Research On Response Of Moisture On Frequency Of Oil-Paper Insulation

Direct to the mechanism of the transformer’s oil-paper insulation aging process, and the research on water factor has a very important sense on state assessment and fault diagnosis and also life prediction of transformer, by analysis of the frequency response of moisture to the oil-paper insulation of power transformers, this article firstly analyzed the hygroscopic properties of pressboard and the presence styles of water, researched on the main source of water in transformer and pointed out the the effects of moisture on insulation aging mechanism to the transformer and the impact of its operational life.Secondly, direct to the balance of moisture in transformer oil paper, analyzed the influencing factors and the hazards of non-uniform distribution of transformer oil-paper insulation systems, and it was given that the transient moisture diffusion model of water distribution in transformer oil-paper insulation. To study the water content changes and moisture transfer law during the oil-paper insulation aging and analyze the law of the different combinations of insulation type of greaseproof paper to moisture changes in the aging process.Finally, to the impact of moisture on the polarization and the dielectric loss of the oil-paper insulation system, introduced several commonly used transformer oil-paper insulation diagnosis and dielectric measurement method, by analysis of the theory of frequency response of the dielectric material, experimental study was carried on, obtained the frequency response of oil-paper insulation was composed by three parts of the frequency response of insulation pressboard frequency response, the frequency response of the transformer oil and the interfacial polarization effect of oil-paper insulation organic overlay composition; the dielectric constant of the oil-paper insulation systems gradually increased with decreasing frequency, and as the moisture content increases, the dielectric constant rise faster, we can see the effects of moisture on the frequency response of the oil-paper insulation system were mainly in the low frequency part, the high frequency part of the dielectric loss curves can almost coincide, that is to say the moisture has little effect on oil-paper insulation system of high-frequency response; When frequency for10-l000Hz, the dielectric loss factor of the oil-paper insulation system is mainly decided by the pressboard. When the frequency is0.01-1Hz, the electrical conductivity of transformer oil from the dominate role in the conductivity of the impact of the oil makes the dielectric loss curves drop rapidly and when the frequency of0.01to0.001, the curve maximum mainly due to greaseproof paper between polarization effect and in frequencies below0.0005Hz, pressboard again play a major role.