POWER SYSTEM PROTECTION & SWITCHGEAR

UNIT-I REALY: Terminology, Basic circuit, realy connection with trip circuit and circuit breaker, objectives of protection, types of relay, construction and operation of instantaneous over current realy. I.DM.T. Relay, directional Unit, differential relay, percentage differential relay, Buchholz relay, Generalized torque expression, logical construction of impedance reactance, MHO and Off-set MHO Relays using generalized torque expression. UNIT-II Protection of Alternators: Differential protection, Protection of stator against phases to ground fault, phase to phase faults, inter turn fault, protection against unbalanced loading, protection of rotor against ground fault, field failure, reverse power, back up protection, field suppression, protection of bus bars, frame leakage protection, differential protection. UNIT III Protection of transformers & Feeders: differential protection of transformers for different winding configurations, difficulties encountered in differential protection and their remedies, protection of feeders, protection of ring main and parallel feeders, protection of radial feeders by over current relays, distance relays and carrier current protection scheme. UNIT IV Static Relays: directional relay, impedance relay, admittance relay and admittance relay, amplitude comparator, phase comparator, duality between amplitude and phase comparators. UNIT V Circuit Breakers and Fuses: Arc formation, arc interruption and restriking voltage, current chopping, resistance switch, Air blast circuit breakers, minimum and bulk oil circuit breakers, SF6 and Vacuum Circuit breakers, circuit breakers rating, testing of CB, definitions of terms in fuses, HRC fuses.