Hybrid traveling wave/boundary protection for bipolar HCDC line

A new hybrid protection scheme, based on traveling wave protection principle and boundary protection principle for a bi-polar HVDC line is proposed. Stationary wavelet transform (SWT) is adopted in the traveling wave protection to process DC signals and then wavelet modulus maxima are used to further represent useful traveling wave signal. Boundary protection based on SWT is used jointly with traveling wave protection to distinguish internal faults from external faults. The effect of border distortion, noise, high ground fault resistance, close-up faults and transients caused by lightning strokes are considered in the paper. The proposed scheme can effectively detect faults, determine the faulty pole and calculate fault location at the same time.