A Simple and Accurate Magnetic Gradient Sensor Configuration Dedicated to Electrical Currents Measurements

International audienceThis paper deals with electrical current identification from stray magnetic field measurements. To satisfy industrial's needs, a new technology is emerging and can allow size and cost reductions of sensors. It consists in placing non-contact magnetic field sensors closes to conductors and deducing the currents' magnitude by inverting the Biot-Savart law. The theoretical study executed in this paper illustrates the advantage of the gradient measurements compared to the field measurement, especially for the rejection of homogeneous magnetic disturbance. It is showing also that the approach of magnetic gradient measurements greatly reduces non homogeneous magnetic disturbance. But, when implementing the practical application for the gradient measurement approach, many difficulties will be appearing; we will list it in the paper sections. Next, we will suppose a configuration solution able to subdue these difficulties; it is based on "round-trip" conductors and consists to laying the two magnetic sensors collinearly along the same axis above the conductor sections to apply gradient measurements. Afterwards, we will apply this configuration for a three-phase system by describing the matrix form, using known geometries and locations of magnetic sensors, and we will explain the manner in which to calculate the reconstruction of the currents which is done by solving the inverse problem. The "round-trip" configuration combined with a simple magnetic shielding and integrated technology can lead to the design of highly accurate and low-cost current sensors