Study of theory and test in a laboratory model for accelerated trip for faults in the second zone of protection of a transmission line using a microcomputer

Analysis of a scheme of accelerated trip for faults in the second zone of a transmission line distance protection is given in this paper. By the use of the two-port network theory, variation of the sequence currents and voltages are analyzed when the fault occurs on the protected line followed by a trip of the circuit breaker on the other side. The analysis is supported by tests performed on a laboratory model of a power system with two sources. The new scheme can improve sensitivity and avoid ma1-operation. Thus, it may be possible to use this scheme instead of pilot protection and alleviate any problems caused by the non-availability of a sufficient number of communication channels for remote control and relaying.