Streamers Optical and Electrical Characteristics Correlations in Liquid Dielectrics Under Alternating Current Stress

This paper is devoted to the analysis of optical and electrical characteristics of positive streamers (namely the emitted light and current signals, electric field, velocity and electrical charge) propagating in mineral oil, tetra-ester and toluene, in a point-plane electrode arrangement, under alternating current voltage. Correlations are established between the different characteristics of streamers especially between the velocity and the current derivative indicating that the streamers present also a certain inductive nature, contrarily to the generally used assumptions where streamers propagating are considered of only resistive and capacitive nature. The frequency spectra of the current pulses are also investigated and enlighten all similarities and differences between the studied oils. Each type of discharge can be well identified in relation with the nature of the liquid by the analysis of the frequency behaviour of the corresponding currents or emitted lights. The behaviour of each current streamer is found to be highly influenced by the liquid temperature of evaporation and its electronic affinity.