Abstract:
The DC transmission line boundary may attenuate the high frequency part of the fault current travelling wave. And for bipolar transmission lines, the high frequency content of the healthy pole induction traveling wave is less than that of the fault pole. This paper presents a novel two-terminal protection method of HVDC transmission lines based on high-frequency cross-correlation function dispersion degree of traveling wave, combining line protection and fault location. Firstly, discrete wavelet transform (DWT) is used to decompose the fault current travelling wave of bipolar DC lines into four layers and obtain high frequency detail contents. Secondly, the cross-correlation coefficients between high frequency detail components of fault pole and healthy pole is calculated. Finally, the fault zone and fault type are determined by the dispersion of the cross-correlation function, and the fault distance can be preliminarily calculated by the maximum coordinate of cross-correlation function. The simulation model is built in PSCAD/EMDTC, and the experimental results show that the criterion can effectively judge the fault type and calculate fault location, which is not affected by transition resistance.