Untangling Non-Contact Power Monitoring Puzzles

Electromagnetic field sensors provide an electronic “stethoscope” that can determine the current and power flowing in the wire without ohmic contact and without the need to physically separate conductors. Isolation is inherent, and non-contact monitors can be installed without special safety precautions. However, the process of reconstructing the detailed conductor currents is an inverse problem subject to subtle and severe complications in real environments. Interference from nearby conductors, incorrect or unconventional wiring, ground leakage, and three-wire connections complicate the interpretation of electric and magnetic fields to infer line currents. Over a year of field monitoring has been conducted to demonstrate signal processing and physical approaches for untangling these problems to produce accurate and reliable multi-phase power measurements with non-contact sensors.