Design and simulation of a new model for air‐gapped current transformers

Abstract

Current transformers (CTs) with air gaps in their iron cores are mainly applied in power systems to prevent saturation-caused malfunctions of current-based relays. However, performing reliable power system studies necessitates accurate modeling of airgapped CTs. This paper presents a new model for air-gapped CTs based on the Preisach Theory, which has the ability to represent the role of air gaps of different lengths in the performance of a CT. The salient feature of this study in comparison with other published works is that it does not require measuring the magnetization curves of the air-gapped core, which is often difficult. In order to validate the effectiveness of the proposed method, several simulations have been performed using PSCAD/EMTDC and MATLAB software packages. Simulation results indicate that the proposed model can accurately represent the characteristics of saturation as well as remanence of air-gapped CTs.