Test rig used durign the experiments
Test rig used durign the experiments (Source: University of Twente)

Lab tests carried out by Dutch scientists have shown that some of today's "smart" electrical meters may give out false readings that in some cases can be 582% higher than actual energy consumption.

The study involved several tests conducted on nine different brands of  "smart" meters, also referred to in the industry as "static energy meters." Researchers also used one electromechanical meter for reference.

Using a simple test rig, portrayed above, researchers connected the smart meters to various power-consuming appliances found in regular homes, such as energy saving light bulbs, heaters, LED bulbs, and dimmers.

Tests lasted for six months

Experiments went on for six months, with individual tests lasting at least one week, and sometimes several weeks. Researchers tried to reproduce regular household energy consumption patterns and didn't focus on putting the smart meters to stressful conditions.

The study was conducted by researchers from the University of Twente and the Amsterdam University of Applied Sciences. As such, the meters were chosen to represent the installed base of energy meters in the Netherlands. Meters used in the tests were manufactured between 2004 and 2014.

Test results varied wildly, with some meters reporting errors way above their disclosed range, going from -32% to +582%. Tests with uncommon results were repeated several times and the results were within a few percents of the original.

Test results matched user complaints

The results of their study matched numbers posted on an online forum by a disgruntled Dutchman complaining about high energy bills.

Overall, five of the nine smart meters gave out readings much higher than the actual amount of power consumed, while two gave lower readings.

The greatest inaccuracies were seen when researchers combined dimmers with energy saving light bulbs and LED bulbs.

After finishing their lab experiment, researchers dismantled the smart meters to understand the problem. Following their efforts, the three-man research team discovered that smart meters which gave abnormally high readings used a Rogowski Coil in their setup, while the smart meters that gave out low readings used Hall effect-based sensors.

Problems blamed on smart meter designs

Researchers blamed all the issues on the design of some smart meters, and, ironically, electrical devices with energy-saving features.

The latter devices, researchers say, introduced a large amount of noise in electrical current waveforms, which disrupt the smart meter sensors tasked with recording power consumption.

"The reason for faulty readings appears to be the current sensor,
and the associated circuitry," said researchers. "The experimental results [...] show that static energy meters can be pushed into faulty reading (positive and negative) if sufficiently fast pulsed currents are drawn by the consumer."

Up to 750,000 faulty smart meters in the Netherlands alone

Since the research only covered smart meters commonly installed in Dutch homes, researchers say that around 750,000 smart meters deployed around the Netherlands may be giving out false readings.

Worldwide, the numbers of possibly faulty smart meters could be in the millions, especially after some governments, especially in the EU, have pushed for smart meters to replace classic electromechanical (rotating disk) meters.

The true impact cannot be assessed, as researchers did not publish the names, makes, and models of the tested smart meters.

The research team's work, titled "Static Energy Meter Errors Caused by Conducted Electromagnetic Interference," has been published in the IEEE Electromagnetic Compatibility Magazine.

UPDATE [March 27, 2017]: ESMIG, which describes itself as |the European voice of the providers of smart energy solutions" has published research that disputes the findings of the Dutch researchers. Here are their main conclusions :

  • The electromagnetic interference phenomena created in the tests of the University of Twente grossly exceed emissions limits allowable under EU regulation for equipment typically used in households.
  • These conditions would not be found in any imaginable normal household scenario.
  • There is no reason to question smart metering technology.

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