Self-Powered, Nonintrusive Electric Power Monitoring System for Home: A Feasibility Study

This article presents a self-powered, nonintrusive monitoring (NIM) unit for voltage and current in a typical two-wire electrical system. This article addresses two new aspects of an NIM unit. The first one is about a simple method to form a capacitive network without affecting the insulation of the cable, and use that to measure the voltage and harvest energy to power the circuit for measurement and communication. The second one is about the development and integration of a simple, easy-to-install current sensor for a two-wire power system. The proposed NIM unit consists of such a current sensor, a capacitive network-based voltage sensor, a power harvester, and a low-power communication module. The monitoring unit also has an energy storage unit and a processor. Though there have been some attempts reported in the literature on nonintrusive energy harvesting or sensing the voltage difference, separately, much attention was not given to optimally combining these two activities, which is beneficial. Most available nonintrusive voltage sensors and some current sensors require an external power supply for operation. In addition, self-powered voltage or current sensors with wireless communications modules are rare, making the available sensors unsuitable for monitoring appliances or loads in less accessible locations. The setup requires significant effort for power supply, communication wiring, and installation. Furthermore, battery-powered modules face the limitation of frequent battery replacement. The proposed work consists of an energy harvesting mechanism to power the NIM module, along with voltage and current measurement features, and transferring the measured information through wireless communications, which relaxes the tiresome installation process and is free from regular maintenance. A suitable laboratory prototype has been developed, and the functionality of the proposed energy harvester, current, and voltage sensing was tested. The energy harvester module developed harvests about 52 mJ from the 230 V, 50 Hz, two-wire cable for every 15 min. This energy is used to power the NIM module.