A model of the current interruption circuit for hybrid high voltage DC circuit breakers to achieve precise current experiments

The current interruption test based on an LC resonance circuit for hybrid DC circuit breakers (HVDC CBs) is widely employed to characterize the current interruption capability of CBs. In order to ensure a high-fidelity replica of the fault current in a high voltage application, this paper firstly proposes an equivalent model of the test circuit, where not only parasitic resistances but also the threshold voltages and on-state resistances of various semiconductor devices are considered. Moreover, the analytical formula of the test current is derived by including the working principle of the HVDC CB. Secondly, the parameter extraction method, which combines finite element analysis and measurements by impedance analyzer, is given in this paper. The extracted result implies that, in current interruption transient, equivalent resistances of the 500 kV CB is as large as 535 mΩ, having a significant influence on current waveforms. Thirdly, the 34 kV/25 kA current interruption test for the 500 kV CB is conducted. The measured results are proved to be consistent with the analytical results obtained from the proposed model, and the relative error is less than 2%.