Improved algorithm of surface charge density distribution and electric field distribution on insulating materials

摘要

Surface charge accumulation on insulating materials is a major factor that greatly distorts the electrical field and thus reduces the insulation level. In this paper, the relationship between the surface charge density distribution and the output voltage of electrostatic probe is discussed, and an improved algorithm is built to calculate the charge density distribution, which employs two-dimensional Discrete Fourier Transformation (2D-DFT) to reduce the amount of calculation and the Wiener filter to reduce the influence of noise. Furthermore, because of the similar relationship between the electric field strength distribution and the surface charge density distribution, the field strength distribution can also be calculated by adopting this algorithm. In addition, the electrostatic probe is taken into consideration in this algorithm, and the spatial resolution of this measurement system including the inverse calculation process is investigated. It is estimated that the spatial resolution of this measurement system with 1mm gap between the electrostatic probe and the surface of the insulation is 0.3341mm. The charge density distribution as well as the field strength distribution is calculated by this improved algorithm when a lightning impulse voltage is applied to a PMMA plate of 1mm thickness, respectively. The results reveal that this algorithm has great accuracy and stability and can exactly calculate the surface charge density distribution and the electric field strength distribution.