Abstract:According to the 35kV reactor which burned in operation, harmonic test and swithing overvoltage test were adopted based on the on-site inspection and disintegration, cause of issue: multi frequency switching over voltage reactor can produce cumulative effect on reactor, due to the cumulative effect, resulting inter-turn insulation damage, cause burning reactor. For this reason the reactor failure analysis, put forward the corresponding prevention and treatment measures: to improve product quality, improve the installation process; strengthen testing and operation monitoring, reduce operational over-voltage and other prevention and treatment measures to improve the reliability of power grid operation.