Fault risk assessment of relay protection based on fault tree and Bayesian network

The fault tree of the relay protection system is an important tool for the risk identification and evaluation of relay protection system. Concerning the difficulty to obtain top-level event rate of fault tree and the inability of reverse reasoning of fault tree, a fault risk assessment method of relay protection based on fault tree and Bayesian network is proposed. In the positive direction, the fault state of the root node of Bayesian network (corresponding to the basic event of the fault tree) is confirmed according to the real-time operational data of relay protection, gives the fault probability of the leaf node of Bayesian network (corresponding to the top event of the fault tree), by the Bayesian network reasoning, realizing the risk prediction of the protection system in advance. In the reserve direction, with the failure of leaf node of Bayesian network, combined with the Bayesian conditional probability formula, calculates the failure probability of root node of Bayesian network, realizing the positioning and traceability of the fault cause after the fault. The proposed method provides a basis for improving the reliability of the protection system and fault diagnosis.