Evaluation of Gas Flow by Multi-point Pressure Measurement using a Self-blast Gas Circuit Breaker Model

The self-blast type gas circuit breaker obtains high pressure by using arc energy to blow high pressure gas into arc. To understand the self-blast phenomenon, it is important to explain the characteristics of the arc as a pressure source for building up pressure in a thermal puffer chamber. In this study, we carried out multi-point pressure measurements to investigate the pressure build-up mechanism and blowing process quantitatively. The measurement points were at the thermal puffer chamber, mechanical puffer chamber, flow path, and in the nozzle throat. It was confirmed that the nozzle throat works as a pressure source at a high current due to arc plasma and the switch to the blowing phase a few milliseconds before current zero. The pressure ratio between the thermal puffer and nozzle throat were well agreed with the pressure ratio calculated from the sound speed condition just around current zero. Therefore formation of sound speed flow in nozzle throat was confirmed, and super sonic flow was established in the nozzle divergent area.