Abstract—The Polarization and Depolarization Current (PDC) analysis is a nondestructive dielectric testing method for determining the conductivity and moisture content of insulation materials in a transformer. The predominant influence of oil conductivity on the initial amplitudes of polarization/depolarization currents can be used to estimate the oil conductivity of a transformer even without performing direct conductivity measurements on its oil sample. In the same way, an estimation of the conductivity of the pressboard can be obtained from the long term values of the polarization and depolarization currents.Moisture and ageing strongly influence the dielectric properties of oil-pressboard insulation system of power transformer. A prototype model is developed that allows us to analyse the dielectric response of the composite oil pressboard insulation system by varying moisture content in a controlled manner. Polarization and Depolarization current measurement technique is used to analyse the effect of moisture in the aforesaid model.

Index Terms—Power transformer, polarization current

The authors are with the National Institute of Technology, Hamirpur,H.P, India

Cite: Amit Kumar, J. Rattan, R.N Sharma, and Sushil Chauhan, "Investigation of Polarization and Depolarization Current for Evaluation of Moisture in Oil-Pressboard Insulation," International Journal of Computer and Electrical Engineering vol. 3, no. 6, pp. 853-856, 2011.