Experience of the applications of FRA methodology to evaluate short-circuit tests in distribution transformers

Abstract

The normalised terminal short-circuit test takes as evaluation approaches the comparison of the results of routine tests carried out before and after the applications followed by visual inspection by means of disassemble of the machine (extraction of the active parts out of the tank). The objective of this work was to see if the evaluation by means of the comparison of the frequency response analysis (FRA) carried out before and after the short-circuit applications can be such a sensitive tool as the suitable ones under applicable standards. More than 120 results from 5 to 1000 kVA distribution transformer tests are obtained in standardised tests and the performance of this method is compared with the standard methods of fault detection. It can be concluded that the FRA methodology is a useful tool in the determination of the fault type and localisation before transformer disassembling.