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Grid (electricity)
Encyclopedia
An electrical grid is a vast, interconnected network for delivering electricity
from suppliers to consumers. It consists of three main components: 1) generating plants that produce electricity from combustible fuels (coal
, natural gas
, biomass
) or non-combustible fuels (wind
, solar
, nuclear
, hydro power
); 2) transmission lines
that carry electricity from power plants to demand centers; and 3) transformers that reduce voltage so distribution lines carry power for final delivery.
In the power industry
, electrical grid is a term used for an electricity network which includes the following three distinct operations:
or may be used to describe a subnetwork such as a local utility's transmission grid or distribution grid.
, the electrical grid has evolved from an insular system that serviced a particular geographic area to a wider, expansive network that incorporated multiple areas. At one point, all energy was produced near the device or service requiring that energy. In the early 19th century, electricity was a novel invention that competed with steam
, hydraulics
, direct heating and cooling
, light
, and most notably gas
. During this period, gas production and delivery had become the first centralized element in the modern energy industry. It was first produced on customer’s premises but later evolved into large gasifiers that enjoyed economies of scale
. Virtually every city in the U.S. and Europe had town gas piped through their municipalities as it was a dominant form of household energy use. By the mid-19th century, electric arc lighting soon became advantageous compared to volatile gas lamps since gas lamps produced poor light, tremendous wasted heat which made rooms hot and smoky, and noxious elements in the form of hydrogen
and carbon monoxide
. Modeling after the gas lighting industry, Thomas Edison
invented the first electric utility
system which supplied energy through virtual mains to light filtration as opposed to gas burners. With this, electric utilities also took advantage of economies of scale and moved to centralized power generation, distribution, and system management.
During the 20th century, institutional arrangement of electric utilities changed. At the beginning, electric utilities were isolated systems without connection to other utilities and serviced a specific service territory. In the 1920s, utilities joined together establishing a wider utility grid as joint-operations saw the benefits of sharing peak load coverage and backup power. Also, electric utilities were easily financed by Wall Street
private investors who backed many of their ventures. In 1934, with the passage of the Public Utility Holding Company Act, electric utilities were recognized as public good
s of importance along with gas, water, and telephone companies and thereby were given outlined restrictions and regulatory oversight of their operations. This ushered in the Golden Age of Regulation for more than 60 years. However, with the successful deregulation of airlines and telecommunication industries in late 1970s, the Energy Policy Act (EPAct) of 1992
advocated deregulation of electric utilities by creating wholesale electric markets. It required transmission line owners to allow electric generation companies open access to their network.
, a more complex environment occurred as opposed to the traditional vertically-integrated monopoly
that oversees the entire grid’s operations. Newer participants entered the market including Independent Power Providers (IPPs
) who decided and constructed the new facility; Transmission Companies (TRANSCOs) who constructed and owned the transmission equipment; retailers who signed up end-use customers, procured their electric service, and billed them; integrated energy companies (combined IPPs and retailers); and Independent System Operation (ISO
) who managed the grid being indifferent to market outcomes. Also, day-to-day to long term operations altered. Infrastructure
additions which were long-term planning now became an investment analysis
with IPPs that decided construction of a new power plant under economic considerations (i.e., taxes, labor
and material costs
) and ability to obtain financing. Load and supply management that fell under mid-term planning became risk management
as private utilities had to manage a portfolio
of end customers and assets with the company’s risk preference. Day-ahead scheduling and real time grid management in the short-term planning which involves forecasting demand and dispatch schedule became asset management as power plants and grid equipment were assets to be scheduled and dispatched. Here, the ISO sets dispatch schedule at the market clearing price where the supply bids of generating units equilibriated with demand bids of retailers.
Many engineers argue the unfortunate disadvantages that stem from deregulation. Where under regulated monopolies, long distance energy lines were used for emergencies as backup in case of generation outage
s, now, particularly in North America, the majority of domestic generation is sold over ever-increasing distances on the wholesale market before delivery to customers. Consequently, the power grid witnesses fluctuating power flows
that impact system stability and reliability. To reduce system failure, the power flow of a transmission line must operate below the transmission line’s capacity. Yet now, companies are continually operating near capacity. Additionally, as utilities exchange power to other utilities, power flows along all paths of connection. Therefore, any change in one point of generation and transmission affects the load on all other points. Oftentimes, this is unanticipated and uncontrolled. Usually, a longer line’s capacity is less than a shorter line’s capacity. If not, power-supply
instability occurs resulting in transmission lines that break or sag. Such phase and voltage fluctuations cause system interruptions as witnessed in the Northeast Blackout of 1965
(which involved a circuit breaker to trip) and 2003
(which involved a sagging line on a tree that rippled in magnitude). Furthermore, IPPs add new generating units at random locations determined by economics that extend the distance to main consuming areas adversely affecting power supply. Also, utilities, because of competitive information needs, do not publicize needed data to predict and react to system stress such as with energy flows and blackout statistics. Overall, the economics of the electrical grid do not align sufficiently with the physics of the grid. Experts advocate for fundamental changes to avoid serious consequences in the near future.
" of a grid can vary considerably. The physical layout is often forced by what land is available and its geology. The logical topology can vary depending on the constraints of budget, requirements for system reliability, and the load and generation characteristics.
The cheapest and simplest topology for a distribution or transmission grid is a radial structure. This is a tree shape where power from a large supply radiates out into progressively lower voltage lines until the destination homes and businesses are reached.
Most transmission grids require the reliability that more complex mesh networks provide. If one were to imagine running redundant lines between limbs/branches of a tree that could be turned in case any particular limb of the tree were severed, then this image approximates how a mesh system operates. The expense of mesh topologies restrict their application to transmission and medium voltage distribution grids. Redundancy allows line failures to occur and power is simply rerouted while workmen repair the damaged and deactivated line.
Other topologies used are looped systems found in Europe and tied ring networks.
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
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.
A wide area synchronous grid
or "interconnection" is a group of distribution areas all operating with alternating current
(AC) frequencies synchronized (so that peaks occur at 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. Interconnection maps are shown of North America (right) and Europe (below left).
Electricity generation and consumption must be balanced across the entire grid, because energy is consumed almost immediately after it is produced. 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
and widespread power outage
. 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 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 Corridor
s, where it believes transmission bottlenecks have developed.
Some areas, for example rural communities in Alaska
, do not operate on a large grid, relying instead on local diesel generators.
High-voltage direct current
lines or variable frequency transformer
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 (above left) with the map of HVDC lines (below right).
when it is connected to several redundant
sources, generally involving long-distance transmission.
This redundancy is limited. Existing national or regional grids simply provide the interconnection of facilities to utilize whatever redundancy is available. The exact stage of development at which the supply structure becomes a grid is arbitrary. Similarly, the term national grid is something of an anachronism
in many parts of the world, as transmission cables now frequently cross national boundaries. The terms distribution grid for local connections and transmission grid for long-distance transmissions are therefore preferred, but national grid is often still used for the overall structure.
. As generation becomes more common from rooftop solar and wind generators, the differences between distribution and transmission grids will continue to blur. Also, demand response
is a grid management technique where retail or wholesale customers are requested 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.
With everything interconnected, and open competition occurring in a free market economy, 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. Furthermore, numerous efforts are underway to develop a "smart grid". In the U.S., the Energy Policy Act of 2005
and Title XIII of the Energy Independence and Security Act of 2007
are providing funding to encourage smart grid development. The hope is to enable utilities to better predict their needs, and in some cases involve consumers in some form of time-of-use based tariff. Funds have also been allocated to develop more robust energy control technologies.
Decentralization of the power transmission distribution system is vital to the success and reliability of this system. Currently the system is reliant upon relatively few generation stations. This makes current systems susceptible to impact from failures not within said area. Micro grids would have local power generation, and allow smaller grid areas to be separated from the rest of the grid if a failure were to occur. Furthermore, micro grid systems could help power each other if needed. Generation within a micro grid could be a downsized industrial generator or several smaller systems such as photo-voltaic systems, or wind generation. When combined with Smart Grid technology, electricity could be better controlled and distributed, and more efficient. Conversely, various planned and proposed systems to dramatically increase transmission capacity are known as super, or mega grids
. The promised benefits include enabling the renewable energy
industry to sell electricity to distant markets, the ability to increase usage of intermittent energy sources by balancing them across vast geological regions, and the removal of congestion that prevents electricity markets from flourishing. Local opposition to siting new lines and the significant cost of these projects are major obstacles to super grids.
continues further, utilities are driven to sell their assets as the energy market follows in line with the gas market in use of the futures and spot market
s and other financial arrangements. Even globalization
with foreign purchases are taking place. Recently, U.K’s
National Grid
, the largest private electric utility in the world, bought New England
’s electric system for $3.2 billion. Also, Scottish Power
purchased Pacific Energy
for $12.8 billion. Domestically, local electric and gas firms begin to merge operations as they see advantage of joint affiliation especially with the reduced cost of joint-metering. Technological advances will take place in the competitive wholesale electric markets such examples already being utilized include fuel cells used in space flight, aeroderivative gas turbines used in jet aircraft
s, solar engineering and photovoltaic systems, off-shore wind farms, and the communication advances spawned by the digital world particularly with microprocessing which aids in monitoring and dispatching.
Electricity will continue to see a growing demand in the future years as the Information Revolution is highly reliant on it, including emerging new electricity-exclusive technologies, developments in space conditioning, industrial process
, and transportation (i.e., hybrid vehicle
s, locomotive
s).
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
from suppliers to consumers. It consists of three main components: 1) generating plants that produce electricity from combustible fuels (coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
, natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
, biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
) or non-combustible fuels (wind
Wind power
Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships....
, solar
Solar power
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...
, nuclear
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
, hydro power
Hydropower
Hydropower, hydraulic power, hydrokinetic power or water power is power that is derived from the force or energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as...
); 2) transmission lines
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
that carry electricity from power plants to demand centers; and 3) transformers that reduce voltage so distribution lines carry power for final delivery.
In the power industry
Electrical power industry
The electric power industry provides the production and delivery of electric energy, often known as power, or electricity, in sufficient quantities to areas that need electricity through a grid connection. The grid distributes electrical energy to customers...
, electrical grid is a term used for an electricity network which includes the following three distinct operations:
- Electricity generationElectricity generationElectricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...
- Generating plantsPower stationA power station is an industrial facility for the generation of electric energy....
are usually located near a source of water, and away from heavily populated areas. They are usually quite large in order to take advantage of the economies of scaleEconomies of scaleEconomies of scale, in microeconomics, refers to the cost advantages that an enterprise obtains due to expansion. There are factors that cause a producer’s average cost per unit to fall as the scale of output is increased. "Economies of scale" is a long run concept and refers to reductions in unit...
. The electric power which is generated is stepped up to a higher voltage-at which it connects to the transmission network. - Electric power transmissionElectric power transmissionElectric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
- The transmission network will move (wheelWheeling (electric power transmission)In electric power transmission, wheeling is a term used to describe either of the following:* the act of transporting electric power over transmission lines, or;...
) the power long distances-often across state lines, and sometimes across international boundaries until it reaches its wholesale customer (usually the company that owns the local distribution network). - Electricity distributionElectricity distributionFile:Electricity grid simple- North America.svg|thumb|380px|right|Simplified diagram of AC electricity distribution from generation stations to consumers...
- Upon arrival at the substation, the power will be stepped down in voltage—from a transmission level voltage to a distribution level voltage. As it exits the substation, it enters the distribution wiring. Finally, upon arrival at the service location, the power is stepped down again from the distribution voltage to the required service voltage(s).
Term
The term grid usually refers to a network, and should not be taken to imply a particular physical layout or breadth. Grid may also be used to refer to an entire continent's electrical network, a regional transmission networkTransmission system operator
File:Electricity grid simple- North America.svg|thumb|380px|right|Simplified diagram of AC electricity distribution from generation stations to consumersrect 2 243 235 438 Power stationrect 276 317 412 556 Transformer...
or may be used to describe a subnetwork such as a local utility's transmission grid or distribution grid.
History
Since its inception in the Industrial AgeIndustrial Age
Industrial Age may refer to:*Industrialisation*The Industrial Revolution...
, the electrical grid has evolved from an insular system that serviced a particular geographic area to a wider, expansive network that incorporated multiple areas. At one point, all energy was produced near the device or service requiring that energy. In the early 19th century, electricity was a novel invention that competed with steam
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...
, hydraulics
Hydraulics
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...
, direct heating and cooling
Cooling
Cooling is the transfer of thermal energy via thermal radiation, heat conduction or convection. It may also refer to:-Techniques:* Air conditioning* Air cooling* Computer cooling* Cryogenics* Conduction * Infrared solar cells* Laser cooling...
, light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
, and most notably gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
. During this period, gas production and delivery had become the first centralized element in the modern energy industry. It was first produced on customer’s premises but later evolved into large gasifiers that enjoyed economies of scale
Economies of scale
Economies of scale, in microeconomics, refers to the cost advantages that an enterprise obtains due to expansion. There are factors that cause a producer’s average cost per unit to fall as the scale of output is increased. "Economies of scale" is a long run concept and refers to reductions in unit...
. Virtually every city in the U.S. and Europe had town gas piped through their municipalities as it was a dominant form of household energy use. By the mid-19th century, electric arc lighting soon became advantageous compared to volatile gas lamps since gas lamps produced poor light, tremendous wasted heat which made rooms hot and smoky, and noxious elements in the form of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
and carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
. Modeling after the gas lighting industry, Thomas Edison
Thomas Edison
Thomas Alva Edison was an American inventor and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. In addition, he created the world’s first industrial...
invented the first electric utility
Electric utility
An electric utility is a company that engages in the generation, transmission, and distribution of electricity for sale generally in a regulated market. The electrical utility industry is a major provider of energy in most countries. It is indispensable to factories, commercial establishments,...
system which supplied energy through virtual mains to light filtration as opposed to gas burners. With this, electric utilities also took advantage of economies of scale and moved to centralized power generation, distribution, and system management.
During the 20th century, institutional arrangement of electric utilities changed. At the beginning, electric utilities were isolated systems without connection to other utilities and serviced a specific service territory. In the 1920s, utilities joined together establishing a wider utility grid as joint-operations saw the benefits of sharing peak load coverage and backup power. Also, electric utilities were easily financed by Wall Street
Wall Street
Wall Street refers to the financial district of New York City, named after and centered on the eight-block-long street running from Broadway to South Street on the East River in Lower Manhattan. Over time, the term has become a metonym for the financial markets of the United States as a whole, or...
private investors who backed many of their ventures. In 1934, with the passage of the Public Utility Holding Company Act, electric utilities were recognized as public good
Public good
In economics, a public good is a good that is non-rival and non-excludable. Non-rivalry means that consumption of the good by one individual does not reduce availability of the good for consumption by others; and non-excludability means that no one can be effectively excluded from using the good...
s of importance along with gas, water, and telephone companies and thereby were given outlined restrictions and regulatory oversight of their operations. This ushered in the Golden Age of Regulation for more than 60 years. However, with the successful deregulation of airlines and telecommunication industries in late 1970s, the Energy Policy Act (EPAct) of 1992
Energy Policy Act of 1992
The Energy Policy Act is a United States government act.It was passed by Congress and addressed energy efficiency, energy conservation and energy management , natural gas imports and exports , alternative fuels and requiring certain fleets to acquire alternative fuel vehicles, which are capable of...
advocated deregulation of electric utilities by creating wholesale electric markets. It required transmission line owners to allow electric generation companies open access to their network.
Deregulation
With deregulationDeregulation
Deregulation is the removal or simplification of government rules and regulations that constrain the operation of market forces.Deregulation is the removal or simplification of government rules and regulations that constrain the operation of market forces.Deregulation is the removal or...
, a more complex environment occurred as opposed to the traditional vertically-integrated monopoly
Monopoly
A monopoly exists when a specific person or enterprise is the only supplier of a particular commodity...
that oversees the entire grid’s operations. Newer participants entered the market including Independent Power Providers (IPPs
Independent Power Producer
An Independent Power Producer is an entity, which is not a public utility, but which owns facilities to generate electric power for sale to utilities and end users...
) who decided and constructed the new facility; Transmission Companies (TRANSCOs) who constructed and owned the transmission equipment; retailers who signed up end-use customers, procured their electric service, and billed them; integrated energy companies (combined IPPs and retailers); and Independent System Operation (ISO
Regional transmission organization
A regional transmission organization in the United States is an organization that is responsible for moving electricity over large interstate areas. Like a transmission system operator , an RTO coordinates, controls and monitors an electricity transmission grid that is larger with much higher...
) who managed the grid being indifferent to market outcomes. Also, day-to-day to long term operations altered. Infrastructure
Infrastructure
Infrastructure is basic physical and organizational structures needed for the operation of a society or enterprise, or the services and facilities necessary for an economy to function...
additions which were long-term planning now became an investment analysis
Valuation (finance)
In finance, valuation is the process of estimating what something is worth. Items that are usually valued are a financial asset or liability. Valuations can be done on assets or on liabilities...
with IPPs that decided construction of a new power plant under economic considerations (i.e., taxes, labor
Labour economics
Labor economics seeks to understand the functioning and dynamics of the market for labor. Labor markets function through the interaction of workers and employers...
and material costs
Capital (economics)
In economics, capital, capital goods, or real capital refers to already-produced durable goods used in production of goods or services. The capital goods are not significantly consumed, though they may depreciate in the production process...
) and ability to obtain financing. Load and supply management that fell under mid-term planning became risk management
Risk management
Risk management is the identification, assessment, and prioritization of risks followed by coordinated and economical application of resources to minimize, monitor, and control the probability and/or impact of unfortunate events or to maximize the realization of opportunities...
as private utilities had to manage a portfolio
Portfolio (finance)
Portfolio is a financial term denoting a collection of investments held by an investment company, hedge fund, financial institution or individual.-Definition:The term portfolio refers to any collection of financial assets such as stocks, bonds and cash...
of end customers and assets with the company’s risk preference. Day-ahead scheduling and real time grid management in the short-term planning which involves forecasting demand and dispatch schedule became asset management as power plants and grid equipment were assets to be scheduled and dispatched. Here, the ISO sets dispatch schedule at the market clearing price where the supply bids of generating units equilibriated with demand bids of retailers.
Many engineers argue the unfortunate disadvantages that stem from deregulation. Where under regulated monopolies, long distance energy lines were used for emergencies as backup in case of generation outage
Outage
Outage may refer to:* Network outage* Sun outage* Power outage* Outing...
s, now, particularly in North America, the majority of domestic generation is sold over ever-increasing distances on the wholesale market before delivery to customers. Consequently, the power grid witnesses fluctuating power flows
Power engineering
Power engineering, also called power systems engineering, is a subfield of engineering that deals with the generation, transmission and distribution of electric power as well as the electrical devices connected to such systems including generators, motors and transformers...
that impact system stability and reliability. To reduce system failure, the power flow of a transmission line must operate below the transmission line’s capacity. Yet now, companies are continually operating near capacity. Additionally, as utilities exchange power to other utilities, power flows along all paths of connection. Therefore, any change in one point of generation and transmission affects the load on all other points. Oftentimes, this is unanticipated and uncontrolled. Usually, a longer line’s capacity is less than a shorter line’s capacity. If not, power-supply
Power supply
A power supply is a device that supplies electrical energy to one or more electric loads. The term is most commonly applied to devices that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy to electrical energy...
instability occurs resulting in transmission lines that break or sag. Such phase and voltage fluctuations cause system interruptions as witnessed in the Northeast Blackout of 1965
Northeast Blackout of 1965
The Northeast blackout of 1965 was a significant disruption in the supply of electricity on November 9, 1965, affecting Ontario, Canada and Connecticut, Massachusetts, New Hampshire, Rhode Island, Vermont, New York, and New Jersey in the United States...
(which involved a circuit breaker to trip) and 2003
Northeast Blackout of 2003
The Northeast blackout of 2003 was a widespread power outage that occurred throughout parts of the Northeastern and Midwestern United States and Ontario, Canada on Thursday, August 14, 2003, just before 4:10 p.m....
(which involved a sagging line on a tree that rippled in magnitude). Furthermore, IPPs add new generating units at random locations determined by economics that extend the distance to main consuming areas adversely affecting power supply. Also, utilities, because of competitive information needs, do not publicize needed data to predict and react to system stress such as with energy flows and blackout statistics. Overall, the economics of the electrical grid do not align sufficiently with the physics of the grid. Experts advocate for fundamental changes to avoid serious consequences in the near future.
Structure of distribution grids
The structure, or "topologyNetwork topology
Network topology is the layout pattern of interconnections of the various elements of a computer or biological network....
" of a grid can vary considerably. The physical layout is often forced by what land is available and its geology. The logical topology can vary depending on the constraints of budget, requirements for system reliability, and the load and generation characteristics.
The cheapest and simplest topology for a distribution or transmission grid is a radial structure. This is a tree shape where power from a large supply radiates out into progressively lower voltage lines until the destination homes and businesses are reached.
Most transmission grids require the reliability that more complex mesh networks provide. If one were to imagine running redundant lines between limbs/branches of a tree that could be turned in case any particular limb of the tree were severed, then this image approximates how a mesh system operates. The expense of mesh topologies restrict their application to transmission and medium voltage distribution grids. Redundancy allows line failures to occur and power is simply rerouted while workmen repair the damaged and deactivated line.
Other topologies used are looped systems found in Europe and tied ring networks.
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
Busbar
In electrical power distribution, a bus bar is a strip of copper or aluminium that conducts electricity within a switchboard, distribution board, substation or other electrical apparatus....
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.
Geography of transmission networks
Transmission networks are more complex with redundant pathways. For example, see the map of the United States' (right) high-voltage transmission network.A wide area synchronous grid
Wide area synchronous grid
A wide area synchronous grid, also called an "interconnection" in North America, is a power grid at a regional scale or greater that operates at a synchronized frequency and is electrically tied together during normal system conditions...
or "interconnection" is a group of distribution areas all operating with alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
(AC) frequencies synchronized (so that peaks occur at 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. Interconnection maps are shown of North America (right) and Europe (below left).
Electricity generation and consumption must be balanced across the entire grid, because energy is consumed almost immediately after it is produced. 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
Cascading failure
A cascading failure is a failure in a system of interconnected parts in which the failure of a part can trigger the failure of successive parts.- Cascading failure in power transmission :...
and widespread power outage
Power outage
A power outage is a short- or long-term loss of the electric power to an area.There are many causes of power failures in an electricity network...
. 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 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 Corridor
National Interest Electric Transmission Corridor
A National Interest Electric Transmission Corridor corridor is a geographic region designated by the United States Department of Energy where electricity transmission limitations are adversely affecting American citizens...
s, where it believes transmission bottlenecks have developed.
Some areas, for example rural communities in Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
, do not operate on a large grid, relying instead on local diesel generators.
High-voltage direct current
High-voltage direct current
A high-voltage, direct current electric power transmission system uses direct current for the bulk transmission of electrical power, in contrast with the more common alternating current systems. For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses...
lines or variable frequency transformer
Variable frequency transformer
A variable frequency transformer is used to transmit electricity between two alternating current domains. The VFT is a relatively recent development...
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 (above left) with the map of HVDC lines (below right).
Redundancy and defining "grid"
A town is only said to have achieved grid connectionGrid connection
In electrical grids, a power system network integrates transmission grids, distribution grids, distributed generators and loads that have connection points called busses. A bus in home circuit breaker panels is much smaller than those used on the grid, where busbars can be 50 mm in diameter...
when it is connected to several redundant
Redundancy (engineering)
In engineering, redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe....
sources, generally involving long-distance transmission.
This redundancy is limited. Existing national or regional grids simply provide the interconnection of facilities to utilize whatever redundancy is available. The exact stage of development at which the supply structure becomes a grid is arbitrary. Similarly, the term national grid is something of an anachronism
Anachronism
An anachronism—from the Greek ανά and χρόνος — is an inconsistency in some chronological arrangement, especially a chronological misplacing of persons, events, objects, or customs in regard to each other...
in many parts of the world, as transmission cables now frequently cross national boundaries. The terms distribution grid for local connections and transmission grid for long-distance transmissions are therefore preferred, but national grid is often still used for the overall structure.
Aging Infrastructure
Despite the novel institutional arrangements and network designs of the electrical grid, its power delivery infrastructures suffer aging across the developed world. Four contributing factors to the current state of the electric grid and its consequences include:- Aging power equipment – older equipment have higher failure rateFailure rateFailure rate is the frequency with which an engineered system or component fails, expressed for example in failures per hour. It is often denoted by the Greek letter λ and is important in reliability engineering....
s, leading to customer interruption ratesPower outageA power outage is a short- or long-term loss of the electric power to an area.There are many causes of power failures in an electricity network...
affecting the economy and society; also, older assets and facilities lead to higher inspection maintenanceMaintenance, repair, and operationsMaintenance, repair, and operations or maintenance, repair, and overhaul involves fixing any sort of mechanical or electrical device should it become out of order or broken...
costs and further repairMaintenance, repair, and operationsMaintenance, repair, and operations or maintenance, repair, and overhaul involves fixing any sort of mechanical or electrical device should it become out of order or broken...
/restorationRenovationRenovation is the process of improving a structure. Two prominent types of renovations are commercial and residential.-Process:The process of a renovation, however complex, can usually be broken down into several processes...
costs. - Obsolete system layout – older areas require serious additional substation sitesSubstationSubstation can refer to:*Electrical substation*Police substation, a mini police station with limited services*The Substation, a Singaporean contemporary arts centre*SubStation Alpha, a subtitle file format...
and rights-of-wayRight-of-wayRight-of-way or right of way may refer to:*Right of way , legally granted access*Right-of-way , a strip of land granted for a transportation facility...
that cannot be obtained in current area and are forced to use existing, insufficient facilities. - Outdated engineering – traditional tools for power deliveryPower deliveryElectricity delivery is the process that goes from generation of electricity in the power station to the use by the consumer.The main processes in power delivery are, by order:* Central generation* Transmission* Distribution* And retailing...
planning and engineering are ineffective in addressing current problems of aged equipment, obsolete system layouts, and modern deregulated loading levels - Old cultural value – planningPlanningPlanning in organizations and public policy is both the organizational process of creating and maintaining a plan; and the psychological process of thinking about the activities required to create a desired goal on some scale. As such, it is a fundamental property of intelligent behavior...
, engineeringEngineeringEngineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
, operating of system using concepts and procedures that worked in vertically integrated industry exacerbate the problem under a deregulated industry
Modern trends
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 generationDistributed generation
Distributed generation, also called on-site generation, dispersed generation, embedded generation, decentralized generation, decentralized energy or distributed energy, generates electricity from many small energy sources....
. As generation becomes more common from rooftop solar and wind generators, the differences between distribution and transmission grids will continue to blur. Also, demand response
Demand response
In electricity grids, demand response is similar to dynamic demand mechanisms to manage customer consumption of electricity in response to supply conditions, for example, having electricity customers reduce their consumption at critical times or in response to market prices...
is a grid management technique where retail or wholesale customers are requested 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.
With everything interconnected, and open competition occurring in a free market economy, it starts to make sense to allow and even encourage distributed generation
Distributed generation
Distributed generation, also called on-site generation, dispersed generation, embedded generation, decentralized generation, decentralized energy or distributed energy, generates electricity from many small energy sources....
(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. Furthermore, numerous efforts are underway to develop a "smart grid". In the U.S., the Energy Policy Act of 2005
Energy Policy Act of 2005
The Energy Policy Act of 2005 is a bill passed by the United States Congress on July 29, 2005, and signed into law by President George W. Bush on August 8, 2005, at Sandia National Laboratories in Albuquerque, New Mexico...
and Title XIII of the Energy Independence and Security Act of 2007
Energy Independence and Security Act of 2007
The Energy Independence and Security Act of 2007 is an Act of Congress concerning the energy policy of the United States...
are providing funding to encourage smart grid development. The hope is to enable utilities to better predict their needs, and in some cases involve consumers in some form of time-of-use based tariff. Funds have also been allocated to develop more robust energy control technologies.
Decentralization of the power transmission distribution system is vital to the success and reliability of this system. Currently the system is reliant upon relatively few generation stations. This makes current systems susceptible to impact from failures not within said area. Micro grids would have local power generation, and allow smaller grid areas to be separated from the rest of the grid if a failure were to occur. Furthermore, micro grid systems could help power each other if needed. Generation within a micro grid could be a downsized industrial generator or several smaller systems such as photo-voltaic systems, or wind generation. When combined with Smart Grid technology, electricity could be better controlled and distributed, and more efficient. Conversely, various planned and proposed systems to dramatically increase transmission capacity are known as super, or mega grids
Super grid
A super grid is a wide area transmission network that makes it possible to trade high volumes of electricity across great distances. It is sometimes also referred to as a "mega grid".-History:...
. The promised benefits include enabling the renewable energy
Renewable energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...
industry to sell electricity to distant markets, the ability to increase usage of intermittent energy sources by balancing them across vast geological regions, and the removal of congestion that prevents electricity markets from flourishing. Local opposition to siting new lines and the significant cost of these projects are major obstacles to super grids.
Future Trends
As deregulationDeregulation
Deregulation is the removal or simplification of government rules and regulations that constrain the operation of market forces.Deregulation is the removal or simplification of government rules and regulations that constrain the operation of market forces.Deregulation is the removal or...
continues further, utilities are driven to sell their assets as the energy market follows in line with the gas market in use of the futures and spot market
Spot market
The spot market or cash market is a public financial market, in which financial instruments or commodities are traded for immediate delivery. It contrasts with a futures market in which delivery is due at a later date...
s and other financial arrangements. Even globalization
Globalization
Globalization refers to the increasingly global relationships of culture, people and economic activity. Most often, it refers to economics: the global distribution of the production of goods and services, through reduction of barriers to international trade such as tariffs, export fees, and import...
with foreign purchases are taking place. Recently, U.K’s
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
National Grid
National Grid
-Electric power transmission systems:*National Grid , the electricity transmission network of Great Britain.*National Grid , the electricity transmission network of Malaysia....
, the largest private electric utility in the world, bought New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
’s electric system for $3.2 billion. Also, Scottish Power
Scottish Power
ScottishPower Ltd. is a vertically integrated energy company with its headquarters in Glasgow, Scotland. It was listed on the London Stock Exchange and was once a constituent of the FTSE 100 Index but in 2006 it became a subsidiary of the Spanish utility Iberdrola...
purchased Pacific Energy
PacifiCorp
PacifiCorp is an electric power company in the northwestern United States.PacifiCorp has three primary subsidiaries:# Pacific Power is a regulated electric utility with service territory throughout Oregon, northern California, and southeastern Washington.# Rocky Mountain Power is a regulated...
for $12.8 billion. Domestically, local electric and gas firms begin to merge operations as they see advantage of joint affiliation especially with the reduced cost of joint-metering. Technological advances will take place in the competitive wholesale electric markets such examples already being utilized include fuel cells used in space flight, aeroderivative gas turbines used in jet aircraft
Jet aircraft
A jet aircraft is an aircraft propelled by jet engines. Jet aircraft generally fly much faster than propeller-powered aircraft and at higher altitudes – as high as . At these altitudes, jet engines achieve maximum efficiency over long distances. The engines in propeller-powered aircraft...
s, solar engineering and photovoltaic systems, off-shore wind farms, and the communication advances spawned by the digital world particularly with microprocessing which aids in monitoring and dispatching.
Electricity will continue to see a growing demand in the future years as the Information Revolution is highly reliant on it, including emerging new electricity-exclusive technologies, developments in space conditioning, industrial process
Industrial process
Industrial processes are procedures involving chemical or mechanical steps to aid in the manufacture of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy industry....
, and transportation (i.e., hybrid vehicle
Hybrid vehicle
A hybrid vehicle is a vehicle that uses two or more distinct power sources to move the vehicle. The term most commonly refers to hybrid electric vehicles , which combine an internal combustion engine and one or more electric motors.-Power:...
s, locomotive
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...
s).
See also
- Critical infrastructureCritical infrastructureCritical infrastructure is a term used by governments to describe assets that are essential for the functioning of a society and economy. Most commonly associated with the term are facilities for:*electricity generation, transmission and distribution;...
- DESERTECDesertecDESERTEC is a concept proposed by the DESERTEC Foundation for making use of solar energy and wind energy. This concept will be implemented in North Africa and the Middle East by the consortium Dii GmbH, formed by a group of European companies and the DESERTEC Foundation...
- Distributed network
- Electric power transmissionElectric power transmissionElectric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
- Electricity distributionElectricity distributionFile:Electricity grid simple- North America.svg|thumb|380px|right|Simplified diagram of AC electricity distribution from generation stations to consumers...
- Electricity retailingElectricity retailingElectricity retailing is the final process in the delivery of electricity from generation to the consumer. The other main processes are transmission and distribution.- Beginnings :...
- Green powerGreen PowerGreen Power is a Hong Kong-based non-governmental organization concerned with the city's environmental issues. The NGO was founded in 1988 by a group of volunteers who made environmental education the foremost priority of the organization....
- Grid energy storageGrid energy storageGrid energy storage refers to the methods used to store electricity on a large scale within an electrical power grid. Electrical energy is stored during times when production exceeds consumption and the stores are used at times when consumption exceeds production...
- Independent System Operator
- Infrastructure securityInfrastructure SecurityInfrastructure security is the security provided to protect infrastructure, especially critical infrastructure, such as airports, highways rail transport, hospitals, bridges, transport hubs, network communications, media, the electricity grid, dams, power plants, seaports, oil refineries, and...
- HohmHohmMicrosoft Hohm is an online web application by Microsoft that enables consumers to analyze their energy usage and provides energy saving recommendations.Announced on June 24, 2009, Microsoft Hohm is built on the Windows Azure cloud operating system...
- Interconnection
- Load managementLoad managementLoad management is the process of balancing the supply of electricity on the network with the electrical load by adjusting or controlling the load rather than the power station output...
- Mains electricityMains electricityMains is the general-purpose alternating current electric power supply. In the US, electric power is referred to by several names including household power, household electricity, powerline, domestic power, wall power, line power, AC power, city power, street power, and grid power...
- National Grid (UK)
- North Sea Offshore GridNorth Sea Offshore GridThe North Sea Offshore Grid, officially the North Seas Countries Offshore Grid Initiative , is a collaboration between EU member-states and Norway to create an integrated offshore energy grid which links wind farms and other renewable energy sources across the northern seas of Europe...
- Off-the-gridOff-the-gridThe term off-the-grid or off-grid refers to living in a self-sufficient manner without reliance on one or more public utilities....
- Public goodPublic goodIn economics, a public good is a good that is non-rival and non-excludable. Non-rivalry means that consumption of the good by one individual does not reduce availability of the good for consumption by others; and non-excludability means that no one can be effectively excluded from using the good...
- Public capital
- Regional Transmission OrganizationRegional Transmission OrganizationA regional transmission organization in the United States is an organization that is responsible for moving electricity over large interstate areas. Like a transmission system operator , an RTO coordinates, controls and monitors an electricity transmission grid that is larger with much higher...
- Renewable energyRenewable energyRenewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...
- Smart meterSmart meterA smart meter is usually an electrical meter that records consumption of electric energy in intervals of an hour or less and communicates that information at least daily back to the utility for monitoring and billing purposes. Smart meters enable two-way communication between the meter and the...