Power Grids

8/3/2019 Power Grids

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ELEV : SANDRU CRISTIAN


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Content

1. Term 2. History

y 2.1 DeRegulation

3. Featuresy 3.1 Structure ofdistribution gridsy 3.2 Geography oftransmissionnetworksy 3.3 Redundancy and defining "grid"

4.Aging Infrastructure

5. Moderntrends 6 .Future Trends 7 .Emerging smart grid


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1. Term

The term gridusually refersto a network, and should notbetakentoimply a particular physical layoutorbreadth. Gridmay alsobe used to referto an entire continent's electricalnetwork, a regional transmissionnetwork or may be used to

describe a subnetwork such as a local utility'stransmissiongrid or distribution grid.


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2. History

Since itsinceptioninthe Industrial Age, theelectrical grid has evolved fromaninsularsystem thatserviced

a particular geographic area toa wider, expansive networkthatincorporated multipleareas. Atone point, all energywas produced nearthe deviceorservice requiring that

energy. Inthe early 19thcentury, electricity was a novelinventionthat competed withsteam, hydraulics,direct heating and cooling.


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2. HistoryBy the mid-19th century, electric

arc lighting soonbecameadvantageous compared tovolatile gas lampssince gaslamps produced poor light,tremendouswasted heatwhich made rooms hot andsmoky, and noxious elementsinthe form ofhydrogenand carbon monoxide.Modeling afterthe gas

lighting industry, ThomasEdison invented thefirst electric utility systemwhich supplied energythrough virtual mainsto lightfiltration asopposed to gas


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2. History

Inthe 1920s, utilities joinedtogether establishing a widerutility grid as joint-operationssawthe benefitsofsharingpeak load coverage andbackup power. Also, electricutilitieswere easily financedby Wall Street privateinvestorswhobacked manyoftheir ventures. In1934,

with the passage ofthe Public Utility HoldingCompany Act (USA), electricutilitieswere recognizedas public goods ofimportance along with gas.


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2. History2.1 DeRegulation

With deregulation, a more complex environmentoccurred asopposed tothe traditional vertically-integrated monopoly thatoverseesthe entire gridsoperations. Newer participantsentered the marketincluding Independent Power Providers(IPPs) who decided and constructed the newfacility; Transmission Companies (TRANSCOs) who

constructed and owned the transmission equipment; retailerswhosigned up end-use customers, procured their electricservice, and billed them; integrated energy companies(combined IPPs and retailers);


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3. Features

3.1 Structure ofdistribution gridsThe structure, or "topology" ofa grid can varyconsiderably. The physical layoutisoftenforced bywhat land is available and its geology. The logicaltopology can vary depending onthe constraintsofbudget, requirementsforsystem reliability, and theload and generation characteristics.

The cheapest and simplesttopology for a distributionortransmission grid is a radialstructure. Thisisa tree shape where powerfrom a large supplyradiatesoutinto progressively lower voltage lines untilthe destination homes and businesses are reached.

Mosttransmission grids require the reliability that morecomplex mesh networks provide. Ifone were toimagine running redundant linesbetweenlimbs/branchesofa tree that could be turned in caseany particular limbofthe tree were severed, thenthisimage approximates how a mesh system operates.The expense ofmesh topologies restricttheirapplicationtotransmission and medium voltagedistribution grids. Redundancy allows line failurestooccur and powerissimply rerouted while workmenrepairthe damaged and deactivated line.


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3. Features

3.2 Geography oftransmissionnetworksTransmissionnetworks are morecomplex with redundant pathways.Forexample, see the map ofthe UnitedStates'(right) high-voltage transmissionnetwork.A wide area synchronous grid or"interconnection" is a group ofdistribution areas all operatingwith alternating current(AC) frequenciessynchronized (sothat peaksoccur atthesame time). This allowstransmissionof

AC powerthroughoutthe area,

connecting a large numberofelectricitygenerators and consumers andpotentially enabling more efficientelectricity markets and redundantgeneration. Interconnection maps areshownofNorth America (right) andEurope (below left).


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3. Features

3.3 Redundancy and defining "grid"

A townisonly said to have achieved gridconnectionwhenitis connected toseveral redundant sources, generallyinvolving long-distance transmission.

This redundancy is limited. Existing nationalor regional gridssimply provide theinterconnectionoffacilitiesto utilizewhatever redundancy is available. The exactstage ofdevelopment atwhich the supplystructure becomes a gridis arbitrary.Similarly, the term national gridissomethingofan anachronism in many partsoftheworld, astransmission cablesnowfrequentlycrossnational boundaries. Theterms distribution gridfor local connectionsand transmission gridfor long-distancetransmissions are therefore preferred,but national gridisoftenstill used fortheoverall structure.


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4. Aging Infrastructure

Despite the novelinstitutional arrangements andnetwork designsoftheelectrical grid, its powerdelivery infrastructuressufferaging acrossthe developed

world.Four contributingfactorstothe currentstate ofthe electric grid and itsconsequencesinclude:Aging power equipment

older equipment have

higherfailure rates, leadingto customerinterruptionrates affecting the economyand society; also, older assetsand facilities lead to higherinspection maintenance costsand

further repair/restoration costs.


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5. Moderntrends

Asthe 21st century progresses, the electric utility

industry seekstotake advantage ofnovel approachestomeet growing energy demand. Utilities are underpressure to evolve their classic topologiestoaccommodate distributed generation. As generationbecomes more commonfrom rooftop solar and windgenerators, the differencesbetween distribution andtransmission gridswill continue toblur.


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6 .Future Trends

As deregulation continuesfurther, utilities are driventosell their assets asthe energymarketfollowsin line with thegas marketin use ofthe futures and spot

markets and otherfinancialarrangements.Even globalization withforeign purchases are takingplace.Recently, U.Ks National Grid,the largest private electric

utility inthe world,bought New Englandselectric system for $3.2billion.Also, ScottishPower purchased PacificEnergy for $12.8billion.


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7 .Emerging smart grid

As mentioned above, theelectrical grid is expected toevolve to a new grid paradigm--smart grid, an enhancementofthe 20th century electrical grid.The traditional electrical grids

are generally used to carrypowerfrom a few centralgeneratorsto a large numberofusersor customers. In contrast,the new emerging smart gridusestwo-way ows ofelectricityand informationto create an

automated and distributedadvanced energy deliverynetwork.


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Conclusions

The difficulty onthe implementationofthe smart-gridtechnologiesbecause ofthe early state ofthe standardizationprocesses.

The lack ofregulationswhich allow and promote the use ofthis

technologies, specially inisolated powersystems.


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FinalConclusion

As main conclusionofthiswork isthatweare with the

technologies presentedenvisioning the future ofthe powersystem inthe

next decade, there ishoweverstill a longpath to go.


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Bibliography

http://en.wikipedia.org

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Power Grids