Abstract
During the last few years, the accuracy of static electricity meters (SEM) has been questioned. Significant metering deviations with respect to a reference meter have been observed at customer premises, and laboratory experimental tests results support such findings. The root cause of such errors remains unknown, as there are multiple elements that could affect the accuracy of electricity meters. Furthermore, standard compliant meters exposed to distorted signals may produce negligible, positive or negative relative error depending on the instrument design. Distorted current signals with fast amplitude transitions have produced the highest error in SEMs reported in the literature. In this paper, the accuracy of an energy metering Integrated Circuit (IC) is evaluated beyond the limits of the standards requirements employing a selection of distorted signals from the standards, real-world captured signals and a set of waveforms designed to test the IC under fast changing currents conditions, which are representative of the waveforms resulting from power electronic devices. The experimental results reveal an accuracy boundary imposed by Gibb’s phenomenon for fast changing current signals and a strong relationship between the IC’s measurement error and two key parameters of the measured waveform: signal slope and phase angle. This paper therefore provides a methodology for the comprehensive analysis of SEMs in future power systems which are dominated with power electronic-controlled electrical demand and contributes to the search for the root cause of error in SEMs exposed to distorted waveforms.
Highlights
The accuracy of static electricity meters under non-sinusoidal situations is an important topic for both academic study and public interest [1]
Different emulated power inputs were applied to the Integrated Circuit (IC), by means of changing the current signal value, whereas the voltage input signal was kept at nominal value Un
This paper shows how typical electricity metering IC technology is capable of measuring electrical quantities from distorted signals with good accuracy
Summary
The accuracy of static electricity meters under non-sinusoidal situations is an important topic for both academic study and public interest [1]. The aforementioned proposals try to provide more realistic scenarios compared to those defined in the standards by means of including harmonic content on the voltage and current signals employing waveform generators, power amplifiers and controlled-current loads [10,11,14,22,23] These methods, despite being useful to evaluate SEM measurements accuracy, treat the instrument as a black box and no strong conclusions can be made on how certain signals and its characteristics contributes to the error (and its propagation) on individual components inside the meter. One of the most important components of SEM is the energy metering IC, which typically implement the metrology engine in an embedded digital signal processor (DSP) This kind of ICs has proved to be fairly accurate in the presence of harmonic content [25], but it is unknown how they perform under fast changing currents conditions. This work will inform suitable tests for other ICs and future standards
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