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Power Systems Engineering Thesis
2020-05-03
PERFORMANCE IMPROVEMENT OF
SECONDARY DISTTRIBBUTION
SYSTTEM THROUGGH EFFECTIVE
TREATMENT OF REACTIVE POWER
MOLLA, HABTAMU
http://hdl.handle.net/123456789/10798
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BAHIR DAR UNIVERSITY
BAHIR DAR INSTITUTE OF TECHNOLOGY
SCHOOL OF RESEARCH AND POST GRADAUTE STUDIES
FACULTY OF ELECTRICAL AND COMPUTER ENGINEERING
PERFORMANCE IMPROVEMENT OF SECONDARY DISTTRIBBUTION
SYSTTEM THROUGGH EFFECTIVE TREATMENT OF REACTIVE POWER
(Case study -Harar Menschen fur Menschen Foundation Agro-technicaland
Technology College Manufacturing Workshop)
BY
HABTAMU MOLLA FEREDE
OCTOBER, 2017.
BAHIR DAR, ETHIOPIA
PERFORMANCE IMPROVEMENT OF SECONDARY DISTTRIBBUTION
SYSTTEM THROUGGH EFFECTIVE TREATMENT OF REACTIVE POWER
(Case study -Harar Menschen fur Menschen Foundation Agro-technicaland
Technology College manufacturing Workshop)
BY
HABTAMU MOLLA FEREDE
A THESIS
Submitted to the school of Research and Graduate Studies of Bahir Dar Institute of
Technology, BDU in partial fulfillment of the requirements for the Degree of
MASTER OF SCIENCE in Power System Engineering in theFaculty of Electrical and
Computer Engineering.
Advisor:Dr.-Ing. BELACHEW BANTEYIRGA
OCTOBER, 2017
BAHIR DAR, ETHIOPIA
DECLARATION
I, HabtamuMolla, declare that the thesis comprises my own work. In compliance with
internationally accepted practices, I have dually acknowledged and referred all materials used in
this work. I understand that non-adherence to the principles of academic honesty and integrity,
misrepresentation/fabrication of any idea/ data/fact/source will constitute sufficient ground for
disciplinary action by the university and can also evoke penal action from the sources which
have not been properly cited or acknowledged.
HabtamuMolla
10/18/17
Bahir Dar
This thesis has been submitted for examination with my approval as a university advisor.
AdvisorName: Dr.-Ing. BelachewBanteyirga
Advisor's Signature: ________________
2017
HABTAMU MOLLA FEREDE ALL RIGHTS RESERVED
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To my family
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ACKNOWLEDGEMENT
First and foremost, profound gratitude to the Almighty God for the strength and courage he has given
me to complete my courses and the thesis work. Thanks for my advisor, Dr.-Ing. BelachewBantyirgafor
constant monitoring and helpful comments. I have very much enjoyed and benefited from the
intellectual discussions that we had during my course of action. His professionalism, knowledge and
keenness inspired and taught me a lot. Again I thank him for sincere priceless guidance in ameliorating
the challenging situations, support and providing valuable suggestions to improve the content of this
thesis work. I need also to express a sincere and special thank for Prof. Donnchadh Mac Carthaigh
President of MfM-ATTC for his continuous support, comments and constant encouragements given in
doing this thesis. And also, I would like to extend my gratitude to Manufacturing department especially
for their hospitality and cooperation in giving methe required information. AtoTesfaye G/Michael ,head
of the manufacturing work shop in ATTC , who hosted me with great pleasure and exhibiting
enthusiasm to my research work and findings .
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ABSTRACT
This research work is done on the founding hypothetical fact that the lack of adequate treatment of
reactive power generated by the commercial loads at the secondary distribution sub system causes the
continuous overloading effect and leads this particular section to operate in un acceptable efficiency
resulting from the considerable losses. The drawback of implementing power factor correction at the
substations is that the reactive power sustaining in the downstream of the secondary distribution system
being not serviced by those capacitors induces thermal loss. Furthermore the distribution system with
its lower voltages and higher current already accounts for the majority of the power system loss.
This thesis work starts assessing the existing level oftreatmentofreactivepower.Data is collected from
the rating plates of the selected loads of induction motors and measurements making use of suitable
measurement. The main instruments used in this research work are FLUK-125and 8230 power quality
analyzer and industrial scope metersand UNITEST ac clamp meter which are designed to facilitate
research works and conduct continuous assessment to maintain the state of power system A load flow
analysis software ,ETAP ,is also used as analysis tool .
A case study has been made on selected commercial sites which comprises induction motorsheavily
,which are the potential sources of reactive power. As the maximum load demand allowed by EEU
regulation for consumers of commercial area, is limited to a maximum of135 KW per consumers, a 100
Kw load from two commercial areas are taken and also the data of the utility transformer is recorded.
Data analysis has been made and the amount of reactive power generated from two sites of the
commercial loads during operation at their full loadare determined. The aggregate of KVA,KW and
Kvarare determined and the equivalent p.f is calculated as 0.81 . With this result the size of required
capacitor bank to raise the power factor to an economic level of 0.95 is determined . After the
deployment of the capacitor bank all the previous parameters are again recorded.
Finally, data after the placement of the capacitor bank is collected through measurement of KVA,KW
and Kvar and the p.f is again calculated resulting 0.95.The result of measurement and calculation is
compared with the result of the load flow analysis using ETAP software and a conclusion has been
drawn from the research work and possible recommendations are given.
Keyword: Lack ofadequate treatment, reactive power, Commercial loads, secondary distribution
system, power system loss, Overloading effect, capacitor bank.
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TABLE OF CONTENTS
ABSTRACT ................................................................................................................................................. i
ACKNOWLEDGEMENT ......................................................................................................................... iii
TABLE OF CONTENTS ........................................................................................................................... vi
LIST OF FIGURES .................................................................................................................................... x
LIST OF ABBREVIATIONS .................................................................................................................... xi
CHAPTER ONE: INTRODUCTION ......................................................................................................... 1
1.1 Back ground of the study .................................................................................................................. 1
1.2 Statement of the problem ..................................................................................................................... 2
1.3 Objectives .......................................................................................................................................... 3
1.4 Significance of the study ............................................................................................................... 4
1.5 Scope and limitation .......................................................................4Error! Bookmark not defined.
1.6 Structure and content of thesis ........................................................................................................ 5
1.7 Literature Review .............................................................................................................................. 5
CHAPTER TWO: BACKGROUND OF THE DISTRIBUTION NETWORK LOSSES ........................ 11
2.1 Overview of Power system ............................................................................................................. 11
2.2Distribution system .......................................................................................................................... 11
2.3 Technical Losses in Distribution system ......................................................................................... 12
2.4 Energy audit for loss reduction ...................................................................................................... 14
2.5 Performance assessment of secondary distribution system ............................................................. 14
2.5.1 Performance assessment of supply transformer ....................................................................... 15
2.5.2 Performance assessment radial feeders and branches .............................................................. 15
2.6 Improvement of system performance and reduction of losses byreactive Power Compensation. .. 16
2.7 Power factor and power factor correction ....................................................................................... 16
2.7.1 Power factor .............................................................................................................................. 16
vii
2.7.2 Power factor correction ............................................................................................................ 17
2.7.3 Design of the capacitor bank with suitable size ...................................................................... 17
2.7.4 Determination of the suitable location of the capacitor bank ................................................... 18
2.7.5 Static vs.Variable compensation ............................................................................................. 21
2.7.6 Fixed power factor correction for transformers ........................................................................ 22
2.8 Benefits of PF Improvement ........................................................................................................... 23
2.8.1 Reduction Internal Distribution System Losses ....................................................................... 23
2.8.2 Increased Distribution System Capacity .................................................................................. 23
2.8.3 Reduction in Contract Demand ............................................................................................... 23
2.8.4 Enhanced Voltage Profile ......................................................................................................... 24
2.9 Harmonic Distortion and Power Factor Correction ........................................................................ 24
2.9.1 The effects of harmonics .......................................................................................................... 25
2.9.2The Options to Reduce Harmonics: ........................................................................................... 25
CHAPTER THREE:RESEARCH METHODOLOGY ............................................................................ 27
3.1 Introduction ..................................................................................................................................... 27
3.2 Procedures ....................................................................................................................................... 27
3.3 Data collection ................................................................................................................................. 28
3.3.1 From rating plates .................................................................................................................... 28
3.3.2 From measuring instruments .................................................................................................... 30
3.4 Determination of the aggregate of reactive power seen by the supplysystem on the basis of total
100 KW of commercial loads 31
3.5 Determining the size of the required capacitor bank to raise the poweractor to 0.95. ................... 32
3.6 Values after the shunt capacitor bank is deployed. ...................................................................... 32
3.7 Simulation with ETAP software ..................................................................................................... 33
3.7.1 Introduction .............................................................................................................................. 33
3.7.2 Single -Line diagram of the system to be simulated ............................................................... 34
CHAPTER FOUR:RESULTS AND DISCUSSIONS .............................................................................. 35
viii
4.1 Result and discussions on the assessment of the presence of the reactive power in the existing
network.................................................................................................................................................35
4.2 After the introduction of the required capacitor bank to raise the power factor to 0.95 KVA, KW
and total current are found...................................................................................................36
4.3 Compensation at the terminals of a transformer to increase its available power ............................ 37
4.4 Harmonic Management ................................................................................................................... 38
4.5 Load Flow Analysis Result ............................................................................................................. 38
4.6 Comparison between the results of the different methods .............................................................. 41
CHAPTERFIVE :CONCLUSION AND RECOMMENDATION .......................................................... 42
5.1 Conclusion ....................................................................................... Error! Bookmark not defined.
5.2 Recommendation. ............................................................................................................................ 43
REFERENCE ............................................................................................................................................ 44
APPENDEX .............................................................................................................................................. 46
ix
LIST OF TABLES Table 2.5 Nominal KW vs. Required reactive power by the capacitor bank for compensation
(Approximate values specified by the BDEW for individual power factor correction of
motors)....................................................................................................................................14
Table2:6Transformer nominal rating vs. required reactive power by the capacitor bank
Forcompensation ……………………………………………………………………………........19
Table 3.1Rating plate data of motors of commercial area-1.................................................................26
Table 3.2 Rating plate data of different motors of commercial area-2.................................................26
Table 3.3 Rating plate data of the utility transformer ..........................................................................27
Table 3.4 Measured data of the complex power of commercial loads-2 ..............................................27
Table 3.5 Measured data of the complex power of commercial loads-1..............................................28
Table 4.1Measurement results of complex power, current and power factor values of commercial load-
1............................................................................................................................................................. 32
Table 4.2 Measurement results of complex power, current and power factor values of commercial
load-2.......................................................................................................................................................32
Table 4.3 Complex power seen by the supply transformer before compensation
Table 4.4 Complex power seen by the supply transformer after compensation
Table 4.5Simulation result of load flow report before compensation.....................................................36
Table 4.6 Simulation result ,summary of total generation, loading and demandbefore compensation…
..................................................................................................................................................................36
Table 4.7 Simulation result of load flow report after compensation ........................................................37
Table 4.8 Simulation result , summary of total generation, loading and
demand after compensation……………………………………………………………………………...37
Table 4.9 Comparison of measurement and calculation results with simulation results…………...........38
x
LIST OF FIGURES
Figure 1:1 Losses of the currently operating power system of Ethiopia.............................2
Figure 2:1 Functional sections of a distribution system ..............................................8
Figure 2:2 Example relief in transformer loading using power factor correction.............11
Figure 2:3 Performance of distribution system as a function of power factor... ................11
Figure 2:4 Power triangle describing power factor..............................................................13
Figure 2:5 Placement of capacitors in individual power factor correction method............15
Figure 2:6 Placement of capacitors in Group power factor correction power
factor correction method......................................................................................................16
Figure 2:7 Placement of capacitors in central power factor correction method...................16
Figure 2:8 Placement of capacitors in hybridpower factor correction method ................17
Figure 2:9 System capacity vs. power factor of the system ...............................................20
Figure 3:1 Placement of capacitors in individual power factor correction method.............30
Figure 3:2 single line diagram for simulation.......................................................................31
Figure 3:2 graphical representation of the complex power before compensation ...............33
Figure 3:3 graphical representation of the complex power after compensation....................34
xi
LIST OF ABBREVIATIONS
BDEWGerman Federation of Energy and water
COS-1 Inverse of cosine
DTDistribution Transformer
EEU- Ethiopian Electric Utility
ETAP- Electronic Teaching Assistant Program
HT- High Tension
KVA, Kva Kilovolt Ampere
KVAR Kvar Kilovolt ampere reactive
KW, Kw Kilowatt
KWH, Kwh Kilowatt hour
LT- Low Tension
LV- Low Voltage
Pact ,P, P1- Active Power
MUT Machine Under Test
PF Power Factor
Q Reactive power in general/ used for inductive reactive power
Qc Capacitive reactive power
𝜃1and𝜃2 Existing and improved power angles respectively
1
CHAPTER ONE:INTRODUCTION
1.1 Back ground of the study
A distribution system is the interface point between the utility and consumer load. Reactive power
generated from the consumers premise unless treated adequately can cause additional loading in addition
to a real power loading across all the distribution system components such as supply feeders, branches,
transformers and affects the entire system. As distribution loss is because of both the real and the
reactive power losses , the performance improvement endeavor has to be in place in controlling the
reactive power by compensation.Researches indicate that in awell-engineered power system the power
system loss reaches 7% of the total power generated out of which 3.6% is the power loss at the
distribution system[1].Obviously, a section of power system that operates with lesser performance is the
distribution system. Hence, performance improvement of this particular section of a power system
requires more attention. Some of the reasons for power system loss are inadequate size of conductor,
harmonic distortion, overrated distribution transformer, placement of distribution transformer on the
wrong location, unbalanced loading , use of low efficiency transformer, inefficient treatment of
inductive reactive power e.t.c .This research work focuses on the maltreatment of the inductive reactive
power generated from the commercial load.
In Ethiopia the power system suffers from significant amount of power loss(technical and commercial)
that amounts to 23% of the total generated power and the majority of this i.e 18% (which is a technical
loss) is exhibited at the transmission and distribution system and particularly 13% of it is supposed to
be distribution losses*. The growing living condition of the consumers brings about a significant
amount of electrical appliances with poor power factor ranging from 0.35-0.8 . Loads with such poor
power factor are capable of generating significant amount of reactive power that contributes in the
overloading of the distribution system, yet it is underestimated in the commercial area. The currently
workingsubstation based reactive power treatment fails to reach and service the reactive power
generated from the consumer premises such as commercial areas, but the reactive power generated by
industries are managed there at the plant level.The substations are where the utilities reduce the voltage
(usuallygreater than 132KV) from the transmission wires to lower voltages (66KV,45KV,33KV and 15
KV) fordistribution throughout the service area.The voltages are further reduced to the range of 220
volts to 380 volts at the transformers on the utility poles located near the customer premises.
* A bill of reform strategy of Ethiopian Electric Utility ,ByDr.Ing. GetahunMekuria, EEU board director
2
Figure 1:1 Losses of the currently operating power system of Ethiopia
The problem with implementing power factor correction at the substations is that the reactive power
generated from the commercial area and injected tothe distribution system, not serviced by those
capacitors, is inducing thermal losses. Furthermore, the distribution system, with its lower voltages and
higher currents, already accounts for the majority of the losses on the system. In addition, more thermal
losses occur on the customer side of electric meter, within the customer premises across feeders and
branches.
1.2 Statement of the problem
In Ethiopia ,the inadequate capacity on the distribution system is becoming an issue of great
concern.With the growing commercial loads comprising induction machines being left untreated and
under estimated are becoming one of the factors for overloading of distribution transformers and
speeding up them to reach their maximum limit of installed capacity unacceptably .
Recently reports indicate that about 1,029 distribution transformers(SDS)has been damaged with in a
year because of overloading*. This research work attempts to clearly find the level of the involvement
of reactive power overloading, being generated from the commercial loads and injected in to the system,
in the apparent overloading of both the real and reactive loadings.
56.6%Distribution Loss
21.7%Transmission Loss
21.7%Other losses
3
Now days electric power becomes a back bone for every business and nonbusiness endeavors and for the
livelihood of every inhabitant in our country. As a matter of fact, consumers are nowsuffering from the
erratic condition of the power supply. One of the problems is the overloading of the secondary
distribution system components such as the feeders and supply transformer which are the victims of
triggered heat to a damaging level because of overloading effect. The main reason for the continuous
overloading of such expensive transformers is not only the actual amount of power being used or
dissipated in a circuit called true or real power but also the reactive loads such as inductors and
capacitors that dissipate zero power, yet they drop voltage and draw current giving the deceptive
impression that they actually do dissipate power. In our country the power factor correction is done at
the substation where it is out of the reach of the consumer premises[2]. Assuming the level of the
reactive power generation of the residential loads is insignificant but in the case of the commercial and
industrial loads is not. Even though the reactive power generated by industrial loads is supposed to be
corrected at the plant level, there is no power factor correction method employed for the reactive power
generated from commercial premises until now.
Even though the utility company (EEU) has deployed two meters, in the commercial premises, one is for
active power consumption and the other is for reactive power consumption measurement and imposing
rules for the inappropriate utilization of reactive power , yet the system remains under burden because of
the sustaining reactive power.
1.3 Objectives
The main objective of this thesis work is reduction of energy losses in low-voltage distribution
network(SDS). Though reactive power treatment is not a new concept , the goal of this research work is
to provide an evidence for the hypothetical fact that the lack of adequate treatment of reactive power
generated from commercial loads is one of factors that worsens the occurrence of sever overloading
effect on distribution transformers that leads to the complete damage.
The specific objectives
To provide experimentally evidenced proposed about the level of presence of reactive power is
the cause of power loss. As reactive power generated by commercial loads and sustaining longer
period not being serviced in both no-load and full-load conditions.
Also the research work shows the overloading effect of the un serviced reactive power across
the secondary distribution transformer.
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* A bill of reform strategy of Ethiopian Electric Utility ,ByDr.Ing. GetahunMekuria, EEU board director
Recommending and insisting the bodies in charge of this issue for example , for the “Loss
Reduction Analysts “ units recently changed their name as “marketing and research” who are
responsible bodies under EEU that the proposed method as a measure to be taken for
performance improvement in general.
Investigating and identifying the commercial loads which are crucial in generating and injecting
and absorbing the reactive power to the system.
Examining the existing method of power factor correction i.e the substation based PFC, whether
is capable of servicing the reactive power generated or not.
Unveiling the subsequent problems that persists in the power system because of the existence of
un acceptable reactive power and its loading effect.
To aware the stack holders and strongly recommend the concerned bodies to implement the
proposed method to minimize the risk of damage of the expensive transformers and pertinent
switching and control gears.
1.4 Significance of the study
This research work is expected to provide a solution related to the problems of maltreatment of the
reactive power generated by commercial loads such as better performance with releasedcapacity of
distribution transformers and reasonable billing for the customers. The beneficiaries of the proposed
method are both utility company and consumers. Improving the system to an acceptable level of
performance means releasing extra energy by minimizing overloading effect on the system
components and making the system more reliable with increased life span[3] . Also provides a means
that the transformers will not reach to their maximum installed capacity limits with in short period of
time. This also enables the distribution system to accommodate more load making the utility company
more profitable avoiding additional investment.
Since the intervention(intervention of adequate treatment) is done at consumer premise, the consumers
electric bill will be minimized. Under the normal situation the consumers electricity bill includes the
power loss because of the sustaining and untreated reactive power and they are paying the financial
term of the excess reactive power to the utility company.
5
1.5 Scope and Limitation
The study is limited to some commercial loads found in Agro-Technical and Technology College
Manufacturing work shop found in Harer City. But selected loads are the most common loads found in
any part of the country which are categorized as commercial loads by Ethiopian Electric Utility (EEU)
i.e loads from 11KW up to loads with rating < 135 KW max.. On top of this the issues related to
harmonics is not covered in details in this work except highlighting the preliminary solutions in relation
to the introduction of capacitor bank for compensation.
1.6 Structure and content of thesis
The thesis is organized into six chapters which are briefly summarized below.Chapter one presents the
introduction, background and statement of the problem, objectives of the study and methodology
followed in the thesis work. In addition, it provides the outline of the thesis.
The second chapter discusses about the theoretical background and literature review of the study topic,
mainly on electric power loss in distribution system , performance analysis , power loss and reactive
power analysis of secondary distribution system.
Chapter three deals with the basic methods and tools employed in the research work with a clear
outline.In this chapter data from rating plates and from measurements will be used as in puts for further
analysis and also the load flow analysis with ETAP software will be compared with the measured
values.
Chapter four presents result and discussion on the findings .
Chapter five come up with conclusion and recommendation.
1.7 Literature Review
A survey of literature has been made on different journals , articles ,reports and books. The aim of
reviewing related literatures is to ground this research work on the previous works and to reinforce
the attempt of the current loss reduction practices in the distribution system specially in our country.
Following are some of the reviews.
[1]ananthapadmanabha,r prakash,manojkumar pujarand venogopal chaval d.v.,, "a methodology for loss
analysis of secondary power distribution system," Journal of Analysis andComputation, vol. 7, no. 1,
January-june 2011.
6
This paper has developed a methodology to analyze secondary distribution system loss by both detailed
three-phase load flow program and regression power loss model. During the preparation of input data
required the connectivity between distribution systems and customers served has been identified by field
survey by the field test over a period. To obtain the consumer load characteristics more precisely load
pattern of each type of customers has been derived by the field test during the study period. The
purposed method will gives more appropriate result as the analysis is made near to the consumer level
and it better to accompany the power loss based on the demand /energy consumption by a group of
consumer of that particular system rather than the entire consumer connected by all the secondary
distribution system to a primary feeder. The sensitivity analysis of power loss with respect to the feeder
loading and power factor, different type and length of the secondary conductors, connected load has
been performed. The regression power loss models are then derived by the regression technique. By
comparing the computer simulation of feeder loss analysis, the mismatch of feeder loss solved by the
detailed three- phase load flow program and the regression power loss model is within 5%. It is
concluded that the regression power loss models to provide an efficient tool to solve the secondary
distribution loss by only considering the physical structure of network and several key factors which can
be obtained very easily from the available data of AMR system.
[2] M.Mamo, "PRILINIMINARY SURVEY ON ELECTRIC ENERGY EFFICIENCY IN
ETHIOPIA:-AREAS OF INTERVENTION," Journal of EEA, vol. 26, 2009.
This paper has demonstrated that there is a lot to be done to improve the electrical energy efficiency
of our utility and industry. Summery of the paper is given below
Improving energy efficiency can reduce new power plant generation requirements and can
contribute to the effort being exerted to curb the energy shortage we are facing.
Energy efficiency in the utilization process can also reduce the industries’ energy cost and
improve their cost competitiveness in the global market.
Recently, the number of students in electrical power engineering area has been declining
globally, as compared to the computer and communication engineering students. We need to
take appropriate action to secure pool of employees and researchers in electrical power
engineering.
[6] Osama A.Al-Naseem and Ahmed Kh.Adi, "IMPACT OF POWER FACTOR CORRECTION
ON THE ELECTRICAL DISTRIBUTION NETWORK OF Kuwait-A CASE STUDY," The online
7
journalon power and energy(OJPEE), vol. 2, no. 1.
From the cast study on the Switchgear Factory, it has been found that in order to have good
performance for the electricity supply system, it is important to optimize the power factor between
0.9 and 0.95. This will eliminate waste in electrical energy and increase the output without the need
to install additional transformers and cables.
PFC in distribution system will indeed release generation and transmission capacities. Moreover,
due to tightly interconnected nature of the system, the exact benefit due to capacity release in these
areas is quite difficult to compute. Capacity releases in generation and transmission levels is
probably more relevant in compensation studies at these areas and hence are left out from the
economic analysis of capacitors application in distribution system.
Improved power factor result in: a) Released system capacity. b) Improved plant efficiency. c)
Reduced overloading of cables, transformers, switchgear, etc.
The implemented investigation had shown that the capacitor pay itself usually within a couple of
years. The positive impacts of improving the power factor in industrial sector represented in saving
money and in improving the system efficiency.
Recommendations for improving the power factor rates are presented hereunder.
[5] Y.G.Loaena, "Investigation and Minimization of Loss in Distribution System," American Journal of
Electrical Power and Energy System, vol. 5, no. 5, pp. 45-50, 2016.
Study of Reactive power flow, power loss and voltage quality problems of distribution system was made
in this paper. Voltage regulation and voltage unbalance factors at the case study area are within the
recommended limits. Percentage power losses at maximum power transfer for some branch circuits in
the case study area are above the recommended value (1 to 4%). Moreover, the overall percentage loss
in the system is 7.4% of the total power input, which is greater than the recommended loss percentage of
3 to 6% in distribution system. Individual reactive power compensation at these branch circuits saves
annual energy loss of 328.5 MWh.
A reduction in the overall cost of electricity can be achieved by improving the power factor to a more
economic level. The supply will be able to support additional load which may be of benefit for an
expanding company. Reducing the load on distribution network components by power factor
8
improvement will result in an extension of their use. It can also be installed in a shorter period of time
and is not subject to environmental considerations such as shading or weather.
[4] Moshin Mahmood,Om Shivam,Pakkaj Kumar Gopal Krishnan, "Real Time Study on technical loss
in Distribution System," International Journal of Advanced Research in Electrical Electronics
andInstrumentation Engineering, vol. 3, no. 1, February 2014.
In this paper study has been made about the technical and nontechnical losses in distribution system. in
the technical losses the flow of current through cables causes the loss and in non-technical it will be
caused by inaccurate meters, improperly read meters, unauthorized connections as well as administrative
errors. as we see the transformer, its efficiency depends upon the operating load.it has two type of
losses: no-load loss and load loss. no-load loss is also called core loss & it occurs when the transformer
is energized, it does not vary with load. Load loss is called as copper loss & it is the power loss on
primary and secondary windings .we can reduce the losses by locating the transformer closed to the load
centre. The additional energy needs to be produced and transferred to cover the technical losses. By
installing the capacitor bank, resizing of conductors, shortening the distances and by phase balancing,
the losses can be reduced.
[8] R.Suthar, REACTIVE POWER LOSS MINIMIZATION IN RADIAL DISTRIBUTION NETWORK
USING BOFA, Punjab (India).
The thesis work was carried out to minimize the reactive power losses in a 33-bus radial distribution
system. The objective was achieved by allocating capacitor banks at different nodes. Solution was found
in two steps, first was determination of location and then finding optimal size. Location was determined
by VSI and LSF and the size was determined by Bacterial Foraging Algorithm. The results thus obtained
were better as the losses were reduced and the voltage profile also improved.
[9] M.P.razanousky, At Load Power Factor correction,LLC, Newyork, August 2010.
The following conclusion has been drawn from the report.
• The power factor is sufficiently low in all of the environments measured that improving it will result in
a substantial energy savings throughout the entire utility system, when measured in KWH.
While aftermarket devices can be used cost effectively to correct power factor in Industrial and
Commercial buildings and refrigerated vending machines, as a general rule we cannot cost effectively
improve the power factor for existing single family homes in the near term using aftermarket devices. In
9
multi-family buildings, depending on the type of mechanical systems, aftermarket devices can be used to
cost effectively correct power factor. The longer the cooling season, the shorter the return on investment.
In New York City, with many older buildings containing discrete window air conditioners, aftermarket
devices are a viable way to quickly reduce load.
• Power Factor Correction is less expensive to implement that most other “Green Technologies” when
measured in Kilowatts saved per dollar of investment in all types of buildings except single family
homes. It can also be installed in a shorter period of time and is not subject to environmental
considerations such as shading or weather.
• Standards need to be modified so that new buildings are designed with a high power factor and a
balanced load as part of the design criteria. Communication must be improved between utilities and
electrical contractors to ensure that all of the distribution circuits are evenly loaded. Compliance with
power factor requirements and balanced load requirements should be verified prior to a Certificate of
Occupancy being issued.
• Power Factor Correction, when installed at the load, does not significantly increase the amount of
harmonics measured at the utility transformer. Large service entrance correction systems don’t save as
much energy as a system installed at the load and also do increase the level of harmonics on the utility
system.
• Power Factor Correction must be load based and must only operate when needed. Excess capacitance
attached to the utility system can be as detrimental as excess inductance. Furthermore, in the event of a
blackout, the excess capacitance would add extra impedance that would have to be energized, applying
extra load to the system during a restart.
• Standards need to be modified so that new appliances are required to have a high power factor as part
of the design criteria. This is the most cost effective way to reduce energy loss and will save the end user
money within two years of purchasing an appliance.
• Standards need to be modified so that new appliances and other electrical devices to be attached to the
utility have more strict limits on the amount of harmonics that they generate per watt of consumption. In
particular, this will apply to computers, televisions and fluorescent lighting. Harmonics adversely affect
electrical efficiency. Furthermore, harmonic mitigation can be very costly to implement. Harmonics are
more of an issue, relative to load, in the single family home than in all of the other types of buildings
10
that we measured. As a result, harmonic mitigation will greatly help power quality and reduce losses in
single family homes.
In the near term, we can cost effectively correct equipment in the field. During the current recession, the
additional work would create jobs that would yield long term positive benefits for the country. The best
long-term solution is to have the equipment manufactured properly from the outset so that it has a power
factor above 0.97 and a low harmonic discharge. The Department of Energy has to require this as part
of the equipment standards. The energy savings and the reduced utility bill will more than pay for the
increased costs of Implementing the efficiency improvements.
11
CHAPTER TWO: BACKGROUND OF THE DISTRIBUTION NETWORK
LOSSES
This chapter contains the literature review that presents the conceptual frame works of power system
andpower system loss and other the founding facts for this research work. Causes of power system loss
are discussed in general and loss related to maltreatment of the reactive power is explained in particular
and in detail.Reviewing several articles, thesis papers ,journals , Books and so on has been made.
2.1 Overview of Power system
Electrical utility has three functional areas namely generation, transmission and distribution. Electricity
is generated at the generating station by converting a primary source of energy to electrical energy. The
generated power will then be transmitted in a very economic way at a higher voltage level. After a long
journey the voltage level is to be reduced to a distribution voltage levels.The industry doing all these or
any of these business processes, Generation, Transmission and Distribution is termed as Electrical
utility.
2.2Distribution system
In the distribution network there are two main distribution network lines namely, primary distribution
lines and secondary distribution lines . Primary distribution lines feed the HT consumers and
distribution transformers. The distribution transformers feed the low voltage distribution networks
which are the secondary distribution lines. Hence low voltage distribution network (LV network) is the
last link connecting the consumers.
Each of the primary distribution line leaves the sub-station as a three-phase circuit and supplies a
number of distribution transformers. On the secondary side of the distribution transformer, the
Secondary distribution lines are connected. The distribution transformers and secondary distribution
lines are rated to maintain the voltage received by consumers within a prescribed tolerance over the full
range of loading conditions. The secondary distribution network is termed as low voltage distribution
network.
12
Figure 2:1 Functional sections of a distribution system
2.3 Technical Losses in Distribution system
The major amount of losses in a power system is in the primary andsecondary distribution lines; while
transmission and sub-transmission linesaccount for only about 30% of the total losses.Therefore the
primary andsecondary distribution systems must be properly planned to ensure that thelosses are within
acceptable limits. Technical losses on distribution systemsare primarily due to heat dissipation resulting
from current passing throughconductors and from magnetic losses in transformers[4]. Technical losses
occur during transmission and distribution. It involves the Substation, transformer, and line related
losses. These include resistive losses of the primary feeders, the distribution transformer losses (resistive
losses in windings and core losses), resistive losses in secondary network, resistive losses in service
connection wires and losses due to nature of consumer loads.
The major factors responsible for technical losses are stated and described briefly as follows:
The wide expansion of electricity distribution network without considering technical losses has
lead to low voltage distribution over long distance both in urban and rural areas. The electrical
13
utilities are doing this as it is less capital intensive than high voltage distribution. Low quality of
equipment and inadequate maintenance also resulted in frequent breakdown leading to poor
quality of supply to consumers.[5]
Inadequate size of conductors: As stated above, rural loads are usually scattered and generally
fed by radial feeders. The conductor size of these feeders should be adequate.
Too many transformation stages from transmission to low voltage supply resulting in high
transformation losses. Use of low efficiency distribution transformers with transformation losses
of 2-3%. No load losses of distribution transformer are more than the permissible limits due to
poor quality of stampings used in the core. Transformation losses in case of higher efficiency
distribution transformers that use amorphous low-loss steal as core material are less than 1%.
Distribution transformers (DT) are not located at load center on the secondary distribution
System.
Consequently, the farthest consumers obtain an extremely low voltage even though a reasonably
good voltage levels are maintained at the secondary of the transformers. This again leads to
higher line losses. Therefore in order to reduce the voltage drop in the line to the farthest
consumers, the distribution transformer should be located at the load center to keep voltage drop
within permissible limits.
Over-rated distribution transformers and hence their Underutilization studies on distribution
feeders have revealed that often the rating of distribution transformer is much higher than the
maximum kVA demand on the feeder. Over-rated transformers draw unnecessary high iron
losses. In addition to these iron losses, it has additional detrimental effect of high capital cost
locked up. From the above it is clear that therating of distribution transformer should be
judiciously selected to match the low voltage distribution network it is feeding.
Low voltage (less than rated voltage) appearing at transformers and consumers terminals:
Whenever the voltage applied to induction motor varied from rated voltage, its
performance is affected. A reduced voltage in case of induction motor results in higher currents
drawn for the same output. For a voltage drop of 10%, the full load current drawn by the
induction motors increase by about 10% to 15%, the starting torque decreases by nearly 19% and
the line losses in the secondary distribution line of low voltage distribution network increases. As
the bulk load of rural areas and small scale industrial areas consists of induction motors, the line
losses in the concerned distribution systems may even touch 20%. The above situation is
corrected by operating an “on load tap changing” in the power transformers situated at high
voltage sub-stations 66/11 KV sub-stations and providing on the 11 KV feeders a combination of
14
switched capacitors and automatic voltage regulators. Further, the “off-load tap changing” in
distribution transformers is adjusted prior to the commencement of agricultural load season.
Lower Power Factor (PF): In most LT distribution circuits, it is found that the PF ranges from
0.65 to 0.8.
A low PF contributes towards high distribution losses. For a given load, if the PF is low, the
current drawn in high. Consequently, the losses proportional to square of the current will be
more. Thus, line losses owing to the poor PF can be reduced by improving the PF. This can be
done by application of shunt capacitors.
Unbalance is a serious power quality problem, mainly affecting low-voltage distribution
systems. Improper load balancing in all three phases of distribution network is a major
concern increasing the energy losses of low voltage distribution network. Low voltage loads are
usually single-phase, e.g. personal computers or lighting systems, and the balance between
phases is therefore difficult to guarantee. It results in overloading of low voltage distribution
network and low voltage profiles for consumers.[6]
2.4Energy auditfor loss reduction
Improvement of system performance and reduction of losses could be effectively achieved by
conducting an energy audit. The term energy audit is commonly used to describe a broad
spectrum of energy studies ranging from a quick walk-through of a distribution network to
identify major problem areas, to a comprehensive analysis of the implications of alternative
methods sufficient to satisfy the technical and financial criteria of electrical utility.
The energy audit is to be attempted starting with the areas known for excessive losses. The aim
of an energy audit is to:
Assess the overall energy loss in a specified area (sub-station or distribution centre)
Identify system elements causing excessive losses
Identify and establish causes of excessive losses, whether it is due to technical or non-technical
factors.
Segregate technical and non-technical losses
Suggest various measures to reduce losses in cost-effective method and working out the pay back
period, effectiveness, longevity and efficiency of each method.
2.5Performance assessment of secondary distribution system
A secondary distribution system is said to be performing wellif there is a minimum loss across
15
the system .The main issue in distribution systems or rather more appropriately the issue confronting
the power sector as a whole, is the reduction of transmission and distribution (T & D) losses to
acceptable minimum levels.
2.5.1 Performance assessment of supply transformer
The performance of the supply transformer has its own role in the entire performance of the secondary
distribution transformer.
Figure 2:2Example relief in transformer loadingusing power factor correction
2.5.2 Performance assessment radial feeders and branches
The performance of such components of the distribution system, keeping the existing
installation as it, is minimizing the current to the design value by making use of the power factor
correction to an economic level
Figure 2:3 Performance of distribution system as a function of power factor
16
The figure above graphically displays the variation of the I2R losses in feeders and branches. Losses are
expressed in percent as a function of power factor. This indicates that, among several factors that affects
the performance of the distribution system onefactories the reactive power generated from consumer
inductive load.
The performance of secondary distribution system depends solely on thetotal currentdelivered and the
total reactive power absorbed by the systemdetermined by vector addition ofPRresistive power
andPLinductive reactive power.The active power is a portion of complex power that is doing the useful
work being converted to some other form of energy where asthe reactive power doesn’t produce useful
work and it is an additional load for the energy supplier. The parameter that defines the consumption of
reactive power is the power factor.[7]
2.6 Improvement of system performance and reduction of losses by
reactive Power Compensation.
Provision of adequate reactive compensation in various distribution lines is required to improve the
transmission capability as well as reduce system losses substantially. As loss is directly proportional to
square of the current there is 2% reduction in current by providing reactive compensation, this results in
about 4% reduction in losses. LT motive power consumers cannot ensure the working of capacitors even
if they are provided at the time of effecting of connections. It is because of lack of requisite knowledge
and skills to decide the level of compensation and check the availability of capacitors. Thus while
planning the distribution system; such practical problems can be taken care by the power utilities by
providing the LT capacitors on distribution transformers. To overcome the seasonal changing load
demand characteristics it would be worthwhile to provide minimum level of compensation at LT level to
meet the average demand and capacitor allocation for demand above average demand.
2.7 Power factor and power factor correction
2.7.1 Power factor
The power factor of a load, which may be a single power-consuming item, or a number of items (for
example an entire installation), is given by the ratio of P/S i.e. kW divided by kVA at any given
moment. The value of a power factor will range from 0 to 1. If currents and voltages are perfectly
sinusoidal signals, power factor equals cos ϕ. A power factor close to unity means that the reactive
energy is small compared with the active energy, while a low value of power factor indicates the
opposite condition.
Power factor is the ratio of working power to apparent power. It measures how effectively electrical
power is being used. A high power factor signals efficient utilization of electrical power, while a low
17
power factor indicates poor utilization of electrical power. To determine power factor (PF), divide
working power (kW) byapparent power (kVA). In a linear or sinusoidal system, the result is also
referred to as the cosine θ. For example, if you had a boring mill that was operating at 100 kW and the
apparent power consumed was 125 kVA, you would divide100 by 125 and come up with a power factor
of 0.80.
Figure 2:4 Power triangle describing power factor
2.7.2 Power factor correction
The parameter that defines the consumption of reactive power is the power factor.Hence ,by raising the
power factor to the value nearer to unity we can control the presence of the reactive power in the
system. This can be done by introducing a capacitor with suitable size and location in the installation.
2.7.3 Design of the capacitor bank
There two approaches to determine the size of the required capacitor
i. Using calculation
Qc = P1(𝑡𝑎𝑛𝜃1 − 𝑡𝑎𝑛𝜃2)
Where 𝜃1 𝑎𝑛𝑑𝜃2 are power factors of the existing one and the one to be raised to
commonly 0.95, respectively. where𝜃2 𝑖𝑠 cos−1 0.95 𝑎𝑛𝑑 ℎ𝑒𝑛𝑐𝑒 tan 𝜃2 𝑖𝑠 𝑎𝑙𝑤𝑎𝑦𝑠 0.329 .
P1 (kw) represents the active e (electrical) power.
ii. Using standard tables
18
Table 2:5 Nominal KW vs. Required reactive power by the capacitor bank for
compensation(Approximate values specified by the BDEW for individual power factor
correction of motors)
2.7.4 Determination of the suitable location of the capacitor bank
In general the following methods are applicable with their brief pros and cones.
2.7.4.1 Individual power factor correction
Figure 2:5Placement of capacitors in individual power factor correction method
Applications:
To compensate the no-load reactive power of transformers
19
For drives in continuous operation
For drives with long power supply cables or cables whose cross section allows no margin for
error
Advantages:
Reactive power is completely eliminatedfrom the internal power distribution system
Low costs per kvar
Disadvantages:
The PFC system is distributed throughoutthe entire facility
High installation costs
A larger overall capacitor power rating is required as the coincidence factor cannot be taken into
account.
2.7.4.2 Group power factor correction
Applications:
For several inductive consumers provided that these are always operated together
Advantages:
Similar to those for individual power factor correction, but more cost-effective
Figure 2:6Placement of capacitors inGroup power factor correction power factor correction method
Disadvantages:
Only for groups of consumers that are always operated at the same time
20
2.7.4.3 Central power factor correction
Figure 2:7Placement of capacitors in central factor correction method
Applications:
Can always be used where the user’s internal power distribution system is not underdimensioned
Advantages:
Clear-cut, easy-to-monitor concept
Good utilization of installed capacitance
Installation usually relatively simple
Less total installed capacitance, sincethe coincidence factor can be taken intoaccount
Less expensive for power distribution systemstroubled by harmonics, as controlleddevices are
simpler to choke
Disadvantages:
Reactive currents within the user’s internal power distribution system are not reduced
Additional costs for the automatic control system
2.7.4.4 Hybrid power factor correction
Economic considerations often show that it is advantageous to combine the three methods described
above
21
Figure 2:8Placement of capacitors in hybrid factor correction method
2.7.5 Staticvs.Variable compensation
2.7.5.1 Static or fixed Power Factor correction
Compensation on the load side of the AC motor starter (motor switched or "at the load").Fixed
capacitors provide a constant amount of reactive power to an electrical system.Primarily, fixed
capacitors are applied to individual motor loads, but they can also be appliedto the main power bus with
proper treatment. Fixed capacitors are suitable for indoor or outdoor use. Fixed capacitors are available
in low voltages (832 volt and below), from 0.5KVAR up to 400 KVAR (If more than 400 KVAR is
required, smaller units are paralleledtogether).
2.7.5.2 Dynamic or bulk Power Factor correction
Central power factor compensation is applied for electrical systems with fluctuating loads.The central
power factor correction is usually installed at the main power distribution. Thecapacitors are controlled
by a microprocessor-based relay, which continuously monitors thepower factor of the total current
supplied to the distribution board. The relay then connects ordisconnects capacitors to supply
capacitance as needed in a fashion to maintain a powerfactor better than a preset limit (typically 0.95).
Ideally, the power factor should be as close tounity as possible.When harmonic distortion is a concern,
systems are built based on the principles explainedunder ‘Harmonic Distortion and Power Factor
Correction’ later in this paper.
22
2.7.6Fixed power factor correction for transformers
The reactive power absorbed by a transformer cannot be neglected, and can amount to (about) 5% of the
transformer rating when supplying its full load. Compensation can be provided by a bank of capacitors.
In transformers, reactive power is absorbed by both shunt (magnetizing) and series (leakage flux)
reactance. Complete compensation can be provided by a bank of shunt-connected LV capacitors
The utility company regulations for the allowable size of capacitors permanently connected to a
transformer vary according to region. Before installing a PFC system of this type, it is therefore
advisable to consult the utility company concerned.
The modern design of transformer features core laminations that only require a small amount of power
for reversal of magnetization. If the capacitor power rating is too high, overvoltage conditions may
occur during no-load operation.
Table2:10Transformer nominal rating vs. required reactive power by the capacitor bank for
compensation
Figure 2:11Typical transformer with permanent power factor correction
23
2.8 Benefits of PF Improvement
The following are the possible benefits that can be achieved by correcting consumer's PF value
2.8.1 Reduction Internal Distribution System Losses
With active power (kW) held constant, as PF decreases, the required apparent power (kVA) increases.
As a result, the electrical system resistance (I2 R) losses are increased. Although these losses are small
(2.5% to 7.5% of a typical industrial load's yearly energy consumption), the effect is much more
pronounced on a national scale.[8]
2.8.2 Increased Distribution System Capacity
Low PF cuts down distribution system capacity. Similar capacity improvements are possible with
cables, circuit breakers, and other electrical equipment. The capacity of all this equipment to provide
useful power is reduced by low PF. In effect, increasing PF will result in increased capacity in existing
electrical distribution systems. This can help offset or reduce expenses for additional system capacity.
The figure below shows the empirical relationship of system capacity vs. power factor. From the figure
one can see that improving power factor from 0.8 to 0.95 shall release approximately 20% system
capacity.
Figure 2:9 System capacity vs. power factor of the system
2.8.3 Reduction in Contract Demand
The contract demand is the demand that the supplier of electric service agrees to have available for
delivery. According to the tariff structure, increasing the PF may allow the consumer to reduce his
contracted power.
24
2.8.4 Enhanced Voltage Profile
While not a reason in itself for installing PF improvement equipment, better voltage stability is
usually an additional benefit of PFC.
2.9 Harmonic Distortion and Power Factor Correction
The harmonics are the components of a distorted waveform and their use allows to analyze any non-
sinusoidal periodic waveform by decomposing it into several sinusoidal components . Linear loads occur
when the impedance is constant; then the current is proportional to the voltage. Simple loads, composed
of one of the elements do not produce harmonics .Non-linear loads occur when the impedance is not
constant; then the current is not proportional to the voltage. Combinations of the components normally
create non-linear loads and harmonics .With non-linear loads it is extremely difficult to correct for poor
power factor without increasing existing harmonic distortion thereby trading one problem for another.
The simple answer is to treat bothproblems simultaneously. The harmonics lead to a higher capacitor
current, because the higher frequencies are attracted to the capacitor. The impedance of the capacitor
decreases as the frequency increases. If the frequency of such a resonating circuit is close enough to a
harmonic frequency, the resulting circuit amplifies the oscillation and leads to immense over-currents
and over-voltages.
Capacitors themselves do not generate harmonics, but under certain conditions they can amplify existing
harmonics. Necessary precautions must be undertaken when selecting the capacitors. If capacitor is
installed in a circuit with harmonics, normally it should be equipped with 6% series reactor. For circuit
with significant 5th harmonic, it should be equipped with 8% series reactor. For the circuit with 3rd
harmonic, like arc furnace, it should be equipped with 13% series reactor. For the capacitor installed as
non-fixed use, it should be equipped with 6% series reactor. If the capacitor is equipped with reactor, its
rated voltage should beincreased 15% - 20% to insure safety and extend lifetime of capacitor.
To minimize the occurrence of harmonic resonance, the resonant harmonic of the system including the
capacitor should be estimated. The resonant frequency can be calculated by:
ℎ = √𝐾𝑉𝐴𝑠𝑐
𝐾𝑉𝐴𝑅 (2.1)
Where
h = calculated system harmonic
KVAsc = short circuit power of the system
KVAR = rating of the capacitor
25
In three-phase, low voltage systems, harmonic values of 5, 7, 11, 13, 17, 19 etc should beavoided as they
correspond to the characteristic harmonics of non-linear loads. This includesall of the odd harmonics,
except for the multiples of 3. Examples of such devices are variablespeed
and variable-frequency ac drives, dc drives, three-phase power-controlled furnacesand many other types
of industrial equipment.
In single-phase, low-voltage systems, generally exhibit the following harmonics: 3, 5, 7, 9, 11,
13 etc. Note that this includes all of the odd harmonics. Examples of such devices are thoseusually
powered by ‘switch mode power supplies’, which include personal computers,fluorescent lighting, and a
myriad of other equipment found in the modern office. It alsoincludes equipment found in hospitals, TV
and radio stations, and control rooms of largeprocessing plants. The harmonics from these devices are
generally richest at the thirdharmonic and continually decrease as the harmonic number increases.
2.9.1 The effects of harmonics
Harmonic currents (high frequencies) cause eddy currents. Eddy currents circulate in mechanic
components and are caused by the magnetic field of the energized conductor.
Harmonic currents create the skin effect. Due to the skin effect, the impedance of the conductor
is increased by shifting the current flow to the outer layer of the cable. The skin effect increases
with the frequency.
Distortion of the network voltage
Low network quality
Overload / failure / malfunction of consumers
Heating of motors, transformers, capacitors, fuses etc.
Early triggering of power switches
Violation of requirements by the energy supplier
Ripple control receivers are disturbed
Shorter lifespan of illuminants and other equipment
2.9.2The Options to Reduce Harmonics:
should beaddressed through harmonic filtering. Failure to address these harmonic issues may lead
toproblems on the electrical distribution system, such as those detailed above. Active Harmonic
Power Correction Filters is a solution. These sense the critical portions of “dirty” power andinject a
correcting element to clean the power. By truly canceling the harmonic component,the true fundamental
26
becomes the only component that is reflected back to the line.Once identified the resonant harmonics
can be avoided in several ways:
2.9.1.1. Change the applied KVAR to avoid unwanted harmonics
Although this is the least expensive way to avoid resonant harmonics, it is not alwayssuccessful because
typically some portion of the applied KVAR is switched on and off as loadconditions require. The
calculation of system harmonics should be repeated for each level ofcompensation. Adjusting the size of
the capacitor(s) may be necessary to avoid the harmonicvalues.
2.9.1.2Add harmonic filters
In order to filter harmonics at a specific site, tuned harmonic filters can be applied. Acapacitor is
connected in series with an inductor such that the resonant frequency of the filterequals the harmonic to
be eliminated. Tuned filters should never be applied without a detailed
27
CHAPTER THREE: RESEARCH METHODOLOGY
3.1 Introduction
This study makes use of measurement and simulation. All required distribution system parameterssuch
as transformer MVA, %Z, %R,feeder length, feeder(cable)impedance/km, feeder resistance/km and
feeder reactance/km that are necessary for simulation purpose are collected from name plates of
equipment .
In general the methods that will be applied are:-
(a) Literature survey:-To be familiar with the concepts of power system loss, loss reduction strategies
and performance improvement using reactive power treatment, literature review was carried out.
Articles and journals are also reviewed to reinforce the current loss reduction practices of the
distribution system.
(b) Data collection: - from rating plates and measuring instruments.
(c) Existing system analysis and system design: - after assessment and analysisof the existing system
performance, the problems related to the existing poorperformance will be improved, in the context of
this research work, by effective treatment of the reactive power.
Additional data are collected from a credible bodies by a telephone interview
• Conduct a call to those persons which are entitled as “loss reduction analysts “under EEU.
3.2Procedures
1. The primary activity of this research work is to conduct an assessment on the existing performance of
the secondary distribution system as this section accounts for the major system loss because of its
inherent nature. The measuring instruments are deployed for direct measurement of important
parameters such as KW, Kvar and KVA of the individual loads. This will be done on the two separate
sites, but under the supply transformer, of the commercial loads. Hence, individual power factors can
easily be determined.
2. Taking the group compensation architecture the two load groups supplied from separate feeders. The
equivalent KW, Kvar and KVA and power factor for each group is calculated .
3.The size of the required capacitor will be calculated and the result is compared with the standard table
of fig 1.5 approximate values of reactive power required(specified by the BDEW ) for a given KW of
motor.
28
Note: the size of the required bank is calculated assuming the power factor is to be raised to the
economic level of 0.95.
4. Connecting these capacitor banks across the loads at each feeders the new data from new
measurements i.e KW, Kvar and KVA are recorded.
5. The load flow analysis using the ETAP software with version 4.0.0c has been made.
3.3 Data collection
A total of around 100KW load is selected for the assessment study from two different location of the
commercial premises but which are supplied by the same utility transformer. Commercial loads-1 are
motors deployed in various parts of the manufacturing workshop that are selected to conduct this
research work and commercial load-2 are those loads which are connected to the system for flour
milling and high power water pump to the grand reservoir. The relevant data, which are helpful to
determine the aggregate of the reactive power generated and injected in to the secondary distribution
system and the average power factor seen by the utility supply transformer, is given below in table-1.
There additional information based on the operational conditions from the operators aresummarized as
follows.
There are 12 motors out of which 6 of them are lathe machines and the remaining 6 are milling
machines.
All of them are involved in work shop practice for 6hrs./day and an average of 25 hrs./month.
The operation mode is continuous.
Flour grinding mill works for a continuous 2hrs. grinding 10 quintal of Teff.
An average of 40 quintal is grinded per month with a total of 8hrs.
The water pump pumps for 0.75hrs. continuously per day.
It works three times per week and with an average 9.5hrs.per month
3.3.1 From rating plates
Data are first collected from the rating plates attached to the motors.
29
Table 3.1Rating plate data of motors of commercial area-1
No.
Type of loads
From Rating plates
Ir(A) V(v) Pr (KW) P.F
1 Lathe machine-1 19 380 9.3 0.82
2 Lathe machine-2 12.8 380 5.5 0.80
3 Lathe machine-3 12.8 380 5.5 0.80
4 Lathe machine-4 6.2 380 3 0.80
5 Lathe machine-5 10.8 380 5.6 0.83
6 Lathe machine-6 6.2 380 3 0.8
7 Milling machine-1 9.4 380 4.4 0.83
8 Milling machine-2 8.9 380 4.1 0.80
9 Milling machine-3 15.4 380 7.95 0.83
10 Milling machine-4 9.4 380 4.4 0.83
11 Milling machine-5 8.9 380 4.1 0.80
12 Milling machine-6 15.4 380 7.95 0.83
13 Bender machine 4.9 380 2.2 0.82
14 Surface grinder 7.1 380 3 0.80
Total 147 380 0.81
Table 3.2Rating plate data of different motors of commercial area-2
No.
From Rating plates
Ir(A) V(v) Prated (KW) P.F
1 Flour mill 22.6 380 11 0.74
2 Water pump 18.2 380 9 0.86
Total 40.8 0.80
30
Table 3.3Rating plate data of the utility transformer
Primary Secondary
Voltage
(KV)
Current
(A)
Voltage
(V)
Current
( A)
Rating
(KVA)
15 12.12 400 454.7 315
Zsc=3.61
3.3.2 From measuring instruments
The measuring instruments employed in this research work are
FLUK 125 power quality Analyzer and Industrial Scope meter
C.A8230 Power Quality Analyzer
UNITEST AC Clamp Meter 93478(See Appendix)
Necessary connections has been made between the instruments and the motor under test(MUT).
A utility transformer of such type can generate a reactive power determined as follows
From the standard table we can see that to make this transformer efficient it requires a capacitor bank
connected in parallel with a total reactance of 7.5Kvar.
Table 3:4 Measured data of the complex power ofcommercial loads-2
No.
From measurement
Pgross(KVA) Pact(KW) Preact(KVAR)
1 Flour mill 15 11.2 10
2 Water pump 12 10.5 6
Total 27 21.8 16
31
Table 3:5 Measured data of the complex power of commercial loads-1
No.
Type of loads
From measurement Calculated
Power Factor
Pgross(Kva)
Pact(Kw)
Preact(KVar)
1 Lathe machine-1 11.9 10.3 7.2 0.82
2 Lathe machine-2 8.4 6.7 5 0.79
3 Lathe machine-3 8.4 6.7 5 0.79
4 Lathe machine-4 4.1 3.2 2.4 0.78
5 Lathe machine-5 7.1 5.9 4.1 0.83
6 Lathe machine-6 4.1 3.2 2.4 0.78
7 Milling machine-1 6.2 5.1 3.6 0.82
8 Milling machine-2 5.9 4.7 3.5 0.80
9 Milling machine-3 10.1 8.4 5.9 0.83
10 Milling machine-4 6.2 5.1 3.6 0.82
11 Milling machine-5 5.9 4.7 3.5 0.80
12 Milling machine-6 10.1 8.4 5.9 0.83
13 Bender machine 3.2 2.6 1.7 0.81
14 Surface grinder 4.7 3.8 2.8 0.80
Total 97.4 78.8 56.6 0.81
3.4 Determination of the aggregate of reactive power seen by the supply
system on the basis of total 100 KW of commercial loads.
Since one of the goals of this research work is to conduct an assessment on the level of maltreatment of
reactive power in the secondary distribution system ,we can see that based on the 78.8-KW commercial
load, the 56.6kvar reactive load and the power factor of approximately 0.81 in the first case and based
on the 21.8-KW commercial load, the 16-Kvar reactive load with the power factor of approximately
0.80 in the second case is observed. Totally based on the 100-KW load more than 72.6 Kvar is generated
with an average power factor of 0.81 is seen by the secondary distribution system.
32
3.5 Determining the size of the required capacitor bank to raise the power
factor to 0.95.
Note: The existing power factor is already determined as 0.80 from the measurement of the total KVA
and Kvarvalues , as depicted Table 3:5.
Two ways can help us to perform this task.
Using the standard formula
𝑄𝑐 = 𝑃1 (tan 𝜃1-tan 𝜃2) (3.1)
Where 𝜃1 𝑎𝑛𝑑 𝜃2 are power factors of the existing one and the one to be raised to
commonly 0.95, respectively. where𝜃2 𝑖𝑠 (cos−1 0.95) 𝑎𝑛𝑑 ℎ𝑒𝑛𝑐𝑒 tan 𝜃2 𝑖𝑠 𝑎𝑙𝑤𝑎𝑦𝑠 0.329 . P1 (kw)
represents the active (electrical) power.
i) For commercial area-1 Using group compensation method
Using calculation
Total KW= 78.8 at equivalent power factor of 0.81=𝜃1 , to raise the power factor to 0.95=𝜃2
Hence, 𝑄𝑐 = 𝑃1 (tan 𝜃1-tan 𝜃2)
= 78.8(0.72- 0.33)
= 30Kvar
Using standard tables( See table 2-10)
35-40% of the KW power = 31 Kvar
ii) For commercial area-2
Using calculation
Total KW= 21.6 with equivalent power factor of 0.8 =𝜃1 , to raise the power factor to 0.95=𝜃2
Hence, 𝑄𝑐 = 𝑃1 (tan 𝜃1-tan 𝜃2)
=21.8(0.75- 0.33)
=9.3Kvar
Using standard tables( See table 2-10)
10 Kvar approximately
3.6 Values after the shunt capacitor bank is deployed.
For commercial load-1
𝑃𝑔𝑟𝑜𝑠𝑠 =𝑃𝑎𝑐𝑡𝑖𝑣𝑒
𝑃.𝐹𝑛𝑒𝑤 (3.2)
= 78.8 /0.95
= 83 KVA
33
Henc, the gross current can be determined as
Igross =83KVA / √3*380 = 126A
From commercial load-2
𝑃𝑔𝑟𝑜𝑠𝑠 =𝑃𝑎𝑐𝑡𝑖𝑣𝑒
𝑃.𝐹𝑛𝑒𝑤
= 21.6 /0.95
= 22.74 KVA
Igross =22.74 KVA / √3*380 = 34.5 A
3.7 Simulation with ETAP software
3.7.1 Introduction
As technological advancements have been made, we are now able to design our experiments in a better
manner. One such advancement is the usage of simulation in the case we can’t conduct the practical
experiment.
Though this research work can readily be done by measurement and calculation only, using the load
Flow software increases the credibility of the research work.A comparison between the result of the
simulation and results from measurement and calculation has been made.
The preferred placement of the capacitor banks is given in the figure belowfor the reasons described in
the literature review. The following method of individual compensation is preferred by first grouping
similar machineries which are starting and stopping at the same time.
Figure 3:1 Placement of capacitors in individual power factor correction method
34
The loads are rearranged in the following manner. The six Lathe machines are taken as a single unit and
six milling machines are categorized as a single unit. The remaining two and the two machines from
commercial area-2 are taken separately. Hence the single line diagram for load flow analysis looks the
following.
3.7.2 Single -Line diagram of the system to be simulated
Figure 3:2single line diagram for simulation
35
CHAPTER FOUR:RESULTS AND DISCUSSIONS
4.1 Result and discussions on the assessment of the presence of the
reactive power in the existing network.
Table 4.1Measurement results of complex power ,current and pf values of commercial load-1
No. Type of loads
Pgross(KVA)
Pact(KW)
Preac(KVAR)
Ir(A)
P.F
1 Lathe machine-1 12.5 10.3 7.2 19 0.82
2 Lathe machine-2 8.4 6.7 5 12.8 0.80
3 Lathe machine-3 8.4 6.7 5 12.8 0.80
4 Lathe machine-4 4.1 3.2 2.4 6.2 0.80
5 Lathe machine-5 7.1 5.9 4.1 10.8 0.83
6 Lathe machine-6 4.1 3.2 2.4 6.2 0.8
7 Milling machine-1 6.2 5.1 3.6 9.4 0.83
8 Milling machine-2 5.9 4.7 3.5 8.9 0.80
9 Milling machine-3 10.1 8.4 5.9 15.4 0.83
10 Milling machine-4 6.2 5.1 3.6 9.4 0.83
11 Milling machine-5 5.9 4.7 3.5 8.9 0.80
12 Milling machine-6 10.1 8.4 5.9 15.4 0.83
13 Bender machine 3.2 2.6 1.7 4.9 0.82
14 Surface grinder 4.7 3.8 2.8 7.1 0.80
Total 96.9 78.8 56.6 147 0.81
Table 4.2 Measurement results of complex power ,current and pf values of commercial load-2
No. Type of
loads
Pgross(KVA) Pact(KW) Preact(KVAR) Ir(A) P.F
1 Flour mill 15 11.2 10 22.6 0.74
2 Water pump 12 10.5 6 18.2 0.86
Total 27 21.8 16 40.8 0.80
From the above assessment the aggregate of the complex power seen by the supply system is
36
Table 4.3 Complex power seen by the supply transformer before compensation
KVA KW KVar P.f Igross
124 100 75 0.80 189
Figure 3:2graphical representation of the complex powerbefore compensation
From the value of the average power factor one can conclude that there is a significant amount or
reactive power persists in the system and the maltreatment of the reactive power is visible. A reactive
power is said to be effectively treated if and only if the power factor is nearer to unity i,e most
commonly 0.95 .
4.2 After the introduction of the required capacitor bank to raise the
power factor to 0.95 KVA, KW and total current are found
From the empirical evidences one can easily understand that result indicates the application of the
proposed method ,at the commercial premises, enables to save 124KVA- 105KVA= 19KVA. If this is
expressed in percentage 15.32% of the total capacity of the supply transformer can be released
producing a reduction of current through the feeders and branches by (189-160= 29) approximately the
same percentage as the KVA. This reduction in current will result lesser losses across feeders and
branches as thermal effect of heat is proportional to the square of the current .
0
20
40
60
80
100
120
140
KVA KW Kvar
124 100 75
37
Table 4.4Complex power seen by the supply transformer after compensation
KVA KW KVar P.f Igross
105.7 100 33 0.95 160
Figure 3:3graphical representation of the complex powerafter compensation
4.3 Compensation at the terminals of a transformer to increase its available
power
The active power available on the secondary of a transformer is all the higher the greater the power
factor of its load. Consequently, to provide for future extensions, or even when an extension is being
added, it is advisable to increase the power factor to avoid having to purchase a new transformer.
A transformer used in this research work has a power of S = 315 KVA and supplies a load with an
active power of P 1 =100 Kw with an average power factor equal to 0.8.
Let us determine:
- the apparent power S1=100/0.8= 125KVA
- the reactive power Q12= S1
2-P12= 1252-1002=75Kvar
Let as assume planned extension requires an extra active power of P2=150kW with average power
factor of 0. 7 .Let us deduce from this the characteristics of this extra power:
- apparent power S2 = 150/0.7= 214kVA
- reactive power Q2 = S22- P2
2 =2142-1502= 152 Kvar
Without compensation, the apparent power at the terminals of the transformer would be:
0
20
40
60
80
100
120
KVA KW Kvar
106 100 33
38
125KVA+214KVA=339KVA which is beyond the capacity hence to be replaced
by another transformer with greater capacity.
Let us determine the minimum power of the capacitors enabling the replacement of the transformer to be
avoided.
The total active power to be supplied is:
P = P1+P2 =100 KW +150KW =250KW
For P= 250KW the maximum reactive power that the 315 KVA can supply is
Qm2= S2- P2 = 3152-2502 = 192 Kvar
The total reactive power supplied to the load before compensation is
Q1+Q2 = 75Kvar +152 Kvar =227 Kvar
The required reactive power supplied by the capacitor bank can be determined as
Qc =227 Kvar - 192Kvar = 35Kvar
We thus obtain a power factor of 250/ 315=0.8
It would be possible to carry out total compensation of power factor =0.95, which would lead to a
power reserve of 315 - 250 = 65 kW; the capacitor bank to be installed would thus be 93kvar. We notice
that total compensation would require a considerable amount of capacitors to be installed for little gain
on the active power available.
4.4 Harmonic Management
Though capacitors are not the very causes of harmonics but they are capable of amplifying the existing
harmonics in the system. Hence, compensation capacitors should be with detuned filters to avoid the
magnification of harmonics.
4.5Load Flow Analysis Result
Load Flow Studies using ETAP software is an excellent tool for system planning. A number of
operating procedures can be analyzed such as the loss of generator, a transmission line, a transformer
or a load. Load flow studies can be used to determine the optimum size and location of capacitors. Load
flow studies determine whether equipment such as transformers and conductors are overloaded. The
main purpose of load flow analysis is to determine the voltage magnitude and angle at bus bars, to
determine the active and reactive power flows through the network components and to determine the
power loss in the network components and entire system. Based on the above mentioned factsfollowing
is the summery of the load flow analysis done using ETAP software version 4.0.0c.
39
a. Before compensation is made Table 4.5Simulation result of load flow report before compensation
Table 4.6Simulation result ,summary of total generation, loading and demand before compensation
40
b. After the compensation is done
Table 4.7 Simulation result of load flow report after compensation
Table 4.8 Simulation result , summary of total generation, loading and demand after compensation
Power Loss: Power loss refers to waste energy along the feeders as a result of current flow. Loss along
distribution lines/cables and distribution transformers, is obtained as the difference of power entering the
line/cable/transformer and leaving the lines/cables/transformer.
41
4.6 Comparison between the results of the different methods
Table 4.9 Comparison of measurement and calculation results with simulation results
Sessions
From Measurement and Calculation
Simulation Result
Before compensation
KVA 124 129
KW 100 108
KVAR 72 66
Itotal 188 185
P.F 0.80 0.85
After compensation
KVA 105
108
KW 100 108
KVAR 32 27
Itotal 160 155
P.F 0.95 99.8
Note :Loss during simulation was recorded as 3.16 KVA before compensation and 2KVA after
compensation.
These results indicates that a total of 21KVA capacity can be released by effective treatment which
is 16% of the supply transformer capacity that can be released with a substantial amount of current
reduction with the same percentage as the released capacity i.e the current reduction is 30A.This 16%
reduction in gross current will result in almost 32% of thermal loss in the system.
42
CHAPTERFIVE:CONCLUSION AND RECOMMENDATION
5.1 Conclusion
Based on the tangible outcomes of this research work one can draw a conclusion about the benefits of
the proposed method from the following four perspectives.
i. Reductionin internal distribution system losses
Raising the power factor from 0.80 to 0.95, as it is seen in this research work, enabled to reduce the
apparent power by 21KVA , i.e 17% of the apparent power before compensation. This results in the
reduction of the gross current by the same percentage. The reduction in current result in the reduction of
the loss significantly.
Note: A total of 21KVA released refers only on the basis of 100KW@ a p.f = 0.80 load . The size of the
released KVA depends on the actual KW rating of load and the corresponding average power factor.
ii. Increased Distribution System Capacity
Low PF cuts down distribution system capacity. The capacity of the secondary distribution transformer
used in this research work is 315 KVA. On the base of 250KW at average power factor of 0.80 the
required capacity of the supply transformer could have been 339 KVA. The supply transformer under
normal circumstance should be replaced by the one with higher KVA.
The deployment of a capacitor bank with a size of 35 KVar near the commercial premises helps the
existing transformer to accommodate the connected load by increasing its capacity. Similar capacity
improvements are possible with cables, circuit breakers, and other electrical equipment. The capacity of
all this equipment to provide useful power is reduced by low PF. In effect, increasing PF will result in
increased capacity in existing electrical distribution systems. This can help offset or reduce expenses for
additional system capacity..
In general this research work has demonstrated that there is a lot to be done to improve the electrical
energy efficiency of our utility using effective treatment reactive power and freeing the system from un
acceptable loading effect from the commercial loads. Improving energy efficiency can reduce new
power plant generation requirements and can contribute to the effort being exerted to curb the energy
shortage we are facing at the distribution system level. It is inevitable that the growing socio-economic
activities in the commercial area with an increasing use of electrical loads of poor power factors can
cause capacity problems. Since the issue of the capacity of transformers is the issue of over loading
which is the aggregate of both real and reactive power loading ,this research work focus on the reactive
power loading .As our county's power factor correction method is primary substation based , it fails to
43
reach and service the reactive power in the commercial premises. Therefore improving the PFC method
by incorporating the suitable size of a capacitor bank at the proper location nearer to the commercial
premises relives the problem related to the reactive power loading enables to achieve a solution for the
existing problem. This without being mitigated, causes a continuous overloading and the system
continues under stress.
5.2 Recommendation.
The problem of overloading on distribution transformers is related to both active and reactive power
overloading. Loss reduction technique related to the reactive power loading is quite different from loss
reduction related to active power loading in that power factor correction or effective treatment is the
only economic option in the former case. The power factor correction should be done at various location
in the power system depending on the required goal. As a matter of fact, the reactive power treatment
method in the currently operating power system of our country is limited at the substation site only.
This has a serious consequences in that the freely oscillating reactive power between the load and the
substation downstream supply systems , is becoming an additional burden. This cannot be
underestimated in the case of the commercial load of the commercial premises which comprises
inductive loads predominantly.
Hence, I strongly recommend that the placement of power factor capacitors nearer to the commercial
premises for adequate treatment of the reactive power will minimize the possibility of the occurrence of
overloading of transformers to a damaging level and increases the transformers period of reaching the
limit of the installed capacity.
44
REFERENCE
[1] ANANTHAPADMANABHA,R PRAKASH,MANOJKUMAR PUJARand VENOGOPAL
CHAVAL D.V.,, "A METHODOLOGY FOR LOSS ANALYSIS OF SECONDARY POWER
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[2] M.Mamo, "PRILINIMINARY SURVEY ON ELECTRIC ENERGY EFFICIENCY IN
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Technology,control and Automation(IJITCA), vol. 4, no. 2, April 2014.
[12] Gaurav Kumar Vanamali,Vinod Vishwakarma, "Power Factor correction in Distribution System
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46
APPENDEX
Major instruments employed in the research work
FLUK 125 power quality Analyzer and Industrial Scope meter
47
C.A8230 Power Quality Analyzer
48
C.A8230 Power Quality Analyzer display
49
UNITEST AC Clamp Meter 93478
50
