC_50 Underground Cable 1.8 39.0 6.6 95.90 N566 UC_50_CU Underground Cable 2.6 46.3 33.1 95.90 N367 UC_50 Underground Cable 47.8 968.7 429.5 95.86 N368 UC_35 Underground Cable 2.2 39.0 13.6 95.85 N369 UC_50 Underground Cable 1.5 31.2 12.4 95.86 N370 UC_50 Underground Cable 39.7 798.0 366.6 95.76 N371 UC_35 Underground Cable 3.7 62.4 29.2 95.76 N372 UC_35_CU Underground Cable 3.6 62.4 24.0 95.75 N373 UC_50_CU Underground Cable 18.0 360.8 165.2 95.70 N374 UC_50_CU Underground Cable 16.2 321.6 156.2 95.68 N375 UC_50_CU Underground Cable 8.1 160.8 78.1 95.68

(Continued)

101 Section Number

Conductor ID

Line Type

Loading (%)

Thru Real Power/ph


Voltage (%)

N387 UC_50 Underground Cable 14.2 295.6 106.4 95.88 N388 UC_35 Underground Cable 5.8 98.3 46.7 95.87 N392 UC_50 Underground Cable 11.9 250.0 87.1 96.00 N393 UC_50 Underground Cable 12.2 249.8 104.2 95.99 N394 UC_50 Underground Cable 6.0 124.9 44.0 95.95 N395 UC_50 Underground Cable 3.1 62.4 29.0 95.95 N401 UC_50 Underground Cable 75.4 1543.0 641.5 94.70 N402 UC_50 Underground Cable 4.9 98.3 42.8 94.69 N403 UC_50 Underground Cable 68.3 1359.8 612.2 94.58 N404 UC_50 Underground Cable 66.8 1326.8 601.2 94.53 N405 UC_50 Underground Cable 28.2 567.2 240.3 94.50 N411 UC_50 Underground Cable 3.1 62.4 24.9 94.49 N424 UC_50 Underground Cable 18.8 379.7 156.1 94.43 N425 UC_50 Underground Cable 15.8 317.0 135.3 94.41 N426 UC_50 Underground Cable 12.7 254.5 108.3 94.40 N427 UC_50 Underground Cable 7.7 156.2 61.3 94.35 N406 UC_50 Underground Cable 6.5 129.6 57.3 94.52 N407 UC_50 Underground Cable 1.5 31.2 12.4 94.52 N408 UC_50 Underground Cable 27.0 531.0 256.3 94.48 N409 UC_50 Underground Cable 8.0 156.1 77.7 94.48 N410 UC_50 Underground Cable 15.9 312.2 152.6 94.46 N432 UC_35 Underground Cable 34.7 616.9 218.4 95.64 N433 UC_35 Underground Cable 3.7 62.4 29.2 95.64 N434 UC_35_CU Underground Cable 24.2 426.8 155.3 95.53 N435 UC_50_CU Underground Cable 9.3 195.2 64.9 95.50 N436 UC_50_CU Underground Cable 6.3 132.7 42.2 95.49 N437 UC_50_CU Underground Cable 1.5 31.2 12.4 95.49 N438 UC_35_CU Underground Cable 3.4 62.4 15.7 95.46 N446 UC_35_CU Underground Cable 7.6 132.7 52.9 95.50 N447 UC_35_CU Underground Cable 1.8 31.2 13.3 95.50 N448 UC_35_CU Underground Cable 3.7 62.4 28.8 95.49 N452 UC_50_AL Underground Cable 2.4 39.0 14.7 96.06 N453 UC_50_CU Underground Cable 56.1 1135.9 506.8 95.78 N454 UC_35_CU Underground Cable 2.2 39.0 15.6 95.78 N455 UC_35_CU Underground Cable 5.8 98.3 47.9 95.78 N456 UC_50_CU Underground Cable 44.6 896.8 408.0 95.59 N457 UC_50_CU Underground Cable 27.7 551.4 263.2 95.55 N458 UC_50_CU Underground Cable 22.8 452.8 218.3 95.52 N459 UC_95_CU Underground Cable 13.6 390.2 191.4 95.51 N474 UC_35_CU Underground Cable 16.4 281.1 125.7 95.55 N475 UC_35_CU Underground Cable 9.1 156.1 69.2 95.53 N476 UC_35_CU Underground Cable 7.4 124.9 59.4 95.52 N469 UC_50_CU Underground Cable 26.7 547.7 225.9 96.02 N470 UC_50_CU Underground Cable 21.9 449.1 182.1 95.83

(Continued)

102 Section Number

Conductor ID

Line Type

Loading (%)

Thru Real Power/ph


Voltage (%)

N471 UC_50_CU Underground Cable 16.1 324.9 146.0 95.76 N472 UC_50_CU Underground Cable 7.9 156.1 75.7 95.75 N483 UC_50_CU Underground Cable 2.0 39.0 18.4 95.76 N326 UC_150_CU Underground Cable 67.6 2681.2 762.5 96.07

Date post:	07-Oct-2014
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