Simulation Study of Capacitor Voltage Transformer based on Overvoltage Measurement Technology

The direct measurement of overvoltage at the secondary side of capacitor voltage transformer (CVT) at high frequency is vulnerable to the interference of electromagnetic unit, so it is impossible to obtain accurate overvoltage wave. The 110kV CVT is modified by placing the voltage sensor in series with the capacitor divider unit. Firstly, the modified CVT model is established by Matlab Simulink to compare and analyze the overvoltage waveforms collected by the voltage sensor with the waveforms from secondary side. The simulation results show that under power frequency overvoltage, waveforms collected at both ends of the voltage sensor can be more accurate and synchronous with input voltage waveform than those measured directly from the secondary side; while, under operating surge overvoltage, the waveforms collected at both ends of the voltage sensor is essentially consistent with the change of input voltage waveforms, and without oscillation. The partial voltage ratio of voltage sensor differs from the design value by only 0.17%, and the simulation results are in good consistence with the theoretical values. The measurement of overvoltage through the installation of sensor on low-voltage arm of capacitor voltage divider can improve the accuracy of overvoltage measurement.