Design of novel structure current transformer with shielding coils for overcoming the saturation of core

The core saturation of current transformers is one of the key obstructions in the development of highly reliable protective approaches and devices of power systems. A novel structure current transformer with shielding coils is introduced and analyzed in this paper. The coils are enwound outside the measurement winding of the current transformer, and each couple of coils are located at the opposite position relative to the diameter of the core, and connected in opposed-polarity. With the opposed-polarity connecting coils the magnetic field in the core produced by its adjacent phase current in a three-phase system can be shielded, so that the core saturation can be avoided. However, the coils do not influence the main magnetic flux that is caused only by the same phase current.