Research on Magnetic Field Enhanced Microampere Insulator Leakage Current Sensor

The current sensing technology based on tunneling magnetoresistance effect is a technical method that can be used for weak current monitoring in power systems. This article proposes a non-contact current monitoring method based on a two single axis tunneling magnetoresistance sensing chips for monitoring the leakage current of transmission line insulators. A magnetic field enhancement structure is designed to concentrate and enhance the magnetic field generated by weak currents. The basic principle and monitoring structure composition of transmission line insulator leakage current monitoring is introduced. A TMR weak current sensor is designed, which includes a magnetic resistance enhanced coil, tunneling magnetic resistance chip, differential amplification circuit, analog-to-digital conversion circuit, main control unit circuit, data transmission circuit, and power circuit. The test results indicate that the output linearity of the sensor within the measurement range of± 10 μA-700 mA is good, and the current measurement error meets ±1 mA@10 μA-20 mA, and ±5^% FS@20 mA-700 mA, with a resolution of no less than 10 μA. The test results indicate that the magnetic field enhancement structure designed in this article can effectively achieve wide range and large dynamic range leakage current measurement. The designed sensor can effectively monitor the leakage current of transmission line insulators and provide data support for subsequent insulator pollution level evaluation and pollution flashover protection. The sensor studied in this article has advantages such as good linearity, accuracy, and resistance to external interference, which can provide a measurement basis for the intelligent perception business of the new power system and provide technical support for digital construction of the power Internet of Things.