In Comparison Between Corona Discharge in Air and Streamer Discharge in Silicone Oil

Corona in air and streamer in silicone oil with viscosity of 100 cS were generated. Needle-plane electrode system was used to make high electric field at the tip of the needle to produce discharges. Sinusoidal, triangular and rectangular high voltage were used. The discharge pulses were measured using personal-computer based partial discharge (PD) measurement system. The system is able to measure phase-resolved PD pulses. The discharge pulse shapes were measured using high sampling rate oscilloscope. Phase-resolved analysis of the discharges was done to interpret the physical processes behind the discharges. The experimental results indicated that discharges in both air and silicone oil took place around the peak of the applied voltage both for positive and negative half cycle. This indicated that discharge occurrence for corona and streamer in silicone oil both strongly governed by the instantaneous applied voltage. Unbalance of PD magnitude and number were observed. Corona discharge and streamer in silicone oil showed higher positive discharges magnitude compared to those negative discharges but negative pulse number is slightly higher than positive. This fact indicated that initial electron ejected from the needle tip was more dominant in initiating the discharge process. Phi-q-n and Phi-n patterns for triangular applied voltage strongly supported the explanation.