CHARACTERISATION OF PARTIAL DISCHARGE CURRENT TRANSFORMER BEHAVIOUR BASED ON SECONDARY-SIDE PARAMETERS AND MODELLING

High-frequency current transformers (HFCTs) are widely used for partial discharge (PD) measurements. Accurate analytical modelling is often hindered by design information and the presence of parasitic components. This study investigates the characteristics of HFCT behaviours through modelling and proposes a simplified small-signal equivalent circuit to address measurable secondary-side parameters. The model introduces analytical relationships between the physical sensor parameters and the resulting frequency response, including cut-off regions and flat-band behaviour, and explains the influence of burden resistance. A practical method is proposed for extracting key model parameters from secondary-side impedance measurements without prior knowledge of the sensor construction. The

approach is experimentally validated using five HFCT sensors of different designs through secondary-side characterisation. The measured and simulated responses show good agreement, confirming that secondary-side-only parameterisation is sufficient to estimate the usable bandwidth and frequency behaviour of unknown HFCTs.