Future template numerical interpretation techniques for PD pulse location in transformer windings

Identification and location of partial discharge (PD) source is an important diagnostic tool for reliable operation of transformer. In this paper, future template numerical interpretation techniques are proposed for location of PD pulse duration from 0.1 s to 5 s in transformer windings using sweep frequency response analysis (SFRA) principle. To analyze the efficacy of the proposed techniques due to different PD pulses, experimental studies are performed on 22 kV transformer windings by injecting a voltage source of PD pulse across each winding section (tapping). According to Parseval’s theorem, energy distributions of the winding responses are calculated to decide on time period/frequency range to be considered for analysis. The measured winding responses obtained due to injection of 1 s reference pulse across the winding are considered as reference responses. If the PD has occurred any where within the winding, numerical interpretation coefficient has to observe real PD response and make a ‘best estimate/best matches’ with reference responses through appropriate mathematical formulation. The best matches will give the originating source of PD. To predict the confidence limits and significances of numerical interpretation coefficients output for PD pulse location, hypothesis test and probable error methods are utilized. © 2014 Elsevier B.V. All rights reserved.