Analysis And Optimization Of High-voltage Exits Insulation Structure For Extra-high Voltage Power Transformers

Power transformers are the major parts of power system, which ensure the normaloperation of the entire power system; the transformers failure would cause severe problemsin the power system, and directly affect the capacity of transmission on power grid, which is ahinder for sustainable development on power grid in China. There are many problems duringhigh-voltage bushings operation, and the reliability and maintenance of HV bushings areimportant to regular operation of supporting electrical installations. The high-voltage leadsconnect the major parts inside the transformer with fixed high potential. The shapes arevarious according to the environment, which affects electric field directly. Lead insulation andreliability of insulating materials are interrelated to overall insulation of transformers.Therefore, the electric field computing and insulation analysis around HV bushings and HVleads are of great significance for the improvement of transformers overall insulation, whichis also an important way to extend the useful life of transformers.This paper analyzed the structure of HV bushing bottom in EHV power transformers. Atwo-dimensional electric field calculation model was estabished firstly, which based on HVbushing bottom in the straight section of the lifting, and was analyzed by commercial FEMsoftware. Then, the weakest part of the insulation in the HV bushing bottom model wasexplored according to the analysis, where the safety margin coefficient was analyzed.Simultaneously, the electric field distribution along the periphery of the equalizing ring wasdrafted. The model was simplified by equivalent media conversion and the structure wasoptimized by genetic algorithm in optimization after the constrast of five optimized algorithms.Finally, it obtained ideal results.This paper analyzed the structure of HV lead connecting bushing and winding in EHVpower transformers. A three-dimensional electric field calculation model was estabished,which based on HV lead in the corner of the lifting, and was analyzed by commercial FEMsoftware. The safety margin coefficient of region with maximun field strength was calculated.According to the structural characteristics of the lead elbow, the simplified model of HV leadwas optimized by sequential nonlinear programming. Finally, it obtained ideal results.