Transient electric field calculation of UHV GIS spacer under lightning impulse

Transient process takes place when a rapidly changing excitation is imposed on a insulation system, like lightening impulse voltage, polarity reversal voltage, et al. In previous studies transient electric field is calculated considering the relative permittivity as a constant. However, a fast changing excitation contains many high frequency harmonic components under which the permittivity may become quite different. In this paper, a frequency division calculation (FDC) method for transient electric field is proposed. For a fast changing excitation applied to a system, its waveform in frequency domain contains many different frequency harmonic components and its response is the sum of the response of each harmonic component. Different frequency component is calculated with corresponding permittivity, therefore the variation of permittivity with frequency is taken into consideration. FDC method is applied to compute the transient electric field (TEF) distribution of a whole ultra-high voltage (UHV) 1100kV GIS spacer under lightning impulse voltage with finite element software ANSYS. Material parameters for calculation are acquired from experiments. Influences of the frequency properties of dielectric medium on FDC method results are also investigated.