Method of Evaluating Dielectric Interruption Capability of High-Voltage Circuit Breaker

Two performance indices using the local dielectric strength are proposed to measure interruption capabilities for breaker terminal fault duties in high-voltage circuit breakers. The dielectric strength at a part in the insulating gas volume between arcing contacts surrounded by an insulating nozzle was evaluated by comparing the applied electric field strength with the critical electric field strength calculated from the gas flow properties. The first index quantifies the effect of suppressing the discharge evolution, which is calculated by integrating the ratio of the critical electric field to the applied electric field in the space between the arcing contacts. The second index expresses the ease of initiating dielectric breakdown, which is calculated by integrating the inverse of the first index in the range of space including the surface of the insulating nozzle. To determine the criteria for the performance indices, gas flow simulations were conducted under experimental conditions with 10–100% of the rated interrupting current. The region excluding failure cases was considered to be the high-performance area.