Transformer failure diagnosis

Abstract—There are several methods applied to diagnosis failures on the activepart of power transformers, which can be categorized into two main groups:traditional and advanced methods. Traditional methods include measurementsof transformer ratio, exciting current, magnetic balance, winding resistance etc.Advanced methods consist of test of Frequency Response Analysis (FRA),Frequency Response of Stray Losses, Frequency Response of LeakageInductance etc. Results derived from the methods should be performed andcombined to enhance the accuracy of failure diagnosis for power transformers.In order to reduce the number of tests while keeping the diagnostic quality, thispaper introduce a study case in which a new method based on only the drivingpointimpedance test analysis is applied to determine transformer parametersfrom which results of almost above-mentioned tests are recoveredappropriately. In addition, the tendency of parameter change in regard withdifferent failures, which may be valuable for diagnosis quality improvement, isalso researched. In the study case, experimental measurements are performedon a 200 kVA 10.40/0.4 kV YNyn6 opened distribution transformer which issimulated under healthy- and faulty conditions.

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