684_SHAKIRAAZEEHANBINTIAZLI2010

SETTING OF DISTANCE RELAY ON POWER TRANSMISSION LINE

USING PSCAD

SHAKIRA AZEEHAN BINTI AZLI

A report submitted in partial fulfilment of the

requirements for award of degree of

Bachelor of Engineering (Electrical)

Faculty of Electrical Engineering

University Teknologi Malaysia

APRIL 2010

ii

iii

Dedicated to my beloved father

PM Dr Azli Bin Sulaiman

Mother

Noor Sharidah Binti Alias

Siblings

Hizaz Shahiela

Izzat Fahmi

Adib Fikri

Amelia Adrina

and

My Entire friend in SEE programme

For their encouragement

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ACKNOWLEDGEMENT

“Praise is to Allah S.W.T, the Most Merciful and the Most Compassionate.

Peace is upon him, Muhammad, the messenger of God”.

I wish to express my sincere appreciation to my project supervisor, Dr

Ahmad Safawi Bin Mokhtar for all his guidance, encouragement and support in

completing the final year project.

I would also like to express my gratitude to all the lectures who have taught

me throughout the years of studying in UTM, thank you for all the knowledge that

has been provided.

My gratitude is also extending to my fellow colleagues for sharing their ideas

and discussions. Last but not least, I would like to thanks my family for their

motivation and moral support.

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ABSTRACT

The role of protective relays in a power system is to detect systems

abnormalities and to execute appropriates commands to isolate swiftly only at the

faulty component from healthy system. One of the protective relays is the distance

relay. High current flows through the network when fault occur. So, the distance

relay will detect the over current by measuring the impedance on the transmission

line and send the tripping signal to the circuit breaker to break the power line. This

project focuses on determining the optimum setting of distance relay and also the

performance of the distance relay when single line-to-ground fault occur in the

system. In this project, the setting can be determined by using PSCAD software.

The system consist of two source, five faults and two 100Km transmission line

which are protected by distance relays. The modelling and analysis of the test

system with corresponding relay circuits are done solely using PSCAD. From the

simulation, it can be observed that the fault voltage and current characteristics are

consistent with those from the theoretical concept. The optimum setting is also

obtained from the analysis.

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ABSTRAK

Peranan geganti perlindungan dalam system kuasa adalah untuk mengesan

ketidakseimbangan sistem dan melaksanakan arahan yang sewajarnya untuk

mengasingkan bahagian rosak sahaja daripada sistem yang normal. Salah satu

daripada komponen sistem perlindungan ialah geganti jarak. Apabila kerosakan

berlaku, arus yang tinggi akan mengalir melalui rangkaian. Oleh itu geganti jarak

akan mengesan lebihan arus dengan mengukur galangan pada talian penghantaran

dan akan menghantar isyarat putus kepada pemutus litar untuk memutuskan talian

kuasa. Projek ini difokuskan untuk menentukan pengesatan optimum geganti jarak

dan analisis penilaian prestasi geganti jarak beroperasi pada kerosakan satu talian ke

bumi. Dalam projek ini, pengesatan optimum geganti jarak dapat ditentukan dengan

menggunakan perisian PSCAD. Sistem ini mempunyai dua penjana, lima kerosakan

dan dua talian penghantaran 100Km panjang yang dilindungi dengan geganti jarak.

Rekaan dan ujian analisa pada sistem dengan litar geganti dijalankan sepenuhnya

dengan PSCAD. Daripada keputusan, ia boleh dilihat bahawa sifat kerosakan voltan

dan arus mematuhi sifat-sifat dalam teori. Pengesatan optimum juga diperolehi

daripada analisis ini.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLE xi

LIST OF FIGURES xii

LIST OF SYMBOLS AND ABBREVIATION xiv

1 INTRODUCTION

1.1 Background 1

1.2 Problem of Statement 2

1.3 Objectives 2

1.4 Scope of the Project 3

viii

1.5 Thesis Outline 3

2 LITERATURE REVIEW

2.1 Faults on Power System 4

2.2 Single Line-to-Ground Fault 5

2.3 Principles of Distance Relay 9

2.4 Distance Protection Scheme 9

3 METHODOLOGY

3.1 PSCAD Software 11

3.2 Process of Analysis 12

3.3 Circuit Construction 12

3.4 Components 14

3.4.1 Source 14

3.4.1.1 Configuration 15

3.4.1.2 Parameters 15

3.4.2 Multimeter 16

3.4.3 Transmission Line 17


3.4.4 Circuit Breaker 18

3.4.5 Fault Component 19

3.4.6 Online Frequency Scanner 20

3.4.7 Sequence Filter 20

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3.4.8 Line to Ground Impedance Component 21

3.4.9 Parameters 21

3.4.9.1 Main Data 22

3.4.9.2 Initializing 23

3.4.10 MHO Circle 23


3.5 Run Simulation 24

4 RESULTS AND DISCUSSION

4.1 Introduction 25

4.2 No Fault Condition 26

4.3 Fault at Location 1 28



5 CONCLUSION AND RECOMMENDATION

5.1 Conclusion 38

5.2 Recommendation 39

x

REFERENCES 40

APPENDIX A 41

APPENDIX B 43

APPENDIX C 45

APPENDIX D 46

xi

LIST OF TABLES

NO. TABLE TITLE PAGE

3.1 Configuration of Voltage Source 17

xii

LIST OF FIGURES

NO. FIGURE TITLE

PAGE

2.1 The Condition of Each Types of Faults 5

2.2 Single Line-to-Ground Fault 6

2.3 Connection of Sequence Network for L-G fault 8

2.4 3-Zone Distance Protection Scheme 10

3.1 Project Flow 12

3.2 Main Circuit 13

3.3 Relay Circuit 13

3.4 Three Phase Voltage Source 14

3.5 Multimeter 16

3.6 Transmission Line 17

3.7 Parameters of Bergeron Model 18

3.8 Circuit Breaker 18

3.9 Three Phase Fault 19

3.10 Online Fast Fourier Transform 20

3.11 Sequence Filter 20

3.12 Line to Ground Impedance 21

3.13 MHO Circle Component 23

4.1 Waveform at No Fault Condition 27

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4.3 Waveform of Breaker 1 when Fault at Location 1 29








A1 Main Circuit Connection 41

A2 Output Channel Connections 42

B1 Relay Circuit Connection 43

B2 Sequence Module for Current 44

B3 Sequence Module for Voltage 44

C1 Breaker Control Circuit 45

D1 Waveform of fault at Location 4 for Relay 1 46




xiv

LIST OF LIST OF ABBREAVIATIONS AND SYMBOLS

Ea - Voltage Source

Ia - Current phase a

Ib - Current phase b

Ic - Current phase c

If - Fault current

I0 - Zero sequence current

I1 - Positive sequence current

I2 - Negative sequence current

Va - Voltage phase a

Vb - Voltage phase b

Vc - Voltage phase c

V0 - Zero sequence voltage

V1 - Positive sequence voltage

V2 - Negative sequence voltage

CHAPTER 1

INTRODUCTION

1.1 Background

Electrical energy is the most popular form of energy because it can be

transported easily at high efficiency and reasonable cost [1]. Modern power

engineering consists of three main subsystems, which is the generation, transmission

and distribution. In order to provide electrical energy to consumers in usable form, a

transmission and distribution system must satisfy some basic requirements. Thus,

the system must [2]:

1. Provide, at all times, the power that consumers need.

2. Maintain a stable, nominal voltage that does not vary by more than +10%.

3. Maintain a stable frequency that does not vary by more than +0.1 Hz.

4. Supply energy at an acceptable price.

5. Meet standards of safety.

6. Respect environmental standards

The electrical power is distributed to a multiplicity of consumers for different

applications. In the process of distributing or transmitting the power, faults

2

sometimes occur due to the physical accidents or insulation breakdowns [3]. Power

system protection deals with the protection from faults through the isolation of

faulted parts from the rest of the electrical network. The objective of a protection

scheme is to keep the power system stable by isolating only the components that are

under faults, whilst leaving as much of the network as possible in operation.

Protective relay system detects abnormal condition such as fault in electric

circuit and the circuit breakers will operates automatically to isolate the fault that

occurs in the system as fast as possible. Distance relays are generally used for phase-

fault primary and back-up protection on transmission lines. Distance relay meet the

requirements of reliability and speed needed to protect the circuit.

1.1 Problem Statement

All faults that occur on a power system circuit must be cleared quickly

otherwise it may result in disconnection of customers, loss of stability in the system

and damage to the equipment. Therefore, in order to minimize the damage, suitable

and reliable protection system should be installed on all of the circuit and

equipments. In this project, distance relay is used to detect the fault that occurs.

1.2 Objective

i. To study the principle and application of Distance Relay in Power

System.

ii. To optimize the performance and the effect of Distance Protection

System.

iii. To obtain the optimum settings of the Distance Relay in a transmission

system.

3

1.3 Scope of the Project

The scopes of the project are as the following:

i. The study on the characteristic, operation and performances of Distance

Relay.

ii. The modeling and simulation of Distance Protection System using

PSCAD.

iii. The use of Single Line-to-Ground fault on the system.

1.4 Thesis Outline

This thesis is divided into five chapters. For the first chapter, the introduction

of the project study is covered, followed by the literature review in the second

chapter. The third chapter is the methodology of the study that covers the software

used for the simulation and its related library tools. The result and discussion is in the

fourth chapter. Last but not least, the last chapter provides the conclusion of the

study and the recommendation for future analysis.

CHAPTER 2

LITERATURE REVIEW

2.1 Faults on Power System

Power system fault is a condition or abnormality of a system which involves

the electrical failure of the equipment such as generator, transformer, busbar,

overhead line and cable. The type of fault can be categorized into two types which is

symmetrical fault and asymmetrical fault. Fault occur as single line to ground faults,

line to line faults, double line to ground faults or three phase fault. Each fault has its

own characteristic and condition that make the fault happen. Since any

unsymmetrical fault causes unbalance currents flow in the system, the method of

symmetrical component is very useful in an analysis to determine the currents and

voltages in all parts of the system after the occurrence of the fault [3]. Figure 2.1

shows the network condition when the faults occur.

5

Figure 2.1: The condition of each types of fault

There are many factors that cause the fault to occur in the transmission line.

For instance, the single line-to-earth fault often occurs because of the physical

contact due to lightning. Line-to-line fault will occur by ionization of air or when

line comes into physical contact due to broken insulator. Others examples of

condition that will make the fault occur at the transmission line are [1]:-

a) Lightning strikes on bus bar

b) Collapse of transmission line

c) Accidental short circuit by snake, kite and bird

d) Tree or bamboo touching line

e) Human mistakes.

2.2 Single Line-to-Ground Fault

The single line to ground fault can occur in any of the three phases.

However, it is sufficient to analyze only one of the cases. Looking at the symmetry

6

of the symmetrical component matrix, it is seen that the simplest way to analyze

would be the phase a which is the single line-to-ground fault as shown in Figure 2.2.

Figure 2.2: Single Line-to-Ground Fault

Assuming the generator is initially on no load, the boundary condition at the

fault point is:

V Z I I I 0 1.1

By substituting for Ib = Ic =0, the symmetrical components of the currents is

given as:

III

13

1 1 11 a a1 a a

I00

1.2

The observation from the equation (1.2) is:

I I I I (1.3)

7

The symmetrical voltage components of voltage are given as:

VVV

0E0

Z 0 00 Z 00 0 Z

III

1.4

The phase a voltage is:

V V V V E Z Z Z I (1.5)

The fault current, If can be found by substituting the equations (1.1), (1.3)

and (1.5) as follows:

3Z I E Z Z Z I (1.6)

I I 3I3E

Z Z Z 3Z

The equation can be obtained from the equivalent circuit as shown in Figure

2.3 which shows the connection of sequence network for a single-line-to ground

fault.

8

Figure 2.3: Connection of Sequence Networks for L-G fault

2.3 Principles of distance relays

Distance relay is used on power system network because the relay meets the

requirement of reliability and speed needed to protect the circuit. Distance relays are

preferred to overcurrent relays because they are not nearly so much affected by

changes in short-circuit-current magnitude as overcurrent relays are and hence, they

are much less affected by changes in generating capacity and in system

configuration. This is because distance relays achieve selectivity on the basis of

impedance rather than current.

Distance relay respond to a ratio of the voltage and current at the relay

location. The ratio has the dimensions of impedance between the relay location and

the fault point is proportional to the distance of the fault [3]. Such a relay is

described as a distance relay and is designed to operate only faults occurring between

the relay location and the selected point, thus giving discrimination for faults that

may occur between different line sections.

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2.4 Distance protection scheme

One of the most critical issues in power system protection is the speed with

which a fault can be cleared quickly to prevent from abnormalities of a system.

Distance relays are classified according to polar characteristics, the number of inputs

and the method by which the comparison is made.

The common types compare two input quantities are compared are essentially

either amplitude or phase comparators. Modern static distance relays, based on

single-phase measurement, use phase comparators to produce the required relay

characteristic.

Due to uncertainty in impedance measurements, when protecting a

transmission line with non-pilot distance protection schemes, it is necessary to rely

on stepped zones of protection. This technique protects any given section of

transmission line with multiple zones.

The usual practice in applying distance protection is to install three sets of

distance relays at each relaying point, creating the 3-zone distance protection scheme

as shown in Figure 2.4. The zone 1 relays have the shortest reach and the fastest

operating speed, while zone 2 and zone 3 relays have successively longer reaches

and slower speeds. Zone 2 acts as a back-up for zone 1 and zone 3 acts as a back-up

for zone 1 and 2.

A common arrangement is to make zone 1 and 2 polarised mho and zone 3

offset mho [3]. The first zone tripping which is instantaneous is normally set to 80%

of the protected line detected by zone 1 unit should be cleared immediately without

the need to wait for other device to operate. The zone 2 will cover the remaining

20% portion of the protected section.

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Figure 2.4: 3-Zone distance protection scheme

CHAPTER 3

METHODOLOGY

3.1 PSCAD SOFTWARE

Power System CAD which is known as PSCAD is a powerful and flexible

graphical user interface to the world-renowned, EMTDC solution engine. PSCAD

enables user to schematically construct a circuit, run a simulation, analyze the results

and manage the data in a completely integrated graphical environment. Online

plotting functions, controls and meters are also included so that user can alter system

parameters during a simulation run and view the results directly.

PSCAD comes with a library of pre-programmed and tested models,

ranging from simple passive elements and control functions to more complex

models, such as electric machines, FACTS devices, transmission lines and

cables. If a particular model does not exist, PSCAD provides the flexibility of

building custom models, either by assembling them graphically using existing

models or by utilising an intuitively designed Design Editor.

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3.2 PROCESS OF ANALYSIS

In order to do the research, several steps have to be taken to obtain the

result of the simulation. The process of the research is shown in Figure 3.1

below.

Figure 3.1: Project Flow

3.3 CIRCUIT CONSTRUCTION

In order to do the simulation, the major step that has to be done is the circuit

construction. This is the process where circuit is designed and build up by using the

PSCAD software. By using the PSCAD software, components are selected from the

master library.

13

The master library consists of different types of components such as the

sources, input and output devices, transmission lines and cables. Each component

has the editing feature that enables user to alter the input depends on the appropriate

parameter of the component. Figure 3.2 and Figure 3.3 shows the two circuits that

were constructed in this project, which is the main circuit and relay circuit.

Figure 3.2: Main Circuit

Figure 3.3: Relay Circuit

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The relay circuit shown in Figure 3.3 is constructed by using line-to-ground

impedance, MHO circle component, comparator and gates. Each of the components

is connected together and connects to the circuit breaker in the main circuit. The

relay circuit is used to detect the fault that occurs in the system. Thus, the relay

circuit will give a signal to the breaker so that the breaker will trip the system.

3.4 COMPONENTS

Components are either network components such as resistors, inductors,

capacitors, switches, ac machines, transformers or power electronic devices and it

can also be measurement, control, monitoring functions, signal processing and

outputs. A component is essentially a graphical representation of a device model,

and is the basic building block of circuits created in PSCAD. Component is usually

designed to perform a specific function, and can exist as either electrical, control,

documentary or simply decorative in type.

3.4 1 SOURCE

Figure 3.4: Three Phase Voltage Source

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The three phase voltage source models which is shown in Figure 3.4 is a 3-

phase AC voltage source, where users may specify the positive sequence and zero

sequence source impedances or select an ideal source.

3.4.1.1 CONFIGURATION

The parameters of the voltage source which consist of voltage, base MVA,

frequency and voltage input time constant that is used in this simulation is shown

in Table 3.1.

Table 3.1: Configuration of Voltage Source

PARAMETERS VALUE

Base Voltage (L-L) 230 KV

Base MVA ( 3-PHASE ) 100 MVA

Base Frequency 50 Hz

Voltage Input Time Constant 0.01 Second

3.4.1.2 PARAMETERS

The positive sequence impedance is calculated based on the equation shown

and the parameters used are as stated in Table 3.1. The positive sequence

impedance is important in the setting of the distance protection relay because it is

used to set the radius of the circle.

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Based on the calculation, the value of the positive sequence impedance used in

this project is 53.16 ⎳ 84.3º Ω.

3.4.2 MULTIMETER

Figure 3.5: Multimeter

The Multimeter performs virtually all possible system quantity

measurements, all contained within a single, compact component. The Multimeter

which is shown in Figure 3.5 is inserted in series within the circuit either 3-phase,

single-line or 1-phase.

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3.4.3 TRANSMISSION LINE

Figure 3.6: Transmission Line

As shown in Figure 3.6, the transmission line that is used in this project is the

Bergeron Model, where the impedance or admittance data can be entered directly to

define the transmission corridor. The Bergeron model represents the L and C

elements of a PI section in a distributed manner.

It is accurate on at the specified frequency and is suitable for studies where

the specified frequency load-flow is most important such as in the relay studies. In

this project, the transmission line is set to a distance of 100 Km for both of the

transmission line.

3.4.3.1 PARAMETERS

The parameters that is used in the Bergeron Model is shown in Figure 3.7

where it is copied to the transmission line format in PSCAD system.

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Figure 3.7: Parameters of Bergeron Model

3.4.4 CIRCUIT BREAKER

Figure 3.8: Circuit Breaker

19

The component shown in Figure 3.8 simulates of single-phase circuit breaker

operation. The ON (closed) and OFF (open) resistance of the breaker is specified

along with its initial state. This component is controlled through a named input

signal where the breaker logic is:

• 0 = ON (closed)

• 1 = OFF (open)

3.4.5 FAULT COMPONENT

Figure 3.9: Three Phase Fault

The fault component is used for generating the fault condition. The three

phase fault component which is shown in Figure 3.9 puts a combination of phase to

phase and phase to ground faults to allow any combination of faults to be selected,

even during multiple runs.

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3.4.6 ONLINE FREQUENCY SCANNER

Figure 3.10: Online Fast Fourier Transform (FFT)

Figure 3.10 shows an online Fast Fourier Transform (FFT), which determines

the harmonic magnitude and phase of the input signal as a function of time. The

input signals first sampled before it is decomposed into harmonic constituents.

Options are provided to use one, two or three inputs. In the case of three inputs, the

component provides output in the form of sequence components.

3.4.7 SEQUENCE FILTER

Figure 3.11: Sequence Filter

21

The component shown in Figure 3.11 is a sequence filter which calculates the

magnitudes and phase angles of sequence components when the magnitudes and

phase angles of the phase quantities are given by the FFT component.

3.4.8 LINE TO GROUND IMPEDANCE COMPONENT

Figure 3.12: Line to Ground Impedance Component

The component shown in Figure 3.12 computes the line-to-ground impedance

as seen by a ground impedance relay and the output impedance is in rectangular

format (R and X).

3.4.9 PARAMETERS

The line-to-ground impedance consist of several parameters that needs to be

calculated. The important parameter that is used in this component is the constant for

ground impedance, K.

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3.4.9.1 MAIN DATA

When the distance of the transmission line is set to 100Km, the constant for

ground impedance is calculated as below:

Z1 = (0.36294X10-4

+ J0.5031X10-3

)(100km)

= 50.44 ∟ 85.87º Ω

Z0 = (0.37958X10-3

+J0.13277X10-2

)(100km)

= 138.089 ∟ 74.05º Ω

Therefore:

K =( Z0 - Z1 ) / Z1

= 1.771 ∟ -18.48º

The constant for ground impedance is used in the setting of the line to

ground impedance component to prevent from overreach and underreach.

Without the constant, the relay will cause underreach or overreach in the

system. Thus, the optimum setting of the relay could not be obtained.

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3.4.9.2 INITIALIZING

• Initializing Time = 0.02 Second

• Output R during initialization = 1 x 106Ω

• Output X during initialization = 1 x 106Ω

3.4.10 MHO CIRCLE

Figure 3.13: MHO Circle Component

The Mho Circle component is classified as an ‘Impedance Zone Element’,

which checks whether or not a point described by inputs R and X, lies inside a

specified region on the impedance plane. R and X represent the resistive and reactive

parts of the monitored impedance. The component produces an output '1' if the point

defined by R and X is inside the specified region, otherwise the output will be '0'.

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3.4.10.1 PARAMETER

• Radius of the circle = 50 Ω

• Z coordinate of the centre = 25

• Theta coordinate of the centre = 1.49766[rad]

The Z coordinate of the centre is calculated based on the equation below:

Z = Z1 / 2 = 50 / 2 = 25

3.5 RUN SIMULATION

To run the project, simply click on the Run button in the Main Toolbar.

When this button is pressed, PSCAD will go through several stages of processing the

circuit before starting the simulation. The simulation will run if no error occur in the

circuit that was constructed. If an error occur, the warning will appear and correction

has to be done. The output of the simulation can be seen based on the graphs and also

the measurement of current, voltage and power.

CHAPTER 4

RESULTS AND DISCUSSION

4.1 Introduction

The final accomplishments and results of the project shall be explained in this

chapter. This chapter discusses on the result, analysis and problems that are

encountered throughout the completion of the project. After the development and

completion of the simulation, it will then be evaluated in order to ensure whether it

had met the outlined objectives successfully. By the methodology as discussed in the

previous chapter, this project has made remarkable result and achievement.

Based on the project that had been done, the results are obtained when Single

Line- to-Ground fault occurs at five different locations in the transmission line

circuit. The performance of the distance relay can be seen when the circuit breaker

trips during fault condition. This section will discuss on the performance of the

distance relay at no fault condition and when the Single Line-to-Ground fault occur

at different locations. The discussion will only focus on the phase a fault which is

the blue line in the output waveform that can be seen in Figure 4.1 which indicates

the Single Line-to-Ground fault.

26

4.2: No Fault Condition

At no fault condition, there are no faults that occur in the circuit. Since there

is no fault in the system, the shape of the voltage and current waveform remains

stable for Relay 1 and Relay 2. From Figure 4.1(a), it can be seen that no voltage

drop occur and the value remains the same as the supply voltage which is 230KV.

Similar to the voltage, the current waveform is also stable and constant.

Since the unit measurement for the current is in kilo ampere (kA), the value of the

current is too small until it seems like there is no current at the transmission line

which is shown in figure 4.1(b).

The distance relay does not detect any fault in the transmission line, so the

circuit breaker behaves in a normal condition where it is in a CLOSE condition.

Since there is no detection of fault in the transmission line, no tripping signals were

sent to the breaker and it has been proved by the relay output signal in Figure 4.1(c)

where the outputs are in’0’ condition at all time.

27

(a)

(b)

(c)

Figure 4.1: Waveform at No Fault Condition

(a) Voltage Waveform (b) Current Waveform (c) Breaker Signal

28

4.3: Fault at location 1

Figure 4.2: Fault at Location 1

As shown in Figure 4.3(c) and Figure 4.4(c), when single line-to-ground fault

is applied at location 1 at t = 0.2 s and duration of 0.1 s, both of the circuit breaker is

not affected. It can be seen that the breaker does not trip and the signal is still in ‘0’

condition.

Since the fault occurred at 0.2 second, the voltage of phase a at breaker 1

which is equal to zero because the fault that occurs is bolted fault. The voltage which

is at phase b and phase c has also been affected, where both of the voltage

magnitudes decrease a little bit.

From the waveform of the fault current in figure 4.3(b) and Figure 4.4(b), the

existing current at the transmission line is only the phase a current. The other phase

b and phase c current are equal to zero when the fault occur. By comparing with the

theoretical, when single line-to-ground fault occur, the value of Ib=Ic=0.

Fault Point

29

(a)

(b)

(c)

Figure 4.3: Waveform of Breaker 1 When Fault at Location 1


30

(a)

(b)

(c)



31

4.4 Fault at Location 2


When single line-to-ground fault occur at location 2, the distance relay will

send a tripping signal to circuit breaker 1. The breaker breaks the circuit at 0.22s

after fault occur at 0.2s, so the voltage at transmission line becomes zero. But, when

the fault clears, the breaker will reclose back at 0.3s and transient voltage occur in

few microseconds.

From the voltage waveform shown in Figure 4.6(a), voltage at phase b and

phase c is not stable. It is cleared and goes back to the normal condition at 0.35s.

This is known as the post-fault. For phase a, voltage becomes zero which means that

there is no voltage at phase a when single line-to-ground fault occur.

Figure 4.6(b) shows current waveform when single line-to-ground fault

occurs at location 2. The existing current at the transmission line is only the phase a

current and the other phases current are equal to zero when the fault occur.

Figure 4.7(c) shows the signal of the circuit breaker for relay 2. The signal is

in ‘0’ condition even though fault occurs at location 2. This is due to the voltage and

current value that flows through the circuit when fault occurs. The fault current that

Fault Point

32

flows from source 2 is lower than the fault current that flows from source 1. The

fault voltages at source 2 are higher than the fault voltage at source 1. The values are

difference because of the total impedance of the transmission line between the fault

location and sources. So, the mho circle characteristic does not detect any fault

because of the total value of impedance is higher than inside the specified region.

33

(a)

(b)

(c)



34

(a)

(b)

(c)



35

4.5 Fault at Location 3


When fault occurs at location 3, relay 1 and relay 2 does not detect the fault.

This is because the fault that occurs is out of the protection zone. As discussed

earlier in Chapter 2, distance relay protects the system if fault occurs at about 85% of

the distance of the transmission line. Since the fault occur at 100Km of the

transmission line, both of the relay cannot detect the fault and the breaker signal is in

‘0’ condition.

The voltage waveform for both of the relay is the same. The output can be

seen from the waveform in Figure 4.9 and Figure 4.10. The voltage for phase a

decrease more then voltage of phase b and phase c at 0.2s, which is during the fault

that occur in the transmission line. The current at breaker 2 increase really high

compared to the current at breaker 1, this is due to the fault that occur is near the

breaker 2.

Fault Point

36

(a)

(b)

(c)

Figure 4.9: Waveform of Breaker 1 When Fault Occur at Location 3


37

(a)

(b)

(c)

Figure 4.10: Waveform of Breaker 2 when Fault occur at Location 3


CHAPTER 5

CONCLUSION AND RECOMMENDATION

5.1 Conclusion

This project involved the usage of PSCAD simulation. To understand the

theories for this project, it is important to understand the concept of distance relay type

mho characteristic and the output waveform. PSCAD software is very useful in terms of

obtaining the waveform of the current and voltage fault. It gives similar result with the

theoretical concept. By referring to the waveform are enough to determine the type of

fault without doing the calculation. It makes the user can know the fault in very short

time.

The optimum setting of the distance relay is when the relay does not overreach or

underreach and the relay only operates in its protection zone as required. The

automatically tripping of circuit breaker by using relay system will protect the generator,

transformer and other electrical equipments that is connected to the network.

39

5.2 Recommendation

For further analysis, simulation can be done by considering:

i. Other types of faults that can occur in transmission line such as the double line-

to-ground fault, line-to-line fault and three-phase fault.

ii. Other types of distance relay such as the Apple Characteristic and Lens

Characteristic.

iii. Other types of system such as the parallel transmission line circuit.

40

REFERENCES

1. Hadi Saadat “Power System Analysis” Mc Graw Hill, 2004.

2. Theodore Wildi “Electrical Machines, Drives, And Power Systems” Pearson

Prentice Hall, 2006.

3. Abdullah Asuhaimi Mohd Zin, Md Shah Majid & Faridah Mohd Taha “

Power System Engineering” Fakulti Kejuruteraan Elektrik, 2009.

4. M.Sanaye-Pasand and H. Seyedi “Simulation, Analysis and Setting of

Distance Relays on Double Circuit Transmission Line” Faculty of

Engineering, University of Tehran, Iran.

5. G.E Alexander and J.G Andrichak “Ground Distance Relaying: Problems and

Principles” General Electric Company Malvern, PA, 1991.

6. G.E Alexander and J.G Andrichak “Ground Distance Fundamentals” General

Electric Company Malvern, PA, 1991.

7. M.I. Gilany, O.P. Malik and G.S. Hope “A Digital Protection Technique For

Parallel Transmission Lines Using A Single Relay at Each End”, Transaction

On Power Delivery, Vol 7 No1, January 1992.

APPENDIX A

MAIN CIRCUIT

Figure A1: Main Circuit Connection

OUTPUT CHANNELS

Figure A2: Output Channel Connections

43

APPENDIX B

REALY CIRCUIT

Figure B1: Realy Circuit Connection

44

Figure B2: Sequence module for current

Figure B3: Sequence module for voltage

45

APPENDIX C

BREAKER CONTROL

Figure C1: Breaker Control Circuit

46

APPENDIX D

1. Fault at location 4

Figure D1: Waveform of fault at location 4 for relay 1

47


48

2. Fault at location 5


49


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