An Error Correction Method for PD Apparent Charge Measurement in Power Transformers

When partial discharge (PD) measurement is performed on power transformers under the IEC60270 standard, a large error will occur in apparent charge estimation due to the winding distributive longitudinal capacitances and unknown location of the PD source. A frequency-spectrum-based PD localization and an apparent charge error correction method are proposed based on winding RLC ladder network gray-box modeling with FRA results and intelligent algorithm. An experiment on a 220 kV inhomogeneous model winding is carried out and the proposed method is applied. The results show that the maximum error of apparent charge has reduced from 37.7 dB to less than 3 dB which shows an error decrease of 70%, verifying the feasibility of this method on real windings. The proposed method requires only single-end PD measurement and follows strictly the IEC60270 standard, which is hopefully to be extended to more complex transformer windings in future research.