The setup of high frequency circuit model for current transformer

A circuit model to simulate the high frequency behavior (0.1-15 MHz) of an inductive current transformer (CT) is presented. This model is based on the frequency characteristics between its terminals over a given range of frequency obtained by measurement. The transfer function model for the PT (potential transformer) is approximated with rational functions by means of vector fitting. A special method of RLC synthesis for the transfer function is used to build the circuit model of the CT. This high frequency circuit model can be used to calculate the disturbing voltage in the secondary circuit caused by transients in the primary through capacitive coupling in an air insulated substation (AIS).