Transformer diagnosis using frequency response analysis: results from fault simulations

This paper presents an assessment of which faults can be detected using frequency response analysis (FRA) and how different faults may be distinguished. The test method and the method used by the author for presenting the results are described. The results of an extensive fault simulation programme on a 100 kVA distribution transformer are presented and discussed. The faults simulated include poor tank ground, no core ground, multiple core ground, foreign object in tank, closed loop in tank (circulating current), poor contacts, additional turns, short-circuited turns and loosened turns. It is concluded that no core ground and foreign objects in tank cannot be detected using FRA, but all the other types of fault can be. It is further concluded that multiple core ground and closed loop in tank cannot be distinguished, but that all the other types of detectable fault can be.