Abstract: In order to detect the inter-turn insulation fault online,this paper proposes an identification method of inter-tun insulation faults based on the analysis of reactor breaking overvoltage characteristics. Based on the distributed parameter model of the inter-turn insulation short-circuit fault of the reactor,the overvoltage model of the reactor with inter-turn insulation short-circuit fault is established. The influence of the inter-turn insulation short-circuit fault on the breaking overvoltage waveform of the reactor is analyzed. The frequency spectrum of the overvoltage waveform is analyzed by the variational mode decomposition algorithm. Finally,the reactor breaking overvoltage simulation model considering inter-turn insulation faults is established to simulate the reactor with different degrees of insulation short-circuit,obtain the data of the reactor breaking voltage waveform and its oscillation frequency,analyze the waveform data and extract its features,and quantify the difference between the maximum amplitude of breaking overvoltage and the oscillation frequency and insulation so that the inter-turn short-circuit fault can be identified effectively.