Research on Dielectric Loss Angle of Capacitive Equipment Based on Blackman Window Improved FFT

摘要

According to the fact that the dielectric loss angle of capacitive equipment is mainly determined by the phase difference between its terminal voltage and leakage current, cutting short the voltage and current signals by Blackman window, and correcting the spectrum of voltage and current signals by three-spectral line interpolation method and 7-order polynomial fitting technique, a simple and practical frequency correction formula and a formula for calculating dielectric loss angle based on improved FFT are given. The results of simulation and measurement show that the spectrum correction method presented in this paper is effective under harmonic interference and frequency fluctuation of power grid, and the measurement results of dielectric loss angle delta are accurate and stable.