Electrical Grid
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An electrical grid is an interconnected network for
electricity delivery Electricity delivery is the process that starts after generation of electricity in the power station, up to the use by the consumer. The main processes in electricity delivery are, by order: * Transmission * Distribution * Retailing See also * E ...
from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power Transmission: Background and Policy Issues. The Capital.Net, Government Series. Pp. 1-42. *
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 of electric power. Power stations are generally connected to an electrical grid. Many p ...
s: often located near energy and away from heavily populated areas * electrical substations to step
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
up or down * electric power transmission to carry power long distances *
electric power distribution Electric power distribution is the final stage in the delivery of electric power; it carries electricity from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmissi ...
to individual customers, where voltage is stepped down again to the required service voltage(s). Grids are nearly always synchronous, meaning all distribution areas operate with
three phase Three-phase electric power (abbreviated 3φ) is a common type of alternating current used in electricity generation, transmission, and distribution. It is a type of polyphase system employing three wires (or four including an optional neutral ...
alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...
(AC) frequencies synchronized (so that voltage swings occur at almost the same time). This allows transmission of AC power throughout the area, connecting a large number of electricity generators and consumers and potentially enabling more efficient electricity markets and redundant generation. The combined transmission and distribution network is part of electricity delivery, known as the "power grid" in
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
, or just "the grid." In the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
,
Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...
,
Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John C. Wells, Joh ...
,
Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...
and
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
, the network is known as the National Grid. Although electrical grids are widespread, , 1.4 billion people worldwide were not connected to an electricity grid. As
electrification Electrification is the process of powering by electricity and, in many contexts, the introduction of such power by changing over from an earlier power source. The broad meaning of the term, such as in the history of technology, economic histor ...
increases, the number of people with access to grid electricity is growing. About 840 million people (mostly in Africa) had no access to grid electricity in 2017, down from 1.2 billion in 2010. Electrical grids can be prone to malicious intrusion or attack; thus, there is a need for
electric grid security Electric grid security in the US refer to the activities that utilities, regulators, and other stakeholders play in securing the national electricity grid. The American electrical grid is going through one of the largest changes in its history, whic ...
. Also as electric grids modernize and introduce computer technology, cyber threats start to become a security risk. Particular concerns relate to the more complex computer systems needed to manage grids.


History

Early electric energy was produced near the device or service requiring that energy. In the 1880s, electricity competed with steam, hydraulics, and especially coal gas. Coal gas was first produced on customer's premises but later evolved into gasification plants that enjoyed
economies of scale In microeconomics, economies of scale are the cost advantages that enterprises obtain due to their scale of operation, and are typically measured by the amount of output produced per unit of time. A decrease in cost per unit of output enables ...
. In the industrialized world, cities had networks of piped gas, used for lighting. But gas lamps produced poor light, wasted heat, made rooms hot and smokey, and gave off
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
and
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
. They also posed a fire hazard. In the 1880s electric lighting soon became advantageous compared to gas lighting.
Electric utility An electric utility is a company in the electric power industry (often a public utility) that engages in electricity generation and distribution of electricity for sale generally in a regulated market. The electrical utility industry is a major pr ...
companies established central stations to take advantage of economies of scale and moved to centralized power generation, distribution, and system management.Borberly, A. and Kreider, J. F. (2001). Distributed Generation: The Power Paradigm for the New Millennium. CRC Press, Boca Raton, FL. 400 pgs. After the
war of the currents The war 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 in the late 1870s and early 1880s; arc ...
was settled in favor of AC power, with long-distance power transmission it became possible to interconnect stations to balance the loads and improve load factors. Historically, transmission and distribution lines were owned by the same company, but starting in the 1990s, many countries have liberalized the regulation of the
electricity market In a broad sense, an electricity market is a system that facilitates the exchange of electricity-related goods and services. During more than a century of evolution of the electric power industry, the economics of the electricity markets had un ...
in ways that have led to the separation of the electricity transmission business from the distribution business. In the United Kingdom,
Charles Merz Charles Hesterman Merz (5 October 1874 – 14 or 15 October 1940) was a British electrical engineer who pioneered the use of high-voltage three-phase AC power distribution in the United Kingdom, building a system in the North East of England ...
, of the
Merz & McLellan Merz and McLellan was a leading British electrical engineering consultancy based in Newcastle. History The firm was founded by Charles Merz and William McLellan in Newcastle upon Tyne in 1902 when McLellan joined Merz's existing firm establishe ...
consulting partnership, built the
Neptune Bank Power Station Neptune Bank Power Station was a coal-fired power station situated on the River Tyne at Wallsend near Newcastle upon Tyne. Commissioned in 1901 by the Newcastle upon Tyne Electric Supply Company, the station was the first in the world to provid ...
near
Newcastle upon Tyne Newcastle upon Tyne ( RP: , ), or simply Newcastle, is a city and metropolitan borough in Tyne and Wear, England. The city is located on the River Tyne's northern bank and forms the largest part of the Tyneside built-up area. Newcastle is ...
in 1901, and by 1912 had developed into the largest integrated power system in Europe. Merz was appointed head of a parliamentary committee and his findings led to the Williamson Report of 1918, which in turn created the
Electricity (Supply) Act 1919 The Electricity (Supply) Act 1919 (9 & 10 Geo. 5. c. 100) was an Act of the Parliament of the United Kingdom which amended the law with respect to the supply of electricity. It established the statutory body of the Electricity Commissioners ‘to ...
. The bill was the first step towards an integrated electricity system. The
Electricity (Supply) Act 1926 The Electricity (Supply) Act 1926 (16 & 17 Geo. 5. c. 51) was an Act of the Parliament of the United Kingdom which amended the law on the supply of electricity. Its long title is: ‘An Act to amend the law with respect to the supply of electricity ...
led to the setting up of the National Grid. The
Central Electricity Board The United Kingdom Central Electricity Board (CEB) was established by the Electricity (Supply) Act 1926. It had the duty to supply electricity to authorised electricity undertakers, to determine which power stations would be 'selected' stations ...
standardized the nation's electricity supply and established the first synchronized AC grid, running at 132 kilovolts and 50
hertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
. This started operating as a national system, the National Grid, in 1938. In the United States in the 1920s, utilities formed joint-operations to share peak load coverage and backup power. In 1934, with the passage of the
Public Utility Holding Company Act The Public Utility Holding Company Act of 1935 (PUHCA), also known as the Wheeler-Rayburn Act, was a US federal law giving the Securities and Exchange Commission authority to regulate, license, and break up electric utility holding companies. It l ...
(USA), electric utilities were recognized as public goods of importance and were given outlined restrictions and regulatory oversight of their operations. The
Energy Policy Act of 1992 The Energy Policy Act of 1992, effective October 24, 1992, (102nd Congress H.R.776.ENR, abbreviated as EPACT92) is a United States government act. It was passed by Congress and set goals, created mandates, and amended utility laws to increase c ...
required transmission line owners to allow electric generation companies open access to their networkMazer, A. (2007). Electric Power Planning for Regulated and Deregulated Markets. John, Wiley, and Sons, Inc., Hoboken, NJ. 313pgs. and led to a restructuring of how the electric industry operated in an effort to create competition in power generation. No longer were electric utilities built as vertical monopolies, where generation, transmission and distribution were handled by a single company. Now, the three stages could be split among various companies, in an effort to provide fair access to high voltage transmission.. (2001). Glover J. D., Sarma M. S., Overbye T. J. (2010) Power System and Analysis 5th Edition. Cengage Learning. Pg 10. The Energy Policy Act of 2005 allowed incentives and loan guarantees for alternative energy production and advance innovative technologies that avoided
greenhouse emissions Greenhouse gas emissions from human activities strengthen the greenhouse effect, contributing to climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. The largest emitters include coal in China and la ...
. In France,
electrification Electrification is the process of powering by electricity and, in many contexts, the introduction of such power by changing over from an earlier power source. The broad meaning of the term, such as in the history of technology, economic histor ...
began in the 1900s, with 700
communes An intentional community is a voluntary residential community which is designed to have a high degree of social cohesion and teamwork from the start. The members of an intentional community typically hold a common social, political, relig ...
in 1919, and 36,528 in 1938. At the same time, these close networks began to interconnect: Paris in 1907 at 12 kV, the Pyrénées in 1923 at 150 kV, and finally almost all of the country interconnected by 1938 at 220 kV. In 1946, the grid was the world's most dense. That year the state nationalised the industry, by uniting the private companies as Électricité de France. The frequency was standardised at 50 Hz, and the 225 kV network replaced 110 kV and 120 kV. Since 1956, service voltage has been standardised at 220/380 V, replacing the previous 127/220 V. During the 1970s, the 400 kV network, the new European standard, was implemented. In China, electrification began in the 1950s. In August 1961, the electrification of the Baoji-Fengzhou section of the
Baocheng Railway Baocheng may refer to *Baocheng, Hainan, a town in Hainan, China *Baocheng, Mian, a township in Mian County, Shaanxi, China *Baocheng River, a river of Hainan *Ji Baocheng, a Chinese educator *Yuan Baocheng, a Chinese politician and Mayor of Donggu ...
was completed and delivered for operation, becoming China's first
electrified railway A railway electrification system supplies electric power to railway trains and trams without an on-board prime mover or local fuel supply. Electric railways use either electric locomotives (hauling passengers or freight in separate cars), ele ...
. From 1958 to 1998, China's electrified railway reached 6,200 miles (10,000 kilometres). As of the end of 2017, this number has reached 54,000 miles (87,000 kilometres). In the current railway electrification system of China
State Grid Corporation of China
is an important power supplier. In 2019, it completed the power supply project of China's important electrified railways in its operating areas, such as
Jingtong Railway Jingtong () is a locale in Pingxi District, New Taipei City, Taiwan. Originally a coal mining town, today it is known mostly for tourism, with numerous souvenir shops and exhibits on the history of the area and the coal mining industry. Touris ...
,
Haoji Railway The Haoji Railway (), fully known as Kholbolji/Haolebaoji to Ji'an railway (), formerly known as Menghua Railway (West Inner Mongolia to Central China), is a freight-dedicated railway in China. It runs from Haolebaoji South railway station in Ux ...
,
Zhengzhou–Wanzhou high-speed railway Zhengzhou–Wanzhou high-speed railway () is a high-speed railway connecting Zhengzhou, the capital of Henan province, and Wanzhou District in Chongqing. The section between Zhengzhou East and Xiangyang East started operation on 1 December 20 ...
, et cetera, providing power supply guarantee for 110 traction stations, and its cumulative power line construction length reached 6,586 kilometres.


Components


Generation

Electricity generation is the process of generating
electric power Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions o ...
from sources of
primary energy Primary energy (PE) is an energy form found in nature that has not been subjected to any human engineered conversion process. It is energy contained in raw fuels, and other forms of energy, including waste, received as input to a system. Prim ...
typically at
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 of electric power. Power stations are generally connected to an electrical grid. Many p ...
s. Usually this is done with
electromechanical In engineering, electromechanics combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems ...
generators driven by
heat engine In thermodynamics and engineering, a heat engine is a system that converts heat to mechanical energy, which can then be used to do mechanical work. It does this by bringing a working substance from a higher state temperature to a lower state ...
s or the
kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
of water or wind. Other energy sources include solar
photovoltaics Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...
and
geothermal power Geothermal power is electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation is currently used in 2 ...
. The sum of the power outputs of generators on the grid is the production of the grid, typically measured in
gigawatts The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wat ...
(GW).


Transmission

Electric power transmission is the bulk movement of electrical energy from a generating site, via a web of interconnected lines, to an electrical substation, from which is connected to the distribution system. This networked system of connections is distinct from the local wiring between high-voltage substations and customers. Because the power is often generated far from where it is consumed, the transmission system can cover great distances. For a given amount of power, transmission efficiency is greater at higher voltages and lower currents. Therefore, voltages are stepped up at the generating station, and stepped down at local substations for distribution to customers. Most transmission is
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 empl ...
. Three phase, compared to single phase, can deliver much more power for a given amount of wire, since the neutral and ground wires are shared. Further, three-phase generators and motors are more efficient than their single-phase counterparts. However, for conventional conductors one of the main losses are resistive losses which are a square law on current, and depend on distance. High voltage AC transmission lines can lose 1-4% per hundred miles. However,
high-voltage direct current A high-voltage direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for electric power transmission, in contrast with the more common alternating curre ...
can have half the losses of AC. Over very long distances, these efficiencies can offset the additional cost of the required AC/DC converter stations at each end. Transmission networks are complex with redundant pathways. The physical layout is often forced by what land is available and its geology. Most transmission grids offer the reliability that more complex ''mesh networks'' provide. Redundancy allows line failures to occur and power is simply rerouted while repairs are done.


Substations

Substations may perform many different functions but usually transform voltage from low to high (step up) and from high to low (step down). Between the generator and the final consumer, the voltage may be transformed several times. The three main types of substations, by function, are: * Step-up substation: these use
transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
s to raise the voltage coming from the generators and power plants so that power can be transmitted long distances more efficiently, with smaller currents. * Step-down substation: these transformers lower the voltage coming from the transmission lines which can be used in industry or sent to a distribution substation. * Distribution substation: these transform the voltage lower again for the distribution to end users. Aside from transformers, other major components or functions of substations include: *
Circuit breaker A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by an overcurrent or short circuit. Its basic function is to interrupt current flow to protect equipment and to prevent the ris ...
s: used to automatically break a circuit and isolate a fault in the system. *
Switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
es: to control the flow of electricity, and isolate equipment. * The substation
busbar In electric power distribution, a busbar (also bus bar) is a metallic strip or bar, typically housed inside switchgear, panel boards, and busway enclosures for local high current power distribution. They are also used to connect high volt ...
: typically a set of three conductors, one for each phase of current. The substation is orgranized around the buses, and they are connected to incoming lines, transformers, protection equipment, switches, and the outgoing lines. *
Lightning arrester A lightning arrester (alternative spelling lightning arrestor) (also called lightning isolator) is a device, essentially an air gap between an electric wire and ground, used on electric power transmission and telecommunication systems to protect ...
s *
Capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...
s for power factor correction


Electric power distribution

Distribution is the final stage in the delivery of power; it carries electricity from the transmission system to individual consumers. Substations connect to the transmission system and lower the transmission voltage to medium voltage ranging between and . Primary distribution lines carry this medium voltage power to
distribution transformer Single-phase distribution transformer in Canada A distribution transformer or service transformer is a transformer that provides the final voltage transformation in the electric power distribution system, stepping down the voltage used in the di ...
s located near the customer's premises. Distribution transformers again lower the voltage to the
utilization voltage Mains electricity or utility power, power grid, domestic power, and wall power, or in some parts of Canada as hydro, is a general-purpose alternating-current (AC) electric power supply. It is the form of electrical power that is delivered to h ...
. Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the subtransmission level. Distribution networks are divided into two types, radial or network. In cities and towns of North America, the grid tends to follow the classic ''radially fed'' design. A substation receives its power from the transmission network, the power is stepped down with a transformer and sent to a
bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...
from which feeders fan out in all directions across the countryside. These feeders carry three-phase power, and tend to follow the major streets near the substation. As the distance from the substation grows, the fanout continues as smaller laterals spread out to cover areas missed by the feeders. This tree-like structure grows outward from the substation, but for reliability reasons, usually contains at least one unused backup connection to a nearby substation. This connection can be enabled in case of an emergency, so that a portion of a substation's service territory can be alternatively fed by another substation.


Storage

''Grid energy storage'' (also called ''large-scale energy storage'') is a collection of methods used for
energy storage Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production. A device that stores energy is generally called an accumulator or battery. Energy comes in ...
on a large scale within an electrical power grid. Electrical energy is stored during times when electricity is plentiful and inexpensive (especially from intermittent power sources such as
renewable electricity Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, the movement of water, and geothermal heat. Although most renewable energy ...
from
wind power Wind power or wind energy is mostly the use of wind turbines to electricity generation, generate electricity. Wind power is a popular, sustainable energy, sustainable, renewable energy source that has a much smaller Environmental impact of wi ...
,
tidal power Tidal power or tidal energy is harnessed by converting energy from tides into useful forms of power, mainly electricity using various methods. Although not yet widely used, tidal energy has the potential for future electricity generation. Ti ...
and
solar power Solar power is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Photovoltaic cells convert light into an electric current using the photovoltaic e ...
) or when demand is low, and later returned to the grid when demand is high, and electricity prices tend to be higher. , the largest form of grid energy storage is dammed
hydroelectricity Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other Renewabl ...
, with both conventional hydroelectric generation as well as
pumped storage hydroelectricity Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential ...
. Developments in battery storage have enabled commercially viable projects to store energy during peak production and release during peak demand, and for use when production unexpectedly falls giving time for slower responding resources to be brought online. Two alternatives to grid storage are the use of peaking power plants to fill in supply gaps and demand response to shift load to other times.


Functionalities


Demand

The demand, or load on an electrical grid is the total electrical power being removed by the users of the grid. The graph of the demand over time is called the ''demand curve''.
Baseload The base load (also baseload) is the minimum level of demand on an electrical grid over a span of time, for example, one week. This demand can be met by unvarying power plants, dispatchable generation, or by a collection of smaller intermittent e ...
is the minimum load on the grid over any given period,
peak demand Peak demand on an electrical grid is simply the highest electrical power demand that has occurred over a specified time period (Gönen 2008). Peak demand is typically characterized as annual, daily or seasonal and has the unit of power. Peak dem ...
is the maximum load. Historically, baseload was commonly met by equipment that was relatively cheap to run, that ran continuously for weeks or months at a time, but globally this is becoming less common. The extra peak demand requirements are sometimes produced by expensive peaking plants that are generators optimised to come on-line quickly but these too are becoming less common. However, if the demand of electricity exceed the capacity of a local power grid, it will cause safety issue like burning out.


Voltage

Grids are designed to supply electricity to their customers at largely constant voltages. This has to be achieved with varying demand, variable
reactive Reactive may refer to: *Generally, capable of having a reaction (disambiguation) *An adjective abbreviation denoting a bowling ball coverstock made of reactive resin *Reactivity (chemistry) *Reactive mind *Reactive programming See also *Reactanc ...
loads, and even nonlinear loads, with electricity provided by generators and distribution and transmission equipment that are not perfectly reliable. Often grids use
tap changer A tap changer is a mechanism in transformers which allows for variable turn ratios to be selected in distinct steps. This is done by connecting to a number of access points known as taps along either the primary or secondary winding. Tap changers ...
s on transformers near to the consumers to adjust the voltage and keep it within specification.


Frequency

In a synchronous grid all the generators must run at the same frequency, and must stay very nearly in phase with each other and the grid. Generation and consumption must be balanced across the entire grid, because energy is consumed as it is produced. For rotating generators, a local
governor A governor is an administrative leader and head of a polity or political region, ranking under the head of state and in some cases, such as governors-general, as the head of state's official representative. Depending on the type of political ...
regulates the driving torque, maintaining almost constant rotation speed as loading changes. Energy is stored in the immediate short term by the rotational kinetic energy of the generators. Although the speed is kept largely constant, small deviations from the nominal system frequency are very important in regulating individual generators and are used as a way of assessing the equilibrium of the grid as a whole. When the grid is lightly loaded the grid frequency runs above the nominal frequency, and this is taken as an indication by Automatic Generation Control systems across the network that generators should reduce their output. Conversely, when the grid is heavily loaded, the frequency naturally slows, and governors adjust their generators so that more power is output (
droop speed control Droop speed control is a control mode used for AC electrical power generators, whereby the power output of a generator reduces as the line frequency increases. It is commonly used as the speed control mode of the governor of a prime mover driving a ...
). When generators have identical droop speed control settings it ensures that multiple parallel generators with the same settings share load in proportion to their rating. In addition, there's often central control, which can change the parameters of the AGC systems over timescales of a minute or longer to further adjust the regional network flows and the operating frequency of the grid. For timekeeping purposes, the nominal frequency will be allowed to vary in the short term, but is adjusted to prevent line-operated clocks from gaining or losing significant time over the course of a whole 24 hour period. An entire synchronous grid runs at the same frequency, neighbouring grids would not be synchronised even if they run at the same nominal frequency.
High-voltage direct current A high-voltage direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for electric power transmission, in contrast with the more common alternating curre ...
lines or
variable-frequency transformer A variable-frequency transformer (VFT) is used to transmit electricity between two (asynchronous or synchronous) alternating current frequency domains. The VFT is a relatively recent development. Most asynchronous grid inter-ties use high-voltage ...
s can be used to connect two alternating current interconnection networks which are not synchronized with each other. This provides the benefit of interconnection without the need to synchronize an even wider area. For example, compare the wide area synchronous grid map of Europe with the map of HVDC lines.


Capacity and firm capacity

The sum of the maximum power outputs (
nameplate capacity Nameplate capacity, also known as the rated capacity, nominal capacity, installed capacity, or maximum effect, is the intended full-load sustained output of a facility such as a power station,
) of the generators attached to an electrical grid might be considered to be the capacity of the grid. However, in practice, they are never run flat out simultaneously. Typically, some generators are kept running at lower output powers (
spinning reserve In electricity networks, the operating reserve is the generating capacity available to the system operator within a short interval of time to meet demand in case a generator goes down or there is another disruption to the supply. Most power sys ...
) to deal with failures as well as variation in demand. In addition generators can be off-line for maintenance or other reasons, such as availability of energy inputs (fuel, water, wind, sun etc.) or pollution constraints. Firm capacity is the maximum power output on a grid that is immediately available over a given time period, and is a far more useful figure.


Production

Most grid codes specify that the load is shared between the generators in
merit order The merit order is a way of ranking available sources of energy, especially electrical generation, based on ascending order of price (which may reflect the order of their short-run marginal costs of production) and sometimes pollution, together w ...
according to their marginal cost (i.e. cheapest first) and sometimes their environmental impact. Thus cheap electricity providers tend to be run flat out almost all the time, and the more expensive producers are only run when necessary.


Handling failure

Failures are usually associated with generators or power transmission lines tripping circuit breakers due to faults leading to a loss of generation capacity for customers, or excess demand. This will often cause the frequency to reduce, and the remaining generators will react and together attempt to stabilize above the minimum. If that is not possible then a number of scenarios can occur. A large failure in one part of the grid — unless quickly compensated for — can cause current to re-route itself to flow from the remaining generators to consumers over transmission lines of insufficient capacity, causing further failures. One downside to a widely connected grid is thus the possibility of
cascading failure A cascading failure is a failure in a system of interconnected parts in which the failure of one or few parts leads to the failure of other parts, growing progressively as a result of positive feedback. This can occur when a single part fails, i ...
and widespread
power outage A power outage (also called a powercut, a power out, a power failure, a power blackout, a power loss, or a blackout) is the loss of the electrical power network supply to an end user. There are many causes of power failures in an electricit ...
. A central authority is usually designated to facilitate communication and develop protocols to maintain a stable grid. For example, the
North American Electric Reliability Corporation The North American Electric Reliability Corporation (NERC) is a nonprofit corporation based in Atlanta, Georgia, and formed on March 28, 2006, as the successor to the North American Electric Reliability Council (also known as NERC). The original ...
gained binding powers in the United States in 2006, and has advisory powers in the applicable parts of Canada and Mexico. The U.S. government has also designated National Interest Electric Transmission Corridors, where it believes transmission bottlenecks have developed.


Brownout

A ''brownout'' is an intentional or unintentional drop in voltage in an electrical
power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a r ...
system. Intentional brownouts are used for load reduction in an emergency. The reduction lasts for minutes or hours, as opposed to short-term
voltage sag Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
(or dip). The term brownout comes from the dimming experienced by incandescent lighting when the voltage sags. A voltage reduction may be an effect of disruption of an electrical grid, or may occasionally be imposed in an effort to reduce load and prevent a
power outage A power outage (also called a powercut, a power out, a power failure, a power blackout, a power loss, or a blackout) is the loss of the electrical power network supply to an end user. There are many causes of power failures in an electricit ...
, known as a blackout.


Blackout

A ''power outage'' (also called a ''power cut'', a ''power out'', a ''power blackout'', ''power failure'' or a ''blackout'') is a loss of the electric power to a particular area. Power failures can be caused by faults at power stations, damage to electric transmission lines, substations or other parts of the
distribution Distribution may refer to: Mathematics *Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations * Probability distribution, the probability of a particular value or value range of a vari ...
system, a
short circuit A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit ...
,
cascading failure A cascading failure is a failure in a system of interconnected parts in which the failure of one or few parts leads to the failure of other parts, growing progressively as a result of positive feedback. This can occur when a single part fails, i ...
,
fuse Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protect ...
or
circuit breaker A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by an overcurrent or short circuit. Its basic function is to interrupt current flow to protect equipment and to prevent the ris ...
operation, and human error. Power failures are particularly critical at sites where the environment and public safety are at risk. Institutions such as
hospital A hospital is a health care institution providing patient treatment with specialized health science and auxiliary healthcare staff and medical equipment. The best-known type of hospital is the general hospital, which typically has an emerge ...
s,
sewage treatment Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding e ...
plants, mines, shelters and the like will usually have backup power sources such as standby generators, which will automatically start up when electrical power is lost. Other critical systems, such as
telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
, are also required to have emergency power. The
battery room A battery room is a room that houses batteries for backup or uninterruptible power systems. The rooms are found in telecommunication central offices, and provide standby power for computing equipment in datacenters. Batteries provide direct cur ...
of a telephone exchange usually has arrays of lead–acid batteries for backup and also a socket for connecting a generator during extended periods of outage.


Load shedding

Electrical generation Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery (transmission, distribution, etc.) to end users or its storag ...
and transmission systems may not always meet peak demand requirements— the greatest amount of
electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...
required by all utility customers within a given region. In these situations, overall demand must be lowered, either by turning off service to some devices or cutting back the supply voltage ( brownouts), in order to prevent uncontrolled service disruptions such as power outages (widespread blackouts) or equipment damage. Utilities may impose load shedding on service areas via targeted blackouts,
rolling blackout A rolling blackout, also referred to as rota or rotational load shedding, rota disconnection, feeder rotation, or a rotating outage, is an intentionally engineered electrical power shutdown in which electricity delivery is stopped for non-overla ...
s or by agreements with specific high-use industrial consumers to turn off equipment at times of system-wide peak demand.


Black start

A ''black start'' is the process of restoring an electric power station or a part of an
electric grid An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...
to operation without relying on the external electric power transmission network to recover from a total or partial shutdown.Knight, U.G. ''Power Systems in Emergencies - From Contingency Planning to Crisis Management '' John Wiley & Sons 2001 section 7.5 The 'Black Start' Situation Normally, the electric power used within the plant is provided from the station's own generators. If all of the plant's main generators are shut down, station service power is provided by drawing power from the grid through the plant's transmission line. However, during a wide-area outage, off-site power from the grid is not available. In the absence of grid power, a so-called black start needs to be performed to bootstrap the power grid into operation. To provide a black start, some power stations have small
diesel generator A diesel generator (DG) (also known as a diesel Genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of engine generator. A diesel compression-ig ...
s, normally called the ''black start diesel generator'' (BSDG), which can be used to start larger generators (of several
megawatt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...
s capacity), which in turn can be used to start the main power station generators. Generating plants using steam turbines require station service power of up to 10% of their capacity for
boiler feedwater pump A boiler feedwater pump is a specific type of pump used to pump feedwater into a steam boiler. The water may be freshly supplied or returning condensate produced as a result of the condensation of the steam produced by the boiler. These pumps are ...
s, boiler forced-draft combustion air blowers, and for fuel preparation. It is uneconomical to provide such a large standby capacity at each station, so black-start power must be provided over designated tie lines from another station. Often hydroelectric power plants are designated as the black-start sources to restore network interconnections. A hydroelectric station needs very little initial power to start (just enough to open the intake gates and provide
excitation Excitation, excite, exciting, or excitement may refer to: * Excitation (magnetic), provided with an electrical generator or alternator * Excite Ballpark, located in San Jose, California * Excite (web portal), web portal owned by IAC * Electron exc ...
current to the generator field coils), and can put a large block of power on line very quickly to allow start-up of fossil-fuel or nuclear stations. Certain types of
combustion turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...
can be configured for black start, providing another option in places without suitable hydroelectric plants. In 2017 a utility in Southern California has successfully demonstrated the use of a battery energy storage system to provide a black start, firing up a combined cycle gas turbine from an idle state.


Scale


Microgrid

A microgrid is a local grid that is usually part of the regional wide-area synchronous grid but which can disconnect and operate autonomously. It might do this in times when the main grid is affected by outages. This is known as
islanding Islanding is the condition in which a distributed generator (DG) continues to power a location even though external electrical grid power is no longer present. Islanding can be dangerous to utility workers, who may not realize that a circuit is st ...
, and it might run indefinitely on its own resources. Compared to larger grids, microgrids typically use a lower voltage distribution network and distributed generators. Microgrids may not only be more resilient, but may be cheaper to implement in isolated areas. A design goal is that a local area produces all of the energy it uses. Example implementations include: *
Hajjah Hajjah ( ar, حَجَّة, Ḥajjah) is the capital city of Hajjah Governorate in north-western Yemen. It is located 127 kilometres northwest of Sana'a, at an elevation of about 1800 metres. As of 2003, the Hajjah City District had a population ...
and
Lahj Lahij or Lahej ( ar, لحج, Laḥj, links=no), also called al-Hawtah, is a city and an area located between Ta'izz and Aden in Yemen. From the 18th to the 20th century, its rulers were of the Abdali branch of the Al-Sallami tribe who trace t ...
, Yemen: community-owned solar microgrids. *
Île d'Yeu Île d'Yeu () or L'Île-d'Yeu, is an island and commune just off the Vendée coast of western France. The island's two harbors, Port-Joinville in the north and Port de la Meule to the south, in a rocky inlet of the southern granite coast, are fam ...
pilot program: sixty-four solar panels with a peak capacity of 23.7 kW on five houses and a battery with a storage capacity of 15 kWh. *
Les Anglais Les Anglais ( ht, Zanglè), French for "The English", is a commune in the Chardonnières Arrondissement, in the Sud department of Haiti. It has 27,182 inhabitants. The eye of Hurricane Matthew made landfall near Les Anglais on 4 October ...
, Haiti: includes energy theft detection. *
Mpeketoni Mpeketoni is a town in Lamu County, on the Kenyan coast. It is a settlement scheme started in 1960s by the first president of the Republic of Kenya, Jomo Kenyatta near a fresh water lake bearing his name. Location Mpeketoni lies in Lamu County, ...
, Kenya: a community-based diesel-powered micro-grid system. * Stone Edge Farm Winery: micro-turbine, fuel-cell, multiple battery, hydrogen electrolyzer, and PV enabled winery in
Sonoma, California Sonoma is a city in Sonoma County, California, United States, located in the North Bay region of the San Francisco Bay Area. Sonoma is one of the principal cities of California's Wine Country and the center of the Sonoma Valley AVA. Sonoma's p ...
.


Wide area synchronous grid

A
wide area synchronous grid A wide area synchronous grid (also called an "interconnection" in North America) is a three-phase electric power grid that has regional scale or greater that operates at a synchronized utility frequency and is electrically tied together during ...
, also known as an "interconnection" in North America, directly connects many generators delivering AC power with the same relative ''frequency'' to many consumers. For example, there are four major interconnections in North America (the
Western Interconnection The Western Interconnection is a wide area synchronous grid and one of the two major alternating current (AC) power grids in the North American power transmission grid. The other major wide area synchronous grid is the Eastern Interconnection ...
, the
Eastern Interconnection The Eastern Interconnection is one of the two major alternating-current (AC) electrical grids in the North American power transmission grid. The other major interconnection is the Western Interconnection. The three minor interconnections ...
, the
Quebec Interconnection Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirteen p ...
and the
Texas Interconnection The Texas Interconnection is an alternating current (AC) power grid – a wide area synchronous grid – that covers most of the state of Texas. The grid is managed by the Electric Reliability Council of Texas (ERCOT). The Texas Inter ...
). In Europe one large grid connects most of continental Europe. A ''wide area synchronous grid'' (also called an "interconnection" in North America) is an electrical grid at a regional scale or greater that operates at a synchronized frequency and is electrically tied together during normal system conditions. These are also known as synchronous zones, the largest of which is the
synchronous grid of Continental Europe The synchronous grid of Continental Europe (also known as Continental Synchronous Area; formerly known as the UCTE grid) is the largest synchronous electrical grid (by connected power) in the world. It is interconnected as a single phase-locked ...
(ENTSO-E) with 667 
gigawatts The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wat ...
(GW) of generation, and the widest region served being that of the
IPS/UPS The IPS/UPS is a wide area synchronous transmission grid of some CIS countries, with a common mode of operation and centralized supervisory control. It has an installed generation capacity of 300 gigawatts, and produces 1,200  terawatt-ho ...
system serving countries of the former Soviet Union. Synchronous grids with ample capacity facilitate
electricity market In a broad sense, an electricity market is a system that facilitates the exchange of electricity-related goods and services. During more than a century of evolution of the electric power industry, the economics of the electricity markets had un ...
trading across wide areas. In the ENTSO-E in 2008, over 350,000 megawatt hours were sold per day on the
European Energy Exchange European Energy Exchange (EEX) AG is a central European electric power and related commodities exchange located in Leipzig, Germany. It develops, operates and connects secure, liquid and transparent markets for energy and related products, inc ...
(EEX). Each of the interconnects in North America are run at a nominal 60 Hz, while those of Europe run at 50 Hz. Neighbouring interconnections with the same frequency and standards can be synchronized and directly connected to form a larger interconnection, or they may share power without synchronization via high-voltage direct current
power transmission line Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines that facilitate this movement form a ''transmission network''. This is d ...
s (
DC tie An interconnector (also known as a DC tie in the USA) is a structure which enables high voltage DC electricity to flow between electrical grids. An electrical interconnector allows electricity to flow between separate AC networks, or to link sy ...
s), or with variable-frequency transformers (VFTs), which permit a controlled flow of energy while also functionally isolating the independent AC frequencies of each side. The benefits of synchronous zones include pooling of generation, resulting in lower generation costs; pooling of load, resulting in significant equalizing effects; common provisioning of reserves, resulting in cheaper primary and secondary reserve power costs; opening of the market, resulting in possibility of long-term contracts and short term power exchanges; and mutual assistance in the event of disturbances. One disadvantage of a wide-area synchronous grid is that problems in one part can have repercussions across the whole grid. For example, in 2018
Kosovo Kosovo ( sq, Kosova or ; sr-Cyrl, Косово ), officially the Republic of Kosovo ( sq, Republika e Kosovës, links=no; sr, Република Косово, Republika Kosovo, links=no), is a partially recognised state in Southeast Euro ...
used more power than it generated due to a dispute with
Serbia Serbia (, ; Serbian language, Serbian: , , ), officially the Republic of Serbia (Serbian language, Serbian: , , ), is a landlocked country in Southeast Europe, Southeastern and Central Europe, situated at the crossroads of the Pannonian Bas ...
, leading to the phase across the whole
synchronous grid of Continental Europe The synchronous grid of Continental Europe (also known as Continental Synchronous Area; formerly known as the UCTE grid) is the largest synchronous electrical grid (by connected power) in the world. It is interconnected as a single phase-locked ...
lagging behind what it should have been. The frequency dropped to 49.996 Hz. This caused certain kinds of
clock A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and the ...
s to become six minutes slow. File:ElectricityUCTE.svg, The synchronous grids of Europe File:NERC-map-en.svg, The two major and three minor interconnections of North America File:Wide area synchronous grid (Eurasia, Mediterranean).png, Major WASGs around the world


Super grid

A ''super grid'' or ''supergrid'' is a wide-area transmission network that is intended to make possible the trade of high volumes of electricity across great distances. It is sometimes also referred to as a ''mega grid''. Super grids can support a global energy transition by smoothing local fluctuations of
wind energy Wind power or wind energy is mostly the use of wind turbines to generate electricity. Wind power is a popular, sustainable, renewable energy source that has a much smaller impact on the environment than burning fossil fuels. Historically, w ...
and
solar energy Solar energy is 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 is an essenti ...
. In this context they are considered as a key technology to mitigate
global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. Super grids typically use
High-voltage direct current A high-voltage direct current (HVDC) electric power transmission system (also called a power superhighway or an electrical superhighway) uses direct current (DC) for electric power transmission, in contrast with the more common alternating curre ...
(HVDC) to transmit electricity long distances. The latest generation of HVDC power lines can transmit energy with losses of only 1.6% per 1000 km. Electric utilities between regions are many times interconnected for improved economy and reliability.
Electrical interconnector An interconnector (also known as a DC tie in the USA) is a structure which enables high voltage DC electricity to flow between electrical grids. An electrical interconnector allows electricity to flow between separate AC networks, or to link s ...
s allow for economies of scale, allowing energy to be purchased from large, efficient sources. Utilities can draw power from generator reserves from a different region to ensure continuing, reliable power and diversify their loads. Interconnection also allows regions to have access to cheap bulk energy by receiving power from different sources. For example, one region may be producing cheap hydro power during high water seasons, but in low water seasons, another area may be producing cheaper power through wind, allowing both regions to access cheaper energy sources from one another during different times of the year. Neighboring utilities also help others to maintain the overall system frequency and also help manage tie transfers between utility regions. Electricity Interconnection Level (EIL) of a grid is the ratio of the total interconnector power to the grid divided by the installed production capacity of the grid. Within the EU, it has set a target of national grids reaching 10% by 2020, and 15% by 2030.


Trends


Demand response

Demand response is a grid management technique where retail or wholesale customers are requested or incentivised either electronically or manually to reduce their load. Currently, transmission grid operators use demand response to request load reduction from major energy users such as industrial plants. Technologies such as smart metering can encourage customers to use power when electricity is plentiful by allowing for variable pricing.


Aging infrastructure

Despite the novel institutional arrangements and network designs of the electrical grid, its power delivery infrastructures suffer aging across the developed world. Contributing factors to the current state of the electric grid and its consequences include: * Aging equipment – older equipment has higher failure rates, leading to customer interruption rates affecting the economy and society; also, older assets and facilities lead to higher inspection
maintenance Maintenance may refer to: Biological science * Maintenance of an organism * Maintenance respiration Non-technical maintenance * Alimony, also called ''maintenance'' in British English * Champerty and maintenance, two related legal doct ...
costs and further
repair The technical meaning of maintenance involves functional checks, servicing, repairing or replacing of necessary devices, equipment, machinery, building infrastructure, and supporting utilities in industrial, business, and residential installa ...
and
restoration Restoration is the act of restoring something to its original state and may refer to: * Conservation and restoration of cultural heritage ** Audio restoration ** Film restoration ** Image restoration ** Textile restoration * Restoration ecology ...
costs. * Obsolete system layout – older areas require serious additional substation sites and
rights-of-way Right of way is the legal right, established by grant from a landowner or long usage (i.e. by prescription), to pass along a specific route through property belonging to another. A similar ''right of access'' also exists on land held by a gov ...
that cannot be obtained in the current area and are forced to use existing, insufficient facilities. * Outdated engineering – traditional tools for
power delivery Electricity delivery is the process that starts after generation of electricity in the power station, up to the use by the consumer. The main processes in electricity delivery are, by order: * Transmission * Distribution * Retailing See also * ...
planning and engineering are ineffective in addressing current problems of aged equipment, obsolete system layouts, and modern deregulated loading levels. * Old cultural value – planning,
engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...
, operating of system using concepts and procedures that worked in vertically integrated industry exacerbate the problem under a deregulated industry.


Distributed generation

With everything interconnected, and open competition occurring in a
free market economy A market economy is an economic system in which the decisions regarding investment, production and distribution to the consumers are guided by the price signals created by the forces of supply and demand, where all suppliers and consumers ar ...
, it starts to make sense to allow and even encourage distributed generation (DG). Smaller generators, usually not owned by the utility, can be brought on-line to help supply the need for power. The smaller generation facility might be a home-owner with excess power from their solar panel or wind turbine. It might be a small office with a diesel generator. These resources can be brought on-line either at the utility's behest, or by owner of the generation in an effort to sell electricity. Many small generators are allowed to sell electricity back to the grid for the same price they would pay to buy it. As the 21st century progresses, the electric utility industry seeks to take advantage of novel approaches to meet growing energy demand. Utilities are under pressure to evolve their classic topologies to accommodate distributed generation. As generation becomes more common from rooftop solar and wind generators, the differences between distribution and transmission grids will continue to blur. In July 2017 the CEO of
Mercedes-Benz Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...
said that the energy industry needs to work better with companies from other industries to form a "total ecosystem", to integrate central and
distributed energy resources 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 to ...
(DER) to give customers what they want. The electrical grid was originally constructed so that electricity would flow from power providers to consumers. However, with the introduction of DER, power needs to flow both ways on the electric grid, because customers may have power sources such as solar panels.


Smart grid

The smart grid would be an enhancement of the 20th century electrical grid, using two-way communications and distributed so-called intelligent devices. Two-way flows of electricity and information could improve the delivery network. Research is mainly focused on three systems of a smart grid – the infrastructure system, the management system, and the protection system. The infrastructure system is the energy, information, and communication infrastructure underlying of the smart grid that supports: * Advanced electricity generation, delivery, and consumption * Advanced information metering, monitoring, and management * Advanced communication technologies A smart grid would allow the power industry to observe and control parts of the system at higher resolution in time and space.Alexandra Von Meier (2013). Electrical Engineer 137A: Electric Power Systems. Lecture 2:Introduction to Electric Power Systems, Slide 33. One of the purposes of the smart grid is real time information exchange to make operation as efficient as possible. It would allow management of the grid on all time scales from high-frequency switching devices on a microsecond scale, to wind and solar output variations on a minute scale, to the future effects of the carbon emissions generated by power production on a decade scale. The management system is the subsystem in smart grid that provides advanced management and control services. Most of the existing works aim to improve energy efficiency, demand profile, utility, cost, and emission, based on the infrastructure by using
optimization Mathematical optimization (alternatively spelled ''optimisation'') or mathematical programming is the selection of a best element, with regard to some criterion, from some set of available alternatives. It is generally divided into two subfi ...
,
machine learning Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence. Machine ...
, and
game theory Game theory is the study of mathematical models of strategic interactions among rational agents. Myerson, Roger B. (1991). ''Game Theory: Analysis of Conflict,'' Harvard University Press, p.&nbs1 Chapter-preview links, ppvii–xi It has appli ...
. Within the advanced infrastructure framework of smart grid, more and more new management services and applications are expected to emerge and eventually revolutionize consumers' daily lives. The protection system of a smart grid provides grid reliability analysis, failure protection, and security and privacy protection services. While the additional communication infrastructure of a smart grid provides additional protective and security mechanisms, it also presents a risk of external attack and internal failures. In a report on cyber security of smart grid technology first produced in 2010, and later updated in 2014, the US
National Institute of Standards and Technology The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical sci ...
pointed out that the ability to collect more data about energy use from customer smart meters also raises major privacy concerns, since the information stored at the meter, which is potentially vulnerable to data breaches, can be mined for personal details about customers. In the U.S., the Energy Policy Act of 2005 and Title XIII of the
Energy Independence and Security Act of 2007 The Energy Independence and Security Act of 2007Pub.L. 110-140, originally named the Clean Energy Act of 2007, is an Act of Congress concerning the energy policy of the United States. As part of the Democratic Party's 100-Hour Plan during th ...
are providing funding to encourage smart grid development. The objective is to enable utilities to better predict their needs, and in some cases involve consumers in a time-of-use tariff. Funds have also been allocated to develop more robust energy control technologies.


Grid defection

As there is some resistance in the electric utility sector to the concepts of distributed generation with various renewable energy sources and microscale cogen units, several authors have warned that mass-scale grid defection is possible because consumers can produce electricity using
off grid Off-the-grid or off-grid is a characteristic of buildings and a lifestyle designed in an independent manner without reliance on one or more public utilities. The term "off-the-grid" traditionally refers to not being connected to the electrical g ...
systems primarily made up of
solar photovoltaic A photovoltaic system, also PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to absorb and c ...
technology. The
Rocky Mountain Institute RMI (Rocky Mountain Institute) is an organization in the United States co-founded by Amory Lovins dedicated to research, publication, consulting, and lecturing in the field of sustainability, with a focus on profitable innovations for energy an ...
has proposed that there may be widescale grid defection. This is backed up by studies in the Midwest. However, the paper points out that grid defection may be less likely in countries like Germany which have greater power demands in winter.


See also

*
Grid code A grid code is a technical specification which defines the parameters a facility connected to a public electric grid has to meet to ensure safe, secure and economic proper functioning of the electric system. The facility can be an electricity gener ...
: a specification for grid-connected equipment *
North American power transmission grid The electrical grid, electrical power grid that powers Northern America is not a single grid, but is instead divided into multiple wide area synchronous grids. The Eastern Interconnection and the Western Interconnection are the largest. Three ot ...
*
North American Electric Reliability Corporation The North American Electric Reliability Corporation (NERC) is a nonprofit corporation based in Atlanta, Georgia, and formed on March 28, 2006, as the successor to the North American Electric Reliability Council (also known as NERC). The original ...
(NERC) *
Rural Electrification Act The Rural Electrification Act of 1936, enacted on May 20, 1936, provided federal loans for the installation of electrical distribution systems to serve isolated rural areas of the United States. The funding was channeled through cooperative ele ...


References


External links


Map of U.S. generation and transmission

U.S. electric system is made up of interconnections and balancing authorities
U.S. Energy Information Administration (EIA).
Open Infrastructure Map
is a view of the world's hidden power infrastructure mapped in the
OpenStreetMap OpenStreetMap (OSM) is a free, open geographic database updated and maintained by a community of volunteers via open collaboration. Contributors collect data from surveys, trace from aerial imagery and also import from other freely licensed g ...
database. {{Authority control Electric power distribution Electric power transmission systems la:Cratis electrica no:Fordelingsnett ta:மின் வலைப்பின்னல்