Design of Open and Close Magnetic Core Weak Current Sensor Based on Tunneling Magnetoresistance

The application of current sensing technology in power system has achieved remarkable results under the rapid development of smart grid and ubiquitous power Internet of Things. A non-invasive weak current sensor based on tunneling magnetoresistive effect is studied in order to meet the application requirements of detecting the grounding current of 110kV single-core power cable safely and reliably. A two-lobe square fillet magnetic core structure is designed, and a voltage stabilizing circuit with isolated power supply and an instrument amplifier circuit with floating common-mode bootstrap structure are designed based on the closed-loop principle. By analyzing the test data of the sensor, the non-invasive weak current sensor based on tunneling magnetoresistive effect designed in this paper has a range of 0-20mA, and has a sensitivity of 20m V/mA and a linearity of 0.52% in this range. Compared with the closed magnetic core structure, the open-close magnetic core structure meets the needs of easy disassembly of the sensor and broadens the application scenarios of the sensor. TMR current sensor has a wider range and higher linearity, which can meet the accurate detection of grounding current.