Metering for billing purposes has always been crucial for fair trade and customer confidence. For many decades, conventional AC electricity meters have been based on the very reliable Ferraris concept, derived from a purely electro-mechanical transducer relating the metered electrical energy to counting the number of revolutions of a disc. Electronic meters use current sensors based on Rogowski coils, shunt resistors, Hall-effect magnetic sensors, or current transformers. As a result, they have no moving mechanical elements, but can rather be seen as an electronic board with sensors, a microprocessor, and an interface port.
Smart meters are electronic meters offering the possibility of recording detailed consumption and two-way communication between the meter and the measurement infrastructure, either by wireless link (mobile networks, radio) or physical link (Ethernet, fiber optic, power line carrier - PLC). They operate in conjunction with a gateway or a data concentrator on the other side of a two-way communication scheme and represent a network of internet-of-things devices. In turn, this requires a high level of IT security to prevent malevolent coordinated intrusions from destabilising the grid control. This is subject to non-harmonised national legislation and, in many instances, remains underestimated.
Recently, the current immunity requirements of the European Measuring Instruments Directive 2014/32/EU (MID) for electricity meters have been put into question. Electricity meters may be subject to much more electro-magnetic interference today, resulting from the use of solar panels and other renewable energy sources, amongst other things. Some electronic meters have shown vulnerability to these under specific circumstances. Research is underway to understand the (non-)immunity of several types of meters to these interferences, and to support the revision of European and international standards for electromagnetic compatibility.
Interest in DC active electrical energy metering is developing fast owing to solar photovoltaic (PV) energy generation, fuel cells, electric energy storage, transport systems, electric vehicles, and DC power distribution in IT networks and data centres. A key challenge will be the development of the required DC power metrology infrastructure and metrologically sound, harmonised legislative frameworks – possibly following similar principles as for AC active energy meters.
