Electrical conduction of aged oil impregnated paper

Oil impregnated paper is an important solid insulation dielectric in power transformers. Thus it is very significant to understand the dielectric properties of the oil impregnated paper. In this paper, a conductivity measuring system was built to explore the conduction mechanism of oil impregnated paper. This measuring system is able to measure the conduction current in the samples. Based on the system, the mathematical relationship between conduction current and field strength was studied firstly. The results show that the conduction current in oil impregnated paper is mainly caused by electrons injected from the electrodes. The Schottky coefficient ßs was calculated both in theoretical and experimental methods, and both results are in good agreement. The reasons for deviation between two results are analysed. The conduction current of aged oil impregnated papers were measured as a function of different electrical fields. The results show that with the increase of aging time, the conductivity of oil impregnated paper increases and the permittivity decreases.