Development of optical fiber current transformer for DC railway power system

A novel DC current transformer (CT) based on the Faraday Effect has developed for DC railway power system. The advantages of the developed optical fiber CT are simple and light structure, easiness to handle and robustness to the external magnetic field caused by the adjacent electric current. The basic characteristics of the optical fiber CT are confirmed and compared with those of the conventional Hall CT and saturable reactor CT. Through the fired test and DC short circuit test, it is shown that the optical fiber CT realizes enough response and enough resolution for the practical application. Furthermore, its strong robustness to the external magnetic field is experimentally confirmed.