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Application of a validated AC black-box arc model to DC current interruption

From a large number of short-line fault tests with high-voltage SF6 AC circuit breakers with rated voltage 72.5 - 550 kV, a validated arc model is derived that describes the current-zero behaviour of the breaker rather well. This model is used to investigate the possibility to interrupt DC current by means of arc current oscillations with increasing amplitude until current zero is reached. Two aspects are of importance: the excitation of the negatively damped oscillation and the capability to interrupt the high-frequency (few kHz) current. In small scale experiments, using an AC current of 1 kA at 16.7 Hz the capability of exciting negatively damped oscillations with a properly tuned parallel LC circuit was confirmed as predicted by the model. Regarding interruption capability, model predictions show that because of the special conditions, the SF6 arc may interrupt higher di/dt than in a typical AC application.