NationMaster - Encyclopedia: Electric energy meter

An electricity meter is generally taken to be a device which measures the amount of electrical energy supplied to a customer of an electricity company. The most common type is more properly known as a (kilo)watt-hour meter or a joule meter. electrical meters apartment File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... electrical meters apartment File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Electricity retailing is the final process in the delivery of electricity from generation to the consumer. ... The kilowatt-hour (symbol: kW·h) is a unit for measuring energy. ... The joule (symbol: J) is the SI unit of energy. ...

Means of operation

Modern electricity meters operate by continuously measuring the instantaneous voltage (volts) and current (amperes) and finding the product of these to give instantaneous electrical power (watts) which is then integrated against time to give energy used (joules, kilowatt-hours etc). Download high resolution version (700x762, 56 KB)photograph of mechanism of an electrical induction meter (kilo-watt hour meter) Image taken by me Ali@gwc. ... Download high resolution version (700x762, 56 KB)photograph of mechanism of an electrical induction meter (kilo-watt hour meter) Image taken by me Ali@gwc. ... This article may be too technical for most readers to understand. ... The volt (symbol: V) is the SI derived unit of electric potential difference. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... In physics, the ampere (symbol: A, often informally abbreviated to amp) is the SI base unit used to measure electrical currents. ... Transmission lines in Lund, Sweden Electric power, often known as power or electricity, involves the production and delivery of electrical energy in sufficient quantities to operate domestic appliances, office equipment, industrial machinery and provide sufficient energy for both domestic and commercial lighting, heating, cooking and industrial processes. ... This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... In calculus, the integral of a function is a generalization of area, mass, volume, sum, and total. ... The joule (symbol J, also called newton metre, or coulomb volt) is the SI unit of energy and work. ...

The most common type of electricity meter is the electromechanical induction meter. This consists of an aluminium disc which is acted upon by two coils. One coil is connected in such a way that it produces a magnetic flux in proportion to the voltage and the other produces a magnetic flux in proportion to the current. This produces eddy currents in the disc and the effect is such that a force is exerted on the disc in proportion to the product of the instantaneous current and voltage. A permanent magnet exerts an opposing force proportional to the speed of rotation of the disc - this acts as a brake which causes the disc to stop spinning when power stops being drawn rather than allowing it to spin faster and faster. This causes the disc to rotate at a speed proportional to the power being used. In engineering, electromechanics combines electromagnetism and mechanics. ... The term induction has more than one meaning in the English language. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ... A disk or disc is anything that resembles a flattened cylinder in shape. ... An induction coil (archaically known as a Ruhmkorff coil) is a type of disruptive discharge coil. ... Magnetic flux, is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. ... This article may be too technical for most readers to understand. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... As the circular plate moves down through a small region of constant magnetic field directed into the page, eddy currents are induced in the plate. ... In physics, a force is an external cause responsible for any change of a physical system. ... Magnetic lines of force of a bar magnet shown by iron filings on paper A magnet is an object that has a magnetic field. ... Angular velocity describes the speed of rotation. ... A brake is a device for slowing or stopping the motion of a machine, and to keep it from starting to move. ... This article is about proportionality, the mathematical relation. ...

The aluminium disc is supported by a spindle which has a worm gear which drives the register. The register is a series of dials which record the amount of power used. The dials may be of the cyclometer type where for each dial a single digit is shown through a window in the face of the meter, or of the pointer type where a pointer indicates each digit. It should be noted that with the dial pointer type, adjacent pointers generally rotate in opposite directions due to the gearing mechanism. Spur gears found on a piece of farm equipment. ... In mathematics and computer science, a numerical digit is a symbol, e. ...

The type of meter described above is used on a single-phase AC supply. Different phase configurations use additional voltage and current coils. The generation of AC electric power is commonly three phase, in which the waveforms of three supply conductors are offset from one another by 120Â°. These three conductors are commonly housed in a single conduit (e. ... It has been suggested that this article or section be merged with :AC power. ... Polyphase electrical systems supply alternating current electrical power in overlapping phases. ...

Some newer meters are solid state and display the power used on an LCD. Most solid-state meters use a current transformer to measure the current. This means that the main current-carrying conductors need not pass through the meter itself and so the meter can be located remotely from the main current-carrying conductors, which is a particular advantage in large-power installations. It is also possible to use remote current transformers with electromechanical meters though this is less common. In physics, the solid state is one of the three phases of matter (solid, liquid, and gas). ... LCD redirects here. ... The word Transformer can also mean: The Transformers toys, and the related comics and animated television series which have run from the 1980s onwards. ...

Solid state meters can also record other parameters of the load and supply such as maximum demand, power factor and reactive power used etc. The power factor of an AC electric power system is defined as the ratio of the real power to the apparent power. ... Reactive power is an abstract quantity, typically used by power engineers to describe a certain type of energy flow in an electric distribution system. ...

Unit of measurement

The most common unit of measurement on the electricity meter is the kilowatt-hour which is equal to the amount of energy used by a load of one kilowatt over a period of one hour, or 3,600,000 joules. Some electricity companies use the SI megajoule instead. Panel-mounted solid-state electricity meter, connected to 2MVA three-phase electricity substation. ... Panel-mounted solid-state electricity meter, connected to 2MVA three-phase electricity substation. ... In physics, the solid state is one of the three phases of matter (solid, liquid, and gas). ... Apparent power is used to describe the power load as seen by the generating source; it is measured in VA volt-amperes (not watts). ... An aerial substation A substation is the part of an electricity transmission and distribution system where voltage is transformed from low to high and vice versa using transformers. ... A modem (a portmanteau word constructed from modulator and demodulator) is a device that modulates an analog carrier signal (sound) to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... The kilowatt-hour (symbol: kW·h) is a unit for measuring energy. ... The kilowatt (symbol: kW) is a unit for measuring power, equal to one thousand watts. ... The hour was originally defined in Egypt as 1/24 of a day, based on their duo-decimal numbering system (which counted finger joints on each hand). ... The joule (symbol: J) is the SI unit of energy. ... The International System of Units (abbreviated SI from the French phrase, SystÃ¨me International dUnitÃ©s) is the most widely used system of units. ... A megajoule (abbreviation: MJ) is a unit of energy equal to 1000000 joules. ...

Variable-rate meters

Electricity retailers may wish to charge customers different tariffs at different times of the day. This is because there is generally a surplus of electricity at times of low demand, such as during the night (see supply and demand). Such tariffs are facilitated by meters which incorporate or are connected to a time switch and which have multiple registers. In the UK such tariffs are branded Economy 7 or White Meter and are commonly used in conjunction with electrical storage heaters. The popularity of such tariffs has declined in recent years, at least in the domestic market, due to the (perceived or real) deficiencies of storage heaters and the low cost of natural gas. Electricity retailing is the final process in the delivery of electricity from generation to the consumer. ... The supply and demand model describes how prices vary as a result of a balance between product availability at each price (supply) and the desires of those with purchasing power at each price (demand). ... A storage heater is an electrical appliance which stores heat at a time when surplus electricity is available at a low price, usually during the night, and releases it during the day. ... Natural gas (commonly refered to as gas in many countries, but note that this is also American and Canadian slang for gasoline) is a gaseous fossil fuel consisting primarily of methane. ...

Domestic variable-rate meters normally only permit two tariffs ("peak" and "off-peak") and in such installations a simple electromechanical time switch may be used. Large commercial and industrial premises may use electronic meters which record power usage in blocks of half an hour or less. This is because on most electricity grids there are demand surges throughout the day, and the power company may wish to give incentives to large customers to reduce demand at these times. These demand surges often corresponding to meal times or, famously, to intervals in popular television programmes. A database query syntax error has occurred. ... A television program is the content of television broadcasting. ...

Means of reading

Most domestic electricity meters must be read manually, whether by a representative of the power company or by the customer. Where the customer reads the meter, the reading may be supplied to the power company by telephone, post or over the internet. The electricity company will normally require a visit by a company representative at least annually in order to verify customer-supplied readings and to make a basic safety check of the meter. Download high resolution version (450x640, 47 KB)Three-phase electromechanical induction electricity meter, metering 100A 230/400V supply. ... Download high resolution version (450x640, 47 KB)Three-phase electromechanical induction electricity meter, metering 100A 230/400V supply. ... Electricity retailing is the final process in the delivery of electricity from generation to the consumer. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Look up post in Wiktionary, the free dictionary. ...

Newer electronic meters can be read automatically. One common means of semi-automated meter reading has a serial port on the meter that communicates by infrared LED through the faceplate of the meter. In some apartment buildings, a similar protocol is used, but in a wired bus using EIA-485 to connect all the meters to a single plug. The plug is often near the mailboxes. In the European Union, the most common infrared protocol is "FLAG", a simplified subset of mode C of IEC 1107. In the U.S. and Canada, the favoured infrared protocol is ANSI C12.18. A male DE-9 serial port on the rear panel of a PC. In computing, a serial port is an interface on a computer system with which information is transferred in or out one bit at a time (contrast parallel port). ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... EIA-485 (formerly RS-485 or RS485) is an OSI Model Physical layer electrical specification of a two-wire, half-duplex, multipoint serial connection. ... IEC 1107 is a computer protocol used to read metering devices in the European Union. ...

Remote meter reading is an application of telemetry. One protocol proposed for this purpose is DLM/COSEM which can operate over any medium. The data can be transmitted by Zigbee, WiFi, telephone lines or over the power lines themselves. Some meters can be read over the internet. Telemetry is a technology which allows the remote measurement and reporting of information of interest to the system designer or operator. ... IEC 62056, also called DLM/COSEM is an internatinoal standard document that describes a computer protocol used to read utility metres in the European Union. ... ZigBee is a published specification set of high level communication protocols designed to use small, low power digital radios based on the IEEE 802. ... Wi-Fi (or Wi-fi, WiFi, Wifi, wifi), short for Wireless Fidelity, is a set of standards for wireless local area networks (WLAN) currently based on the IEEE 802. ... A telephone line is a single-user circuit on a telephone communications system. ... This article needs to be cleaned up to conform to a higher standard of quality. ...

Accuracy

An electricity meter will be designed to operate across a specified range of voltage, current and frequency. Mechanical meters normally have an accuracy of better than 2%. Solid-state meters may have an accuracy better than 0.8%. The accuracy of the meter will be poorest at the extremes of its specified operating conditions.

Most domestic electricity meters do not account for reactive power but more sophisticated meters which do measure reactive power may be used in commercial and industrial environments where low power factor loads may be present. Reactive power is an abstract quantity, typically used by power engineers to describe a certain type of energy flow in an electric distribution system. ... The power factor of an AC electric power system is defined as the ratio of the real power to the apparent power. ...

In most countries, the required accuracy of the meter is specified by law. The accuracy of a meter may decline with age and mechanical meters may be affected by events such as voltage spikes caused by lightning strikes on the supply. The manufacturer will generally guarantee the accuracy of the meter for a certain number of years and after that period the electricity company must replace or recalibrate the meter. Critical legal studies Jurisprudence Law (principle) Legal research Letter versus Spirit List of legal abbreviations Legal code Pointless law Natural justice Natural law Philosophy of law Religious law External links Wikibooks Wikiversity has more about this subject: School of Law Look up law in Wiktionary, the free dictionary. ... Voltage spikes are fast, short duration surges in the electric potential in a given circuit. ... Lightning over Pentagon City in Arlington County, Virginia Cloud to cloud lightning Lightning is a powerful natural electrostatic discharge produced during a thunderstorm. ... Manufacturing is the transformation of raw materials into finished goods for sale, or intermediate processes involving the production or finishing of semi-manufactures. ... Calibration is the determination, by measurement or comparison with a standard, of the correct value of each reading on a measuring instrument. ...

Ownership

Due to the deregulation of electricity supply markets in many countries, the company responsible for an electricity meter may not be obvious. Depending on the arrangements in place, the meter may be the property of the electricity distributor, the retailer or for some large users of electricity the meter may belong to the customer. Deregulation is the process by which governments remove selected regulations on business in order to (in theory) encourage the efficient operation of markets. ... Electricity distribution is the penultimate process in the delivery of electric power, the part between transmission and user purchase from an electricity retailer. ... Electricity retailing is the final process in the delivery of electricity from generation to the consumer. ...

The company responsible for reading the meter may not always be the company which owns it. Meter reading is now sometimes subcontracted and in some areas the same person may read gas, water and electricity meters at the same time. A residential gas meter A gas meter is used to measure the flow of fuel gases such as natural gas and propane. ...

Location

The location of an electricity meter varies with each installation. Possible locations include on a power pylon serving the property, in a street-side cabinet or inside the premises adjacent to the consumer unit / distribution board. Electricity companies may prefer external locations as the meter can be read without gaining access to the premises but external meters may be more prone to vandalism. For pylons of overhead lines, see Electricity pylon Pylon Noun from Greek πυλώνας gateway tower like structure, usually one of a series, used to support high voltage electricity cables. ... Wylex standard consumer unit fitted with rewirable fuses A consumer unit is a box of fuses or breakers usually arranged in a single row. ... A distribution board (known in the United States as a circuit breaker panel or just breaker panel) is a mounting enclosure for multiple electrical circuit breakers. ... Vandalism is the conspicuous defacement or destruction of a structure or symbol. ...

As stated above, the use of current transformers permits the meter to be located remotely from the current-carrying conductors. This arrangement is commonly used in larger installations, for example an outdoor substation serving a single large customer may have metering equipment installed in a nearby cabinet without the need to bring the very heavy cables leading out of the substation into the cabinet. Current transformers used as part of metering equipment for three-phase 400Amp electricity supply. ... Current transformers used as part of metering equipment for three-phase 400Amp electricity supply. ... The word Transformer can also mean: The Transformers toys, and the related comics and animated television series which have run from the 1980s onwards. ... Three phase systems have 3 waveforms (usually carrying power) that are 2/3π radians (120 degrees,1/3 of a cycle) offset in time. ... An aerial substation A substation is the part of an electricity transmission and distribution system where voltage is transformed from low to high and vice versa using transformers. ...

Connection

In North America, it is common for smaller electricity meters to clip into a standardised base unit. This arrangement allows the meter itself to be replaced without disturbing the supply and load cables which terminate in this base unit. Some base units may have a facility to bypass the meter whilst it is removed for service. The amount of electricity used without being recorded during this small time is considered insignificant when compared to the inconvenience which might be caused to the customer by cutting off the electricity supply.

In the UK, the supply and load terminals are normally provided in the meter housing itself, at least for smaller meters (up to around 100 amps).

Security

Some customers may attempt to manipulate the meter such that it under-registers or even runs backwards, effectively using power without paying for it. Some may justify this by reference to the increasing costs of energy, profits of the electricity company, etc. Most would consider this to be fraud and such behaviour is probably illegal in most countries. Profit is defined as the residual value gained from business operations. ... Illegal, or unlawful, is either prohibitted or not authorized by law. ...

Techniques vary from unsubtle means such as physically breaking the meter housing and jamming the mechanism to more sophisticated methods involving applying magnets to the outside of the meter or altering the characteristics of the load with the intention of temporarily or permanently altering the characteristics of the meter. Magnetic lines of force of a bar magnet shown by iron filings on paper A magnet is an object that has a magnetic field. ...

The owner of the meter may employ a number of means to secure the meter against such actions. Most consist of physical means such as sealing the meter in such a way that the connections and mechanism cannot be tampered with without breaking the seal. Meter readers are also trained to spot signs of tampering.

Prepayment meters

The standard business model of electricity retailing involves the electricity company billing the customer for the amount of energy used in the previous month or quarter. If the retailer believes that the customer may for whatever reason not pay the bill then a prepayment meter may be fitted. This requires the customer to make advance payment before electricity can be used. If the available credit is exhausted then the supply of electricity is cut off by a relay. Download high resolution version (1164x522, 72 KB) Electricity prepayment meter, and prepayment tokens. ... Download high resolution version (1164x522, 72 KB) Electricity prepayment meter, and prepayment tokens. ... A magnetic stripe, sometimes called a magstripe, refers to a band of magnetic material on credit cards, transit fare cards or identification cards to store information. ... Relay is also the name of a series of medium-altitude satellites; the first of which was launched in 1962. ...

In the UK, mechanical prepayment meters used to be common in rented accommodation. Disadvantages of these included the need for regular visits to remove cash, risk of theft of the cash in the meter and the lack of a means of applying a standing charge. Cash usually refers to money in the form of currency, such as bills or coins. ...

Modern solid-state electricity meters in conjunction with smart card technology have removed these disadvantages and such meters are commonly used for customers considered to be a poor credit risk. A smartcard or smart card is a tiny secure cryptoprocessor embedded within a credit card-sized or smaller (like the GSM SIM) card. ... Credit risk is the risk of loss due to a counterparty defaulting on a contract, or more generally the risk of loss due to some credit event. Traditionally this applied to bonds where debt holders were concerned that the counterparty to whom theyve made a loan might default on...

Power export

Many electricity customers are installing their own electricity generating equipment, whether for reasons of economy, redundancy or environmental reasons. Gas turbines, wind turbines and photovoltaic cells are all in common use. When a customer is generating more electricity than required for his own use, the surplus may be exported back to the power grid. Green energy is a term used by some environmentalists to describe what they deem to be environmentally friendly sources of power. ... A gas is one of the phases of matter. ... WWII era steam turbine used for ship propulsion. ... A tall tower holds a wind turbine aloft where winds are consistently stronger. ... A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). ... Transmission towers Transmission lines in Lund, Sweden Electric power transmission, or more accurately Electrical energy transmission, is the second process in the delivery of electricity to consumers. ...

This exported energy may be accounted for in the simplest case by the meter running backwards during periods of net export, thus reducing the customer's recorded energy usage by the amount exported. More sophisticated meters permit such exported energy to be recorded and accounted for separately. Net-metering is a simplified method of metering the energy consumed and produced at a home or business that has its own renewable energy generator, such as a wind turbine. ...

See also Net metering. Net-metering is a simplified method of metering the energy consumed and produced at a home or business that has its own renewable energy generator, such as a wind turbine. ...

Other types of electricity meter

In addition to the types of meter described above which directly measure the amount of energy used, other types of meter are available.

Meters which measure the amount of current (coulombs) used, known as amp-hour meters, were used in the early days of electrification. These were dependant upon the supply voltage remaining constant for accurate measurement of energy usage which is not a likely circumstance with most supplies. The coulomb, symbol C, is the SI unit of electric charge, and is defined in terms of the ampere: 1 coulomb is the amount of electric charge (quantity of electricity) carried by a current of 1 ampere flowing for 1 second. ...

Some meters measured only the length of time for which current flowed, with no measurement of the magnitude of voltage or current being made. These were only suited for constant load applications.

External links

Categories: Electric power | Measuring instruments Wikibooks Wikiversity has more about this subject: School of Mathematics Wikiquote has a collection of quotations by or about: Mathematics Look up Mathematics on Wiktionary, the free dictionary Wikimedia Commons has more media related to: Mathematics Bogomolny, Alexander: Interactive Mathematics Miscellany and Puzzles. ... Since antiquity, people have tried to understand the behavior of matter: why unsupported objects drop to the ground, why different materials have different properties, and so forth. ...

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