Development of multi-band ultra-high-frequency sensor for partial discharge monitoring based on the meandering technique

To design high-sensitivity sensors is one of the critical issues to be solved for ultra-high-frequency (UHF) partial discharge (PD) detection in substations. Commonly-used UHF sensors usually use ultra-wideband antennas for the frequency bands ranging from 300 MHz to 1.5 GHz. To avoid interference in the frequency bands, such as signals generated from mobile phones, a new multi-band UHF sensor is proposed based on the loop antenna theory and meandering technique, which reduces the sensor size, provides high sensitivity and exhibits omnidirectional performance. The sensor works in the bandwidth ranges of 480-520, 800-850 and 1100-1200 MHz, and has sensitivity of more than 10 mm. The PD detection platform was set up, three typical insulation defects, such as corona discharge, surface discharge and free metal particle discharge, were designed, and then the tests were performed to compare the performance of the multi-band sensor and broadband sensor. The results show that the multi-band sensor´s bandwidth covers the main spectra of PD signals, thereby can be used for detecting most kinds of PD signals. The sensor´s sensitivity is higher than that of the broadband sensor with its size occupying only 5% of the latter, meeting the requirements for detection of PD sources in substations.