Distributed Optical Fiber Detection Based on BOTDR for Buffer Layer Defects of High-Voltage XLPE Cable With Corrugated Aluminum Sheath

In recent years, buffer layer defects have occurred in high-voltage (HV) crosslinked polyethylene (XLPE) cable frequently, which affects its safe and stable operation, while there are no effective detection methods yet. In this article, a 110 kV cable sample was prepared, embedded with single-mode optical fiber. Meanwhile, a distributed optical fiber detection system for buffer layer defects based on Brillouin optical time domain reflectometry was built. The partial discharge (PD) test and Brillouin optical time-domain reflectometer (BOTDR) detection test for defective cable were conducted to study the relationship between Brillouin frequency shift (BFS) variation of built-in fiber and temperature rise resulting from dielectric loss, white powder, and damaged insulation. During applying voltage of 96 kV for 7 h, the BFS variations within white powder and damaged insulation defects are significantly larger than that within non-defect which is only determined by dielectric loss. The BFS variations are closely related to the number and depth of damaged insulation holes, as well as circumferential angle of holes against optical fiber. But the BFS variations within moisture water blocking tape, poor electrical connection, and damaged insulation screen cannot be distinguished from that within non-defect.