A Novel Algorithm for UHF-Based Partial Discharge Localization in Power Transformers

Power transformers are key elements of a power system. Monitoring systems and condition-based maintenance is applied to ensure their reliability. Partial discharges (PD) lead to a progressive deterioration of the transformer's insulation system. Therefore, detecting and localizing PDs in early stages enables the operators to have a maintenance plan for the transformer and extend its lifetime. This paper is aimed to detect and localize PDs using ultrahigh frequency (UHF) measurement technique. The main challenge in UHF PD based measurement for localization is a precise determination of signal arrival time in noisy batch data. The more precise determination of PD signal onset, the more exact localization is possible. An algorithm is proposed for this purpose, in which two methods are introduced to detect the arrival time of the signals received by the UHF probes. This algorithm is based on receiving several signal sets and a detailed discussion is presented on how the accuracy of the localization algorithm can be affected by increasing the number of evaluated PD-signal sets. Finally, the efficiency of the proposed algorithm is evaluated by modelling possible scenarios that represent the propagation of the Electromagnetic (EM) waves emitted due to the PDs through paper insulation and the windings in a power transformer. Hereby, a PD fault model is placed inside a transformer tank and different barriers are placed around it to evaluate the localization accuracy under various circumstances.