Electric Power Distribution

1027 Pages·2012·35.245 MB·English

by  A.S. Pabla

Electric Power
Distribution
Sixth Edition
Electric Power
Distribution
Sixth Edition
Amarjit Singh Pabla
Consulting Engineer
and
Former Chief Engineer
Punjab State Electricity Board
Tata McGraw Hill Education Private Limited
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RAAYCRXCDBXYD
To
My wife Surinder
and
The memory of my parents
Preface to The Sixth Edition
The book has gone through five editions since it was first published in
1981. For the last three decades, the book has been catering solutions to
the problems inherent in the large expanse of electric power distribution.
The fifth edition of the book became very popular and had seen thirteen
re-prints. In addition, McGraw-Hill, New York, published its US
Edition.
Demand for electricity is rising fast, and sub-transmission and
distribution capacity developments need to keep pace. The challenges
of the 21st Century are:
· Rising electricity costs
· Poor reliability and quality of power
· Inseparate/Improper regulatory framework for renewable energy
· Poor quality materials particularly distribution transformers and
energy meters
· Energy inefficiency
· Wasteful expenditure
· Corporate governance deficit
Since the inception of the Electricity Act 2003, the electric utilities are
moving towards unbundled model of generation companies (GENCOs),
transmission companies (TRANSCOs) and distribution companies
(DISCOs). Power markets, energy service companies (ESCOs) and
electricity franchisee (EF) are other emerging entities, which are
expanding fast. Thus, power system planning engineers will have to
achieve sustainability. Dynamic Regulatory Commissions need to be
more pro-active to provide momentum to renewable energy sector and
address the perennial energy deficit. Enlightened centre/state electricity
regulators can study reports, investigate the violations and put penalty if
it occurs.
viii
Preface to the Sixth Edition
Distribution will become more active in the future to deliver maximum
value to consumer. Smart grids will be soon adding consumer values.
Open access will grow. Implementation of best practices will optimise the
financial, human and natural capitals for attaining excellence and
sustainability of electric power distribution system.
In short, the area of electrical power distribution is experiencing
unprecedented change. In the light of this, revision of the book became
essential. In this revised sixth edition, the following chapters have been
added.
Chapter 9—Meter, Billing and Collection: Electricity metering is
undergoing its greatest transformation. Smart metering and billing is
moving closer to full automation, computerisation and smart grid
deployments, promising major energy savings.
Chapter 21—Natural Distribution System: Sustainable distribution
system development is the only future choice. We are to reinvent energy
resources and their use.
The book is enlarged by adding content to different existing chapters.
Numereous examples have been added in different chapters. Real-life
problems are added at the end of each chapter as exercise. Solutions to
these problems are available for download from the Instructors’ Manual
from the website: http://highered.mcgraw-hill.com/sites/0070144559
This book will serve as a valuable reference for working engineers,
regulatory commissions and consultants to find the adequate solutions to
the day-to-day power distribution problems. It will help the students for
active learning.
I am very grateful to Parveen Sharma, Engineering Services Manager,
Metering Information, Integral energy, Sydney, Australia, for very
valuable suggestions and advice on metering. I am thankful to Parwinder
Singh, Executive Engineer, Mobile Metering Testing Unit, Punjab State
Power Corporation Limited, for useful discussions on metering in
service. I am especially thankful to my daughter Kirandeep, who gave
great assistance in typing the manuscript, without which it would have
been difficult to complete the task.
I welcome any comments, corrections and questions. You can contact
me at e-mail: [email protected]
AMARJIT SINGH PABLA
Preface to The First Edition
In India, electric power distribution has been treated mostly on conven-
tional lines. There is no specific book which covers this important sub-
ject comprehensively; although isolated topics have been discussed in
several books and papers. There has been considerable scientific devel-
opment in the field of power generation and transmission but distribu-
tion has yet to be given due attention. I personally feel that there is a
long-felt need for professional engineers and students alike to deal with
electric distribution in an integrated manner.
Outages or failures on the distribution system immediately affect the
consumer. In fact, about 90% of consumer interruptions can be
attributed to the distribution system. In addition, distribution systems
are generally more vulnerable and have less back-up capacity than bulk
power supply systems and generation.
In India, distribution losses vary up to about 75% of the overall system
losses; poor voltage regulation being the usual problem at peak hours.
There are frequent cycles of power shortage, imposing on distribution
restrictions. The average annual load factor at station bus-bars in India
has been low. It is imperative to reduce all these deficiencies for the
general well-being of our society.
It is planned to increase the power generation capacity from 31,000 to
50,000 MW (which is still short of the projected demand) during the
1980-85 period. The Working Group on energy policy of the
Government of India (1979) has projected the minimum peak demand
and installed capacity as 78,000 and 1,10,000 MW respectively for 2000
A.D. The effective installation of the distribution system is essential to
obtain this power capacity.
This book presents an inter-disciplinary approach to give a coherent
working familiarity in the subject for professional engineers in various
electricity boards, electric supply companies, and consultancy and
research groups. It will prove useful to graduate engineers entering the
x
Preface to the First Edition
field, senior undergraduate and postgraduate students in electrical
engineering, giving them a broader and deeper understanding of the
subject. The prerequisite for the study of this book is a preliminary
knowledge of matrices, statistics and probability theory. However,
wherever possible, care has been taken to explain these concepts.
Relevant elements of sub-transmission have also been briefly touched
upon, wherever necessary. The first seven chapters are concerned with
the system and commercial aspects and the remaining nine chapters deal
with technical matters. The various cases are illustrated with practical
examples. A useful bibliography is given at the end of each chapter for
further study and application.
This work has been developed from my working experience in the
Punjab State Electricity Board and the study notes prepared at the
University of New South Wales, Australia. It is but natural that in spite of
best efforts, there may still be some mistakes in the book. I would be
grateful if these are pointed out.
I am greatly indebted to many of my friends for their helpful
discussions in the preparation of the manuscript. I am grateful to
Biccotest Limited, UK for their permission to reproduce the photograph
of the digital cable fault locater, ‘T-233’ and Rural Electrification
Corporation Limited for granting permission to publish certain REC
standard practices. Finally, my particular thanks are due to Punjab State
Electricity Board for permitting me to publish the manuscript.
This book is dedicated to my wife, Surinder, whose constant
encouragement and understanding made this project possible.
A S PABLA
Contents
Preface to the Sixth Edition vii
Preface to the First Edition ix
1. Power System 1
1.1 General Concept 1
1.2 Distribution of Power 4
1.3 Quality of Supply 14
1.4 System Study 15
1.5 Benchmarking 16
1.6 Electricity Reforms 19
1.7 Future Distribution Systems 20
2. Electricity Forecasting 25
2.1 Power Loads 25
2.2 Connected Load 32
2.3 Load Forecasting 39
2.4 Definitions of Some Basic Concepts in Statistics 40
2.5 Regression Analysis 43
2.6 Correlation Theory 49
2.7 Analysis of Time Series 50
2.8 Factors in Power System Loading 54
2.9 Unloading the System 58
2.10 Forecast of System Peak 63
2.11 Strategic Forecasting 65
2.12 Spatial Load Forecasting 66
xii
Contents
2.13 Technological Forecasting 68
2.14 Scenario Planning 70
2.15 Sources of Error: Regulating the Model 74
3. System Planning 78
3.1 Planning Process 78
3.2 Planning Criteria and Standards 87
3.3 System Development 89
3.4 Distributed Generation 94
3.5 Distribution System Economics and Finance 98
3.6 Mapping 102
3.7 Enterprise Resource Planning (ERP) 108
3.8 Modelling 110
3.9 System Calculations 112
3.10 Introductory Methods 114
3.11 Network Elements 121
3.12 Load Flow 126
3.13 Automated Planning 132
3.14 Fault Studies 143
3.15 Effect of Abnormal Loads 151
3.16 Line Circuits 152
3.17 Urban Distribution 154
3.18 Outsourcing 155
4. Design and Operation 162
4.1 Engineering Design 162
4.2 Operation Criteria and Standards 167
4.3 Sub-transmission 170
4.4 Sub-station and Feeder 173
4.5 Low Voltage—Three-phase or Single-phase 181
4.6 Practices 181
4.7 Location of Sectionalizer 185
4.8 Voltage Control 186
4.9 Harmonics 196
4.10 Load Variations 209
4.11 Impact Loading of Transformer 217
4.12 Ferroresonance 218
4.13 System Losses 220
4.14 Energy Management 236
4.15 Model Distribution System 240