Fault identification and fault location methods for VSC-HVDC transmission lines based on the traveling waveform difference

•The backup protection including fault identification and location methods is proposed for VSC-HVDC transmission lines.•The waveform difference in same/different-mode traveling waves between faulty and unfaulty lines is elaborated in theory.•The protection can identify the double-pole-to-ground fault with unequal positive and negative pole fault resistances.•The waveform difference between 1-mode differential forward and backward currents can locate faults rapidly and accurately.•The methods can improve the protection selectivity, reliability, rapidity, and sensitivity.