Partial Discharge Distributed Locating in Power Cable Joints Using Φ-OTDR Optical Fiber System

To address the challenges of real-time insulation monitoring and accurate partial discharge (PD) location in cable joints, a distributed optical fiber sensing system with polarization compensation module (PCM) is established to detect the ultrasonic signal of PD. The locating range of optical time-domain reflectometer (Phi-OTDR) is analyzed, and a variance variable mathematical model based on Rayleigh scattering coherent light signals is established to denote weak ultrasonic characteristic signals of PD in cable joints. The polarizing beam splitter (PBS) is devised in the Phi-OTDR detection circuit to improve the stability of polarization states. Four optical fiber ring sensors are wound on the cable joint to locate and detect the PD point of the cable joint. Then, the signal characteristics of PD measured by the electrical measurement method and optical fiber acoustic measurement method are compared, and the positions of four optical fiber ring sensors are calibrated based on piezoelectric sensors. It shows that when the test fiber length is 600 or 1125 m, the locating deviation is less than 1.9 m, which is verified by a high accuracy of optical fiber sensing system in detecting PD. It provides a feasible monitoring method for real-time sensing of insulation status of transmission equipment.