A discussion about the effect of the MID directive on the calibration of electrical energy meters

The measurement of the electrical energy and its billing for tax purpose are of great relevance. In spite of its importance, in the past a scarce attention was given to issues as the calibration and the traceability of the electrical energy meters, so that, at least in Italy, more than 30 millions of energy meters operate and put a tariff without proper metrological characterization. This situation is caused by both the absence of specific laws and the high cost related to the traceability process. In this ambit, a new European Directive on measuring instruments (MID) was introduced in 2004 with the aim to provide a high level of metrological protection in order that any party affected can have confidence in the result of measurement. In Italy the MID has been receipt by a legislative decree and has imposed that: (i) each active electrical energy meter puts into service has to be kept in test for a period as to verify its operating; (ii) after the test period, with positive result, the meter has to be calibrated at most twice in the year. With the aim to give a contribution to these questions, the paper proposes a discussion about the issues of active electrical energy meter calibration and the analysis of requirements of the MID. Finally, the design of a device that may resolve the problem of the traceability to national standards in easy and economic way is reported.