Table Of ContentHANDBOOK OF
SWITCHGEARS
HANDBOOK OF
SWITCHGEARS
BHEL
Bharat Heavy Electricals Limited
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FOREWORD
It gives me immense pleasure to be writing the Foreword to this book.
Bharat Heavy Electrical Limited (BHEL) is the largest engineering and manufacturing enter-
prise of its kind in India, and one of the leading international companies in the field of power
equipment manufacturing. BHEL started manufacturing switchgears in 1961 and has since made
significant strides in the field. In this book, efforts have been made to reflect and put forward the
vast experience and expertise gained by BHEL over these 44 years. The book fulfils the long felt
need of practicing power engineers, who had otherwise to refer to several articles to solve their
various queries on switchgear design, application, and protection. It makes clear that the choice
and use of switchgear is far from standard, and that a thorough knowledge of the matter is a
must.
I personally find this book, brought out by one of the leading organisations in the switchgear
manufacturing industry in India, informative, exhaustive, and practical in its approach.
The book covers not only the general concepts but also provides consolidated information on
switchgears in the context of Indian conditions. This approach is beneficial for the utilities practis-
ing engineers. Starting from the basics, it enables even engineering students to understand the
subject. The topics of each chapter have been skillfully selected and cover all aspects of switchgears.
I sincerely hope that this book will serve as a useful reference, not only to practicing switchgear
engineers but also to institutions and academicians.
I wish all success to this publication.
Prof. Dr. René Peter Paul Smeets
KEMA High-Power Laboratories
The Netherlands
PREFACE
Switchgear is an important link in any power system network, including transmission and distri-
bution systems. These days, increased emphasis is being given to designing the best possible
switchgear and associated equipment system. This book aims to provide a holistic view of all the
aspects of switchgear, and highlights the role it plays alongwith its associated systems, in the
control and regulation of power flow in power system network.
Bharat Heavy Electricals Ltd (BHEL) is a pioneer in the switchgear industry having more than
40 years experience with various circuit breaker technologies. This book is the collective effort of
22 experts from BHEL, a leading switchgear manufacturer in India.
Chapter 1 explains comprehensively the technological aspects of medium and high voltage
circuit breakers ranging from 3.3 kV to 800 kV class and also the comparison of various switching
technologies. The arcing phenomenon has been discussed in detail to explain and establish the
superiority of the technology. Different types of operating mechanisms, viz. spring, pneumatic,
hydraulic, electrical and magnetic have been elaborated along with their relative advantages and
disadvantages. It is rare to find all these details in one place in a consolidated manner and as such
serves as very useful information for practising engineers and learners.
The requirements of conventional low voltage switchgear and emerging trends for various
applications have been briefly brought out in Chapter 2.
Chapter 3 deals elaborately with medium voltage switchgears rated from 3.3 kV to 33 kV class
and provides information about various forms of construction in metal enclosed, metal clad and
porcelain clad design. To bring more clarity on constructional aspects, the definition of various
terms have been taken from relevant IEC and IS. Present and future trends in medium voltage
switchgears have also been explained.
High voltage circuit breaker ranging from 66 kV to 800 kV class have been covered in
Chapter 4. This elaborates on the historical background, present status and future outlook of
technological developments. The chapter also provides insight into various interrupting media
like air, oil and SF6 gas. The latest trends in the design of SF6 gas circuit breakers and operating
mechanisms are discussed.
Since the information available on GIS is mostly with reference to global conditions, efforts
have been made in Chapter 5 to provide details relevant to the Indian environment with reference
to material availability, operating conditions at site and conditions in Indian industry.
viii Preface
Chapter 6 is entirely devoted to establish usefulness of auto-reclosers and sectionalisers. The
case study on auto-reclosers clearly highlights the great potential this product has for rural elec-
trification and power distribution to important load centres in India.
The theory, design and constructional aspects of instruments transformer along with applica-
tion and testing requirements have been fully covered in Chapter 7. The details of instruments
transformer testing and analysis of testing results along with standardisation and cost considera-
tions have been provided based on BHEL experience and expertise gathered during long associa-
tion with switchgears.
Chapter 8 narrates various types of surge arresters, their characteristics, construction and
application aspects. The details of experimental study in the use of combinations of surge protec-
tion devices forms very useful information for all practicing engineers.
The basics of various relay technologies have been dealt with in Chapter 9. The cost compari-
son of numerical relay with electromechanical and static relay and their advantages are covered
in this chapter. This information is useful for learners in protection field.
Chapter 10 strives to explain various aspects of application of medium voltage switchgear and
highlights the considerations for selection of suitable circuit breakers for different applications.
The details given are based on BHELs rich experience in the field of switchgears.
Energy metering, as covered in Chapter 11, emphasises the features of modern static meters
and state-of-the-art technology which BHEL has adopted in many prestigious power projects.
Chapter 12 traces a variety of control and interlocking schemes used in medium voltage
switchgear which are mostly application specific. These schemes are based on experience gath-
ered by BHEL over a period of time.
Protection schemes for medium voltage switchgears have been dealt with in Chapter 13 and
cover all protection aspects. The details are expected to provide an insight to beginners and
students of protection philosophy.
Chapter 14 deals with generator protection for large generators rated 500 MW and above. The
details regarding classification of tripping and grouping of protection is the result of extensive
experience and expertise gained by BHEL in the manufacturing of large generators and their
protection systems.
Information on EHV transmission system control and protection is provided in Chapter 15,
fully based on the latest practices in manufacturing of control and relay panels for switchyard
projects up to 400 kV class.
Chapter 16 covers the basics of integrated protection and control system for sub-station and is
based on experience gained during the development of numerical protective relays and SCADA
system at corporate R&D unit of BHEL.
Chapter 17 captures the erection and commission requirements of switchgear. All aspects
regarding requirements and precautions for erection and commissioning of indoor and outdoor
switchgear for satisfactory performance have been covered in this chapter.
The operation and maintenance aspects of switchgear under various conditions have been
covered in Chapter 18. It provides useful information about the dos and donts to be followed
during site work, inspection and on maintenance procedures.
Preface ix
The performance of a switchgear under normal/abnormal conditions is verified by subjecting
it to different type of tests as per the guidelines laid down in national/international standards.
Chapter 19 briefly covers the significance and procedures used for different tests with as many
practical cases as possible.
Chapter 20 is a compilation of details of all major standard organisations and various applica-
ble standards for switchgear products. This serves as readily available information for practising
engineers.
The details regarding statutory requirements and electricity rules covered under Chapter 21
provides necessary guidelines to switchgear designers and site engineers to ensure safety of
personnel and property.
The book reflects the expertise gained by BHEL in the field of switchgears and offers a wide
and thorough coverage. The work here is informative as it follows a practical approach and
highlights all salient features of switchgear. I am confident that the book will serve as a useful
reference for all practising engineers and students.
P.T. Deo
Executive Director
BHEL, Bhopal
ACKNOWLEDGEMENTS
We acknowledge with thanks the permission given by the management of Bharat Heavy Electricals
Ltd. (BHEL) for publishing this book.
This book is a result of collective effort of experts in the field of switchgears at BHEL, a leading
switchgear manufacturer in India. Thanks are due to all the authors who took pains and contrib-
uted chapters to it.
Selecting the chapters to cover various aspects in detail and at the same time integrating the
entire material and presenting it as a homogenous whole was an uphill task. Our grateful thanks
are due to Shri S G Dehspande, an editorial committee member, who put in exemplary and
untiring efforts without which this book could not have taken shape.
We would like to extend our sincere thanks to Prof. Dr Rene Peter Paul Smeets, KEMA High
Power Laboratories, The Netherlands for his Foreword and Shri P T Deo, Executive Director,
BHEL Bhopal for his Preface to this book.
Thanks are also due to Tata McGraw-Hill for publishing this book.
R K Shukla
Chief (Switchgear Engineering),
BHEL, Bhopal
EDITORIAL COMMITTEE
Shri R K Shukla, Chief (Switchgear Engineering), has eight years
experience in transformer and tap changer design, plus 25 years in
switchgear design and development. He holds a BE in Electrical from
Ravishankar Shukla Technology, Raipur.
Shri Indrapal, Additional General Manager, has 30 years experience in
LV and MV switchgears. He holds a BSc Engg (Electrical) from Aligarh
University.
Shri S G Deshpande, Sr. Dy. General Manager, has 32 years experience
in design of control and protection for power system application. He
holds a BE Electrical from Devi Ahilya University, Indore.
CONTRIBUTORS
H S Jain, Addl. General Manager, has 30 years experience in
development of switchgear and gas insulated power equipment at Corp.
R&D. He has a BE Electrical from Jiwaji University, Gwalior, and a Ph D
from IIT, Bombay.
M P Soni, Addl. General Manager, has worked for 28 years in R&D of
power system controls and protection at Corp. R&D. He holds a BE
Electrical and a Masters in Control Systems from Jabalpur University,
and a Ph D from lIT, Mumbai.
N N Shenoy, Addl. General Manager, has worked on design of tap
changer for 10 years and on switchgear application for 20 years. He
holds a BE Electrical from Kerala University.
S K Sahasrabudhe, Sr. Dy. General Manager, has 15 years experience
in design of control and protection for power system application and 11
years in switchgear application, He has a BE Electrical from Pune
University and an M Tech in Power Systems from Nagpur University.
