Breakdown characteristics of reactor interturn insulation under AC superimposed pulse oscillation voltage

Dry type air core shunt reactor plays a role in improving the ability of transmission capability in long-distance electric transmission line and perfecting voltage distribution along the line and reducing system overvoltage. In recent years, there have been a lot of fire accidents about dry type air core shunt reactor in the actual operation, overvoltage is one of the fundamental reasons for these accidents, among which switching overvoltage is the most frequent and harmful, and the switching overvoltage is mainly a voltage waveform superimposed with pulse oscillation at the peak of AC voltage. In this paper, a method of generating superimposed pulse oscillation voltage at AC peak is proposed, and a set of superimposed pulse oscillation high voltage test equipment at AC peak is set up. Using the test equipment, the breakdown test of the reactor turn to turn insulation test sample has been carried out. The research results show the superposition method proposed in this paper is feasible, and the output of the superposition device can well simulate the switching overvoltage waveform. It is found that the pulse oscillation voltage is superposed near the peak value of AC voltage, and the AC voltage and pulse oscillation voltage can be continuously regulated in the range of 0~30kV. The ball gap discharges two times per second. In AC superimposed pulse oscillation voltage, sample under AC lower breakdown voltage, high breakdown voltage in pulse oscillation voltage, breakdown voltage in AC superimposed pulse oscillation voltage greater than that in pure AC voltage and pure impulse voltage. The maximum value of the breakdown voltage varies with the power frequency voltage at both ends of the sample. The breakdown in AC superimposed pulse oscillation voltage occurs in the way of creepage.