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Electric power distribution is the final stage in the
delivery Delivery may refer to: *Delivery (commerce), of goods, e.g.: **Pizza delivery **Milk delivery Film and television *Delivering (film), ''Delivering'' (film), a 1993 short film by Todd Field *Delivery (film), ''Delivery'' (film), a 2005 animated sho ...
of
electric power Electric power is the rate, per unit time, at which electrical energy Electrical energy is energy derived as a result of movement of electrically charged particles. When used loosely, ''electrical energy'' refers to energy that has been conve ...
; it carries electricity from the
transmission system :''See Transmission (mechanics) for a car's transmission system'' In telecommunications, a transmission system is a system that transmits a signal from one place to another. The signal can be an electrical, optical or radio signal. Some transmi ...

transmission system
to individual consumers. Distribution
substations
substations
connect to the transmission system and lower the transmission voltage to medium
voltage Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is the ...

voltage
ranging between and with the use of
transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple Electrical network, circuits. A varying current in any one coil of the transformer produces a varying magnetic flux ...

transformer
s. ''Primary'' distribution lines carry this medium voltage power to
distribution transformer A distribution transformer or service transformer is a transformer A transformer is a passive electrical device that transfers electrical energy from one electrical circuit to another, or multiple Electrical network, circuits. A varying current ...
s located near the customer's premises. Distribution transformers again lower the voltage to the
utilization voltage Mains electricity (Commonwealth English The use of the English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventually become ...
used by lighting, industrial equipment and household appliances. Often several customers are supplied from one transformer through ''secondary'' distribution lines. Commercial and residential customers are connected to the secondary distribution lines through
service drop In electric power distribution Electric power distribution is the final stage in the delivery Delivery may refer to: *Delivery (commerce), of goods, e.g.: **Pizza delivery **Milk delivery Film and television *Delivering (film), ''Delivering'' ...

service drop
s. Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the subtransmission level. The transition from transmission to distribution happens in a power , which has the following functions: *
Circuit breaker A circuit breaker is an electrical safety device designed to protect an electrical circuit An electrical network is an interconnection of electrical component An electronic component is any basic discrete device or physical entity ...

Circuit breaker
s and switches enable the substation to be disconnected from the transmission grid or for distribution lines to be disconnected. * Transformers step down transmission voltages, or more, down to primary distribution voltages. These are medium voltage circuits, usually . * From the transformer, power goes to the
busbar In , a busbar (also bus bar) is a metallic strip or bar, typically housed inside , , and for local high current power distribution. They are also used to connect high voltage equipment at electrical switchyards, and low voltage equipment i ...

busbar
that can split the distribution power off in multiple directions. The bus distributes power to distribution lines, which fan out to customers. Urban distribution is mainly underground, sometimes in
common utility duct A utility tunnel, utility corridor, or utilidor is a passage built underground or above ground to carry utility lines such as electricity, steam Steam is water in the gas phase. This may occur due to evaporation, to due to boiling, where heat i ...
s. Rural distribution is mostly above ground with
utility pole A utility pole is a or post used to support s and various other public utilities, such as , , and related equipment such as and s. It can be referred to as a transmission pole, telephone pole, telecommunication pole, power pole, hydro pole, tel ...

utility pole
s, and suburban distribution is a mix. Closer to the customer, a distribution transformer steps the primary distribution power down to a low-voltage secondary circuit, usually 120/240 V in the US for residential customers. The power comes to the customer via a
service drop In electric power distribution Electric power distribution is the final stage in the delivery Delivery may refer to: *Delivery (commerce), of goods, e.g.: **Pizza delivery **Milk delivery Film and television *Delivering (film), ''Delivering'' ...

service drop
and an
electricity meter North American domestic analog electricity meter. Electricity meter with transparent plastic case (Israel) North American domestic electronic electricity meter An electricity meter, electric meter, electrical meter, energy meter, or kilowat ...
. The final circuit in an urban system may be less than , but may be over for a rural customer.


History

Electric power distribution became necessary only in the 1880s when electricity started being generated at
power stations A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the electricity generation, generation of electric power. Power stations are generally connected to an el ...
. Before that electricity was usually generated where it was used. The first power distribution systems installed in European and US cities were used to supply lighting: arc lighting running on very high voltage (around 3000 volts)
alternating current Alternating current (AC) is an electric current An electric current is a stream of charged particle In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'natu ...
(AC) or
direct current Direct current (DC) is one-directional flow Flow may refer to: Science and technology * Flow (fluid) or fluid dynamics, the motion of a gas or liquid * Flow (geomorphology), a type of mass wasting or slope movement in geomorphology * Flow (math ...
(DC), and
incandescent lighting image of the tungsten Tungsten, or wolfram, is a chemical element with the Symbol (chemistry), symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identi ...

incandescent lighting
running on low voltage (100 volt) direct current. Both were supplanting
gas lighting Gas lighting is production of artificial light from combustion Combustion, or burning, is a high-temperature exothermic In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and te ...

gas lighting
systems, with arc lighting taking over large area and street lighting, and incandescent lighting replacing gas for business and residential lighting. Due to the high voltages used in arc lighting, a single generating station could supply a long string of lights, up to long circuits. Each doubling of the voltage would allow the same size cable to transmit the same amount of power four times the distance for a given power loss. Direct current indoor incandescent lighting systems, for example the first Edison
Pearl Street Station Pearl Street Station was the first commercial central power plant in the United States. It was located at 255–257 Pearl Street in the Financial District of Manhattan Manhattan (), known regionally as the City and the urban core of the Ne ...
installed in 1882, had difficulty supplying customers more than a mile away. This was due to the low 110 volt system being used throughout the system, from the generators to the final use. The Edison DC system needed thick copper conductor cables, and the generating plants needed to be within about of the farthest customer to avoid excessively large and expensive conductors.


Introduction of the transformer

Transmitting electricity a long distance at high voltage and then reducing it to a lower voltage for lighting became a recognized engineering roadblock to electric power distribution with many, not very satisfactory, solutions tested by lighting companies. The mid-1880s saw a breakthrough with the development of functional transformers that allowed the AC voltage to be "stepped up" to much higher transmission voltages and then dropped down to a lower end user voltage. With much cheaper transmission costs and the greater
economies of scale In microeconomics Microeconomics is a branch of mainstream economics Mainstream economics is the body of knowledge, theories, and models of economics, as taught by universities worldwide, that are generally accepted by economists as a basis ...

economies of scale
of having large generating plants supply whole cities and regions, the use of AC spread rapidly. In the US the competition between direct current and alternating current took a personal turn in the late 1880s in the form of a "
war of currents The war of the currents, sometimes called battle of the currents, was a series of events surrounding the introduction of competing electric power transmission systems in the late 1880s and early 1890s. It grew out of two lighting systems developed ...
" when
Thomas Edison Thomas Alva Edison (February 11, 1847October 18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation Electricity generation is the process of generating electric power from s ...

Thomas Edison
started attacking
George Westinghouse George Westinghouse Jr. (October 6, 1846 – March 12, 1914) was an American entrepreneur Entrepreneurship is the creation or extraction of value. With this definition, entrepreneurship is viewed as change, generally entailing risk beyond wh ...

George Westinghouse
and his development of the first US AC transformer systems, pointing out all the deaths caused by high-voltage AC systems over the years and claiming any AC system was inherently dangerous. Edison's propaganda campaign was short-lived, with his company switching over to AC in 1892. AC became the dominant form of transmission of power with innovations in Europe and the US in designs and the development of engineered ''universal systems'' allowing the large number of legacy systems to be connected to large AC grids. In the first half of the 20th century, in many places the
electric power industry The electric power industry covers the generation A generation is "all of the people born and living Living or The Living may refer to: Common meanings *Life, a condition that distinguishes organisms from inorganic objects and dead organisms ...
was
vertically integrated In microeconomics Microeconomics (from Greek prefix ''mikro-'' meaning "small" + ''economics'') is a branch of economics that studies the behavior of individuals and Theory of the firm, firms in making decisions regarding the allocation o ...
, meaning that one company did generation, transmission, distribution, metering and billing. Starting in the 1970s and 1980s, nations began the process of
deregulation Deregulation is the process of removing or reducing state regulations, typically in the economic sphere. It is the repeal of governmental regulation of the economy. It became common in advanced industrial economies in the 1970s and 1980s, as a r ...
and
privatisation Privatization (or privatisation in British English British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codificati ...
, leading to
electricity market In economic terms, electricity is a commodity capable of being bought, sold, and traded. An electricity market, also power exchange or PX, is a system enabling purchases, through bids to buy; sales, through offers to sell. Bids and offers use sup ...
s. The distribution system would remain regulated, but generation, retail, and sometimes transmission systems were transformed into competitive markets.


Generation and transmission

File:Electricity grid simple- North America.svg, 380px, Simplified diagram of AC
electricity delivery Electricity delivery is the process that starts after generation of electricity in the power station A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the ...
from generation stations to consumers'
service drop In electric power distribution Electric power distribution is the final stage in the delivery Delivery may refer to: *Delivery (commerce), of goods, e.g.: **Pizza delivery **Milk delivery Film and television *Delivering (film), ''Delivering'' ...

service drop
. rect 2 243 235 438
Power station A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation A generation is "all of the people born and living Living or The Living may refer to: ...

Power station
rect 276 317 412 556
Transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple Electrical network, circuits. A varying current in any one coil of the transformer produces a varying magnetic flux ...

Transformer
rect 412 121 781 400
Electric power transmission Electric power transmission is the bulk movement of electrical energy Electrical energy is energy derived as a result of movement of electrically charged particles. When used loosely, ''electrical energy'' refers to energy that has been convert ...

Electric power transmission
rect 800 0 980 165
Transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple Electrical network, circuits. A varying current in any one coil of the transformer produces a varying magnetic flux ...

Transformer
desc bottom-left
Electric power begins at a generating station, where the potential difference can be as high as 33,000 volts. AC is usually used. Users of large amounts of DC power such as some
railway electrification system A railway electrification system supplies electric power Electric power is the rate, per unit time, at which electrical energy Electrical energy is energy derived as a result of movement of electrically charged particles. When used loos ...

railway electrification system
s,
telephone exchange A telephone exchange, telephone switch, or central office is a telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, Optical system, optical, or other Electromagnetism, el ...

telephone exchange
s and industrial processes such as
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
smelting use
rectifier A rectifier is an electrical device that converts Religious conversion is the adoption of a set of beliefs identified with one particular religious denomination A religious denomination is a subgroup within a religion Religion is ...

rectifier
s to derive DC from the public AC supply, or may have their own generation systems. High-voltage DC can be advantageous for isolating alternating-current systems or controlling the quantity of electricity transmitted. For example,
Hydro-Québec Hydro-Québec is a public utility A public utility company (usually just utility) is an organization that maintains the infrastructure Infrastructure is the set of fundamental facilities and systems that support the sustainable functionalit ...
has a direct-current line which goes from the
James Bay James Bay (french: Baie James, cr, ᐐᓂᐯᒄ Wînipekw meaning ''Dirty Water'') is a large body of water located on the southern end of Hudson Bay in Canada. Both bodies of water extend from the Arctic Ocean, of which James Bay is the southe ...
region to
Boston Boston (, ), officially the City of Boston, is the capital city, capital and List of municipalities in Massachusetts, most populous city of the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States and 21st List of Unit ...

Boston
. From the generating station it goes to the generating station's switchyard where a step-up transformer increases the voltage to a level suitable for transmission, from 44 kV to 765 kV. Once in the transmission system, electricity from each generating station is combined with electricity produced elsewhere. Electricity is consumed as soon as it is produced. It is transmitted at a very high speed, close to the
speed of light The speed of light in vacuum A vacuum is a space Space is the boundless three-dimensional Three-dimensional space (also: 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called paramet ...
.


Primary distribution

Primary distribution voltages range from 4 kV to 35 kV phase-to-phase (2.4 kV to 20 kV phase-to-neutral) Only large consumers are fed directly from distribution voltages; most utility customers are connected to a transformer, which reduces the distribution voltage to the low voltage "utilization voltage", "supply voltage" or "mains voltage" used by lighting and interior wiring systems.


Network configurations

Distribution networks are divided into two types, radial or network. A radial system is arranged like a tree where each customer has one source of supply. A network system has multiple sources of supply operating in parallel. Spot networks are used for concentrated loads. Radial systems are commonly used in rural or suburban areas. Radial systems usually include emergency connections where the system can be reconfigured in case of problems, such as a fault or planned maintenance. This can be done by opening and closing switches to isolate a certain section from the grid. Long feeders experience
voltage drop Voltage drop is the decrease of electrical potential along the path of a current flowing in an electrical circuitCircuit may refer to: Science and technology Electrical engineering * Electrical circuit, a complete electrical network with a ...

voltage drop
(
power factor In electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics The field of electronics is a branch of ph ...
distortion) requiring
capacitor A capacitor is a device that stores electric charge in an electric field An electric field (sometimes E-field) is the physical field that surrounds electrically-charged particle In physics Physics (from grc, φυσική (ἐπ ...

capacitor
s or to be installed. Reconfiguration, by exchanging the functional links between the elements of the system, represents one of the most important measures which can improve the operational performance of a distribution system. The problem of optimization through the reconfiguration of a power distribution system, in terms of its definition, is a historical single objective problem with constraints. Since 1975, when Merlin and Back introduced the idea of distribution system reconfiguration for active power loss reduction, until nowadays, a lot of researchers have proposed diverse methods and algorithms to solve the reconfiguration problem as a single objective problem. Some authors have proposed Pareto optimality based approaches (including active power losses and reliability indices as objectives). For this purpose, different artificial intelligence based methods have been used: microgenetic, branch exchange, particle swarm optimization and non-dominated sorting
genetic algorithm spacecraft antenna. This complicated shape was found by an evolutionary computer design program to create the best radiation pattern. It is known as an evolved antenna. In computer science Computer science deals with the theoretical found ...

genetic algorithm
.


Rural services

Rural electrification Rural electrification is the process of bringing electrical power Electric power is the rate, per unit time, at which electrical energy Electrical energy is energy derived from electric potential energy or kinetic energy. When used loosely, ...
systems tend to use higher distribution voltages because of the longer distances covered by distribution lines (see
Rural Electrification Administration The United States Rural Utilities Service (RUS) administers programs that provide infrastructure or infrastructure improvements to rural communities. These include water and waste treatment, electric power, and telecommunications services. it is a ...
). 7.2, 12.47, 25, and 34.5 kV distribution is common in the United States; 11 kV and 33 kV are common in the UK, Australia and New Zealand; 11 kV and 22 kV are common in South Africa; 10, 20 and 35 kV are common in China. Other voltages are occasionally used. Rural services normally try to minimize the number of poles and wires. It uses higher voltages (than urban distribution), which in turn permits use of galvanized steel wire. The strong steel wire allows for less expensive wide pole spacing. In rural areas a pole-mount transformer may serve only one customer. In
New Zealand New Zealand ( mi, Aotearoa ''Aotearoa'' (; commonly pronounced by English English usually refers to: * English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon Engl ...

New Zealand
,
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Australia
,
Saskatchewan, Canada ("Strength from Many Peoples") , image_map = Saskatchewan in Canada 2.svg , Label_map = yes , coordinates = , official_lang = English language, English , capital = Regina, Sa ...
, and
South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. With over 60 million people, it is the world's 23rd-most populous nation and covers an area of . South Africa has three capital citie ...

South Africa
,
Single-wire earth return Single-wire earth return (SWER) or single-wire ground return is a single-wire transmission line which supplies single-phase electric power from an electrical grid to remote areas at low cost. Its distinguishing feature is that the earth ...
systems (SWER) are used to electrify remote rural areas. Three phase service provides power for large agricultural facilities, petroleum pumping facilities, water plants, or other customers that have large loads (Three phase equipment). In North America, overhead distribution systems may be three phase, four wire, with a neutral conductor. Rural distribution system may have long runs of one phase conductor and a neutral. In other countries or in extreme rural areas the neutral wire is connected to the ground to use that as a return (
Single-wire earth return Single-wire earth return (SWER) or single-wire ground return is a single-wire transmission line which supplies single-phase electric power from an electrical grid to remote areas at low cost. Its distinguishing feature is that the earth ...
). This is called an ungrounded wye system.


Secondary distribution

Electricity is delivered at a frequency of either 50 or 60 Hz, depending on the region. It is delivered to domestic customers as
single-phase electric power 173px, A single-phase polemount stepdown transformer in Canada. One supply phase (phase-to-neutral) from the utility is converted to split-phase for the customers. In electrical engineering, single-phase electric power is the distribution of alter ...
. In some countries as in Europe a
three phase Three-phase electric power (abbreviated 3φ) is a common type of alternating current used in electricity generation, Electric power transmission, transmission, and Electric power distribution, distribution. It is a type of polyphase system emplo ...
supply may be made available for larger properties. Seen with an
oscilloscope An oscilloscope, previously called an oscillograph, and informally known as a scope or o-scope, CRO (for cathode-ray oscilloscope), or DSO (for the more modern digital storage oscilloscope A digital storage oscilloscope (DSO) is an oscillosco ...

oscilloscope
, the domestic power supply in North America would look like a
sine wave A sine wave or sinusoid is any of certain mathematical curves that describe a smooth periodic oscillation Oscillation is the repetitive variation, typically in time, of some measure about a central value (often a point of Mechanical equilib ...

sine wave
, oscillating between −170 volts and 170 volts, giving an effective voltage of 120 volts RMS.
Three-phase electric power Three-phase electric power (abbreviated 3φ) is a common type of alternating current Alternating current (AC) is an electric current An electric current is a stream of charged particle In physics Physics (from grc, φυσική ...
is more efficient in terms of power delivered per cable used, and is more suited to running large electric motors. Some large European appliances may be powered by three-phase power, such as electric stoves and clothes dryers. A
ground Ground may refer to: * Soil File:Stagnogley.JPG, Surface-water-Gley soil, gley developed in glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Earth's body ...
connection is normally provided for the customer's system as well as for the equipment owned by the utility. The purpose of connecting the customer's system to ground is to limit the voltage that may develop if high voltage conductors fall down onto lower-voltage conductors which are usually mounted lower to the ground, or if a failure occurs within a distribution transformer.
Earthing system An earthing system (UK and IEC) or grounding system (US) connects specific parts of an electric power system with the Ground (electricity), ground, typically the Earth's conductive surface, for safety and functional purposes. The choice of ear ...
s can be TT, TN-S, TN-C-S or TN-C.


Regional variations


220–240 volt systems

Most of the world uses 50 Hz 220 or 230 V single phase, or 400 V 3 phase for residential and light industrial services. In this system, the primary distribution network supplies a few substations per area, and the 230 V / 400 V power from each substation is directly distributed to end users over a region of normally less than 1 km radius. Three live (hot) wires and the neutral are connected to the building for a three phase service. Single-phase distribution, with one live wire and the neutral is used domestically where total loads are light. In Europe, electricity is normally distributed for industry and domestic use by the three-phase, four wire system. This gives a phase-to-phase voltage of wye service and a single-phase voltage of between any one phase and neutral. In the UK a typical urban or suburban low-voltage substation would normally be rated between 150 kVA and 1 MVA and supply a whole neighbourhood of a few hundred houses. Transformers are typically sized on an average load of 1 to 2 kW per household, and the service fuses and cable is sized to allow any one property to draw a peak load of perhaps ten times this. For industrial customers, 3-phase is also available, or may be generated locally. Large industrial customers have their own transformer(s) with an input from 11 kV to 220 kV.


100–120 volt systems

Most of the Americas use 60 Hz AC, the 120/240 volt split-phase system domestically and three phase for larger installations. North American transformers usually power homes at 240 volts, similar to Europe's 230 volts. It is the split-phase that allows use of 120 volts in the home. In the
electricity sector in Japan The electric power industry The electric power industry covers the generation, transmission, distribution and sale of electric power to the general public and industry. The commercial distribution of electric power started in 1882 when elec ...
, the standard voltage is 100 V, with both 50 and 60 Hz AC frequencies being used. Parts of the country use 50 Hz, while other parts use 60 Hz. This is a relic from the 1890s. Some local providers in
Tokyo Tokyo (Japanese language, Japanese: , ''Tōkyō'' ), historically known in the west as Tokio and officially the Tokyo Metropolis (, ''Tōkyō-to''), is capital of Japan, the capital and most populous Prefectures of Japan, prefecture of Japan ...

Tokyo
imported 50 Hz German equipment, while the local power providers in
Osaka is a designated city in the Kansai region The or the , lies in the southern-central region of Japan , image_flag = Flag of Japan.svg , alt_flag = Centered deep red circle on a white rectangle , ...

Osaka
brought in 60 Hz generators from the United States. The grids grew until eventually the entire country was wired. Today the frequency is 50 Hz in Eastern Japan (including Tokyo, 
Yokohama is the second-largest city in Japan Japan ( ja, 日本, or , and formally ) is an in . It is situated in the northwest , and is bordered on the west by the , while extending from the in the north toward the and in the south. Ja ...

Yokohama
Tohoku, and
Hokkaido , officially Hokkaidō Circuit Prefecture, is the second largest island of Japan Japan ( ja, 日本, or , and formally ) is an in . It is situated in the northwest , and is bordered on the west by the , while extending from the in t ...

Hokkaido
) and 60 Hz in Western Japan (including 
Nagoya } is the largest city in the Chūbu region The , Central region, or is a region in the middle of Honshū , historically called , is the largest and most populous main island of Japan , image_flag = Flag of J ...

Nagoya
Osaka is a designated city in the Kansai region The or the , lies in the southern-central region of Japan , image_flag = Flag of Japan.svg , alt_flag = Centered deep red circle on a white rectangle , ...

Osaka
Kyoto Kyoto (; Japanese language, Japanese: , ''Kyōto'' ), officially , is the capital city of Kyoto Prefecture in Japan. Located in the Kansai region on the island of Honshu, Kyoto forms a part of the Keihanshin, Keihanshin metropolitan area along w ...

Kyoto
Hiroshima is the capital of Hiroshima Prefecture is a prefecture of Japan , image_flag = Flag of Japan.svg , alt_flag = Centered deep red circle on a white rectangle , image_coat = Imperi ...
Shikoku is one of the five main islands of Japan Japan ( ja, 日本, or , and formally ) is an in . It is situated in the northwest , and is bordered on the west by the , while extending from the in the north toward the and in the sout ...
, and
Kyushu is the third largest island of Japan Japan ( ja, 日本, or , and formally ) is an island country An island country or an island nation is a country A country is a distinct territory, territorial body or political entity. It ...

Kyushu
). Most household appliances are made to work on either frequency. The problem of incompatibility came into the public eye when the
2011 Tōhoku earthquake and tsunami The occurred at 14:46 JST (05:46 UTC) on 11 March. The magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object ...
knocked out about a third of the east's capacity, and power in the west could not be fully shared with the east, since the country does not have a common frequency. There are four
high-voltage direct current A high-voltage, direct current (HVDC) electric power transmission Electric power transmission is the bulk movement of electrical energy Electrical energy is energy derived from electric potential energy or kinetic energy. When used loosely, ...
(HVDC) converter stations that move power across Japan's AC frequency border.
Shin Shinano is the designation of a back-to-back connection#Power transmission, back-to-back high-voltage direct current (HVDC) facility in Japan which forms one of four frequency changer, frequency converter stations that link Japan's western and eastern ...
is a
back-to-back Back to Back or back-to-back may refer to: Music Songs *Back to Back (Drake song), "Back to Back" (Drake song), 2015 *Back to Back (Jeanne Pruett song), "Back to Back" (Jeanne Pruett song), 1979 *"Back to Back", a song by Pretty Maids from the ...
HVDC facility in
Japan Japan ( ja, 日本, or , and formally ) is an island country An island country or an island nation is a country A country is a distinct territory, territorial body or political entity. It is often referred to as the land of an in ...

Japan
which forms one of four
frequency changer A frequency changer or frequency converter is an Electronics, electronic or electromechanical device that converts alternating current (Alternating current, AC) of one frequency to alternating current of another frequency. The device may also cha ...
stations that link Japan's western and eastern power grids. The other three are at Higashi-Shimizu, Minami-Fukumitsu and
Sakuma Dam The is a dam on the Tenryū River, located on the border of Toyone, Aichi, Toyone, Kitashitara District, Aichi, Kitashitara District, Aichi Prefecture on the island of Honshū, Japan. It is one of the tallest dams in Japan and supports a 350 MW ...
. Together they can move up to 1.2 GW of power east or west.


240 volt systems and 120 volt outlets

Most modern North American homes are wired to receive 240 volts from the transformer, and through the use of split-phase electrical power, can have both 120 volt receptacles and 240 volt receptacles. The 120 volts is typically used for lighting and most . The 240 volt circuits are typically used for appliances requiring high watt heat output such as ovens and heaters. They may also be used to supply an
electric car An electric car or battery electric car is an automobile A car (or automobile) is a wheeled motor vehicle Electric bicycles parked in Yangzhou's main street, Wenchang Lu. They are a very common way of transport in this city, in some a ...

electric car
charger.


Modern Distribution Systems

Traditionally, the distribution systems would only operate as simple distribution lines where the electricity from the would be shared among the customers. Today's distribution systems are heavily integrated with
renewable energy Renewable energy is energy that is collected from renewable resource File:Global Vegetation.jpg, Global vegetation A renewable resource, also known as a flow resource, is a natural resource which will replenish to replace the portion resou ...
generations at the distribution level of the power systems by the means of
distributed generation Distributed generation, also distributed energy, on-site generation (OSG), or district/decentralized energy, is electrical generation and storage performed by a variety of small, grid-connected or distribution system-connected devices referred t ...
resources, such as
solar energy Solar energy is Solar irradiance, radiant light and heat from the Sun that is harnessed using a range of technologies such as solar power to generate electricity, solar thermal energy including solar water heating, and solar architecture. It ...

solar energy
and
wind energy Wind power or wind energy is the use of wind turbine A wind turbine is a device that converts Religious conversion is the adoption of a set of beliefs identified with one particular religious denomination A religious denomination ...

wind energy
. As a result, distribution systems are becoming more independent from the transmission networks day-by-day. Balancing the supply-demand relationship at these modern distribution networks (sometimes referred to as
microgridA microgrid is a decentralized group of electricity sources and loads that normally operates, connected to and synchronous with the traditional wide area synchronous grid (macrogrid), but is able to disconnect from the interconnected grid and to func ...
s) is extremely challenging, and it requires the use of various technological and operational means to operate. Such tools include
battery storage power station A battery storage power station is a type of energy storage power station that uses a group of Rechargeable battery, batteries to store electrical energy. Battery storage is the fastest responding source of power on grids, and is used to stabilise ...
,
data analytics Analytics is the systematic computational analysis of data or statistics. It is used for the discovery, interpretation, and communication of meaningful patterns in data. It also entails applying data patterns towards effective decision making. It c ...
, optimization tools, etc.


See also

*
BackfeedingBackfeeding is the flow of electric power Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt The watt (symbol: W) is a unit of Power (physics), power ...
*
Cost of electricity by source Different methods of electricity generation Electricity generation is the process of generating electric power Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. The SI unit of p ...

Cost of electricity by source
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Dynamic voltage restoration Dynamic voltage restoration (DVR) is a method of overcoming voltage sags and voltage swell, swells that occur in electrical power distribution. These are a problem because spikes consume power and sags reduce efficiency of some devices. DVR saves ...
* Electric utility * Electricity distribution companies by country *
Electricity generation Electricity generation is the process of generating electric power Electric power is the rate, per unit time, at which electrical energy Electrical energy is energy derived as a result of movement of electrically charged particles. When use ...
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Electricity retailing Electricity retailing is the final sale of electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position In physics, motion ...
* Network protector *
Power distribution unit A power distribution unit (PDU) is a device fitted with multiple outputs designed to distribute electric power, especially to racks of computers and networking equipment located within a data center. Data centers face challenges in power protect ...
* Power-system automation – IEEE standard to interconnect tele-protection and multiplexer devices of power utility companies * Power system simulation *
Transmission system operator File:Electricity grid simple- North America.svg, 380px, Simplified diagram of AC electricity grid from generation stations to consumers rect 2 243 235 438 Power station rect 276 317 412 556 Transformer rect 412 121 781 400 Electric power transmiss ...
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High-voltage transformer fire barriers High-voltage transformer fire barriers, or transformer firewalls, transformer ballistic firewalls, transformer blast walls, are outdoor countermeasures against cascading failures in a national electric grid. The purpose of these barriers, like c ...


References


External links


IEEE Power Engineering SocietyIEEE Power Engineering Society Distribution SubcommitteeU.S. Department of Energy Electric Distribution website
{{Authority control Electrical engineering