SWITCHGEAR AND PROTECTIVE DEVICES
SWITCHGEAR AND PROTECTIVE DEVICES (3-1-0)
MODULE-I (10 HOURS)
Protective Devices: Philosophy of protection, Nature, Causes and consequences of faults, Zone of
protection, Requirements of a protective scheme, Basic terminology components of protection scheme.
Relay classification, Principle of different types of electromagnetic relay. General equation of phase and
magnitude comparators, Duality of comparators, Electromagnetic relays, over current relays Directional
relays, Distance relay- impedance, Reactance and Mho type, Differential relays.
MODULE-II (10 HOURS)
Feeder: Protection: Over current and earth fault protection, Distance protection, Pilot wire protection,
Carrier current protection.
Generator Protection: Biased differential protection, restricted earth fault protection, Field suppression,
Negative sequence protection, Earth fault detection in rotor circuit
Power transformer Protection: Biased differential protections, restricted earth fault protection, Buchholz
relay Protection of combined transformer and alternator.
Bus Zone Protection: frame leakage and circulating current scheme-use of Translay relay.
MODULE-III (10 HOURS)
Circuit Breakers: Formation of arc during circuit breaking. Characteristics of electric arc. Theories of arc
Interruption. Recovery and restriking voltage, interruption of capacitive and inductive currents. Current
chopping. Principle of A.C. and D.C. circuit breaking requirements of good circuit breaker circuit breaker
Different types of circuit breakers. Air break and Air blast circuit breaker. Plain break and controlled
break all circuit breakers. Minimum oil circuit breakers. Vacuum circuit breaker, SF6 circuit breaker.
D.C. Circuit breaker.
H.R.C. Fuse: Construction and characteristics
MODULE-IV (10 HOURS)
Static Relays : Development and classification of static relays, Different types of phase and amplitude
capacitors, Basic static relays used in protective scheme, Elementary idea about digital & numerical
protection. Testing and maintenance of protective gear, Protection against surge-surge absorber, Surgediverter.
Arrangement of Bus bar, Circuit breaker and isolator. Current limiting reactors in power system and their
arrangement calculation of fault MVA for symmetrical short circuits. Circuit breaker capacity.