Field trial of optical current transformer using optical fiber as Faraday sensor

The optical current transformers (OCTs) using silica optical fiber as Faraday sensor were manufactured and tested in the field (275 kV substation) for 2 years to confirm their long-term reliability. Regarding the initial performance the current characteristic or the ratio error of the OCT for measurement satisfied the Japanese Electrotechnical Committee (JEC)-1201 class 1PS and that of the OCT for protection satisfied class 1T in the range from -20/spl deg/C to 55/spl deg/C. Regarding the field performance the ratio error of the OCT for measurement was stable within /spl plusmn/1% for 2 years. The current characteristic of the ratio error of the OCT for measurement satisfied class 1PS and a good result was also obtained for the OCT for protection. Also the OCTs measured accurately transient current that arose from a fault in the system. Therefor we confirm the long-term reliability of the OCT in the field through the field trial.