基于隧道磁电阻效应的宽频带电流无线测量装置

Wideband current wireless measuring device based on tunneling magnetoresistance effect

宽频带电气量数据包含大量故障暂态信息,传统互感器带宽受限难以精确全面地测量宽频暂态信号。针对该问题,提出一种含精确时标的非侵入式电流测量方法并设计原理样机。通过隧道磁电阻(TMR)芯片测量线路电流感生磁场,根据被测导体与TMR传感器的相对位置计算变比并通过微处理器进行录波和读数。设计低噪声、可变增益的传感器模组电路和暂态录波无线测量传输模组电路,精确感知宽频信号;根据传感器实际安装位置推导传变关系式,实现对一次电流的精确计算。搭建测试平台对测量装置直流、交流及暂态信号传变能力开展测试,在10 kV配电网进行接地故障电流测量对比实验。分析了影响磁阻传感器测量精度的主要因素,结果表明其直流和工频信号测量误差小于1%,高频信号测量误差小于3%。

Wideband electrical quantity data contains a large amount of fault transient information.Due to the limited bandwidth of the traditional transformers,it is difficult to measure the wideband transient signal accurately and comprehensively.Aiming at this problem,a noninvasive current measurement method with precise time scale is proposed and a principle prototype is designed.The magnetic field induced by the line current is measured by the tunneling magnetoresistance(TMR)chip.The transformation ratio is calculated according to the relative installation position between the measured conductor and the TMR sensor and the wave is recorded and read by the microcontroller unit(MCU).The sensor module circuit with wideband,low noise and variable gain,and the transient recording wireless measurement transmission module circuit are designed to accurately perceive wideband signals.Then,according to the actual installation position of the sensor,the transfer relationship formula is deduced to realize the accurate calculation of the primary current.The testing platform is built to test the DC,AC and transient signal transmission capability of the measuring device,and the grounding fault current measurement comparison experiment is carried out by 10 kV distribution network.The main factors affecting the measurement accuracy of the TMR sensor are analyzed.The results show that the measurement error of DC and 50 Hz signals of TMR sensor is less than 1%and the measurement error of high frequency signal of TMR sensor is less than 3%.