Study On Partial Discharge From Suspended And Mobile Bubble In Power Transformer Oil

When the running oil-immersed power transformer is being fixed, oiled and maintained, a certain concentration of gas will enter inevitably, it is a typical bubble insulation defect which causes power transformer partial discharge. The bubbles in the transformer keep suspened and mobile, when there are a lot of bubbles in the transformer, partial discharge will happen, it will led to further deterioration of oil-paper insulation, and produce more harmful gases, and greatly reduce the strength of equipment insulation, and lead to insulation breakdown of equipment when it is seriously. At present, a lot of research in partial discharge of static bubble have been done at home and abroad.However, little of research in partial discharge of suspended and mobile bubble. It is meaningful to detect and diagnose partial discharge in suspended and mobile bubble in power transformer oil.According to the characteristics of suspended and mobile bubble defect in transformer oil, the corresponding device model has been designed, the parameters and performance situations of various parts of the device have been introduced, the size of the oil channel model has been theoretically analysed, bubble has been poured into device to simulate suspended and mobile bubble in the transformer oil. At the same time, the voltage and electric field distribution of suspended and mobile bubble in transformer oil have been simulated with COMSOL Multiphysics.In order to obtain the characteristics of partial discharge of suspended and mobile bubble in transformer oil. The deformation mechanism of bubble in oil under different motion states has been analysed from the view of mechanical. The bubble deformation parameter has been delimited.Electric field distribution around the bubble with the change of c have been simulated. The partial discharge of static and suspended and mobile bubbles have been measured with UHF and pulse current method. Differences in time-frequency characteristics of discharge has been analysed. The ? ? u ? n discharge three-dimensional map has been constructed. To get ready of transformer fault diagnosis and pattern recognition.In order to study the affects of partial discharge of suspended and mobile bubble. Single pulse discharge and characteristic quantities of ? ? u ? n discharge three-dimensional map have been collected.Discharge rules of different affects have been fitting analysed. The results show that,the partial discharge was more severe with the increase of voltage. Initiation voltage was enhanced with the increase of velocity. The increase of velocity was good to the strength of oil insulation. Initiation voltage was enhanced with the increase of temperature. The increase of temperature was good to the strength of oil insulation.Initiation voltage was droped with the increase of bubble content. The increase of bubble content was bad to the strength of oil insulation.