Effect of Incorporation of Air Gap to Depress DC Components in Current Transformers

Current transformers with anti-DC component function are meaningful to achieve accurate measurements in power transmission systems. In this paper, new structure of magnetic core in an anti-DC component current transformer was studied. Ansys Maxwell is used to model and analyze the core structure of anti-DC transformers. Application of material with low and constant permeability in composite cores can expand the flux margin, and allow them to work properly in DC environment. Introduction of an air gap in the magnetic linkage in a high permeability core can reduce the permeability and improve its tolerance to saturation. A new structure with partial air gap in the magnetic core was designed to achieve anti-DC performance. Effect of geometry of the air gap on depression of DC components in a transformer was researched. The simulation results show that the integrated magnetic core with partial air gap can improve anti-DC characteristics in terms of accuracy and linearity. And the proposed magnetic core structure has potential to be manufactured with low cost.