Abstract: Optical calculation method and system for relay protection based on Faraday magneto-optical rotation effect are provided. A cascaded optical computing approach is employed, where three optical current transformers are connected in series on a single optical path. Final output optical signal represented as a cascaded multiplication of outputs of three optical current transformers, carries a Faraday rotation angle containing differential current information. Differential current required for protection is computed by modulation ratio which is calculated by use of a carrier and modulation wave signals of the output optical signal detecting by filtering circuit from the third optical current transformer.

Abstract: Optical calculation method and system for relay protection based on Faraday magneto-optical rotation effect are provided. A cascaded optical computing approach is employed, where three optical current transformers are connected in series on a single optical path. Final output optical signal represented as a cascaded multiplication of outputs of three optical current transformers, carries a Faraday rotation angle containing differential current information. Differential current required for protection is computed by modulation ratio which is calculated by use of a carrier and modulation wave signals of the output optical signal detecting by filtering circuit from the third optical current transformer.

Abstract: A schematic diagram of a wideband measurement system for mixed-connected CVT based on an optical voltage sensor is provided. The wideband measurement system comprises a CVT power frequency measurement section and an optical wideband measurement section. In the optical wideband measurement section, a low-voltage capacitor is connected in series between the low-voltage terminal and the ground terminal of the medium-voltage capacitor in the capacitor voltage divider. An optical voltage sensor is connected in parallel across the terminals of the low-voltage capacitor to measure the wideband voltage signal under test. The wideband measurement system for mixed-connected CVT described in the invention enables the CVT to have wideband measurement capabilities while ensuring the accuracy of conventional CVT power frequency measurements.