Study On The Harmonic Transfer Characteristics Of Capacitor Voltage Transformer

In the power system, nonlinear load may generate amounts of harmonics, which may result in influence on the grid. Accurate measurement of the harmonic level is the basis for monitoring and governance. Harmonics are measured through capacitor voltage transformer(CVT) in high voltage system, but the results exist errors. That study on harmonic transfer characteristics and analyze how to accurately grasp the harmonic content through CVT is of great importance.This paper analyzed the structure principle of CVT, established its mathematical model and the transfer function, and obtained the CVT frequency characteristics curve and the effect resulting from key parameters. Based on the platform of power quality disturbance, carried out some experiments of 110 k V CVTs such as the harmonic measurement error experiment. The simulation and experimental results show that CVT harmonic measuring results exist big errors, but there having certain regularity of harmonic transfer characteristics through CVT : Stray capacitance may affect the CVT frequency characteristics, the certain harmonic transfer coefficient would not change with the content of fundamental and harmonic, transmission characteristics of CVT different from manufacturers and types,while basically identical of the same manufacturer and type.This paper presented that the CVT exist transfer coefficient of each harmonic. For solving the problem of harmonic measuring distortion in high voltage system, paper proposed an idea that correcting measuring results base on the transfer coefficient. A new method is put forward that inputting pure harmonic to resonant boost device to measure CVT transfer coefficients and using neural network to identify and predict transfer coefficients.