A retrot current sensor for non-intrusive power monitoring at the circuit breaker

Abstract

This thesis presents a new sensor for power monitoring that measures current flow in a circuit breaker without permanent modification of the breaker panel or the circuit breaker itself. At the breaker panel, an inductive pickup and low-power amplifier sense current from the breaker face. Two coupled resonators form an inductive link that serves as a communication channel through the steel breaker panel door. A passive, balanced JFET mixer circuit transmits the sensed current signal through the inductive link by impedance modulation. Outside of the breaker panel door, sense circuitry detects the impedance modulation, and a digitally implemented compensator inverts the non-uniform frequency response of the analog sensor circuitry to reconstruct the original current signal. This sensor provides a solution for low-cost, non-intrusive retrofit of any circuit breaker panel for centralized power monitoring.