Electricity meter

The electricity meter is an integral over a time course measuring device for detecting the amount of a delivered or consumed electric size.

Preferably, the term current meter (also electricity meter ) used for devices with which, however, not electrical current, but effective electrical power is summed over time, whereby electrical energy is measured. The physically correct term is so energy meter. Are counted in these devices mechanically the revolutions of a wheel whose speed is proportional to the active power, or electronically corresponding pulses.

The display involves the conversion factor on the energy or work. The associated physical unit is the joule ( with the unit symbol J ) or watt second (Ws ); However, when electricity meters, the measured value in the larger unit kilowatt-hour is specified (kWh).

Furthermore, there is also a meter, the actual sum of electrical current into direct current applications, ie electric charge capture ( with the unit ampere hour). But you have no more importance.

• 5.1 Ferraris meters
• 5.2 Double - and multi-tariff electricity meter
• 5.3 Electronic Energy Meter
• 5.4 Electronic Energy Meter with remote readout
• 5.5 Retrofit Meter Reader
• 5.6 Treasurer, coin-operated, Prepaymentzähler
• 5.7 load profile meter
• 5.8 Energy Cost Meter
• 5.9 DC or STIA counter

• 7.1 errors permitted
• 7.2 Legal calibration
• 7.3 Technical Quality

General

If the current versus voltage has a phase shift or distortion, is to differentiate performance between active and apparent power. Only the active component of the power and the energy detected by the usual measuring instruments.

The spread in German households counter for consumption billing capture the active current (either AC or three-phase ) and the applied AC voltage. Can be calculated using the instantaneous values ​​of current and voltage, by multiplying ( as in the active power measurement ) and subsequent integration over time of the used active energy, which was purchased from the power grid.

Besides the usual household electricity meters for 10 (60 ) A are for commercial use (including construction sites, festival events ) distributed or electricity meter for 200A. This directly measuring current meters are designed for the rated voltage 230 V ( corresponding to 400 V between phase conductors ).

Downstream of the nominal current or the maximum limiting current is measured in amperes in brackets, which can withstand continuously the counter, without being damaged. Up to this current value and the calibration error limits must be adhered to. The rated current is relevant primarily for calibration, refer to this value, the measurement points that are checked during the calibration process.

Larger energy loss in the industry is often measured by so-called transformer meter. These counters multiply the measurement data from current transformers and voltage transformers. The secondary side of this transformer has generally nominal current 5 A or 100 V nominal voltage, for which the meter is designed. Current transformer meter are also subject to legal according to the Weights and Measures Act.

Counter for greater technical equipment, in addition to the active energy also display the current active power or even detect the reactive energy in kVArh. Some counters store load profiles, in particular the amount and the timing of peak load. Other meters have pulse outputs for further processing of the instantaneous power or energy measurement.

For the new generation include the smart meter.

Statement

Is calculated by small consumers ( households ), only the removed active energy, ie the time integral of the active power.

The integral of the reactive power is also measured at large consumers (industry) and calculated, because this form of power additionally burdened the supply networks. It requires both stronger lines and transformers and causes increased conduction losses. Therefore, the reactive energy is an accounting feature of the energy supplier.

Tariff switching

For residential customers in Germany, for example, households, if necessary, the version is used with two Tarifzählwerken. Thus, the power consumption for the customer can be billed cheaper in times of low demand. This is agreed to supply in the so-called low-load periods, usually in the afternoon and at night, electrically operated heat storage heaters. For electric utilities, a balance in the network load is achieved by this connection or disconnection of consumers to generate heat.

There are electromechanical energy meter with two or more counters in order to settle accounts with respect to time may be different tariffs. Between these counters, for example, through built-in or external ripple control receiver ( which are controlled by centralized ripple control systems in the energy supply company) switched.

When customers ( industry) more electro mechanical counters for energy measurement were common. Here is fully converted to electronic counter with a recording of the instantaneous values ​​of the load profile. In many cases, these meters are equipped with a data line, for example, to the telephone network, connected to settle without delay can. Also, electronic meters with wireless transmission of data over mobile networks are widespread.

Tariff switching is controlled either by a timer or remote control systems. In the ripple control system, the control signals are sent via the power grid. The pulses are modulated in a low frequency range (up to about 1 kHz) to the line voltage of 50 Hz.

Conversion to electronic counter

After new electronic meters are used for industrial applications for some time, they find for some years they were introduced into the household. The distribution there is very different depending on the power company. For example, the spread in Germany is below 10%, while in Sweden over 90 % of households have been converted.

Electronic meters can be equipped with tariff switches, allowing for an agreed time-dependent tariff setting.

New electronic meters are read via data interfaces via remote reading of energy utilities and building automation. With electronic meters without the classification procedure can be changed in the counter. It will not require any electro-mechanical counters in the meter more. These counters should be noted that the indicator for the high- price fares (HT) and low-price tariffs ( NT) may be arranged differently ( HT and NT display up display below).

In Germany, after the amendment of the Energy Industry Act ( Energy Act ) and the new Metering Access Ordinance ( MessZV ) (both entered into force in September 2008) since 1 January 2010 the obligation to use so-called smart meters in new construction and modernization projects.

Also in Germany, smart meters are being increasingly used in the context of state-supported pilot projects for the introduction of smart metering technology. Since early 2006, state-sponsored field trials with continuous connections over Internet ( DSL ) take place. Since late 2008, all utilities offer Scorers with data network connection.

In several countries (eg in the U.S.) is available as a supplement to the electronic counter an integrated shutdown option (remote disconnect ). This allows the power company disconnect remotely control the consumer from the power supply, for example, if this has not paid his bill. To a relay is installed in the counter.

Due to a non-regulated Störfrequenzbereichs between 3 kHz and 150 kHz, there may be significant variations in measurements compared to the real amount of energy in electronic meters. Especially with the connection of renewable energy via inverters this is a known problem in practice since 2010 at the latest.

Load shedding

Main article: load shedding ( power supply )

If an agreed tariff feature is exceeded, a load can be thrown off by a set limiting the power value or the amount of energy. Alternatively, a different tariff is used as a basis for such excess loads for the duration. Such rates can no longer be detected with simple counters.

Types of electricity meters

Ferraris meters

Widely used are the Ferraris meters by the induction principle, named after the Italian Galileo Ferraris. Here, a rotating magnetic field is induced by the single-or multi -phase alternating current, and line voltage in a Ferrari rotor ( aluminum disc, even Ferraris disk ) which generates in it due to eddy currents torque. This is proportional to the product of current and voltage and therefore to the effective power in the temporal mean at every moment. The disc runs in a current of a permanent magnet eddy current brake which generates a braking torque proportional to speed. The disk, the edge of which is visible as a section through a window from the outside, thereby having a rotational velocity which is proportional to the electrical active power. The counting of the revolutions is then to actually related electrical energy proportional.

Ferraris counters add up in their usual structure even at high vibration or displacement power factor shares, only the active power. There are similarly structured reactive energy meters, which sum the inductive or capacitive reactive power. Your inner circuit corresponds to the circuit in reactive power measurement.

With the aluminum disc a drum- connected, so that the energy flow can be read as a numeric value in kilowatt-hours (kWh). Use the attached specified on the meter revolutions per kilowatt hour you can visually identify the current performance by observing the revolutions over a given period and counts.

Double and multi-tariff electricity meter

These counters can the consumption in two or more rates are divided, see Section tariff switching and the adjacent figure of a two-rate meter with integrated ripple control receiver.

Electronic Energy Meter

The electronic energy meter for several years newly developed contain no moving elements. The current flow is detected either by means of current transformers, current sensing systems with Rogowski coils, shunt resistors or Hall sensors. The further processing of the measured values ​​with an electronic circuit. The result is supplied to an alpha-numeric display (typically liquid crystal display, LCD).

Electronic energy meters with remote reading

In Italy, the power company Enel since 2000 every 30 million meters, even in households, to remote-controlled devices to. These are means of PLC ( Power Line Communication ) read. The customer has on display a wealth of information available, come on request up to three different rates (side, main and peak time ) are used. Defaulting customers the power is not turned off completely, but cut back by remote control, the power available to a few hundred watts.

As data interfaces infrared, S0 interface, M-Bus, potential free contact, KNX are (formerly EIB), 20 mA current interface ( connected to GSM, PSTN modem ) or Power Line Carrier (PLC ) are common. The pulse outputs (S0) generally provide a pulse value of 2000 to 5000 pulses per kWh. This value must then depend on the counter, multiplied by a fixed factor, for example 30 or 50, in order to obtain the accumulated measured value.

Retrofit Meter Reader

For counter conventional design with mechanical fuel gauge, it is possible to provide them with a reader. These devices record the count of mechanical fuel gauge with the help of an optical device. Using Character Recognition ( OCR) is transforming the captured image into an electronic information. This information can then be transmitted, as in the electronic energy meter via various data interfaces on. This is an automatic meter reading possible (English: AMR, Automated Meter Reading) and the manual reading can be omitted.

Treasurer, coin-operated, Prepaymentzähler

(English for prepaid, prepaid ')

In some countries there are also cashier counters ( coins), which allow through the ball of money, tokens or more recently, by smart cards, chip key or entering a PIN to retrieve a defined amount of electrical energy.

In Germany and Switzerland, such counters in laundry rooms of apartment houses, and also isolated from power company customers are used with non-payers. They also prevent the build-up of debt money. Prepaymentzähler with smart cards are widely used, for example, in South Africa, with a chip key in the UK.

Load profile meter

For large customers (from 100,000 kWh / a ), the power consumption is not only the basis of the energy used ( in kWh) and reactive charged any registration period ( in kVArh ), but in addition to or just after the energy used. For this interval meters are installed, the log a reading after each registration period. This is called registering power measurement ( RLM).

In a load profile meter several load profiles can be recorded and stored at the same time. Typically, these meters are read remotely reading.

The registration period is set in Germany on 15 minutes. The saved measurement can

• Average power used in kW or kvar
• Meter reading in kWh or kvarh
• Energy consumption in kWh or kvarh

Be the last registration period. For smaller customers, the load profile using a standard load profile is simulated (eg H0 for household customers ).

Energy cost meter

With energy costs measuring the power consumption of individual devices can be measured over a longer period of time. This is useful for devices such as refrigerators that do not have equal power consumption. Often you can enter the price per kWh, and then sees the costs caused by a device. When buying an instrument, it is important to pay attention to the measurement limit and accuracy. Many of the supposedly inexpensive devices are often very inaccurate and can not be processed accurately smaller power consumption, for example, less than 4 watts and high reactive components and crest factors. For private consumers, it is often possible to borrow energy monitoring devices for free at the electricity suppliers or consumer centers. Thus, the acquisition of a usually only temporarily to save energy used for the detection of device resources can be avoided.

DC or STIA counter

Direct current meters have no meaning because of the general supply of all countries with AC networks. Most are DC railways, steel mills or electroplating plants, the typical large consumer operated in private networks that are powered from the AC mains.

Ancient DC meter working on the same principle as the Ferraris meters described above, however, the power is proportional to the torque generated by a direct current motor, the excitation generated by a traversed by the load current coil, and the armature current is obtained through a series resistor in the supply voltage.

A component that can be called a true power meter, is sometimes used as an operating hours counter: it consists of an agreement with an electrolyte of mercury similar to a small thermometer. When current flows through the mercury is fed to the opposite end, whereby the region of the electrolyte passes through the column. The current-time product from the electrolyte volume appears linear distance traveled on the container serving as a glass tube. If the component is a resistor operated at constant voltage, can determine the operating time. After the time expires, the unit can be reversed reused - the area of the electrolyte migrates back now.

When mercury electrolyte counter, also STIA counter ( mercury electricity meter ) or Edison counter called, not of the (fixed ) was measured precipitation, but the decomposition products - mercury and hydrogen. He was its development after the expiration of the patents of Edison electrolytic meter. The mercury fell during the passage of current in a glass tube. This was installed on a scale, which represented the kilowatt hours. The disadvantage of this technique was that after a certain time, the glass tube was completely filled and no further counting was impossible. Therefore, the counter must be read, and then the measuring tube can be tilted in order to allow a re- running counter in a relatively short time intervals. The Stia counter used mainly for small customers (name = Stia Schott Jena; Inventor: Max Grossmann, Jena, 1922) worked with a mercury anode, between the anode and cathode was located a porous wall Scheid. Many old counters have the labels on the name of sub - Stia. This means that these counters (eg, multiple dwelling) acted as a counter in a larger electrical system.

Hydrogen counter functioned similarly. For them, the resulting hydrogen at the cathode was collected and then also read the consumption of a scale.

Electrolyte counter had a high measurement accuracy ( ± 1%) and were relatively simple. Therefore, they asked for the detection of small amounts of power consumption is an alternative to the motor counters dar.

With the conversion to alternating current, the time of the electrolyte counter came to an end.

Standardize

The valid European standards for electronic energy meter are: IEC 62053-21 to -23. For the data interface IEC 62056-21 and IEC 62056-42 are -46 -53 ( DLMS ) and IEC 870 used.

Accuracy

Maximum permissible errors

The relative error limits as a measure of the accuracy of the meter is in the household sector at 2%. At high to be counted electrical work are also meters of accuracy classes 1, 0.5 and 0.2 (usually in conjunction with instrument transformers ). Deployed The highest demands are made, for example, at the transition point from the power plant to the grid or from transmission networks. The accuracy class is indicated on the counters now and then. This information may look like this: as a circle, in which a number is or class 2 or (1 ), where the number always indicates the relative error limit as a percentage. Toroidal Cores constructed of special alloys allow recently high-precision electronic energy meter in DC tolerant execution.

Legal calibration

Each energy meter which is used for the billing of energy consumption, will contribute in Germany so far a calibration mark for the Weights and Measures Act.

Electricity meters, which are used in commercial operations, subject to the verification requirement in Germany. At the end of the verification period ( 8 years with electronic meters, 12 years for mechanical transducer counter with induction work [ with rotor disc ] or 16 years for mechanical meters with factory induction ) the instrument must be replaced or the calibration validity be extended. Exceptions are possible. A common method for extending the calibration validity is the sampling inspection.

The calibration is performed at test centers ( state-approved ). Many network operators and manufacturers have their own testing. However, there are also companies that specialize in the calibration. As a state agency responsible for the certification is in Germany, the PTB in Braunschweig.

Technical quality

The European Measuring Instruments Directive (MID ) controls since 30 October 2006, the placing on the market of various new for the end user of certain instruments in Europe - among others also provide the active power meter. It does not regulate the mandatory verification and the requirements for the placing on the market or commissioning. This remains subject to national law. However, Member States must justify before the Commission and the other Member States if they do not regulate this. MID - compliant measuring instruments must be no longer calibrated before first use.

The MID requirements are replacing many valid national requirements for calibrated meters (for example, in Germany, Austria, Switzerland and the Scandinavian countries). They are mostly identical to the PTB approval in Germany, sometimes a bit harder. For older approvals (eg PTB ) is considered a transitional period to 30 October 2016. All counters present on 30 October 2006 at the market with PTB approval means that up October 30, 2016 continue to be placed on the market. Only newly introduced instruments must comply with the MID. The examination is only incidentally performed in Germany by the PTB, but can be applied in all Member States and must be recognized in all Member States.

For electricity meters MID formally valid only for active energy meter. This results in a problem for counters that measure both active and reactive power: For device part of the active measurement, a MID - declaration of conformity is required. An initial verification may not be required, the part for the Blind measurement must be conventionally approved or verified by the respective calibration law.

Household electricity meter in emerging markets

Populous countries such as China and India are very dedicated in introducing household electricity meter coverage for years. Here, the installation of electronic meters is favored with number systems on chip card base.

Assembly

In many countries (USA, Scandinavia, China) household electricity meters are often placed outside the house. In Germany, the systems are usually in the house on a so-called counter or table, conforms to standards installed in a meter cabinet (see distribution ). For this counter cabinets, there was the so-called TAB ( technical connection condition ) of the respective utility company. Use the TAB in 2000, an attempt was made ​​to unify this variety of TABs. The TAB 2000 and their successors are now applied by most utilities and adapted by attachments to their own needs ( web forms, control loads, ...). The TAB 2000 and their successors have meanwhile entered the VDE standards in the form of application rules.

In one-and two-family dwellings, the installation can be done either on a free space within the building or in a special house connection. In some regions, there are also house connection boxes outdoors, on the plot or on the building. With newer apartment buildings, a house connection is required.

In single-family homes are often in the meter cabinet the fuses for the individual rooms and equipment as well as the distribution of data technology ( Sat-/Kabelanschluß, networking, telephone). For multi-family homes, it is common to divide the backup into several levels and to accommodate the final stage in sub-distributions in each residential unit.