Deriving an equivalent circuit of composite oil paper insulation for understanding the Frequency Domain Spectroscopic measurements

Results of Frequency Domain Spectroscopy measurements are known to be largely influenced by insulation conditions, predominantly moisture content and temperature. In this paper, the dielectric behaviour of a composite oil paper insulation system has been explained from the properties of Debye basic model. The measurement has been performed at controlled temperatures and moisture content in the paper. The equivalent circuit parameters of a laboratory made oil paper condenser bushing model were obtained using a non-linear optimization procedure. Since the dielectric parameters values are geometry dependent, poles, calculated from resistances and capacitances, were used as they are independent of the geometry. It was shown that the poles can be regarded as parameters able to be used for insulation condition assessment.