Research On Automatic Verification Technology Of Three-phase Combined Transformer

Three-phase combined transformer is used in 6 ~ 35 kV distribution network by the current transformer(CT)and voltage transformer(PT)assembled into one of the electrical equipment,it carries on the electric energy metering and the voltage monitoring to the high voltage users,and its quality performance and error conditions in the power sector will directly affect the safe operation and economic benefits.Therefore,it is of great practical significance to study the automatic verification technology of three-phase combined transformer in accordance with the relevant national standards and industry regulations.In this paper,the related work is as follows: Firstly,the error influencing factors of the three-phase combined transformer are analyzed in detail by theory and experiment,including the interaction between CT and PT and the measurement of CT leakage current,and gives the error calibration method of three-phase combined transformer;Secondly,a direct measurement method of CT magnetic saturation margin based on proportional converter is proposed,which solves the excess current problem of load box,transformer calibrator and standard current transformer,it realizes the seamless connection between current transformer calibration and magnetic saturation margin detection process automation,and gives the principle and steps of the test load error curve extrapolation for three-phase voltage transformer.Thirdly,this paper develops an integrated movable three-phase combined transformer verification device,and realizes the automatic verification of CT and PT and insulation resistance and power frequency withstand voltage test process under the operating condition,which also solves the problem of three-phase combination transformer because of its heavy weight,large volume,low manpower movement efficiency,labor intensity and low safety factors.At the same time,this paper also built a mobile three-phase combination of transformer storage area verification system,which can communicate and share data with backstage management system through WLAN.Finally,according to the procedure,insulation and withstand voltage and error tests for mobile three-phase combined transformers are carried out,the test results meet the requirements.