How to choose an electric meter

15-06-2018
Heating

Unfortunately, to date, alternative power sources have not received such distribution as we would like. This is due to the high price of individual modules and sufficient maintenance costs. For this reason, the population consumes energy from the central network, and accounting is done using electricity meters. In this regard, it is necessary to know how to choose an electric meter.

Determine the required parameters

Before proceeding to the choice of one of the existing options for the electric meter for an apartment or house, you need to know the parameters of the network, which is incorporated in the project or has already been carried out in a residential area. See which device is installed. If this is not possible, check out the documentation or contact the appropriate structure.

Determine the operating conditions

To decide on the choice of the electric meter, you must answer the following questions:

  • Where will the metering device be mounted: indoors or outdoors?
  • What is the approximate maximum load?
  • Are you planning to connect high-powered consumers in the future?
  • What current strength is required for comfortable simultaneous operation of most devices?
  • How many phases will be let down?
  • What class of accuracy is preferable in specific circumstances?
  • Do you plan consumption breakdown by tariffs?
  • What are the temperature conditions of operation?
  • Will there be single-phase consumers or only three-phase consumers?
  • Should there be additional functions in the device?

Some items may be marked immediately. Others will need to consider additional information, which will be provided below.

What to choose

Single tariff single phase

All electricity metering devices are divided into two large groups:

  • Single phase. Provided projects for a private house or apartment. Thanks to them, it is possible uninterrupted operation of conventional household appliances. Three-phase motors will then be started through a capacitor.
  • Three phase. Can also be installed in some residential apartments and houses. Usually, an additional application is submitted for this with a justification of the need for an additional phase. It is irreplaceable when heating of all area is carried out at the expense of an electric boiler. Most of them are present at various production facilities. In turn, this option has two subspecies: three-wire and four-wire. The first are applied when only three-phase consumers are planned. The latter come with zero, which means that with proper wiring and connection, you can easily use conventional 220 V units.

Three phase

Depending on the method of connecting to the central network, these types of three-phase meters are distinguished:

  • Three-phase straight-through meter
    Direct-flow. No additional modules are installed on the way to the device. Wires are simply inserted into the terminals, according to the marking and the planned wiring. Products of this type are used in the case of a total load that will not exceed 50 kW, and the current is 100 A. But if the presence of three-phase consumers is minimal or they are switched on infrequently, then it is important to control the phase imbalance. If the figure exceeds 20%, then this can lead to the failure of one of the conductors. The consequence may be a failure or inability to start three-phase units.
  • Semi-indirect. Are provided for those cases when the calculated variable load will be in limits above 60 kW. The main line is supplied to the device through special current transformers. There is a certain loss during the conversion, so when you pay the bill, you must multiply the readings by the factor that is indicated on the converters. There are 4 different input schemes: ten-wire, current transformer into a star, through a test terminal block, with combined current and voltage circuits.
  • Indirect. Most often used for industrial purposes. Like the previous view, they are connected through voltage transformers, but a large voltage - 6-10 kV, as well as current transformers. In this case, the maximum permissible load increases significantly. This means that the start-up of the engines of various machines will take place without much difficulty. Have their two subspecies. The first one is for transformers with a specific conversion factor value. The second is universal and supports various indicators.

Three phase meter connection

There are solutions that have a narrower focus and are applied in certain regions, localities or depending on previously agreed conditions. For example, among them there are:

  • Active and reactive energy meter
    Products that measure active and reactive energy. The energy that is received by the consumer and has been completely transformed and consumed is considered active. For example, this applies to incandescent bulbs, electrical heaters, fireplaces, irons, etc. In this case, with a power of 2 kW, it is considered that the appliance consumed 2 kW over a period of time. The situation is completely different with the units in whose construction there are transformers, capacitors and other components. The essence of their work lies in the fact that at first the energy that is supplied is partially stored and only then turns into useful work. For example, in order to start the engine, it is necessary to store a pulse in a capacitor, which then transfers it to the windings. This also applies to ordinary household power tools. The power of 1000 W can be indicated on the drill, but in fact it will consume 1700 W. In order to determine the exact figure, usually, the coefficient? Is indicated, into which the specified power should be divided. It can be in the range of 0.5 to 0.9. The higher it is, the less is the loss of reactive energy. Counters that take into account two types of consumption are most often installed at industrial facilities, where there is a large number of high-power equipment. In this case, the company receives an extract with two digits. In certain cases, it is possible to compensate for losses using a special module. For the average person, the consumption of reactive energy is not taken into account.
  • With prepaid rates. The bottom line is that the delivery of such a quantity of media that was paid is available. In order for the data to be transmitted to the device itself, plastic cards or iButton keychains are used. In this case, you can pay without waiting in line or waiting. The disadvantage of this solution is to disable even one payment in case of delay.
  • With maximum load limit. In this case, in the device itself, a power control circuit is implemented or a limiter is built in. In the first variant, when the declared value is exceeded, a signal is sent to the disconnecting device, which trips. In the second - the power device itself produces breaking the chain. The installation of such products has become increasingly required in the development of an individual plan. This is due to the desire to rationalize and make more uniform consumption in one area. In some cases, this can create a problem, for example, if you wish, besides gas, you can also heat the room with electrical appliances. Since such a load was not foreseen, a permanent shutdown will occur. Before installing such a unit, it is necessary to agree on all the nuances of the maximum available power.
  • With remote data transmission
    With wireless data transmission or telemetry. In this case, the device may contain a GSM wireless module or a special port for reading. In the first case, the testimony is sent to the service, even without using the controller. In the second, nothing needs to be written, it is enough to read the data with a special device. For the end user, this makes almost no difference, except in cases where someone wants to trick the counter and the violation signal can be immediately transmitted.
  • Single phase multitariff
    Single tariff and multi tariff. The first are used in each apartment. But the latter is a very profitable solution for those who can transfer the main period of high-power devices to night time. The essence of the idea is as follows: from 7 am to 23 pm, accounting is based on one price, and already from 23 on another. Sometimes the difference reaches 2 or more times. In some countries, in order to encourage residents to install such devices, at night electricity is released free of charge.
  • With the ability to sell electricity. In a sense, a novelty, but actively used in farms, where there is a system for converting solar energy or heat into electricity. When there is an active use of electricity on an overcast day, the missing part is purchased from the supplier. But when it is produced too much, then it is given to the network and this is displayed on the testimony. Under ideal conditions, you can go to zero or even a plus.

With prepaid rates

Certain markings are usually applied to the meters. To make it easier to understand, we give a description of the basic values. For example, the letter P means that it is a device for reactive energy, L - active, O - single-phase, Y - universal. Figures 3, 4 - the number of wires in the connection. Additional bonuses in the device can be the display backlight, which allows you to take readings in dark rooms. In others, a small battery is built in that allows you to display values ​​even in the absence of electricity.

Range of counters

Principle of operation

Up to a certain point, electromechanical or induction devices were most common. These are the units in which there is a rotating disk. The principle of its work is based on the behavior of the body in an induction field. The latter is formed due to the presence of two coils. One of them is connected in parallel - a voltage coil, the other in series - a current coil. Between them begin to flow magnetic interference, which pass through the disk and cause it to rotate. He, in turn, sets in motion cylinders with numbers, which represent the final value of consumption. The higher the load, the stronger the effect of interference, the faster the plate rotates. In order for all processes to occur in this way, a phase shift of 90 ° is required.

Induction Counter Operation Scheme

The advantages of such devices are:

  • High reliability. Even in the event of short circuits, they are able to continue working after the elimination of all the consequences.
  • Long service life. The countdown begins with 15 years and more. Some units have not been replaced for 30 years or more.
  • No need for additional configuration. All that is required is to make the proper wiring.
  • Price category is lower compared to electronic.
  • Adaptability to networks of low quality.

The disadvantages are:

  • Decreased accuracy with reduced consumption. This is due to a decrease in the electromagnetic field.
  • Small class accuracy. It does not exceed the value of 2 units.
  • Failure to track with a sharp change in load currents.
  • Ease of implementation of the scheme for unwinding electricity or stopping the disk.
  • High rate of domestic consumption. Those. the meter itself is able to partially affect the amount in the receipt for electricity.
  • The need to use two different devices for the calculation of active and reactive electrical energy.
  • Relatively large size.

The principle of operation of the electronic meter remains the same, but the components have changed slightly. Instead of windings, two sensors are used: voltage and current. After they receive the signal, they transmit it to the converter. His task is to change the signal to digital and send it to the microprocessor. After analysis, the data is displayed on a built-in display or other device.

The scheme of the electronic meter

The advantages of this solution are:

  • Compact dimensions in comparison with induction devices.
  • Lack of mechanical parts which are most subject to wear.
  • High grade accuracy.
  • The ability to use a single product for counting energy in different directions.
  • The minimum error.
  • The ability to remotely send readings.
  • The advantage of calculating losses in a particular area.

There are some shortcomings:

  • Instability to strong drops in the network and the effects of lightning.
  • High enough price. Especially when it comes to multitariff devices.
  • Difficulty in performing repair work.
  • Sensitivity to sudden changes in temperature.
  • The complexity of determining the element in the chip, which has failed.

In some places, authorized organizations will replace instruments. This can occur both at the expense of the consumer, and for free. It is important to clarify this nuance before installation.

Accuracy class

Accuracy class

Accuracy class indicates the accuracy of the device. The larger the number, the higher the defect. Usually it goes in favor of the consumer. Therefore, in the case when there is freedom of choice, they try to stay at a more advantageous solution. In total, in Russia and some other countries, the following quantities are distinguished:

  • 5.0;
  • 2.0;
  • 1.0;
  • 0.5;
  • 0.2.

Often the decimal part may be missing. Also in some situations, the letter S is added, it signals what material the windings are made of. The greatest deviation is usually in induction units, so residents of houses are reluctant to replace them with modern electronic ones.

Someone is still trying to trick the metering device, stopping it, or making efforts to unwind the readings. But most often such tricks do not pass without consequences. It is always easy to track burnt contacts. It threatens with a considerable fine.

Types of installation

In less cases, the installation of the meter is allowed inside the apartment or house. More often they are carried to the landing or to the front wall of the house. This is done in order to complicate the task of the user to make any modifications. There are two main ways of installation:

  • on DIN rail;
  • on a special stand.

With remote control

In the first case, there is an advantage to combine the unit itself and the switchboard. On the back of it there is a special groove that exactly matches the size of the metal plate. The second option has been and is still being used in private homes and apartments. At the same time, an automatic switch or plugs are also installed on the board for protection against overloads and short circuits.

In order to prevent problems with ingress of moisture when installed on the street, a special sealed box is used. It is usually made of plastic that is resistant to UV light. It is important that the viewing window is covered with glass, and not with a polymer patch. In the second case, it becomes cloudy with time and has to be eliminated in order to take readings. Holes for carts should also be closed with special rubber inserts. The dimensions and parameters of the boxes for single-phase and three-phase solutions are different.

Be sure to ensure that the seal was installed in its place. If it is accidentally damaged or disrupted, then you should immediately inform the controller. Without doing this in a timely manner, it will be difficult to get rid of a small penalty.

Calculation of total power and current strength

Electricity meter selection

Conducting such calculations is useful not only for the correct selection of the meter, but also for the purchase of wires with the necessary cross-section, which will prevent damage to the entire system. In order to realize this, you need to do:

  • Take a clean sheet of paper.
  • List on it all the devices that will be powered from the network.
  • Next to each of them it is necessary to rewrite its power consumption.
  • At the end, the values ​​are summed and the total is displayed.

But it is worth remembering that not all of them will work at the same time. Therefore, you should make a unpacking of what will be included most often. Summing up their consumption, it will be possible to determine whether there is enough automatic with the recommended value of the current. If it is revealed that this is not the case, then a corresponding application is submitted with a request to increase the threshold.

There is an opinion that the device should be bought with maximum “freshness”. Part of this advice is justified. But it is worth remembering that the main one is not the release date, but the date of the last calibration. For its designation the corresponding mark is made in the passport, as well as on the seal.

After reading the article, you can return to the questions that are at the beginning and fill in the missing spaces. Given all the tips you can choose exactly what suits you personally.

Video

In this short video, the expert will share his opinion on choosing the counter: