10.1 An Energy Measurement Front-End with Integrated In-Situ Background Full System Accuracy Monitoring Including the Current and Voltage Sensors

Abstract

Millions of utility electricity meters are deployed globally to determine billable energy consumption. These devices are factory calibrated, and then perform measurement without interruption over their lifetime. Once in the field their accuracy is unknown due to component aging and high voltage/current events [1]. Meters are periodically replaced as a preventive measure, leading to the unnecessary replacement of perfectly good meters while some inaccurate meters may remain in field. This paper presents an energy-measurement front-end that enables continuous background Condition Base Monitoring (CbM) over the lifetime of a meter. Crucially it monitors the performance of its voltage and current sensors, which are typically the largest sources of inaccuracy and drift. During normal operation, small test signals (“stimuli”), with adaptable but well-defined characteristics are injected into the sensors. Their amplitudes at the front-end’s output are then extracted to determine the gain accuracy of the full signal chain. In order to do this, the system must meet 3 main challenges. First, it must be able to generate and inject highly stable and accurate stimuli signals into the sensors. Second, it must have a wide dynamic range in order to accurately extract the stimuli in the presence of unknown and significantly larger load signals. Third, it must incorporate all the digital signal processing involved with stimuli signal selection, extraction and removal. This paper describes the circuit techniques used to address the first two challenges.