Reasons for "overstating" the readings of electronic meters. The hell is in the details!

  • Dec 14, 2020
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Electrical energy is a popular resource that can be used to solve various tasks: from performing computer calculations, to lighting, heating and performing mechanical work. The volume of electricity consumption is taken into account by electric meters, according to the indications of which the subscriber is billed.

In Russia, by now, the transition to electronic meters has been completed, which, as has been established empirically, “overestimate” the readings. There is a widespread opinion among consumers about the alleged uncleanliness of electricity supply companies, which specifically are forcing property owners to switch to electronic meters, Figure 1, which allows them to obtain unjustified profit.

Picture 1. Electronic electricity meter
Picture 1. Electronic electricity meter

Is it really?

Feature of alternating current as an energy source

Overestimation of meter readings is detected by many users by comparing two parameters:

  • the power of the device as an electrical load indicated in the passport or directly on the nameplate;
  • energy consumption, which is recorded by the meter.
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Moreover, the difference can reach 10 - 15%, which is very sensitive for some segments of the population. The most famous justification for this state of affairs comes down to conspiracy theory: the developers of the meters initially overestimate the actual consumption in their design.

The reason, however, lies in the peculiarity of the alternating current, which the electromechanical meters did not account for. They recorded only the useful active power, while on alternating current, a significant so-called. reactive power. The latter is added to the active power according to the square law, as shown in Figure 2, and their sum forms the total power. Reactive power appears due to the presence of significant inductance or capacitance in the circuit. For example, an electric motor has a high inductance.

Important! The electronic meter records exactly the full power, and in the device passport only the value of the active component is indicated, which becomes the reason for the discrepancy.
Figure 2. Power triangle

Reactive power is considered harmful. It is reflected from the load, going back to the network, then reflected from the source, etc. This process continues until until the energy corresponding to it is uselessly dissipated in the wires, which have, albeit small, but finite resistance.

Connection of active and reactive power

The relationship between active and apparent power (Pa and Pp, respectively) sets the power factor k. There is the following simple relationship between these characteristics:

Pa = kRp.

In the passport of the electrical device, the value of Pa is given, and the electronic counter measures Pp. For a better separation of these parameters, Pa is indicated in Watts (kW, MW, ...), then the unit of Pp is VA (kVA, MVA, ...).

To determine the actual value of the total power Pp, you can use a household meter, which for ease of use is made in the form of a through-socket outlet, Figure 3. Older models of such devices can also measure the power factor k.

Figure 3. Household power meter with power factor measurement

Conclusion

A modern electronic electricity meter is distinguished by a higher accuracy in determining the actual consumption of electricity, recording its consumption in kVA. The latter is not entirely beneficial from the point of view of manufacturers of household electrical appliances, who prefer to indicate only the active power of their products.

Therefore, you need to prepare for some excess of electricity consumption compared to advertising materials and promises of sellers.

Large losses of electricity in industry have led to the development of reactive power compensators. Unfortunately for zealous owners, their household counterparts are unknown.

It is only possible to determine the amount of excess consumption by a corresponding meter, and losses are reduced only by the acquisition of energy-saving equipment.