Personal computer (PC) based scheme for testing protective relays

The authors present the design and development of a personal computer (IBM PC/XT compatible) based hardware scheme for testing protective relays. Due to the standardisation of PCs, its low cost and the availability of software and hardware support, a PC based relay test scheme enables comprehensive testing of relays, quite accurately in less time. The test procedure simulates realistic relaying signals corresponding to both steady state and transient power system operating conditions. Mathematical modelling of the power system is carried-out on the PC itself and the fault data obtained from such studies are used to simulate highly complex fault signals for a variety of system fault conditions. The transient test signals are computed offline using the Electromagnetic Transient Package (EMTP). Typical results of the tests conducted on commercial solid state relays such as distance relay, differential relay and overcurrent relay demonstrate the efficiency of the proposed technique for conducting tests on commercial relays