Experimental validation of using frequency response analysis method in measuring interwinding capacitance of power transformers

Abstract

The interwinding capacitance of transformers describes the diagnostic status of winding‐insulation and its geometry. Naturally, there is a constant drive in improvising the existing methods and to attain accurate information while measuring interwinding capacitance of a transformer. In this regard, frequency response analysis method is increasingly used in measuring the interwinding capacitance of transformers. The primary reason for applying this method is to establish a faster evaluation method for diagnosing the status of the winding‐insulation through the interwinding capacitances. However, the pertinent measurement procedures are inadequate as they tend to resolve the interwinding capacitances along with the electromagnetic influence of winding‐core assembly, thus making it difficult to diagnose the status of the winding‐insulation. This intricacy could be overcome by making an optimal choice of terminal configuration, that is, a combination of terminal connection, system function, mode of excitation that would minimize the electromagnetic influence of winding‐core in their respective spectra. In this context, the theoretical aspects of making an optimal choice of terminal configuration have already been investigated, and the suitability of the same on actual in‐service power and distribution transformers needs to be validated. This forms the primary focus of this article. A rigorous and systematic experimental study is adapted to verify the existing findings and validate the same on larger power and distribution transformers. After verification, the proposed method may be identified as sensitive in determining the interwinding capacitance of transformers and further recommended during frequency response measurements.