An Accurate Current Transformer Model Based on Preisach Theory for the Analysis of Electromagnetic Transients

This paper presents a new and accurate Current Transformer (CT) model for the analysis of electromagnetic transients, based on representation of core magnetization characteristics using the Preisach Theory. Unlike the existing CT models, the proposed model determines shapes of hysteresis minor loops independent of the hysteresis major loop. This results in a higher precision and more flexibility to fit the model hysteresis loops with the actual core material hysteresis loops of the CT. The proposed model has been implemented in the PSCAD/EMTDC software environment. As an application of the model, transient behavior of a CT due to a fault and its subsequent reclosure attempts is investigated and compared with the Electromagnetic Transients Program Reactor Type-96 based CT model and the IEEE Power System Relaying Committee CT model. Time-domain simulation studies show that the transient behavior of the CT is significantly different, if different hysteresis minor loop trajectories but the same hysteresis major loop are adopted. This paper concludes that both hysteresis major and minor loops must be represented to accurately simulate performance of a CT for the reported case studies.