BHARATHIDASAN ENGG COLLEGE, NATARAMPALLI
COURSE MATERIAL (LECTURE NOTES)
To introduce the students to the various abnormal operating conditions in power system and
describe the apparatus and system protection schemes. Also to describe the phenomena of current interruption to study
the various switchgears. OBJECTIVES:
i. To discuss the causes of abnormal operating conditions (faults, lightning and
switching surges) of the apparatus and system. ii. To understand the characteristics and
functions of relays and protection schemes. iii. To understand the problems associated
with circuit interruption by a circuit breaker.
UNIT I INTRODUCTION
Importance of protective schemes for electrical apparatus and power system. Qualitative review of faults and fault
currents - relay terminology – definitions - and essential qualities of protection. Protection against over voltages due to
lightning and switching - arcing grounds - Peterson Coil - ground wires - surge absorber and diverters
Power System earthing – neutral Earthing - basic ideas of insulation coordination.
UNIT II OPERATING PRINCIPLES AND RELAY CHARACTERISTICS 9
Electromagnetic relays – over current, directional and non-directional, distance, negative sequence, differential and under
frequency relays – Introduction to static relays.
UNIT III APPARATUS PROTECTION 9
Main considerations in apparatus protection - transformer, generator and motor protection protection of bus bars. Transmission line protection - zones of protection. CTs and PTs and their applications in protection
UNIT IV THEORY OF CIRCUIT INTERRUPTION 9
Physics of arc phenomena and arc interruption. DC and AC circuit breaking - restriking voltage and recovery voltage rate
of rise of recovery voltage - resistance switching - current chopping - interruption of capacitive current.
UNIT V CIRCUIT BREAKERS
Types of circuit breakers – air blast, air break, oil, SF6 and vacuum circuit breakers – comparative merits of different
circuit breakers – testing of circuit breakers.
TOTAL : 45 PERIODS
1. M.L. Soni, P.V. Gupta, V.S. Bhatnagar, A. Chakrabarti, ‘A Text Book on Power System
Engineering’, Dhanpat Rai & Co., 1998. (For All Chapters 1, 2, 3, 4 and 5).
2. R.K.Rajput, A Tex book of Power System Engineering. Laxmi Publications, First
Edition Reprint 2007.
1. Sunil S. Rao, ‘Switchgear and Protection’, Khanna publishers, New Delhi, 1986.
2. C.L. Wadhwa, ‘Electrical Power Systems’, Newage International (P) Ltd., 2000.
3. B. Ravindranath, and N. Chander, ‘Power System Protection & Switchgear’, Wiley Eastern Ltd.,1977.
4. Badri Ram, Vishwakarma, ‘Power System Protection and Switchgear’, Tata McGraw Hill, 2001.
5. Y.G. Paithankar and S.R. Bhide, ‘Fundamentals of Power System Protection’, Prentice Hall of India Pvt. Ltd., New
EE 2402 PROTECTION & SWITCHGEAR UNIT-I