Improvement of insulation performance of solid/gas composite insulation with embedded electrode

Abstract

Solid insulated switchgear (SIS) has been developed as a substitution for medium voltage sulfur hexafluoride (SF6) gas insulated switchgears. Its main circuit including a vacuum interrupter is coated with epoxy resin. Therefore, a solid/gas insulation system is composed. For further miniaturization and higher stress design of SIS, improvement of the insulation performance is required. In the solid/gas insulation system, the breakdown strength along the surface is lower than that of solid. Then, the authors investigated the surface insulation performance of the solid/gas insulation system containing an embedded electrode. In the present study, the sizes of the embedded electrode and the solid insulation material were varied and the partial discharge inception voltage and the surface breakdown voltage were measured. As a result, it was found that the surface breakdown voltage varied considerably with the radius of the embedded electrode. From the result, it was deduced that the surface insulation performance could be improved by choosing the size of the embedded electrode appropriately. Moreover, the effects of the thickness of the insulation material and of the surface distance on the surface insulation performance were clarified.

Basic study on surface insulation design of solid/gas composite insulation system with embedded electrode

“…In the previous study [4], the authors measured the surface breakdown voltage (BDV) and the partial discharge inception voltage (PDIV) under ac or impulse voltage application. The measurement was done by changing the radius of the embedded electrode ( e ), thickness of the disc-shaped epoxy resin plate ( ) or the radius of the epoxy resin plate ( p ).…”

Estimation of surface breakdown voltage of solid/gas composite insulation with embedded electrode

“…In the previous study [3], the authors investigated on the surface breakdown voltage (BDV) and the partial discharge inception voltage (PDIV) by varying the radius of the embedded electrode ( e ), thickness of the disc-type epoxy resin plate ( ) or the radius of the epoxy resin plate ( p ) under ac or impulse voltage application. As a result, it was found that the surface discharge initiated at the point of the maximum electric field strength along the surface and it propagated in both directions towards the center rod electrode and towards the ground electrode.…”

“…Equation A model of composite insulation system with embedded electrode. p is the radius of the disc-type epoxy resin plate, e is the radius of the embedded electrode and is the thickness of the epoxy resin plate [3].…”

“…Figure 10 shows the relation between impulse breakdown voltage (BDV) and the radius of the embedded electrode, e . Surface breakdown voltage was measured in the previous study [3] method. Voltage elevation was started from around 80 % of the estimated breakdown voltage and the step was about 1 kV.…”

“…In the previous study [3], metal electrode was embedded into the insulation material of epoxy resin and its effect on the insulation performance was investigated. In the present study, the surface discharge propagation characteristics were measured and the characteristics were found to be expressed with an equation derived from the empirical equation presented by Toepler.…”