Selection of Tripping Times for Distance Protection Using Probabilistic Fault Trees with Time Dependencies

Distance protection of electrical power system is analyzed. This protection is based on local and remote relays. Hazard is the event: remote circuit breaker tripping provided the local circuit breaker can be opened. Coordination of operation of protection relays in time domain is important and difficult problem. Incorrect values of delay times of protection relays can cause the hazard. In the paper, the impact of delay time settings on performance of protective scheme is analyzed using probabilistic fault trees with time dependencies (PFTTD). PFTTD are introduced in the paper and used for the above-mentioned hazard analyzes. The outcomes are hazard probabilities as a function of delay time values.