DEVELOPMENT OF MICROPROCESSOR BASED RELAY FOR GENERATOR PROTECTION AGAINST STATOR SHORT CIRCUIT AND EXCITER FAILURES

Abstract

It is required to install varieties of relays on a generator to, protect it against various abnormalities. The protective relays and relaying practices in this regard have been critically reviewed here. Some of these abnormalities have been selected for developing micro-processor bases relays• The first relay is based on differential principle and protects the generator against all internal short circuits except inter-turn fault (which is the inherent shortcoming of generator differential relay)• The second relay monitors field current and there-from provides protection to the generator against (i) asymmetrical stator faulty including inter-turn short circuits, (ii) rotor over-heating due to stator unbalance and (iii) field failure. Either relay is based on 8 bit microprocessor 8085 and uses A/D converter to interface the input relaying signals to the microprocessor. . Both relays have been successfully tested with signals simulat-ing relevant generator condition.