Optimal Test Current Shape for Accurate Arc Characteristic Determination

Arcs under high-current gradients ( >50 kA/ms) are created during fault interruption in passive resonant circuits of HVDC circuit breakers. Black-box models have been successfully applied to model the dynamic arc-network interaction for such breakers. This requires accurately known parameters, such as arc cooling power P(g) and thermal arc inertia τ(g) as a function of conductance. Their experimental determination is difficult and requires significant measurement effort. In a previous work, it was shown that these parameters can be determined more accurately with step-wise current measurements compared to sinusoidal test currents. In this contribution, the optimal nonsinusoidal current waveform is addressed, which maximizes the accuracy of τ at a minimum of required experiments. With a novel arbitrary current source complex, step-, slope- and spike-current waveforms are applied to a wall-stabilized arc. The best results have been obtained from a gradually increasing current slope of 0.3 kA/ms superimposed with repetitive current spikes of 5-15 kA/ms slopes. This enables a large number of evaluation points that showed high accuracy during a single experiment.