Smart Grid Monitoring: Non-Contact Phase Current Sensing with GMR Sensors

Power distribution networks face challenges in improving reliability, reducing maintenance costs, and enhancing operational safety. Conventional contact-based sensors, like Current Transformers and Hall-effect sensors, are costly to install, pose safety risks during setup, and can be affected by electromagnetic interference. Traditional options such as Rogowski coils have limited sensitivity over a wide bandwidth, while Tunnel Magneto-Resistance (TMR) and Anisotropic Magneto-Resistance (AMR) face issues with magnetic saturation or cost.

Researchers have developed a promising non-contact solution involving Giant Magneto-Resistance (GMR) sensors, positioned at a distance beneath overhead distribution lines. The GMR system achieved relative accuracy ranging from 64.64% to 91.49%, with most phases exceeding 80% accuracy. Reconstructed current waveforms closely matched reference Hall-effect measurements, keeping residual current errors within +/- 2 Amp.

However, under non-linear loads, which include devices like CFLs, microwave ovens, and air conditioners, odd-order harmonics increased distortion, leading to higher residual error on the neutral conductor (35.36% NMAE).

Error factors primarily arise from physical mounting tolerances, minor axis misalignments, and sensor hysteresis. These factors are targeted for improvement through post-assembly AC calibration. The findings, presented in the paper "Real-time Load Current Monitoring of Overhead Lines Using GMR Sensors" at the 2026 IEEE/PES Transmission and Distribution Conference and Exposition (T&D) in Chicago, IL, USA, highlight the potential of non-contact GMR sensor systems for enhancing the efficiency and safety of power distribution networks.