AN OPTICAL CURRENT COMPARATOR FOR ABSOLUTE CURRENT MEASUREMENT

The design and performance of an optical current comparator based upon a triangular-shaped bulk glass sensing element are presented. The eff ect of the Faraday rotation produced in the sensing element by an unkn own large current is nulled by a smaller known current of opposite pol arity, thus giving an absolute measurement of the unknown current. The design requirements of the sensor configuration are analysed theoreti cally by computer simulation and tested experimentally for both ideal and non-ideal sensors. The sensor may have many applications in the po wer distribution industry, as both absolute and differential a.c. and d.c. measurements up to very high currents are possible.