An accurate evaluation method of the thermal interruption limit of power circuit breakers

In this paper, a simplified test method has been proposed and implemented for evaluating the thermal interruption capability of the power circuit breakers. It has been shown that the thermal interruption limit of the circuit breaker can be evaluated in a more accurate way using the proposed method in comparison to the conventional synthetic test methods due to the avoiding the influences of the arc voltage. To validate the proposed test circuit, a series of experiments have been carried out on a 24 kV SF6 gas circuit breaker with rated short circuit of 25 kA and the successful interruption zone in terms of the time derivative of the current before current zero (di/dt) and rate of rise of recovery voltage (dv/dt) has been determined. The experimental results are in good accordance with the theoretical model predictions.