Study On The Shielding Method In High Electric Field Of UHV Transformer

For the energy distribution and need is imbalance in our country,and also we need to control the air pollution,so we need to develop large-capacity,long-distance transmission.Development UHV becomes the focus of our national energy strategy.The UHV transformer's design and manufacturing standards restricting the transmission capacity and the scale of construction of UHV transmission project,and the safety and reliability of UHV transformer is important to ensure the safe operation of UHV project.The voltage level and capacity of UHV transformer are usually very large.With the rated capacity and voltage level increases,the transformer magnetic flux leakage significantly increase,to control the stray loss of tank and the core structure is important.In order to reduce the stray loss,usually install shielding on the tank and the core structure,in this way we can reduce the leakage flux in these metal parts.For the outlet of MV winding in 1000 kV transformer is on the end of winding,and its voltage level is 500 kV.In this high electric field,if the shielding structure design is unreasonable,the shielding effect is often deviation,there may even be low discharge position,and affect the safe operation of the transformer.This paper introduces the technical parameters and structure of 1000kV transformer,on the basis,the three-dimensional model of the iron core and the oil tank is established.The magnetic flux leakage is analyzed by using Infolvtica software.The rationality of the shield structure is verified,and the temperature riseof the core structure is ensured.Next established the eclectic model in 1000kV end lead,MV winding lead,shielding ball of MV bushing.For these models,the MI software,which is from VEI Corporation in Russian,is used in simulation analysis,and obtained the maximum and average field strength and the location which the maximum value appeared,calculated the minimum insulation margin.In the aspect of transformer shielding structure and manufacturing process,this paper discusses the characteristics of shielding methods and the development of shielding material.And put forward the way to place the copper shield on the edge of the shielding cover and use copper to shielding the edge of magnetic shield.In the manufacturing technique,this paper discuses the manufacture methods and the matters that need to attention in the production process.In order to prevent the deformation of the magnetic shield,the paper propounds the measures of toast in vacuum drying autoclave.Combined with the workshop production,optimize the binding method of core shielding,and design a banding machine used for binding the shielding material of core,these measures assurance the making quality of transformer's shielding.