To improve the accuracy and the efficiency of fault diagnosis

a diagnosing method based on reasoning chain that makes use of the timing sequence of data is presented

solving the problem of existing fault diagnosing methods’ inability to synthetically consider reclosing protection

failure protection and the protection of general components. The diagnosis result has the ability of explaining the deductive process of the fault and the characteristic of judging the cause of fault from the fact of the known fault. The concept of the event set is introduced and the logic model of the fault information is developed

thus simplifying the problem. A fault diagnosing method based on reasoning chain is provided while the causal logic relationships between event sets are determined and the constraint conditions defined. The redundant reasoning chain combination is constructed to get the optimum result based on the likelihood function of the prior data. An actual case of the power system fault has verified the algorithm.