Predicting Thermal Interruption Characteristics of a 72.5-kV CO2 Circuit Breaker

Abstract

This paper represents the prediction of the thermal interruption characteristics of a 72.5-kV CO2 circuit breaker (CB). An analysis method to simulate CO2 arc plasma was developed. The principle phenomena of CO2 arc plasma—nonideal gas behavior, radiative heat transfer (RHT), and nozzle ablation—were considered. In addition, the electric field analysis to compute ohmic heating in the arc region and the analysis of turbulent flows were conducted. The absorption coefficients used in RHT were simplified into mean values of 10 frequency bands to represent the entire absorption spectrum. The proposed method was verified through experimental tests of pressure rise and arc voltage. To predict the thermal interruption characteristics, post arc current (PAC) was computed. PAC is the minute current existing between the contacts of a CB after current zero, and has important value to comprehensively understanding thermal interruption. For comparison, a 72.5-kV CO2 CB was manufactured and tested, and the results were compared with the results of the thermal interruption tests.