Research And Application Of The Key Technology Of OLTC EHV Auto-transformer

At present,the super-high voltage(EHV)power grid has a certain scale.EHV transformer as one of the important equipment in the system,will directly affect the security and stability of system.The purpose of this study is to develop a EHV transformer with constant flux voltage variation(CFW)structure.The structure effectively reduces the tap-changer insulation level,adopt public winding terminal CFVV structure.It reduces the design difficulty,reduces the manufacturing cost and reduces the floor area.In this paper,the characteristics of the OLTC EHV auto-transformer are carried out in the following four aspects.Firstly,research on the layout of transformer overall structure.The change of windings arrangement will affect the design of insulation structure and the manufacturing cost.Therefore,determine the general structure ac-cording to the parameters,is the key technology of product design.Secondly,the im-pedance calculation method.The transformer adopts a special structure with double body.As one of the important parameters,impedance calculation method is also the key technology of design.Thirdly,the structure of internal insulation.Compared with conventional transformers,the internal insulation structure of the transformer with double active-part is more complex.So the optimal insulation structure is one of the technical difficulties.Fourthly,transformer temperature rise control.Temperature rise directly affects the insulation life of the transformer,and how to control the tempera-ture rise is also a technical difficulty in the complex large-capacity dual active-part transformer.This paper studies the above issues.Combine research results and previous expe-rience to make a prototype of OLTC EHV auto-transformer.The test verification of the prototype was carried out.