Transient Electric Field Calculation of Zinc oxide arrester under Lightning Impulse Voltage

For a fast changing excitation like lightning impulse voltage which is applied to a zinc oxide arrester, its waveform in frequency domain contains many different frequency harmonic components and its response is the sum of the response of each harmonic component. Nevertheless, the existing simulation analysis of electric power equipment's lightning withstand performance almost doesn't consider the effects of some materials, like varistors, whose permittivity vary with frequency. Moreover, in the IEC, the lightning impulse withstand voltage test of zinc oxide arrester's polymeric house is without the varistors or with transformer oil instead of the varistors. In this paper, the variation of permittivity with frequency is considered, and material parameters for calculation are acquired from experiments. By using software MATLAB and Fourier analysis, the lightning wave is resolved into a sum of different frequency waveforms. The transient electric field (TEF) distribution of a zinc oxide arrester under lightning impulse voltage is computed with finite element software COMSOL. Other two same models without considering the variation of permittivity and with transformer oil instead of the varistors are computed separately. The three results are compared and the relative increase of maximum electric field strength can be as high as 20.18%. Therefore, this method for calculating the transient electric field (TEF) distribution of the zinc oxide arrester is more accurate and more meaningful, and can be promoted to other electric power equipment.