The traditional closed magnetic circuit current transformer is liable to be influenced by DC component, resulting in magnetic saturation. Anti-DC performance of current transformer is defined in this paper. Based on the equivalent model of air-gap-core current transformer considering secondaly side load conditions, the influence of air gap length on effective permeability and error of current transformer is analyzed. the air-gap-core current transformer has good anti-DC performance from the B-H hysteresis loop based on the J-A model. A method of anti-DC performance of current transformers based on proportional DC superposition is proposed. The influence of air gap length and DC component on the performance of air-gap-core current transformer is tested. The ari-gap-core current transformer takes into account both anti-DC performance and metering characteristics by error compensation, it provides a theoretical basis for the accurate measurement of current transformer under DC load.
