ELUCIDATION OF CREEPING STREAMER PROPAGATION MECHANISMS IN SOLID-LIQUID INTERFACE

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The creepage discharge phenomena and discharge propagation mechanisms in a air/solid and a liquid/solid interfaces were investigated.In a air/solid insulation system, the creepage discharges traveling over the surface of aerial insulated wire were investigated under a lightning impulse voltage condition. The polarity effect both on the shapes and the lengths of the creepage discharge was clarified under dry and wet conditions of the wire surface. It was worthy of notice that the lengths of a negative creeping streamer in the dry condition of wire were separated into two regions (increase and decrease) as a function of the voltage. This phenomenon was explained by the transition of the discharge aspects from clinging type to jumping type. It was also found that the streamer propagation was significantly affected by the electric field strength of wire surface.In a lipuid/solid insulation system, firstly, the effect of a polyethylene insulator inserted along the plane of symmetry of a bla … More de-plane electrode geometry on the conduction characteristics in transformer oil under D.C.stresses was investigated. It was found that conduction currents were exceedingly decreased by the presence of the insulator. This phenomenon was discussed on the basis of the electrohydrodynamic (EHD) motion as well as the electric field of the blade edge taking into account the insulator surface charging. Secondly, the behavior of the creepage discharges on the solid insulator surface in transformer oil was investigated under a lightning impulse voltage application. It was found that the creepage discharges were significantly affected by the presence of a surrounding grounded metal electrode. Thirdly, the impulse creepage discharge phenomena on the polyethylene insulator surface in liquid nitrogen were investigated under the various pressure conditions. The relationship between the discharge length and the vaporization of the lipuid was clarified. The effect of insulator surface charging on the discharge propagation was also clarified. Less