Parametric Design Of Insulation Structure And Analysis Of The Electric Field At Winding End Of Transformer

Power transformer is the important electric apparatus in power system, andthe power transformer fault is mostly due to the insulation breakdown. Reliableoperation and service life of the power transformer largely depend on therationality of power transformer insulation structure design. In order to designinsulation structure reasonably, having a certain degree of insulation margin, wemust know that the electric field distribution in the insulation structure, themaximum electric intensity value and its position, so it is necessary to analyzethe electric field of transformer critical zones.Taking a three-coil SFSZ11-63000/220as an example, this paper developedthe parametric modeling of insulation structure at the winding end using VB andPro/E, and the model can be imported to FEM software Ansoft.This paper analyzed the electric field of winding end, high voltage upperyoke clamping zone and bushing shielding ball zone using3D analysis methodby Ansoft software. The maximum electric intensity value and its position wereobtained through a detailed analysis of the electric field at the winding end. Themethods and results can provide a useful reference for insulation structure design.In terms of electric field analysis in high voltage upper yoke clamping zone,the electric field distribution of limb was shown in this paper. It is also illustratedthat2D analysis method can only take into account the electrode which belongsto the plane in the asymmetric structure, so2D analysis method can not obtainthe accurate analysis result. On the basic of electric field analysis, the paperstudied the impact of HV lead layout mode on the electric field of limb, andpresented the method that covers the insulating layer on the limb surface toreduce the electric field intensity around the limb. After analyzing the electricfield with different insulation layer thicknesses, the insulation structure has beendeveloped. All the methods can provide a useful reference for ultrahigh voltage power transformer insulation structure design.At last, the paper analyzed the electric field of bushing and shielding ballzone detailedly, and studied the impact of shielding ball radius and hoist seatdiameter on the maximum electric intensity value of shielding ball. Then, theinsulation structure was improved based on the transformer manufacturing costwhen the insulation margin was satisfied.