A Wide-Range Self-Powered Current Measurement Method Based on Induced Current Multiplexing for Online Monitoring Devices in Transmission Lines

To address saturation issues in current measurement devices under high currents, a winding wound on the core, driven by a power amplifier, is utilized to counterbalance the magnetic field generated by the measured current in the traditional method. However, this method consumes a significant amount of energy, and the power consumption increases under higher currents, limiting its applicability. To address this vital problem, a wide-range self-powered current measurement method is proposed in this work. The dual-core structure-based self-powered current measurement system integrates a magnetic field energy harvester (MFEH) and a current measurer (CM). In this system, the windings of the MFEH and the CM are connected in series, and the induced current of the MFEH is multiplexed. On one hand, it flows through the load for energy harvesting. Simultaneously, it flows into the CM, reducing the magnetic field within the air gap, and thereby broadening the range of current measurements. Besides, the equivalent circuit model of the dual-core structure is established to analyze the principles of current measurement and energy harvesting. Subsequently, a voltage regulation circuit based on an active rectifier is implemented, which can mitigate the saturation of the magnetic core over a wide current range. A laboratory prototype is built to verify the effectiveness of the proposal. The results show that the output voltage can be maintained at 3.3 V, ensuring stable voltage output. At 300 Arms, the maximum harvesting power reaches 1.83 W. Additionally, the upper limit of the measured current can reach 600 Arms, with a maximum error of 0.54%.