Research On Wideband Equivalent Circuit Of 1000kV Capacitor Voltage Transformer

Compared with the conventional electromagnetic voltage transformer, capacitor voltage transformer(CVT) has high dielectric strength, hardly generates ferroresonance with the system, can be used for carrier communication and has lower prices etc. CVT is widely used in the grid above 110 k V. In 1000 k V UHV substation, during the switching of the series compensation platform, the operation of isolation switch lead to a bad transient environment, easily lead to the damage accident of UHV CVT. When simulate the transient process, the component model of commonly used power system transient simulation software(EMTP, PSCAD etc.) can only be applied to the frequency domain fewer than 10 k Hz, but the frequency domain of the transient shocks caused by switching operations covered beyond 10 k Hz. Therefore the establishment of UHV CVT wideband equivalent circuit model is significant to study the platform side UHV series compensation of damage CVT mechanism and failure analysis, then can use this model to simulation and propose some protective measures.In this paper, the wideband modeling method and application of 1000 k V UHV CVT is carried out, the main work includes the following sections:(1)Study the current measuring method of electrical equipment's wideband parameters, according to the UHV CVT's larger size characteristic and the demand of the failure analysis develop measurement solutions, and then use the vector network analyzer measure the wideband impedance parameters of the capacitors and the s parameters of the electromagnetic unit.(2)Research the current wideband modeling methods, and build the wideband model of the UHV CVT by these methods, then analyze the defect of these method.(3)According to the defect of the current methods, propose a new idea based the image method and genetic algorithms. Build the wideband model of the UHV CVT, and the model is strictly passive, then use the frequency scan function of EMTP prove the accuracy of the model in wideband frequency domain.(4)Use the established wideband UHV CVT's equivalent circuit model to transient simulation, provide a theoretical basis for the research of UHV CVT's transient fault.