Wide-band high-voltage cable current wireless measurement device based on TMR

Wide-band electrical data contains abundant fault transient characteristics, but traditional transformers are difficult to accurately capture wide-band transient signals due to bandwidth limitations. To address this issue, this paper innovatively proposes a non-intrusive current measurement scheme based on an accurate time scale and develops a prototype device. A Tunnel Magnetoresistance (TMR) chip is used to detect the magnetic induction intensity generated by cable current, the ratio coefficient is derived from the spatial position of the high-voltage cable and the sensor, and data recording and real-time display are realized by a microprocessor. A low-noise adjustable gain sensing circuit and a transient signal wireless acquisition module are designed to improve the wide-band signal sensing capability; a mathematical model of the sensor installation position is established to achieve accurate reconstruction of the primary current. A validation platform is built to conduct measurement tests of Direct Current (DC), Industrial Frequency (IF), and transient processes, and a comparative experiment of ground fault current is carried out in a 110 kV high-voltage cable. The study identifies the key factors affecting the measurement accuracy of magnetoresistive sensors, and the experiments show that the measurement errors of DC and IF are controlled within 1 %, and the measurement errors of high-frequency signals do not exceed 3 %.This device adopts a combined power supply of solar cells and current transformer online power supply, which can provide up to 10 W of electrical power, with a lithium-ion polymer battery integrated inside as the energy storage module; the instrumentation op-amp is composed of three discrete operational amplifiers to meet the high bandwidth requirement for wide-band signal measurement.