High frequency modeling of protection / measurement current transformers for partial discharge detection

This paper investigates the choice of using preinstalled protection and measurement current transformers (CTs) for the detection of high frequency partial discharge (PD) signals in medium voltage cables by conducting frequency response analysis (FRA) of these CTs and by frequency response modeling. Researchers have developed many high frequency models, mainly for the transient behavior of CTs. While the energy of the high frequency signals in these models is very high, the energy content associated with PDs is very low. The transformer core behavior will be different in both cases and, as far as the authors could ascertain, there is little information on the FRA of such CTs for low energy high frequency input. A high frequency model of the current transformer is presented. The Jiles-Atherton model is used to analyse the behavior of the CT core in a high frequency partial discharge environment. A method for obtaining model parameters such as parasitic capacitances, leakage inductance, winding resistance, and iron loss component is proposed.