An Ultra-wide Band Partial Discharge Sensor for High-voltage Power Transformers

Online monitoring of Partial Discharges (PDs) for high-voltage power transformers is vital as it continuously tracks PD activities within a power transformer and warns about possible insulation failures at an early stage. Wall-mounted UHF PD sensors are convenient for non-contact online PD monitoring inside power transformers. Conventionally used wall-mounted UHF PD sensors offer limited operating frequency band, that fall within the UHF band i.e. 300-3000MHz. As a result, PD monitoring with such sensors becomes challenging, especially during multiple PD events. This paper presents a novel multi-layered wall-mounted UHF PD sensor design, fabrication, and testing. The proposed PD sensor designed to provide an ultra-wide operating frequency band. The physical design of the prototype sensor suits mounting over the inspection hatches of an oil-filled high-voltage power transformer tank. The prototype sensor's ultra-wide band sensitivity performance curves have been validated through testing with a vector network analyser (VNA). The real-life PD sensing performance of the prototype sensor has been tested in the laboratory with different types of PD sources. The performances of the prototype sensor have also been compared with a conventional sensor. Results show that the prototype sensor has potential usage in the power industries for its enhanced multiple PD monitoring ability over traditional sensors.