Research On Moisture Diffusion And Dielectric Characteristics Of Vegetable Oil-Paper Insulation

With the development of social economy and the growing shortage of oil resources, It has become a consensus of the world to search for a new type green, environmental friendly, good electrical, physical and chemical properties dielectric liquid which can replace the mineral insulation oil. Vegetable oil has become a hot research for scholars both at home and abroad because it is superior to the traditional mineral insulating oil in many respects such as environmental protection, biodegradable, renewable and high ignition point, which has important strategic significance and economic value for releasing the tense situation of energy and the application of new type of insulating medium in high voltage electrical equipment.The general situation of at home and abroad was expounded from different aspects. And on this basis we choose the FR3vegetable oils, mineral insulation oil and ordinary kraft papers as experimental material. The moisture diffusion of plant oil paper insulation and mineral oil paper insulation experimental platform was built and double permeability test was designed in this paper, the moisture diffusion equation was solved, the distribution of moisture in paper changing with thickness were calculated by using the results; the moisture concentration of vegetable oil and mineral oil paper insulation were measured at30℃、50℃、70℃、90℃after60h diffusion; Two kinds of oil paper insulation diffusion coefficient were obtained and the effectiveness of the diffusion model was verified, The factors influencing the equilibrium time was analyzed and the relationship between the balance time and temperature, the thickness of the insulating paper, and the initial moisture content was obtained. And the difference of two kinds of oil paper insulation diffusion was illustrated from the point of view of molecular structure. The results show that the established model can well describe the paper insulation moisture diffusion, the diffusion coefficient of vegetable oil paper insulation is smaller one order of magnitude than mineral oil paper insulation. Vegetable oil can effectively inhibit water spreading inside the insulating paper due to internal hydrophilic group, which delays the ageing of the insulation paper.Frequency domain dielectric spectroscopy (FDS), as a non-destructive diagnostic technology, is widely used in mineral oil paper insulation condition assessment, we built the test platform under laboratory conditions and investigated the changing regularity of frequency domain spectroscopy under different measurement temperatures, different moisture contents, and different aging degree of vegetable oil and vegetable oil impregnated paper by using the IDAX300.The frequency domain dielectric spectrum changing with temperature, moisture and aging time was obtained. And the internal mechanism was explained.