AMR current sensors for evaluating the integrity of concentric neutrals in in-service underground power distribution cables

In this paper, we present a new method to diagnose the integrity of concentric neutral wires in underground power distribution cables. This method uses a commercially available 3-axis anisotropic magnetoresistive (AMR) magnetic field sensor chip. The AMR sensor is passed once along the energized cable axially, and the cable's 3-axis magnetic field is plotted as a function of position over the cable. Peaks corresponding to the individual concentric neutral currents are observed, and can be analyzed to diagnose breaks in concentric neutrals due to total corrosion or other means.