The Application of Non-Invasive Sensor in Unbalanced Three-Phase Current Detecting

Unbalanced three-phase loading conditions in demand side can be utilized as a useful indicator of faulted electric appliance or abnormal operation scheme. Existing detection method is commonly invasive, i.e., a set of current transformers have to be installed on individual conductors serving the appliance, so as to measure and calculate if the three- phase currents are balanced or unbalanced. However, limited by space or safety considerations, a non-invasive detection method is practically preferred. This work provides a novel noninvasive detection scheme using magnetic sensor array, it is able to measure the magnetic field outside an enclosed multiconductor cable and derive the three-phase currents on each individual conductors. An efficient and robust algorithm based on nonlinear least square is proposed. The effectiveness of the proposed method is validated by laboratory experiment using a practical aluminum-armored multi-conductor cable.