Analytic Computation of Power-Line Voltage Drop Produced by Magnetic Energy Harvesting Device

For power-line monitoring, autonomous wireless power-line sensors are hung from overhead power-lines and transmit the data collected from measurement systems using internet-of-things technology. Since these sensors require a continuous power supply, some have proposed using self-powered monitoring devices to harvest magnetic energy using a current transformer (CT) with a toroidal core structure, as shown in Fig. 1a [1], [2]. However, those studies only focused on the power transfer efficiency of the CT without considering the effect of eddy-current loss in the CT and impedance matching for maximum power transfer to the load. Even though this device produces voltage drop and impedance changes in the power-line, no analysis of the CT impact on the power quality of the power-line has been done. The power quality is very important issue that power supplier cannot ignore. Impedance changes by CT in power-lines can induce power factor distortions in the electric power system. This paper presents analytical methods for calculating voltage drop and impedance changes in power-lines. Voltage drop and impedance change were found to increase as load impedance decreased under the impedance matching condition.