Impact of Transformer Modeling in Assessing Dielectric Failure Analysis

In this paper we analyze the possible causes of two dielectric failures that occurred in a hydropower s ubstation. To investigate the possible causes, the substation was modeled in detail and distinct transformer models were considered: a simple RLC circuit given by the manufacturer and fitted rational modeling of the transformer admittance matrix. The rational modeling was implemented as a multi-phase RLC circuit and a companion network in ATP. Accuracies issues regarding the realization of the rational modeling in ATP are als o presented. The obtained waveforms were further analyzed using a detailed winding model of the transformer. The results indic ated that higher overvoltages occurred across some parts of t he winding.

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