An Electro-Optic Direct Current Sensor With Periodic Fiber Loss Self-Calibration

In this letter, we present a novel electro-optic dc sensor, which utilizes a fast variable optical attenuator (FVOA) with closed-loop feedback placed in the high-voltage (HV) environment, with the feature of high accuracy and low power consumption. The optical output power of the FVOA is proportional to the voltage of the shunt resistor, from which the value of the primary current can be calculated. In addition, a self-calibration structure is engineered to counteract optical loss by periodically injecting 0 V as a calibration reference through a laser-managed CMOS single-pole double-throw switch. The module in the HV with a power consumption of 2.2 mW is powered by a silicon photocell and a 915 nm laser. Experiments were made in which the accuracy, frequency response, and step response of the sensor were tested. Results show that ratio errors are below 0.24% when the current increases from 5% to 100% of the rated value. And ratio errors and phase errors are below 1.61% and 32.79 μs, respectively, over a frequency range of 50–1200 Hz. Moreover, the overshoot of 17.5% and the stabilization time of 361.22 μs are proved in the step response test. The accuracy performance of our sensor meets the requirements of GB/T 26216.1-2019 Class 0.1 [2019] and IEC 61869-14:2018 Class 0.1 [2018].