AC meters Electronic meters

The use of electromechanical meters in electricity metering is still in the majority today. In the age of new electronic and computer technologies, we may well wonder why, unlike many other applications, electromechanical meters have not been systematically replaced by electronic ones. The main reason is that the electricity meter is a device that has to be extremely robust and reliable, while at the same time being placed in a relatively "hostile" environment: the voltage of the power grid, on the one hand, and destructive disturbances such as power surges and lightning strikes, on the other, not to mention human intervention in the case of fraud. Proof of this is the difficulty of effectively protecting a computer or other computing device connected to an electrical network. For meters intended for residential use, the accuracy and advanced functions required of the meter are no more important than its robustness, reliability and resistance to fraud. This is accentuated by the fact that the residential electricity meter has to be a low-cost device, and the need for effective protection interfaces has a definite economic impact on the electronic meter. Remember that an electromechanical meter has an average service life of over thirty years, and a return rate for repair of less than one per thousand per year.

To set the scene, here are the typical features of an electronic meter for residential customers:

• current measurement range from 30 mA to 100 A ;

• accuracy and linearity to IEC 62052-21 within this measurement range ;

• withstands temperatures ranging from - 20 ˚C to + 70 ˚C ;

• insensitivity to radio frequency, electromagnetic and electrostatic interference in accordance with stringent standards (IEC 62052-21) ;

• system reliability and durability of over 20 years ;

• power consumption less than 2 W ;

• cost comparable to that of an equivalent electromechanical meter.

Today, the most difficult feature to achieve is a long service life, while the other features are now considered accessible, even those concerning the low cost of the device. Under these conditions, as long as the electricity distribution company is willing to accept the reduced life expectancy of its meters, there is little reason not to switch to electronic meters. There are also factors that now favor the implementation of electronic meters:

• the possibility of using anti-fraud devices, such as the use of two measuring circuits instead of one;

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