Electromagnetic Current Transformer (CT) is one of the main equipment in power system, and the remanence in the measuring or protective windings of CT will influence the stability of the power system. Measuring CT is mainly used for the electric energy measurement in normal working condition, focusing on the steady operation state; while protective CT is usually used in fault or short-circuit condition, and the transient transfer characteristic is of significant important. Considering high remanence operation environment in the power system, the numeric analytical model of CT, which is working in the saturation condition, is depicted in this paper. With analyzing the amount of exciting current caused by remanence and deducing the transfer characteristic of CT, the influence of the remanence on the relay protection and the corresponding precautions are proposed, providing accurate and reliable theoretical basis for the protective CT’s correct action and safety operation after system failure. Finally, the electromagnetic transient model of protective CT (TPY) is built in PSCAD, the simulation result of which shows the validity and practicability of the proposed model.
