Distributed Online Monitoring Method and Application of Cable Partial Discharge Based on $\varphi$ -OTDR

Partial discharge (PD) is an early manifestation of multiple cable faults. The traditional PD monitoring method has a weak monitoring effect and low positioning accuracy when monitoring the PD of cable. This paper proposes a distributed on-line monitoring method for cable PD based on phase-sensitive fiber-optic time domain reflection (φ-OTDR) principle. Firstly, the production and propagation model of the partial discharge ultrasonic wave (PDUW) of the cable was established and simulated, and the distribution of PDUW inside the cable with different conditions and different structures was obtained. Then we established a model of cable PDUW, and the backscattered Rayleigh light intensity in fiber and theoretically analyzed and experimentally verified the relationship between the cable PDUW and backscattered Rayleigh light intensity in fiber. The experimental results are consistent with the theoretical analysis. When the cable has PD, the backscattered Rayleigh light intensity change of the PD position is higher than the intact position. We analyzed the experimental data and obtained the judgment conditions of the cable PD. Finally, we calculate and obtain the sensitivity of the monitoring method to different cables and the warning value when cable PD is abnormal.