Discharge Propagation in Localized High-temperature SF6 Gas with Breakdown Voltage Measurement

The pressure and temperature between electrodes in a high-voltage circuit breaker are non-uniform because of gas blown from the puffer chamber and controlled by nozzles. The dielectric strength between electrodes is locally high, especially at a stagnation point. We made withstand-voltage measurement equipment to evaluate the insulation strength in non-uniform field with high temperature gas to reproduce the region with non-uniform temperature and pressure. The high-temperature gas was generated by an arc. From these preliminary experiments, we obtained the result that breakdown voltage changed with an amount of high-temperature gas. In the case that low-temperature gas remained in vicinity of electrode, the breakdown voltage became high in comparison with the assumed breakdown voltage that was determined by the discharge initiation criteria of local hot gas. It was presumed that the discharge caused by the high-temperature gas region was suppressed in the low-temperature gas region.