Combined fault location algorithm for HVDC transmission lines based on natural frequency

In frequency domain, there is a certain mathematical relationship between the natural frequency and the fault distance. But model mixing is still the problem haven´t been solved well yet, it brings difficulty in gaining the natural frequency. A combined fault location algorithm for HVDC transmission line based on natural frequency is proposed in this paper, in which time domain and the frequency domain is combined together. On the one hand, in time domain, wavelet analysis was used to calculate rough fault distance. Then through the relationship between the fault distance and the natural frequency, the rough natural frequency was obtained. On the other hand, wavelet packet was used to divide the frequency into several specific ranges, and then find out the range of rough frequency. At last, multiple signal classification algorithm was used to obtain the frequency, and the fault distance was obtained. The algorithm has been performed a lot in PSCAD. The validity of the algorithm has been verified.