New Methodology for Enhancement of Residual Life of Power Transformers

Abstract

The measurement of the frequency response on power transformers is a diagnostic test technique for detecting winding displacement and deformation (among other mechanical and electrical failures), which are among the most important causes of mechanical failure in transformers. There are two different methods to carry out the measurement of frequency response: Sweep Frequency Response Analysis - SFRA and Low Voltage Impulse - LVI. SFRA presents some important advantages over LVI such as: higher signal to noise ratio, bigger repeatability and reproducibility and less requirements regarding measurement equipment. It is based on comparison between; 1) earlier measurement on same transformer, 2) measurement on sister transformers, or 3) phase to phase comparison on same transformer with higher signal to noise ratio, higher repeatability and reproducibility and less requirement regarding measuring equipment. SFRA is an electrical test that provides information relating to transformer mechanical integrity. This paper details the use of sweep frequency response as a diagnostic tool to detect winding deformation and core displacement in power transformers. Practical case studies are presented that demonstrates the effectiveness of this technique.