Automated localization of partial discharge in transformer winding using noninvasive capacitively-coupled pulse injection

In an electric power system, transformers are crucial, expensive components, and their failure can cause serious problems. Local electrical discharges called partial discharges (PD) can occur in transformer insulation, causing damage to the insulation over time. To ensure reliable transformer operation, PD detection and localization are essential. It is, however, difficult to locate the source(s) of PD within a transformer winding since their internal sections and turns are not accessible. This work proposes an electrical method for PD localization in a transformer winding, which involves injecting PD pulses into a winding at different locations and recording the propagated signals at the winding terminals. The performance of the proposed approach is investigated using a transformer winding simulation model and then verified experimentally. The adopted model takes the variation in the radius of winding turns into account, providing a more accurate representation of the winding at high frequencies. It was applied to two different configurations of high-voltage transformer windings. The performance of the model to accurately represent the windings was investigated using measured input admittance of the windings. To simulate PD inception, the pulses were injected into every disk of the winding through a capacitive coupling and the current pulses at the winding terminals were determined using the axial multiconductor transmission line (AMTL) model. The recorded current pulses were analysed in both time and frequency domains and a number of features were extracted from them. These features were then analysed for their correlation with the pulse injection location. In the experimental part of this work, a capacitive coupling device was developed to implement noninvasive electrical access to any internal turns. Using the capacitive coupling, the PD-induced pulses were injected into an arbitrary disk of the winding and measured at the terminals. The effect of the PD pulse i