| Oil-immersed power transformer is applied widely and the most critical power equipment in the transmission of electricity, whose main insulation system is composed of oil-paper composite insulation, which is directly related to the quality and reliability of the operation of the transformer life and carry electricity safely and reliably. Oil-paper insulation will produce the aging products such as water, organic acids in the running process, oil-paper insulation will produce the aging products such as water, organic acids in the running process, which not only improves the conductivity of the oil-paper insulation, but also serious corrodes metal components and catalyzs the hydrolysis of cellulose paper, which will do greatly harm to the transformer. In these products, water is the biggest "killer" for oil-paper insulation because much content and more dangerous. The traditional detection method is that regularly taking samples from the running transformer and measuring water content in oil,and then comparing with moisture steady-state distribution curve such as Oommen curve to obtain the moisture content in insulation paper. This approach is inconvenient operation, large testing error and difficult to establish a direct mapping relationship between the aging status and measurement results, thus being replaced by a new test method gradually. Dielectric response method is a nondestructive testing method in oil-paper insulation condition diagnosis recently which has drawn the attention of the scholars at home and abroad. Among them, the recovery voltage measurement (RVM) and frequency domain spectroscopy (FDS) have been widely studied and achieved fruitful results in the assessment of water content in oil-paper insulation duo to carrying rich information and simple method. However, organic acids have similar properties with moisture, The most important aging form of insulation paper is hydrolysis under the acidic conditio. Thus, the generation law of organic acids in the oil-paper aging process. Organic acids and water have synergistic effect on thermal aging of insulation paper and mechanism.Organic acids make a difference in RVM and FDS characteristic parameters as well as assessing moisture content in oil-paper insulation, which are urgent research topic. To sum up, this article has important practical significance to research acid on the thermal aging of oil-paper insulation and dielectric response.Firstly, the paper got the general mathematical expression for recovery voltage using extended Debye model and the Laplace transform to illustrate the mechanism of recovery voltage. Secondly, design the oil-paper thermal aging test to reasearch the production law and mechanism of organic acid in the aging process of transformer oil and insulation paper, and also study the influence of acid on RVM characteristic parameters. Finally, formic acid and stearic acid on behalf of low molecular weight acids and high molecular weight acids respectively as the focus.The distribution characteristics of formic acid and stearic acid in transformer oil and insulation paper by experimental method respectively. The distribution characteristics of formic acid and stearic acid in transformer oil and insulation paper by experimental method, on which temperature and moisture have effect. Study on the influence of formic acid and stearic acid on FDS of dry and damp oil-paper insulation respectively at different temperature. Studying on formic acid and stearic acid and water have synergistic effect on insulation paper aging, and establishing the relationship between activation energy and the chemical reaction rates of the insulation paper by the zero order kinetics model of paper degradation and Arrhenius equation, which help us deeply analyze the aging mechanism of acids on oil-paper insulation from the micro levels. |
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