Simulation Analysis of Non-Uniformity Moisture Dampness of Oil-Immersed Bushing

Oil-immersed bushings are widely used in power systems due to their excellent insulation and heat resistance. During the operation of oil-immersed bushings, water vapor may enter the sealed parts such as the general cap due to rainy or humid weather, causing moisture to enter the bushing. When the bushing is moistened, the moisture diffuses into the transformer oil and accumulates in it. As the density of oil is less than that of water, the water always sinks to the bottom of the capacitor core. Currently, when assessing the moisture state of traditional oilimmersed bushings, the assessment result is the overall moisture degree of the main insulation of the capacitor core. However, according to the actual disassembly of the bushing, it is found that the main insulation of the core inside the oil-immersed bushing is not uniformly moistened, with the lower part being more moistened and the upper part less so. In the lower moistened area of the bushing, the dielectric constant of the paperboard changes, causing the internal electric field of the bushing to change and thus altering its working performance. Therefore, this paper conducts electric field simulation of oil-immersed bushings with different degrees and heights of uneven moisture based on the COMSOL Multiphysics software.