A study performed by analysts at the University of Twente in the Netherlands has resulted in some concern about the accuracy of smart meters.
The study found smart electricity and gas meters can give readings six or seven times higher than they should be.
The news comes at a time when countries across Europe are attempting to roll out the devices, as part of an overall more user-controlled smarter energy system.
In experiments at Twente, more than half — five of nine — gave readings that were much bigger than the amount of power used.
The problems were linked to the design of the meters — and how they were unable to accurately measure usage with energy efficient devices and modern switches such as dimmers. In contrast, two had readings 30 per cent lower, according to the findings.
The meters tested were connected via an electric switchboard to items such as energy saving light bulbs, heaters, LED bulbs and dimmers. The researchers then compared the actual consumption of the system with the electronic energy meter’s readings.
The greatest inaccuracies were seen when dimmers combined with energy-saving light bulbs and LED bulbs were connected to the system.
Some electronic energy meters can give false readings that are up to 582% higher than actual energy consumption. The author of the report, Professor Frank Leferink, estimates that potentially inaccurate meters have been installed in the meter cabinets of at least 750,000 Dutch households.
Professor Leferink told Power Engineering International that ‘more research is needed’ but pointed an area of concern the study pinpointed as problematic for the success of smart metering – electromagnetic compatibility (EMC). As stated in the report, ‘An overview of techniques used by integrated circuit manufacturers such as Texas Instruments, Analog Devices, ST and Maxim, shows that there are various options for signal processing. In case the reactive power and energy are measured, the different metrics corresponding to different mathematical models can provide conflicting results for non-sinusoidal conditions , e.g. 90° shifting of the voltage by means of an integrator, or by means of a time shift of a quarter of a period, or digital implementation of the definition of the “non-active power”.
“EMC is more or less excluded because ‘it is too difficult’,” Leferink said. “That is a key problem.”
Asked if the meters sampled were used in other jurisdictions outside the Netherlands, he added, “We did not and do not publish the meter types. It was just a sample of the most used meters. The sensitive meters used Rogowksi coils and meters with Hall sensors gave a lower reading.”
“Smart meters are simply a static meter with some communication capability. There are no differences between the type of sensors/measuring methodologies.”
The study was carried out by the University of Twente (UT), in collaboration with the Amsterdam University of Applied Sciences (AUAS). The report is published in the scientific journal IEEE Electromagnetic Compatibility Magazine.
The Dutch government, in common with member states across the EU, wants smart meters in every household by 2020.
Smart Energy GB, the voice of the industry in the UK issued a statement on the matter, stating, “The study in question took place in a laboratory in Holland and tested nine individual meters. In Britain, all energy meters, including smart meters, undergo a rigorous testing process, and by law must comply with the Measuring Instruments Regulations. Anyone with a question about the accuracy of their smart meter should contact their energy supplier.”
At the present time Power Engineering International have contacted the University’s team to find out what make and model of device was tested and whether it is being used in other countries besides the Netherlands.
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