Detection of Transformer Faults Using Frequency Response Analysis with Case Studies

Power transformers encounter mechanical deformations and displacements that can originate from mechanical forces generated by electrical short-circuit faults, lapse during transportation or installation and material aging accompanied by weakened clamping force. These types of mechanical faults are usually hard to detect by other diagnostic methods. Frequency response analysis, better known as FRA, came about in 1960s (Lech & Tyminski 1966) as a byproduct of low voltage (LV) impulse test, and since then has thrived as an advanced non-destructive test for detecting mechanical faults of transformer windings by comparing two frequency responses one of which serves as the reference from the same transformer or a similar design. This chapter provides a background to the FRA, a brief description about frequency response measuring methods, the art of diagnosing mechanical faults by FRA, and some case studies showing typical faults that can be detected.