Stationary Wavelet Transform Based HVDC Line Protection

A novel HVDC line protection algorithm based on traveling wave theory is presented in this paper. Stationary wavelet transform (SWT) is adopted to process the rectifier side DC voltage and then wavelet modulus maxima are used to further represent useful traveling wave signal. The effect of border distortion is considered and a new denoising method is proposed. The proposed protection algorithm can distinguish DC line-to-ground faults from transients caused by AC faults. The algorithm performs well even under high resistance ground faults. A possible relay implementation is also proposed.