Impulse testing of power transformers using the transfer function method

The transfer function of a transformer winding is deconvoluted in the frequency domain from the digitally recorded neutral current and high voltage applied during impulse tests. The integrity of the winding insulation is determined by comparing the transfer function obtained at full and reduced test voltage. Differences between the transfer function plots reveal local breakdowns in the winding that can be dissociated from partial discharges. Thus the method permits unambiguous acceptance or rejection if the transformer and, since the transfer function is theoretically immune to changes in the applied impulse, also allows evaluation of the chopped-impulse test. Some 100 windings of large HV power transformers have been tested using the transfer function method, which on several occasions has revealed transformer faults as well a test setup problems that would have been missed or misinterpreted by conventional techniques. >

[1]  Ryszard A. Malewski,et al.  Measuring Properties of Fast Digitizers Employed for Recording HV Impulses , 1983, IEEE Transactions on Instrumentation and Measurement.

[2]  J. Leohold,et al.  Berechnung elektromagnetischer Schwingungen in Transformatorwicklungen , 1985 .

[3]  J. H. Hagenguth.  Progress in impulse testing of transformers , 1944, Electrical Engineering.

[4]  L. C. Aicher,et al.  Experience with Transformer Impulse Failure Detection Methods , 1948, Transactions of the American Institute of Electrical Engineers.

[5]  S. L. Foster,et al.  The Use of Neutral Current Measurements During Chopped-Wave Impulse Tests on Transformers , 1957, Transactions of the American Institute of Electrical Engineers. Part III: Power Apparatus and Systems.

[6]  Ryszard Malewski,et al.  Digital Monitoring Technique for HV Impulse Tests , 1985, IEEE Power Engineering Review.

[7]  F. J. Maginniss,et al.  Fundamental Oscillations of Coils and Windings [includes discussion] , 1954, Transactions of the American Institute of Electrical Engineers. Part III: Power Apparatus and Systems.

[8]  E.P. Dick,et al.  Transformer Diagnostic Testing by Frequuency Response Analysis , 1978, IEEE Transactions on Power Apparatus and Systems.

[9]  A. J. Schwab,et al.  Einsatz digitaler Datenerfassungssysteme zur Stosspannungsprüfung von Transformatoren , 1983 .

[10]  P. A. Abetti,et al.  Survey and Classification of Publisled Data on the Surge Performance of Transformers and Rotating Machines , 1958, Transactions of the American Institute of Electrical Engineers. Part III: Power Apparatus and Systems.

[11]  L. C. Aicher.  Some Aspects of Ground-Current Measurements during Transformer Impulse Tests , 1960, Transactions of the American Institute of Electrical Engineers. Part III: Power Apparatus and Systems.