A TMR-based Wide-range Current Measurement Method with Shunt Branch for Grid Transmission Line

The online current measurement is essential for the safe and stable operation of the grid. To accommodate the measure precision requirements of varied current levels in transmission line, the current measurement range should be wide at the same time. In this work, a novel current measurement method is proposed to achieve high detect accuracy for wide-band current. Within a limited bilateral air gap in the magnetic core, the tunnel magnetoresistive (TMR) sensor is placed to detect the magnetic field variation. Besides, an additional shunt branch is wounded on the core, which can convert a portion of the excitation current to the secondary current. With the guarantee of detect accuracy, the reduction in excitation current prevents the TMR chip from magnetic saturation, ultimately resulting in the expansion of the measured current range. Finally, the effectiveness of the method is verified by experiments. The experimental results show that when a 0.1Ω load resistance is connected in the shunt branch, the current measurement range can be expanded by 1.68 times, and the maximum measurement error in the linear region declines from 0.180% to 0.162%.