Contactless Current Measurement for Enclosed Multiconductor Systems Based on Sensor Array

How to measure ac currents in a bundle of inaccessible, enclosed conductors has been a challenging problem but with many potential applications. This paper presents a method to solve the problem using an array of magnetic field sensors. The proposed method consists of two novel ideas. The first idea is to use an off-site calibration method to establish sensor parameters including sensing position and angle, which provides more accurate sensor parameter estimation than their nominal values. The second idea is to "measure" (i.e., calculate) conductor currents and positions based on the sensed magnetic fields and preestablished sensor parameters. This process is simplified since the sensor information is obtained by the first idea. Both calibration and measurement tasks are formulated as nonlinear least square problems and solved efficiently. The proposed method is demonstrated for the cases involving ideal three-conductor system and practical residential service cable enclosed in a plastic conduit. The method has the potential for contactless current measurement of Romex cables and overhead distribution lines.