Current and Emitted Light Characteristics of Streamers in Insulating Liquids under AC Voltages

Summary

This paper is aimed to investigate the streamer characteristics of a mineral oil – Gemini X and an ester liquid – Midel 7131 in a divergent AC electric field. A point-to-plane electrode configuration with a gap distance of 30 mm and etched tungsten wire with tip radius of 50 µm were used. Streamer current and emitted light signals were measured by adopting a current shunt and a photomultiplier tube (PMT), respectively. Both streamer initiation and propagation stages were studied. It was found that 50% streamer initiation voltage of the ester liquid is slightly lower than that of the mineral oil. Positive streamers those occurred during the positive half cycle of AC voltage contain a continuous dc component superimposed with intensive pulses for both current and light signals, whereas the negative streamers those occurred during the negative half cycle of AC voltage consist of a train of discrete pulses. The magnitude of the current and light signals increases with applied voltage for both the mineral oil and the ester liquid. At the same voltage, the maximum peak of current pulses of the ester liquid is higher than that of the mineral oil.

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Authors

Wang Devi, Claudi Albert