A lifting wavelet-based protection strategy against DC line faults for Zhangbei HVDC Grid in China

A four-terminal overhead line demonstration high voltage direct current (HVDC) grid for renewable energy power integration and transmission will be constructed around 2019 in Zhangbei district, northwest of Hebei province of China. As the high failure probability of the overhead and the low damping coefficient of DC grid, the suitable ultra-high speed protection against DC line fault needs to be developed. In this paper, the characteristics of travelling wave of HVDC gird caused by the short circuit fault and lightning are studied. On this basis, a lifting wavelet-based non-unit protection scheme is proposed to detect and identify the fault within several million seconds. Considering the impact of short-circuit resistance, fault location and fault type, the proposed protection strategy is studied and verified by various simulations based on the PSCAD/EMTDC software platform.