Research on Optical Fiber Sensor Localization Based on the Partial Discharge Ultrasonic Characteristics in Long-Distance XLPE Cables

To improve the safety and antielectromagnetic interference performance of partial discharge detection in high-voltage DC cables, partial discharge of cables is used as a criterion for characterizing insulation defects. An ultrasonic detection method for the partial discharge of optical fiber detection is carried out in a long-distance high-voltage DC operating environment. By analyzing the partial discharge mechanism and ultrasonic characteristics of DC cables, a correlation model between partial discharge ultrasonic waves and discharge quantity is established. The partial discharge charge of several common insulation defects is obtained experimentally, and an ultrasonic characteristic Sagnac fiber detection system is realized. Standard ultrasonic time domain signal detection and fiber-optic sensing probe directional experiments are performed. The influence of fiber sensing probes with different lengths on the sensitivity of partial discharge signals is investigated based on the frequency distribution characteristics of partial discharges. The ultrasonic wave is measured based on a fiber-optic probe and can perform multipoint detection, and the partial discharge of the ±320 kV flexible DC transmission system was tested based on the developed optical fiber sensing system. The experimental results show that the partial discharge signal detection of 6 km long cable can be realized, and the localization accuracy is less than ±80 m. It provides a practical monitoring method for the perception of long-distance transmission equipment operating states.