A method for measuring dielectric loss angle via FFT based on the maximum side lobe decay window-spectral sequence transformation

Abstract

In the measurement of the dielectric loss angle, the Fast Fourier Transform (FFT) is widely adopted due to its high precision and strong anti-interference capability. However, when asynchronous signal acquisition occurs, spectral leakage is prone to arise during the FFT process, thereby affecting the measurement accuracy of the dielectric loss angle. To address the causes of spectral leakage in the FFT algorithm, this paper proposes a high-precision modified FFT algorithm based on the Maximum Side lobe Decay (MSLD) window combined with a seven-point transformation, and applies it to the detection of the dielectric loss angle in capacitive equipment. The MSLD window exhibits excellent sidelobe suppression performance, while applying a seven-point weighted transformation to the FFT output sequence further accelerates the decay rate of the sidelobe spectral components. Accordingly, the proposed method first applies a six-term MSLD window function to the signal under analysis and then performs a weighted transformation on the FFT results, thereby significantly enhancing the measurement accuracy of the dielectric loss angle via FFT and effectively suppressing errors induced by spectral leakage. Furthermore, the influence of parameters such as fundamental frequency, harmonic component ratio, and number of sampling points on the measurement results is also discussed. Simulation results demonstrate that the proposed method achieves high measurement accuracy and good reliability.