UNIT - I Protective Relays : Introduction, Need for power system protection, effects of faults, evolution of protective relays, zones of protection, primary and backup protection, essential qualities of protection, classification of protective relays and schemes, current transformers, potential transformers, basic relay terminology. Operating Principles and Relay Construction : Electromagnetic relays, thermal relays, static relays, microprocessor based protective relays. (Chapter - 1) UNIT - II Over-Current Protection : Time-current characteristics, current setting, over current protective schemes, directional relay, protection of parallel feeders, protection of ring mains, Phase fault and earth fault protection, Combined earth fault and phase fault protective scheme, Directional earth fault relay. Distance Protection : Impedance relay, reactance relay, MHO relay, input quantities for various types of distance relays, Effect of arc resistance, Effect of power swings, effect of line length and source impedance on the performance of distance relays, selection of distance relays, MHO relay with blinders, Reduction of measuring units, switched distance schemes, auto re-closing. (Chapter - 2) UNIT- III Pilot Relaying Schemes : Wire Pilot protection, Carrier current protection. AC Machines and Bus Zone Protection : Protection of Generators, Protection of transformers, Buszone protection, frame leakage protection. (Chapter - 3) UNIT - IV Static Relays : Amplitude and Phase comparators, Duality between AC and PC, Static amplitude comparator, integrating and instantaneous comparators, static phase comparators, coincidence type of phase comparator, static over current relays, static directional relay, static differential relay, static distance relays, Multi input comparators, concept of Quadrilateral and Elliptical relay characteristics. Microprocessor Based Relays : Advantages, over current relays, directional relays, distance relays. (Chapter - 4) UNIT - V Circuit Breakers
