Risk evaluation model for relay protection considering communication delay and bit error

摘要

This paper proposes a risk evaluation model to assess the impact of communication delay and bit error on relay protection. First, the mechanism of mal-function of relay protection caused by communication delay and bit error is introduced. In general, a channel's consistent delay or bit error results in refuse-operation, while a channel's inconsistent delay normally causes false trip. Based on the analysis of probability distributions of communication delay and bit error, the probabilistic models of false trip and refuse-operation are proposed. With the probabilistic models, risk of power system failure caused by relay protection's malfunctions can be calculated. Simulations results, using current differential protection as an example, are given to validate the proposed evaluation model.