Disadvantages of Low Power Factor - Electrical Technology PDF

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8/22/2017

DisadvantagesofLowPowerFactorElectricalTechnology

 Electrical Technology  08/31/2013  Generation Transmission and Distribution, Over Head Lines, Power factor, Power System, Single Phase AC Circuits, Three Phase AC Circuits  57,162 Views

PowerfactorplayanimportantroleinACcircuitsandpowerdissipationdependsonthisfactor.Forinstant, weknowthat; PowerinaThreePhaseACCircuit=P=√3VxICosФ AndCurrentinaThreePhaseACCircuits=I=P/(3VxCosФ) I∝1/CosФ….…(1) Also, PowerinaSinglePhaseACCircuits=P=VxICosФ AndCurrentinaThreephaseACCircuits=I=P/(VxCosФ) I∝1/CosФ………(2) Itisclearfrombothequations(1)an(2)thatCurrent“I”isinverselyproportionaltoCosФi.e.PowerFactor. Inotherwords,WhenPowerFactorincreases,CurrentDecreases,andwhenPowerFactordecreases, CurrentIncreases. Now,IncaseofLowPowerFactor,Currentwillbeincreased,andthishighcurrentwillcausetothe followingdisadvantages. 1.)LargeLineLosses(CopperLosses): WeknowthatLineLossesisdirectlyproportionaltothesquireofCurrent“I2” PowerLoss=I2xRi.e.,thelargerthecurrent,thegreaterthelinelossesi.e.I>>LineLosses Inotherwords, PowerLoss=I2xR=1/CosФ2…..RefertoEquation“I∝1/CosФ”….…(1) Thus,ifPowerfactor=0.8,thenlossesonthispowerfactor=1/CosФ2=1/0.82=1.56timeswillbegreater thanlossesonUnitypowerfactor. 2.)LargekVAratingandSizeofElectricalEquipments: AsweknowthatalmostallElectricalMachinery(Transformer,Alternator,Switchgearsetc)ratedinkVA.But, itisclearfromthefollowingformulathatPowerfactorisinverselyproportionaltothekVAi.e. CosФ=kW/kVA Therefore,TheLowerthePowerfactor,thelargerthekVAratingofMachinesalso,thelargerthekVArating ofMachines,ThelargertheSizeofMachinesandTheLargerthesizeofMachines,TheLargertheCostof machines. 3.)GreaterConductorSizeandCost: Incaseoflowpowerfactor,currentwillbeincreased,thus,totransmitthishighcurrent,weneedthelarger sizeofconductor.Also,thecostoflargesizeofconductorwillbeincreased. 4.)PoorVoltageRegulationandLargeVoltageDrop: VoltageDrop=V=IZ. NowincaseofLowPowerfactor,Currentwillbeincreased.SotheLargerthecurrent,theLargerthe VoltageDrop. AlsoVoltageRegulation=V.R=(VNoLoad–VFullLoad)/VFullLoad IncaseofLowPowerFactor(laggingPowerfactor)therewouldbelargevoltagedropwhichcauselow voltageregulation.Therefore,keepingVoltagedropintheparticularlimit,weneedtoinstallExtraregulation equipmentsi.e.Voltageregulators. 5.)LowEfficiency: IncaseoflowPowerFactor,therewouldbelargevoltagedropandlargelinelossesandthiswillcausethe systemorequipmentsefficiencytoolow.Forinstant,duetolowpowerfactor,therewouldbelargeline losses;therefore,alternatorneedshighexcitation,thus,generationefficiencywouldbelow. 6.)PenaltyfromElectricPowerSupplyCompanyonLowPowerfactor ElectricalPowersupplyCompanyimposesapenaltyofpowerfactorbelow0.95lagginginElectricpowerbill. SoyoumustimprovePfabove0.95.

https://www.electricaltechnology.org/2013/08/disadvantagesoflowpowerfactor.html

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8/22/2017

DisadvantagesofLowPowerFactorElectricalTechnology

Youmayalsoreadabout: PowerFactor Active,Reactive,ApparentandComplexPower.Simpleexplanationwithformulas. CausesoflowPowerFactor PowerFactorimprovementMethodswithTheiradvantages&Disadvantages AdvantagesofPowerfactorimprovementandCorrection HowtoCalculatetheSuitableCapacitorSizeinFarads&kVARforPowerfactorImprovement(Easiestway ever) HowtoConvertCapacitorFaradsintokVARandViceVersa(ForPowerfactorimprovement)

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