According to the deficiency of fault ranging methods for high voltage direct current（ HVDC）transmission lines

a new fault ranging method for HVDC transmission lines is proposed. Because it is difficult to extract traveling wave head in time domain by traveling wave method

the precision of fault ranging is low

and the spectrum of fault traveling wave can reflect the amplitude-frequency characteristics of traveling wave. Fault spectrum is used to analyze on fault of HVDC transmission line. This method effectively improves the precision of fault ranging and the fault spectrum is transmitting. Natural frequency signals are often generated in the process of broadcasting. Main frequency and the amplitude and doubled frequency are used as input training samples

and the fault distance is used as output training samples. The initial weights and thresholds of the Elman dynamic neural network（ ENN） are optimized by ant colony optimization（ ACO） algorithm. PSCAD and MATLAB software are used for joint simulation. The results show that the algorithm can make the system stable

fast convergence and has high ranging precision.