Research on the performance of a fiber optical current transformer for high voltage filtering capacitor unbalanced current measurement

Abstract

Subject of study. A fiber-optic measurement scheme for the unbalanced current of a high-voltage filtering capacitor is proposed, where an all-fiber temperature sensor based on temperature birefringence is presented to realize the real-time correction of temperature errors. Method. Prototypes of an all-fiber filter unbalanced fiber optical current transformer type and a magneto-optical crystal type with a rated current of 1 A and a rated voltage of 258 kV have been developed and performance tested. Main results. After temperature correction, the accuracy of the all-fiber filter unbalanced fiber optical current transformer type in the range of −40∘C to 70°C meets the error limit requirements of class 0.2 specified in the Chinese Standard GB/T 20840.8-2007 (Instrument transformers—Part 8: Electronic current transformers standard), whose accuracy, integration, reliability, and anti-interference ability are better than the magneto-optical crystal type. The proposed scheme has the ability of small current (less than 20 mA) measurement in high voltage (more than 110 kV) scenarios.