Relocatable Ultrasonic Array and UHF Combined Sensor Applied to PD Location in Oil

A relocatable combined sensor is designed to locate partial discharge (PD) in a transformer. Based on the sensor, PD location experiments are conducted. The sensor consists of a conformal L-shaped ultrasonic array of 13 elements and includes an ultra-high-frequency electromagnetic sensor. The L-shaped array achieves the effect of 97 virtual elements expanded with high-order cumulants processing technology. It greatly improves the aperture and direction sharpness of the array. The PD location experiments were carried out on a PD experiment platform. The result shows that the combined sensor can distinguish and locate one or multiple PD sources with average relative locating error 2.1% and 4.8%, respectively. Virtual expansion of an array with fewer number elements helps to design a miniaturized and combined sensor. This work should provide as a foundation for application of array technology in power equipment.