Distributed Fiber-Optic Sensing for Partial Discharge Detection of Stress Cone Dislocation Defects in High Voltage Cable Joints

One of the most important methods for evaluating the insulation condition of power equipment is the on-site partial discharge test. Fiber-optic sensors based on various principles have been developed to detect the acoustic signal of partial discharge due to their high immunity to electromagnetic interference and ability to be embedded within power equipment capabilities. A novel distributed fiber-optic acoustic sensor based on phase-sensitive optical time-domain reflectometry Φ-OTDR) was proposed in this paper for the detection of partial discharge acoustics on power cable joints. The Φ-OTDR-based partial discharge acoustic detection system measured the coherent Rayleigh backscattered (RBS) light in a single-mode optical fiber route, which carries the acoustic perturbation occurrences somewhere along the fiber route, and is transmitted back to the near-end of the optical fiber. The target phase shift-collected by the distributed fiber-optic sensors under partial discharge- induced acoustic perturbations is present in both the amplitude- modulated and phase-modulated terms of the RBS signal, and then the acoustic-related phase shift terms can be demodulated by introducing the Hilbert transform based signal processing algorithms. Its effectiveness for partial discharge ultrasonic detection of 15 kV cable joints has been validated, and the Φ-OTDR detection system was also used to measure the stress cone dislocation defect of a 220 kV cable joint, and the test results of the piezoelectric measurement method were compared to validate the effectiveness of Φ-OTDR distributed fiber sensors. The experimental results show that the proposed distributed fiber-optic sensing system can effectively detect and locate the partial discharge signal.