Analysis Of Electric Field Of HV Lead And Bushing In Ultrahigh Voltage Power Transformer

Practice shows that the transformer fault lies mainly in the insulation. Therefore improving insulation capacity of transformer and carrying on the reasonable analysis of insulation become the primary tasks of the transformer designs. HV lead is one of the key components of power transformer; hence HV lead insulation is essential for the main insulation of transformer. In order to determine insulation structure, HV lead electric field distribution should be known. Bushing is a core component of HV lead insulation of a large transformer, its inherent quality and performance are of great significance to the transformer matching tests and reliable operation.This paper establishes six kinds of electric field analysis models: two and three dimensional 330kV transformer lead model, two and three dimensional 500kV transformer lead model, two and three dimensional 750kV transformer lead model on the basis of understanding the insulation structure of HV lead of ultrahigh voltage power transformer. Six electric field finite element models are established by ANSYS software, and the computation are also completed by ANSYS. Studied the HV lead insulation in design and manufacturing processes defects on the impact of electric field on the lead, in order to reduce the field intensity around the lead, increasing the thickness of lead insulation, increasing the lead radius or increasing the distance between the lead and the oil tank is adopted, and also trying to avoid some defects appear in lead and insulation has been done. At last, taking 500kV transformer as an example, five methods are put forward to improve HV lead insulation and received very good results.Insulation structure of different bushings are analyzed in this paper, on this basis, there are three models: transformer oil-impregnated paper condenser bushing model, ultrahigh voltage composite insulation gas bushing model, wall bushing model. Above models are calculated by ANSYS software, and the maximum electric field intensity value and their positions are shown. The cause is analyzed and the corresponding measures to reduce the maximum field intensity are taken. The results and some conclusions of practical significance can provide a useful reference for engineering design.