A Hybrid Electro-Optic Current Transducer Using a Photodiode-Based Primary Supply

A hybrid electro-optic current transducer for protective relaying application is presented. The transducer combines a Rogowski coil with a reflective mirror based MEMS device located in the high-voltage environment. A Si-based photodiode pumped by close-loop PWM light wave is carefully designed as the optical primary power supply due to the 0.5 mW power consumption of MEMS module. Experiments were made in which the steady-state, transient, frequency and temperature response of the transducer were tested. Test results show that a maximum ratio and phase error of 0.5% and 19 min are respectively achieved for currents over 20-480 A range. In addition, the maximum error drifts of 1% and 16 min were observed over the temperature range of -20 to 80 °C. The transducer has the feature of low-power consumption and cost-effective, and can be widely used in electric power industry.