A High-precision Positioning Method for Cable Incipient Fault

The initial fault of the cable is a latent fault, and its online positioning can improve the stability of the power system. Aiming at the problem that the frequency fluctuation of are discharge is not considered in the traditional initial fault, and the wave velocity attenuation of the fault traveling wave in the cable is not considered. Based on the time-frequency distribution of the fault signal, this paper proposes a high-precision positioning method for the initial fault of the cable. Firstly, aiming at the distributed circuit model of cable, the refraction and reflection of high frequency traveling wave in lossy medium are extracted, and the fault location model of traditional traveling wave method is proposed. After that, by calculating the time-frequency distribution of the high-frequency signal in the cable, the traveling wave velocity under the single discharge intensity is calculated by the frequency center of the signal, and the wave velocity attenuation under different transmission distances is extracted at the same time. The discrete wave velocity and time matrix are constructed to obtain the high-precision positioning equation of the cable initial fault. Finally, the proposed method is verified by establishing a fault line in PSCAD / EMTDC. The findings indicate that the relative error of the proposed method is 1.42%, which has high positioning accuracy. At the same time, by analyzing the positioning results under different noises, the maximum error is not more than 2%, which shows that the proposed method has strong anti-interference ability. The proposed method provides a good solution for the fault signal location with strong discharge fluctuation.