Electricity meters have to be accurate and reliable. Otherwise there can be no assurance that customers are not paying too much or too little for their electricity. In Germany, it is the calibration authorities who ensure that we can rely on our electricity meter readings. In addition to the calibration authorities, officially recognized testing agencies contribute their superb technical expertise toward driving technical progress in these times of smart metering and energy efficiency.
Once it had been successfully tested, assessed and sworn-in by the calibration board for the state of Hessen at the end of May 2010, the “Officially recognized testing agency for electricity measuring equipment EF 9” at the VDE Institute was officially registered.
Electricity meters and their components can now be calibrated, and meter and special tests performed at the VDE Institute. These activities are governed by the requirements stipulated in the calibration regulations, which include the deployment of suitable trained personnel and test rooms, and the use of recognized testing equipment. The testing agency must act as an independent unit in organizational terms and the VDE Institute must ensure the impartiality of the testing staff. The calibration authority monitors compliance with these requirements very closely.
The integration of the testing agency in the impartial and independent VDE Institute is an absolute first in the history of Hessen’s calibration authority. To date, most of the 13 testing agencies that are now recognized in Hessen are domiciled at the energy supply companies. A particularly important task is the meter testing in order to discover whether they have been subjected to any manipulation. Dennis Schulz, who has been sworn-in as director of the testing agency, and his deputies Matthias Hübner and Josef Winzig therefore expect to spend a lot of time focusing on this fascinating detective work. They are also well equipped to perform the basic task of calibrating electricity meters.
In addition to inspecting the outer condition and insulation, the meter calibration also involves testing the accuracy of the meter’s counting mechanism under reference conditions. To this end, the counter is connected to a highly accurate, electronic reference test counter. A sensor measures the optical impulses at specifically defined test points (while starting up, in idle state and under normal operating conditions), which are then displayed on the electronic counter’s LED. The difference to the referential test meter is then calculated by a deviation calculator. The PTB test regulations specify exactly how high these deviations may be. The jurisdictional act of calibration is performed once compliance with all specifications has been verified.
Particular care must be taken over preparation and subsequent documentation. This also applies to the conditions in the test laboratory. The room temperature may not be more than 2°C above or below 23°C at a humidity level of 70% maximum.
Irrespective of the “officially recognized testing agency”, the VDE Institute can also perform further tests – such as safety and mechanical tests, tests under the widest range of climate conditions, and tests for electromagnetic compatibility – on the electricity measuring equipment.