A TMR Sensor Array for Non-Invasive Current Measurement in Three-Phase Cable and Error Analysis

The inevitable trajectory of future distribution network evolution is characterized by automation and digitization. With the development of tunnel magnetoresistance (TMR) sensor technology, the application of non-invasive and non-contact current detection technology is receiving more and more attention. Based on the analysis of the magnetic field around the three-phase cable, this paper presents a non-invasive current measurement system using a magnetic field sensor array. The system employs 8 TMR sensors arranged in a circular array surrounding the measured cable to reconstruct the currents flowing in individual conductors within the cable. Characteristics of magnetic field distribution in the external space of cables and its influence on the measurement error were investigated by finite element simulation. The performance of the TMR sensors was tested using a dedicated platform to ensure stable measurements. The sensor array was calibrated using the method proposed for sensitivity, phase shift, spatial position, and direction deflection angle to minimize measurement errors. The current reconstruction method was introduced by minimizing the difference between the measured and calculated magnetic flux density using a stochastic optimization algorithm. Simulation and experimental results demonstrate that the proposed system can accurately reconstruct current with an error of less than 2% after calibration, highlighting its potential for non-invasive current monitoring in three-phase power cables.