Characteristics of the partial discharge in oil-paper cavity under the valve voltage waveform of converter transformer

In this paper, the partial discharge (PD) in oil-paper insulation cavity is conducted under the voltage of AC, Y/Δ connection and Y/Y connection, respectively. The low-amplitude and high-repetition PD under the AC voltage is observed, the high-amplitude and a low-repetition PD is acquired under the given valve voltages. The discharge mainly occurs at the rising edge of the valve voltage waveforms. The Q _max of the discharge of Y/Δ and Y/Y connections is 2 and 2.5 times the Qmax under the AC voltage, respectively. The average discharge Q _mean of Y/Δ and Y/Y connections is 3 and 2 times Qmean obtained under the AC voltage, respectively. The total discharge Qtatol of both valve voltage waveforms is higher than that under the AC voltage. The test results also show that the PD is severely affected by the voltage waveform as the voltage distortion is observed in the experiment. This work may provide a reference for the improvement of insulation design and the factory test of converter transformers.