Fault Location Method Considering Variation Characteristics of Wave Speed based on the Backward Wave

The fault location methods of UHVDC transmission lines can be divided into traveling-wave-based algorithm, fault-analysis-based algorithm and natural-frequency-based algorithm according to the principle. This paper presents a novel fault location algorithm, when the DC line fault occurs, the first backward-wave has not been reflected, and it is not affected by the frequency variation of the reflection coefficient, the backward-wave head is easy to identify, so the backward-wave is used for fault location in this paper. And when the DC line uses two different types of wires, the calculation is performed with different wave speeds to improve the range accuracy further. Compared with the existing fault location algorithm, the reliability of the wave head identification of this algorithm is improved, and since the variation of the wave speed is taken into consideration, the ranging accuracy is improved further when different types of wires are used in the DC line.