电力系统基础知识Basic knowledge of power system.docx

电力系统基础知识Basic knowledge of power system.docx

《电力系统基础知识Basic knowledge of power system.docx》由会员分享，可在线阅读，更多相关《电力系统基础知识Basic knowledge of power system.docx（6页珍藏版）》请在冰豆网上搜索。

电力系统基础知识Basicknowledgeofpowersystem

电力系统基础知识16532（Basicknowledgeofpowersystem16532）

I.compositionofanelectricpowersystem

Acompletepowersystemconsistsofvarioustypesofdistributionaroundthepowerplant,thestep-upandstep-downsubstation,transmissionlinesandpowerusers,theyarecompleteelectricalproduction,voltagetransformation,powertransmissionanddistributionanduseofenergy.

Two.Divisionofpowernetworks,powersystemsandpowersystems

Powernetwork:

anetworkconsistingofpowertransmissionequipment,substationequipment,anddistributionequipment.

Powersystem:

powergenerationequipmentonthebasisofthepowergrid.

Powersystem:

Basedonthepowersystem,thepowerplantparts（suchasthermalpowerplantboiler,steamturbineandhydropowerplantreservoir,hydraulicturbineandnuclearpowerplantreactoretc.）areincludedinthesystem.

Three.Characteristicsofpowersystemoperation

First,thetotalamountofeconomyisbig.Atpresent,China'spowerindustryassetsizehasmorethan2trillion,accountedforatotalof1/4ofthestate-ownedassets,electricityproductiondirectlyaffectsthehealthydevelopmentofthenationaleconomy.

Thetwoisatthesametime,alargenumberofelectricitycannotbestored,unitycomposedofallsectorscannotbeseparated,thetransitionprocessisveryrapid,instantproductionpowermustbeequaltothemomentforeveryaspectofpower,sothepowerproductionofthepowergeneration,transmissionanddistributionareveryimportanttotheuser.

Thethreeisconcentrated,electricityproductionishighlycentralizedandunified,nomatterhowmanypowerplants,powercompanies,powergridmustbeunified,unifiedmanagement,unifiedmanagement;safetyproduction,organizationanddiscipline,occupationmoralityhasstrictrequirements.

Thefourisapplicability,theserviceobjectofpowerindustryisall-round,involvingallthepeopleinthewholesociety,powerquality,electricitypricelevelandtheinterestsofthevastnumberofpowerusersarecloselyrelated.

Fiveisadvance,thedevelopmentofthenationaleconomy,electricitymustfirst.

Four.Ratedvoltageofpowersystem

Thereisalevelofpowergridvoltage,ratedvoltageisreasonableaccordingtotheneedsofnationaleconomicdevelopment,technologyeconomyandelectricalequipmentmanufacturinglevel,throughthecomprehensiveanalysisanddemonstration,enactedbythenationalunity.

Five、neutraloperationmodeofpowersystem

Inthepowersystem,neutralgroundingorneutralsmallimpedance（lowresistance）groundingsystemiscalledgroundingsystem,neutralorneutralPetersencoilgroundedsystemiscalledsmallcurrentgroundingsystem.Theoperationmodeofneutralpointmainlydependsontheinsulationrequirementofelectricalequipmentandthereliabilityofpowersupplyinsinglephasegrounding.

Comparisonofadvantagesanddisadvantagesofdifferentoperationmodes

Neutralpointdirectgroundingmode:

whenarelativeinsulationfailureoccurs,thesingle-phaseshort-circuitisformed,thepowersupplyisinterrupted,andthereliabilityisreduced.However,underthismode,thenonfaultrelativevoltageisconstant,andtheinsulationleveloftheelectricalequipmentcanbeconsideredintermsofphasevoltage.The220V/380Vand110KVinourcountryuseneutralpointdirectgroundingtohighersystem,andoperateinlargecurrentgroundingmode.

Ungroundedorgroundedbyarcsuppressioncoil:

whensingle-phasegroundingfaultoccurs,thelinevoltageisconstant,andthenonfaultphasevoltagetophasevoltageoftheoriginaltick3times,uninterruptedpowersupply,highreliability.The10KVand35KVsystemsinourcountryuseneutralungroundedorarcsuppressioncoilstooperateinsmallcurrentneutralgroundingmode.

Six、powersupplyquality

Voltage,frequency,andreliabilityaretheindicatorsthatdeterminethequalityoftheuser'spowersupply.

1.voltage

Theidealsupplyvoltageshouldbeathree-phasesymmetricalsinusoidalvoltagewhoseamplitudeisconstant.Duetothepresenceofimpedance,powersupplysystemwiththechangeofpowerloadandelectricityloadpropertiesandotherfactors,theactualsupplyvoltageregardlessoftheamplitude,waveformandphasesymmetryandidealvoltageexistsbetweenthedeviation.

（1）voltagedeviation:

voltagedeviationisthedifferencebetweentheactualvoltageandtheratedvoltageofthepowergrid.Theactualvoltageistoohighorlow,whichhasanimpactonthegoodoperationofthepowerequipment.

Thenationalstandardprovidesthattheallowablevalueofvoltagedeviationis:

Aand35thousandvoltsandabovevoltagesupply,thesumoftheabsolutevalueofvoltagepositiveandnegativedeviationshallnotexceed10%oftheratedvoltage;

B,10thousandvoltsandbelowthree-phasepowersupply,voltagedeviationisratedvoltageof+7%.Inthe

C,220voltssingle-phasepowersupply,voltagedeviationisratedvoltageof+7%,-10%.

Theallowablevalueofvoltagefluctuationisstipulatedbythenationalstandard:

10KVandbeloware2.5%

35to110KVis2%

220KVandaboveis1.6%

（3）harmonicgeneration:

thegenerationofhigherharmonicsisnonlinearelectricalequipment,whichisputintooperationinthepowergrid,whichmakesthevoltageandcurrentwaveformsofthenetworkdistortedindifferentdegreesanddeviatedfromthesinewave.

Inadditiontothebackgroundharmonicsofthepowersystem,

Itismainlycausedbynonlinearpowerequipment,suchaslargepowerconverterandelectricarcfurnace.Theexistenceofhigherharmonicsleadstotheincreaseofenergyconsumption,theagingofelectricalequipmentinsulation,andinterferencewiththenormaloperationofautomationdevicesandcommunicationfacilities.

（4）three-phaseasymmetry:

three-phasevoltageasymmetryreferstotheamplitudeandphaserelationofthethreephasevoltages.Thethree-phaseasymmetryismainlycausedbytheasymmetryofthesystemoperatingparametersandtheunbalancedthree-phaseload.Theasymmetricoperationofpowersupplysystemisharmfultothepowersupplyequipmentandpowersupplyanddistributionsystem.Theasymmetricaloperationofthelow-voltagesystemwillleadtodeviationoftheneutralpoint,thusendangeringthesafetyofthepeopleandequipment.

Underthenormalmodeofoperationofthecommonconnectionpointofthepowersystem,theallowablevalueoftheimbalancebytheStateshallbe2%,notexceeding4%forashortperiodoftime,andnomorethan1.3%oftheindividualusers

2.permissibledeviationofsupplyfrequency

Thesinusoidalalternatingcurrentgeneratedbyageneratorinagridiscalledfrequencypersecond,andthestandardfrequency50HZ.isspecifiedinChina

China'snationalstandardstipulatesthattheallowablevalueofthenormalfrequencydeviationofthepowersystemis+0.1Hz,andinactualimplementation,whenthesystemcapacityislessthan300Mv,thedeviationvaluecanberelaxedto+0.5Hz.

3.reliabilityofpowersupply

Thereliabilityofpowersupplyreferstothetimeandfrequencyofthepowerfailureofapowersupplyenterpriseduringacertainstatisticalperiod,whichdirectlyreflectsthecontinuouspowersupplycapabilityofthepowersupplyenterprise.

Powersupplyreliabilityratereflectsthenationaleconomycanmeetthepowerneedsoftheelectricpowerindustry,hasbecomeoneofthestandardmeasureofacountry'slevelofeconomicdevelopment;thepowersupplyreliabilitycanbemeasuredwiththefollowingyearaseriesofindicators:

powersupplyreliabilityrate,theaverageuseroutagetime,useraveragepowerfrequency,theaverageuserfaultoutagetimes.

Thereliabilityrateofurbanpowersupplyprescribedbythestateis99.96/100.Thatis,theaverageannualoutagetimeisnotmorethan3.5hours;

Electricalload:

thesumoftheactualpowerusedbyauser'selectricalequipmentatagivenpoint.

Therearemanymethodstoclassifypowerload,andthemostsignificantistoclassifytheloadclassificationaccordingtothetimethattheloadoccurredinthepowersystemandthedegreeoflosscausedbythesuddeninterruptionofpowersupply.

Loadclassificationbytime

1,peakload:

referstothepowergridortheuserinaday'stimethemaximumloadvalue.Theaveragedailyloadis24hoursaday.Theaverageloadisthemaximumload,usuallywith1monthpeakloadandonemonthpeakload.

2,minimumload:

referstothepowergridortheuserin24hoursaday,theminimumelectricityconsumptionload.Usually,thereare1monthsdailyminimumload,onemonthminimumloadandsoon.

3.Averageload:

theaveragehourlypowerconsumptionofagridorauseratacertainperiodoftime.

Classificationofdegreeofdamagecausedbyinterruptionofpowersupply

1,aload:

asuddenpoweroutagewillcausecasualtiesorcauseseriouspollutiontothesurroundingenvironment,causinghugeeconomiclosses,suchaslargeimportantequipmentdamage,importantproductsorrawmaterialsfortheproductionofalargenumberofscrapproducts,continuousproductionprocessisdisrupted,ittakesalongtimetoresumeproduction;andasuddenpoweroutagewillcauseseriouspublicdisorderorinpoliticshavesignificantadverseeffects,suchastheelectricityloadimportanttransportationandcommunicationhub,internationalsocialplacesetc..

2,twoload:

asuddenpoweroutageintheeconomywillcausemorelosses,suchastheproductionofmajorequipmentdamage,largenumberofscrappedproductsorproduction,continuousproductionprocesstakesalongtimetorecover;andasuddenpowerfailurecancausesocialdisorderorinpoliticscausedgreatinfluence,suchastransportationandcommunicationshub,thecity'smainwatersourceel