Electrical Power Systems

979 Pages·2010·5.94 MB·english

by  C. L. Wadhwa

Electrical
Power
Systems
C L WADHWA
New Academic Science
NEW
ACADEMIC
SCIENCE

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Electrical
Power Systems
C L WADHWA
Former Professor & Head
Electrical Engineering Department
Delhi College of Engineering
Delhi, India
NEW
ACADEMIC
SCIENCE
New Academic Science Limited
The Control Centre, 11 A Little Mount Sion
Tunbridge Wells, Kent TN1 1YS, UK
www.newacademicscience.co.uk • e-mail: [email protected]
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“Electrical Power System” has been written primarily for the undergraduate students in
Electrical Engineering. The book covers conventional topics like the basics of power systems,
line constant calculations, performance of lines, corona, mechanical design of overhead lines
etc., and the more advanced topics like load flows studies, economic load dispatch, optimal
power flows, state estimation in power systems etc. The book covers a very wide spectrum of
electrical power system studies which is normally not available in one single book. The book is
so comprehensibly written that at least five to six courses on power systems can be designed.
It has been the constant endeavour of the author to understand the difficulties of his
students in the classroom and accordingly prepare the lecture notes after consulting various
journals and books on electrical power systems. The present book is an outcome of these notes
and some research work the author carried out.
Chapters 1 to 9 deal into the electrical and mechanical design of overhead and
underground transmission networks. The analysis and performance of the system in terms of
line constant calculations, efficiency and regulations, corona loss and interference of power
lines with communication networks have been studied. A chapter on mechanical design of
lines gives in a nutshell all the important aspects of erection of overhead lines. Chapter 5 on
HVDC transmission discusses combined characteristics of rectifiers and inverters. Various
controls like constant ignition angle, constant extinction angle, and constant currents have
been discussed. Advantages and disadvantages of HVDC vs HVAC have been explained. Also,
the role of HVDC link in improving system stability has been discussed.
Chapter 10 is devoted to the study of voltage-reactive power problems on transmission
lines.
Chapter 11 defines an effectively grounded system, discusses and compares various
systems of neutral grounding.
Chapter 12 describes transients in power systems. Travelling waves on transmission
lines, capacitance switching and lightning phenomenon have been discussed.
Chapter 13 discusses calculation of symmetrical and asymmetrical fault conditions on
the system, concept of infinite bus and short circuit capacity of a bus.
Electric Power System is the most capital intensive and the most complex system ever
developed by man. Not only that the system should be operated most effectively and efficiently,
any abnormality in the operation of the system must be detected fast and reliable operation of
the protective system must be ascertained. Protective relays is the subject of Chapter 14 of the
book wherein various types of relays from conventional electromechanical relays to digital
protective relays have been discussed.
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Chapter 15 presents material on the conventional circuit breakers like air break C.B.,
oil C.B., airblast C.B. etc., and the more advanced ones like the vacuum C.B. and SF circuit
6
breakers.
With the higher and higher operating voltages the impulse insulation levels of the system
are increasing. Chapter 16 is devoted to the insulation problems of the system and the solutions
in terms of coordinating the insulation levels economically of various equipments on the system
have been discussed.
Chapter 17 deals into power system synchronous stability for a single machine connected
to an infinite bus and multi-machine systems. Various techniques have been explained using
algorithms and flow charts.
With the advent of digital computers and modern methods of network solution, it has
now been possible to analyse the present day large interconnected systems with greater accuracy
and short computational effort. Various techniques of load flow solutions of large networks
have been discussed and explained using flow charts in Chapter 18. Various techniques have
been compared in terms of their complexities and computational efforts.
With the advancement in technology of generation and load dispatching it has been
possible to maintain the cost of electrical energy almost same even though the cost of fuel and
other components have multiplied over the years. Chapter 19 on economic load dispatching
discusses some of the classical techniques which even today are being used by the electric
utilities. The techniques have been explained with the help of flow charts, algorithms and
suitable examples.
Chapter 20 deals into the load frequency control or automatic generation control problems
of the system.
The economics of a.c. power transmission has always forced the planning engineers to
transmit as much power as possible through existing transmission lines. The need for higher
index of reliability, the availability of hydro-power over long distances from the load centres,
the difficulty of acquiring right-of-way for new transmission lines (the so-called corridor crisis)
and the increased pressure to maximise the utilisation of both new and existing lines has
helped to motivate the development and application of compensation system. Chapter 21 on
compensation in power system discusses elaborately both the series and shunt compensation
of overhead lines. The concept of FACTS (Flexible A.C. Transmission Systems) has also been
introduced.
The voltage stability also known as load stability is now a major concern in planning
and operation of electric power system. Chapter 22 on power system voltage stability discusses
various factors which lead to this problem and methods to improve the voltage stability of the
system.
State estimation is the process of determining a set of values by making use of the
measurements made from the system and since the measurements may not be precise due to
inherent errors associated with measuring devices, statistical methods have been discussed in
Chapter 23, using the line power flows and maximum likelihood criterion have been discussed
in detail with a number of solved problems. Techniques to detect and identify bad data during
measurements have also been discussed.
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Unit commitment is a way out to suggest just sufficient number of generating units
with sufficient generating capacity to meet a given load demand economically with sufficient
reserve capacity to meet any abnormal operating conditions. This aspect has been nicely dealt
with suitable examples in Chapter 24.
Chapter 25 deals into economic scheduling of hydro-thermal plants and optimal power
flows including the multi-objective optimal power flows.
Appendix A on formulation of bus impedance matrix is given which is very useful for the
analysis of the system, especially for short circuit studies. Power transmission and synchronous
machines as power systems elements have been discussed in Appendices B and C respectively.
A suitable number of problems have been solved to help understand the relevant theory.
At the end of each chapter unsolved problems with their answers have been suggested for
further practice. At the end, a large number of multiple choice questions have been added to
help the reader to test himself. An extensive bibliography will help the reader to locate detailed
information on various topics of his interest.
Any constructive suggestions for the improvement of the book will be gratefully
acknowledged.
Last but not the least, I wish to express my gratitude to my wife Usha, daughter Meenu
and son Sandeep for their patience and encouragement during the preparation of the book.
C.L. WADHWA