Tadashi SATO and Isamu SONE

Power & Industrial Systems R&D Division, Hitachi, Ltd., 1-1-1, Kokubu, Hitachi, Ibaraki, 316 Japan

(Received July 10, 1996; Accepted September 9, 1996)

Bulk-optic current sensors have been developed for electric power systems. This current sensor has a glass ring type Faraday cell, where a light beam circulates around a current-carrying-conductor to precisely measure the current. Fundamental performances and practical applications are described.

Key words : optical sensor, Faraday effect, electrical current measurement, electrical power system