Application of SFRA method for evaluation of short-circuit tests of power transformers

Short-circuit tests are among the standard tests of power transformers. Stressing of transformer winding with large short-circuit currents creates a force action that the transformer must withstand up to some limits. During these kind of tests, the mechanical condition of the transformer winding is usually diagnosed by measuring the short-circuit winding reactance. Recently, the SFRA method has been increasingly used for this purpose. The SFRA methods are based on comparing the transmission characteristics of power transformers before and after the test. The paper is focused on the research of possible use of SFRA methods in short circuit tests. Different methods of evaluation of measured transfer characteristics on real power transformers are compared. As a result, the sensitivity of the method to winding deformations and the possibility of early fault prediction during short-circuit tests are assessed. Early prediction of a possible fault is important for the safe conduct of the test without damage to the test equipment.