Research On Broadband Equivalent Circuit And Transfer Characteristics Of 110kV Capacitor Voltage Transformer

The capacitor voltage transformer(CVT)not only has all the functions of electromagnetic voltage transformer(PT),but also has the advantages of good insulation performance and carrier communication.Therefore,CVT is widely used in power system.The capacitor voltage transformer can measure voltage signal effectively and truly under power frequenc y.But under high frequency condition,influenced by transient overvoltage and instantaneous large current,parasitic parameters inside the voltage transformer will change the transmission characteristics and voltage ratio of the transformer,which will re sult in the decrease of measurement accuracy of the transformer.Therefore,it is necessary to consider the influence of parasitic parameters on the transmission characteristics of the transformer,and establish a wide-frequency transient circuit model of capacitor voltage transformer,which has theoretical significance and engineering application value for the study of the transmission characteristics of the transformer under transient overvoltage.In this paper,with the support of the science and technol ogy project "high performance capacitor voltage transformer technology research on series compensation platform side of UHV project",this paper establishes a wide frequency circuit model of capacitor voltage transformer at 110 k V voltage level,and makes simulation analysis and Research on its transmission characteristics.The main research contents can be divided into three aspects:1.Comparing with the common measurement methods of voltage transformer impedance parameters,the measurement scheme of trans former model parameters is established in this paper.The measurement method of short circuit impedance is adopted to measure the power frequency parameters of capacitor voltage transformer accurately,which lays a solid foundation for the establishment of the subsequent equivalent model.2.Combined with the true structure of voltage transformer,the traditional equivalent circuit model of voltage transformer under power frequency condition is established by using ATP EMTP electromagnetic transient simulat ion software.The voltage ratio of the model is calculated and verified.Considering the parasitic parameters and frequency variation effects in high frequency,based on the power frequency circuit model,the equivalent circuit model of 110 k V capacitor vol tage transformer considering parasitic parameters in the wide frequency transient is established,which provides the basis for the analysis of the transmission characteristics of the next model.3.Based on the wide frequency transient equivalent circuit m odel of capacitor voltage transformer,the impedance characteristics and transfer functions of the transformer are obtained.The influence of parasitic parameters on the transmission characteristics of voltage transformer is analyzed.The effectiveness of the model is verified by comparing with the experimental data,which provides a theoretical basis for improving the accuracy of transient overvoltage measurement of voltage mutual inductor.