SFRA Ratio Test on Transformer

This month’s Featured Technical Paper is from the Proceedings of the 2018 International Conference of Doble Clients. The paper is titled: SFRA Ratio Test on Transformer.


SFRA test is a powerful and sensitive method for assessing the mechanical integrity of the transformer components and two standard procedures are the Open-Circuit (OC) and Short-Circuit (SC) tests. Both procedures test the complex network of inductances, capacitances and resistors of the windings; and provide the information about the overall condition of the network that include the interaction circuits between the windings. Therefore, a turn-to-turn failure in one winding can influence the measurement of each winding and this renders the identification of the failed winding difficult. This paper proposes the test method called SFRA Ratio that allows to identify the winding with defect. Furthermore, the SFRA Ratio test may provide additional characteristics of the winding structure. Five case studies are included, two from healthy units with different winding configuration and three from failed units with different side of defective winding.

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