UHF detection of PD in power transformers: The influence of disturbances

Ultra-high frequency partial discharge sensors are often deemed to be immune to disturbance, i.e., signals generated by partial discharge sources outside the transformer itself. In this paper, the above claim is investigated resorting to both computer simulations and experimental tests. The results indicate that corona from power lines in proximity of a transformer, or surface discharges on the surface of bushings can provide signals that are comparable with those generated by PD sources. These findings suggest that care must be taken when evaluating data coming from this type of sensors, as false alarms can be obtained.