A new diagnostic method to support standard frequency response analysis assessments for diagnostics of transformer winding mechanical failures

摘要

The standardized frequency response analysis (FRA) method that measures four different frequency responses of transfer functions of voltage ratios, such as end-to-end opencircuit (EEOC), end-to-end short-circuit (EESC), capacitive (CAP), and inductive (IND) interwinding, is considered useful for detection of mechanical failures in transformer windings since the failures cause certain changes on measured frequency responses at frequencies from several tens of kilohertz to several hundreds of kilohertz where the interaction between electrical parameters of windings take place [1]??[7]. However, the current draft standards can only provide a nonphysical assessment based on explanation of waveform change and evaluation of statistical coefficients calculated from comparisons of the standard frequency responses [1]??[4]. It is therefore required that detailed information of physical electrical parameters of windings should be accompanied for a better diagnostic, since the current nonphysical assessment is not really efficient for all transformers with different power/voltage ratings in reality.