Electric Field Analysis Of Main Insulation In500kV Power Transformer

Practice has proved that transformer fault is mostly due to insulation breakdown,however the transformer operating stably largely depend on the rationality of itsinsulation structure design. Of course, it is necessary to have a certain degree ofinsulation margin as well as to give full consideration to the low-cost. In atransformer, the regions with higher electric field strength require higher insulation;Contrarily, other regions with lower electric field strength, the insulation requirementbecomes lower. So calculating the distribution of electric field in such regions andfinding out the max electric field intensity position are much essential.In this paper, we mainly studied the electric field distribution for the powertransformer ODFS-334000/500, using the UG mechanical design software modelingwinding, winding end and high voltage bushing regions separately, and thenanalyzing the electric field of these regions via Ansoft finite element analysissoftware. In order to achieve the insulation requirements, the model size andcalculation analysis had been repeated again and again.During the transformer winding electric field analysis, we mainly research onthe upper end of medium and low voltage, the middle part of high and mediumvoltage, the bottom of high and medium voltage, finding out the max electric fieldintensity position and calculating the insulation margin situation of these regions. Wealso researched how did the curvature radius of medium voltage static ring bottomend and the distance between iron yoke and electrostatic ring influence theelectrostatic ring surface electric field.In term of electric field analysis on pinout and high voltage bushing regions,this paper selected three dimensional electric field analysis owing to the complexstructure of pinout and high voltage bushing, relatively high voltage, non-uniformelectric field distribution. In the process of calculating pinout electric field, weverified whether the max electric field strength position could meet the insulationmargin or not; To avoid the impact of coils on high voltage bushing among previousanalysis, the coils and high voltage bushing were analyzed together in this paper. We also discussed the electric field variation on shielding ball surface when it wascovered by insulator with different thickness, which provided basis for optimizinginsulation.