A novel combined in-oil PD sensor with AE and UHF methods for PD detection in transformer, part 1: structural design and development

According to the disadvantages and advantages of electromagnetic and acoustic partial discharges (PD) measurements shown in IEC TS 62478 Edition 1.0 2016-08, a combined in-oil PD sensor with acoustical emission (AE) and Ultra high frequency (UHF) methods for PD detection in transformer is designed and developed in this paper. It is formed by placing an AE sensor inside the end part of UHF probe, and can be mounted on the oil valve, pushed inside the transformer to measure the acoustic and electromagnetic signals from PD simultaneously. The structure design of a combined UHF/AE in-oil PD sensor considering signals coupling and oil sealing are given in detail, with AE sensor and UHF antenna working independently of each other based on two output channels to avoid the application of different bandwidth hardware filters. Tests of discharges in air show that the novel combined UHF/AE in-oil PD sensor designed and developed can couple the electromagnetic and acoustic signals generated by discharge pulse at the same time effectively.