Abstract
Detecting partial discharge (PD) sources in transformer bushings under service conditions is challenging as it requires separation of different PD sources from each other and from external noise. In this study, a new method for PD detection in transformer bushings was tested both in a laboratory setup and on a 132/49 kV transformer in service. The bushings were of resin-bonded paper (RBP) type. Both conventional (IEC 60270) and non-conventional PD integration settings were used. The PD measurement impedances were connected both directly to the bushing measurement taps and differentially between the measurement taps of each of the three bushing phases. The differential measurements allowed location of the PD sources to specific bushings. The results show that the differential PD measurement method can be a useful technique for condition assessment of transformers and other multi-phase high voltage apparatus energized from the grid.