Partial discharges measurements for condition monitoring and diagnosis of power transformers: a review

Power transformers are key electrical assets in power networks. Their lifetimes are estimated to be around 40 years if they are properly maintained. However, thermal, electrical and mechanical stresses can cause the apparition of partial discharge (PD) activity in the insulation system that can lead to its degradation. Thus, the presence of PD activity can be considered as indicator of failure. Conventional PD acquisitions can be done in accordance with IEC-60270 and IEC-60076-3 standards. In the last decades, unconventional methods, depicted in the IEC-TS-62478 standard, based on acoustic and electromagnetic measurements are being combined with the conventional ones for monitoring power transformers identifying and localizing PD sources. In this paper, the necessity of PD monitoring in power transformers is highlighted and a review of different methods for measuring PD is featured. Besides, some technological trends are depicted. Finally, PD modelling is presented as a promising compliment for PD diagnosis.