Error analysis and experimental research of closed-loop fiber optic current sensor

A fiber optic current sensor suitable for electric power system is introduced. In order to improve the measurement accuracy of FOCT, a closed-loop signal detection method based on DSP+FPGA is presented. Some main error sources and corresponding suppression methods are analyzed. According to IEC 60044-8, various accuracy tests of FOCT are designed. The experimental results indicate that the ratio errors of FOCT prototype for the input AC and DC current are all less than ±0.2% within -40~ +60°C. At room temperature, AC current metering accuracy of prototype exceeds 0.1%, and phase delay is less than 129.6'. Measurement accuracy of FOCT for harmonic current within 51 orders is less than 0.5%. The designed FOCT prototype reaches 0.2 class in IEC60044-8 in metering accuracy.