Obtaining the parameters of an RC model to know the insulation condition of a distribution transformer

Abstract

Because it is a topic of great interest in the study of the insulation system of oil immersed Transformers, methods have been sought to determine the moisture content and aging of the pressboard, paper and dielectric oil from Transformers, measuring the response of the dielectric materials, which are characterized by known polarization phenomena. One of these techniques is dielectric spectroscopy in the time domain, measuring the polarization-depolarization currents, with this the parameters of an equivalent RC circuit (Debye model) are determined. Using the Debye model (T. K. Saha, P. Purkait y F. Muller, 2005) and obtaining the polarization current through the insulation resistance test, the parameters to establish the condition of the transformer oil-paper insulation system will be determined, using exponential curve fitting of the data obtained from the insulation resistance test with the high vs. Low connection plus tank, the parameters of the time constant τ, the resistance R and the capacitance C of the equivalent circuit are obtained and with this information, the condition of the transformer insulation system is evaluated and decisions are made regarding maintenance actions.