Hiroyuki KATSUKAWA and Seigo YOKOI

NGK INSULATORS, LTD., 2-56, Suda-cho, Mizuho-ku, Nagoya, 467 Japan

(Received June 20, 1996; Accepted September 9, 1996)

Two types of optical current transducers (OCTs) have a bulk Faraday sensor inserted into the gap of an iron core and a porcelain insulator with optical fiber. The sensor consists of Bi₁₂SiO₂₀ (BSO) single crystal, a polarizer, and an analyzer. The OCTs satisfied the target performance requirement for fault location and metering and demonstrated maintained performance at some power utilities in Japan and the US. We have developed a fault location system that immediately detects the fault current with the OCTs, there by locating the fault section. The OCT can easily replace the existing support insulators for the disconnecting switch without any modifications to structure height or bus-bar. For metering requiring 0.3% class accuracy, use of a BSO with right optical rotatory power combined with BSO with left optical rotatory power results in a Faraday sensor with improved temperature characteristics. The OCT demonstrated 0.3% class accuracy for metering described in the current transformer Specifications of IEEE C57-13, 1993.

Key words : optical current transducer, Bi₁₂SiO₂₀, bulk Faraday sensor, optical fiber, optical activity, power system.