Effect of different terminating resistors on the FRA method sensitivity

Frequency Response Analysis (FRA) method proved to be very useful in detecting the mechanical deformations inside a power transformer. Several configurations are possible for FRA method and it is better to use the one with the best sensitivity to mechanical changes. In this paper, the effect of terminating resistors on the FRA traces is studied in order to find the most sensitive ones. The sensitivity to disc space variation, which is a common mechanical defect, is studied particularly. Four usual connection methods are used with 12 different resistor pairs in an experimental setup. In order to perform the sensitivity analysis, three numerical indices are employed. The results and general conclusions are provided regarding the use of terminating resistors, but more research need to be conducted for other typical mechanical variations in power transformers.