A high frequency transfer function model of potential transformer in GIS

For an accurate simulation of the voltage stress in secondary circuits caused by very fast transients (VFT) in gas insulated substation (GIS), a sophisticated modelling of the inductive potential and current transformers (PT/CT) is of vital importance. In this paper, we present a high frequency transfer function model of the potential transformer in GIS. The model's set up is based on the frequency response from 1 MHz to 60 MHz which was obtained by testing. We use rational function consisting of real poles as well as complex conjugate poles and zeros to approximate the frequency response. A new fitting method based on vector fitting to fit the frequency response only based on the magnitude frequency characteristics of the PT is proposed.