Reliability analysis of protective relays in fault information processing system in China

The reliability indices of protective relays are first put forward in this paper. A Markov probability model is then established to evaluate the reliability of relay protection. With the state space analytical method, all the steady state probabilities and state transition probabilities can be calculated utilizing the data stored in the fault information processing system. We can get an equation that represents the influence of routine test intervals on relay unavailability. Based on this, the optimum routine test interval for protective relays can be determined. This paper also proposes an efficient method of processing large amount of information by the fault information processing system and evaluating the reliability of protective relays with it, and the corresponding software package is also developed. The application of it to an actual power system in China proves the method to be correct and effective