Research on the magnetic field of the concentric magnetic ring for high-precision TMR-based current measurement in power distribution networks

The 10kV power distribution network, as a crucial part of the power distribution system, requires current detection for ensuring system safety and optimizing energy efficiency. Traditional current measurement techniques suffer from limitations such as insufficient measurement accuracy and high-power consumption. Tunnel Magneto Resistance (TMR) sensors have shown great potential in current measurement in power systems due to their high sensitivity, low power consumption, and excellent temperature stability. However, the presence of large currents at the hundred-ampere level and complex magnetic environments in the 10kV distribution network can cause the magnetic field of the current to exceed the measurement range of the TMR sensor and result in non-uniform distribution. To address this issue, this study designs a TMR concentric magnetic ring aimed at controlling the magnetic field of the current to be measured within the 0 to 50mT range of the TMR sensor through specific structural design, ensuring uniform distribution of the magnetic field within the detection area. This paper investigates the magnetic field characteristics of the TMR concentric magnetic ring using a multi-scale simulation method. The focus is on the structural design dimensions of the ring, including the effects of the air gap opening size (S), depth (D), and the width of the concentric magnetic ring (W) on the magnetic flux density. Through simulation analysis, optimized dimension parameters are determined to ensure that the magnetic field is not disturbed by external factors and that the magnetic field to be measured is uniform. The results show that an air gap opening size of 5mm, an opening depth of 3mm, an inner diameter of 26mm, and an outer diameter of 42mm can produce a magnetic field within the measurement range of the TMR sensor for current ranges from 10A to 500A. Additionally, the study considers the impact of cable eccentricity on measurement accuracy and finds it to be minimal. This research not only provides a theoretical basis for the structural design of the TMR concentric magnetic ring but also lays the foundation for future physical processing and testing, ensuring the accuracy and reliability of the design and further advancing the development of current detection technology in power distribution networks.