CH-2_PPEE.ppt

Notes

1. Unit No: 2
Loads on Power Plant
1

2. Syllabus
UnitNo.02:LoadsonPowerPlant
•Introduction,classificationofloadsonpowerplant,
Differentloadcurvesandloadfactors,Effectof
variableloadonpowerplant,design&operation,
comparisonofthethermal,hydroelectric,nuclearand
dieselpowerplants.(Numericaltreatment)
•Classificationofplants,Requirementsofpeakload
plant,Pumpedstorageplants,Compressedairstorage
plants,Loadsharingbetweenbaseload&peakload
powerstations.
2

3. About Title of Subject
3
•Loads:Loadreferstotheamountofpowerintheelectrical
grid.Theloadmustbebalancedsothatsupplycontinuously
meetsdemandlevelswhicharesubjecttovariationsand
changesthatimpactthegrid.Thus,loadisseparatedinto
baseload,andpeakload.
•PowerPlant:Itisanindustrialfacilitythatgenerates
electricityfromprimaryenergy.
•Baseloadistheminimum
levelofelectricitydemand
requiredoveraperiodof24
hours.Itisneededtoprovide
powertocomponentsthatkeep
runningatalltimes(alsoreferred
ascontinuousload).
•Peakloadisthetimeofhigh
demand.

4. 4
Anelectricalloadisadeviceoranelectricalcomponentthat
consumeselectricalenergyandconvertitintoanotherformof
energy.Electriclamps,airconditioners,motors,resistorsetc.
aresomeoftheexamplesofelectricalloads.
The various Types of Load in Power System are :
•Domestic load
•Commercial load
•Industrial load
•Municipal load
•Irrigation load

5. Importance of Chapter
•Itrepresentsthemaximumpowerconsumedby
theloadduringaspecificperiodoftime.Italso
representsthemaximumpowergeneratedbyapower
stationduringthatperiodoftime(neglectingthe
transmission losses). Knowing the
MaximumLoadisimportantasithelpsindetermining
thecapacityofthepowerplant.
•Thischapterisimportanttoknowaboutvariousloadon
plant,differentloadcurvestheirfactors.Alsoitis
importanttoknowvariousplantsandtheircomparison
studyandrelatedcalculationofloads.
5

6. 6
Power
generation
transmission
and
distribution
diagram

7. 7
Powergenerationtransmissionanddistribution
diagram

8. 8
Classification of Base load Power plants
The plant supplying “Base Load”
1. Hydroelectric Power Plants:
Operating cost is minimum.
Maintenance cost is lower.
Initial cost is high
Can’t be located near to load.
2.Steam Power Plants:
Capital cost is more
Can be located near to load center.
Maintenance requirement is slightly higher.

9. 9
Classification of Base load Power plants
The plant supplying “Base Load”
3.Run of river Plants:
use of water when it comes.
4. Nuclear Power Plant:
Initial Cost is High
Limited availability of fuel
Whenever they are constructed they are used as base load plants due to
constant supply.
5. Wind and Solar:
Depend randomly on wind and solar rays
6. Nuclear Power Plants:
they are not used as peak load plants.

10. 10
Classification of Peak load Power plants
The plant supplying “Peak Load”
1. Hydroelectric Plants:
can be considered as peak load plant.
It can be easily started.
No fuel required.
2. Diesel Power Plants:
can be used for peak load plants
Easily start from cold conditions.
Number of auxiliaries required is limited, so less maintenance.
They have good overload capacity.
They have high thermal efficiency therefore less operating cost
than steam power plants.

11. 11
DIFFERENT LOAD
Daily Load
Monthly load
Annual Load
Domestic load
Commercial load
Industrial Load
Municipal load
Irrigation load
Traction load

12. 12
TypesofLoads
Adevicewhichtapselectricalenergyfromtheelectricpowersystem
iscalledaloadonthesystem.Theloadmayberesistive(e.g.,electric
lamp),inductive(e.g.,inductionmotor),capacitiveorsome
combinationofthem.Thevarioustypesofloadsonthepowersystem
are:
(i)Domesticload.Domesticloadconsistsoflights,fans,
refrigerators,heaters,television,smallmotorsforpumpingwateretc.
Mostoftheresidentialloadoccursonlyforsomehoursduringthe
day(i.e.,24hours)e.g.,lightingloadoccursduringnighttimeand
domesticapplianceloadoccursforonlyafewhours.Forthisreason,
theloadfactorislow(10%to12%).
(ii)Commercialload.Commercialloadconsistsoflightingforshops,
fansandelectricappliancesusedinrestaurantsetc.Thisclassofload
occursformorehoursduringthedayascomparedtothedomestic
load.Thecommercialloadhasseasonalvariationsduetothe
extensiveuseofairconditionersandspaceheaters.

13. 13
iii)Industrialload
Industrialloadconsistsofloaddemandbyindustries.Themagnitude
ofindustrialloaddependsuponthetypeofindustry.Thussmallscale
industryrequiresloadupto25kW,mediumscaleindustrybetween25kW
and100kWandlarge-scaleindustryrequiresloadabove500kW.Industrial
loadsaregenerallynotweatherdependent.
(iv)Municipalload
Municipalloadconsistsofstreetlighting,powerrequiredforwater
supplyanddrainagepurposes.Streetlightingloadispracticallyconstant
throughoutthehoursofthenight.Forwatersupply,waterispumpedto
overheadtanksbypumpsdrivenbyelectricmotors.Pumpingiscarriedout
duringtheoff-peakperiod,usuallyoccurringduringthenight.Thishelpsto
improvetheloadfactorofthepowersystem.

14. 14
(v)Irrigationload
Thistypeofloadistheelectricpowerneededforpumps
drivenbymotorstosupplywatertofields.Generallythis
typeofloadissuppliedfor12hoursduringnight.
(vi)Tractionload
Thistypeofloadincludestramcars,trolleybuses,railways
etc.Thisclassofloadhaswidevariation.Duringthemorning
hour,itreachespeakvaluebecausepeoplehavetogototheir
workplace.Aftermorninghours,theloadstartsdecreasing
andagainrisesduringeveningsincethepeoplestartcoming
totheirhomes.

15. 15
DefinitionofLoadCurve:-
Thecurveshowingthevariationofloadonthepower
stationwithrespecttotime.
Thepowerdemandsofdifferentconsumersvaryin
accordancewiththeiractivities.
Theresultofthisvariationindemandisthatloadona
powerstationisneverconstantratheritvariesfromtime
totime. DailyLoadcurve

16. 16
TYPE OF LOAD CURVES
Daily load curve –Load variations during the whole
day
Monthly load curve –Load curve obtained from the
daily load curve
Yearly load curve -Load curve obtained from the
monthly load curve

17. 17
IMPORTANCE OF DAILY LC
The daily load curves have attained a great importance in generation as
they supply the following information readily :
The daily load curve shows the variations of load on the power station
during different hours of the day.
The area under the daily load curve gives the number of units generated
in the day.
Units generated/day = Area (in kWh) under daily load curve.
The highest point on the daily load curve represents the maximum
demand on the station on that day.
The area under the daily load curve divided by the total number of hours
gives the average load on the station in the day.

18. 18
IMPORTANCE OF DAILY Load Curve
The ratio of the area under the load curve to the total area of
rectangle in which it is contained gives the load factor.
The load curve helps in selecting the size and number of
generating units.
The load curve helps in preparing the operation schedule of
the station.

19. 19

20. 20
Types of Load Curves orTypes of Customers:
1.Residential Load Curve
2.Industrial Load Curve
3.Commercial Load Curve
4.Urban Traction Load Curve
5.Street Lighting Load Curve

21. 21
1.Residential Load Curve

22. 22
2. Industrial Load Curve

23. 23
3. Commercial Load Curve (Shop, Office, Hospitals)

24. 24
4. Urban Traction Load Curve

25. 25
5. Street Lighting Load Curve

26. 26

27. 27
Variable Loads on Power Plant:
•Theloadonpowerstationvariestimetotimeduetouncertain
demandsfromcustomerandisknownasvariableloadonstation.
•Apowerstationisdesignedtomeetrequirementscustomer.
•Anidealpowerplantisdesignedtooperatetheequipmentsand
machinesconstantmagnitudeandsteadyconditions.
•Butsuchsteadyloadonpowerstationwillnotremainconstantit
variesw.r.t.Time.
•Thecustomerneedstheloadaspertheirdemandsandactivities.
•Theloaddemandofonecustomeratanytimeisdifferentthan
other.
•Theresultisthatloadonpowerstationvariestimetotime

28. 28
Effect Variable Loads on Power Plant Design
& Operation:
•NeedAdditionalEquipments
•IncreaseinProductionCost
•Invariableloadsgeneratormustabletotakevariableloadas
quickaspossiblewithoutchangeinvoltage&frequency.
•Whenloadongeneratorincreasesitsfirsteffectistoslow
downrotor&primemoverT.F.Toreducethefrequency.
•FrequencyStabilizerareusedtomaintaintheitconstant.
•Thedesignofthermalpowerplantforvariableloadismore
difficultascomparetodieselorhydraulicpowerplantanditis
alwaysdesirabletooperatethermalpowerplantasBaseLoad
Plant.

29. 29
Requirement of Peak Load Plant:
•Peakingpowerplants,alsoknownasPeakerplants,and
occasionallyjust“Peakers",arepowerplantsthatgenerallyrun
onlywhenthereisahighdemand,knownaspeakdemand,for
electricity.
•Tocaterthedemandpeaks,peakloadpowerplantsareused.
Theyarestartedupwheneverthereisaspikeindemandand
stoppedwhenthedemandrecedes.
•Examplesofgasloadpowerplantsare:Gasplant.

30. 30
Requirement of Pumped storage plants :
•Apumped-storageplantisdesignedwithtworeservoirs–upperandlower.
Likeeveryotherhydroelectricplant,apumped-storageplantgenerateselectricity
byallowingwatertofallthroughaturbinegenerator.
Need:
Pumped storage
projects store and
generate energy by
moving water between
two reservoirs at
different elevations.
It is the most
competitive and
reliable way of storing
electricity, enabling
both theefficient use
of surplus energy and
the returning of a
significant amount of
energy back on the
grid.

31. 31

32. 32
Requirement of Compressed Air Storage Plants :
•Compressed-airenergystorage(CAES)plantsoperatebyusingmotorsto
drivecompressors,whichcompressairtobestoredinsuitablestorage
vessels.Theenergystoredinthecompressedaircanbereleasedtodrivean
expander,whichinturndrivesageneratortoproduceelectricity.
•Whentheenergyisneeded,thiscompressedairisthenreleasedinto
turbinegeneratorssoitcanbeusedaselectricityagain.
•ThefivekeybenefitsofCAESincludeenergysavings,betterairquality,
improvedpressurestability,reducedmaintenancecosts,andenhanced
compressorservicelife.
•Insteadofcompressingtheairwithvaluablegas,lowercostexcessenergycan
beusedduringoffpeakperiods

33. 33
Compressed Air Storage Plants:

34. 34
Load Duration Curve:
•Loaddurationcurveindicatesthevariationoftheload,butwith
theloadarrangedindescendingorderofmagnitude.
•Loaddurationcurvegivethenumberofhoursforwhicha
particularloadlastsduringaday.

35. 35
•Theloaddurationcurvegivestheminimumloadpresent
throughoutthespecifiedperiod.
•Itauthorizestheselectionofbaseloadandpeakloadpowerplants.
•Anypointontheloaddurationcurverepresentsthetotalduration
inhoursforthecorrespondingloadandallloadsofgreatervalues.

36. 36
LoadSharingbetweenBaseLoadPlants&
PeakLoadPlants:

37. 37
LoadSharingbetweenBaseLoadPlants&
PeakLoadPlants:

38. 38
LoadSharingbetweenBaseLoadPlants&
PeakLoadPlants:
•Ifloadissuppliedfromonepowerplantonlytheninsuchcase
Installedcapacityofpowerplant=Peakloadormore
•Suchpowerplantwillbeuneconomicalsincethepeakloadis
occurredonlyforshortperiodoftime.
•Therefore,thecapacityequaltodifferencebetweenbaseloadand
peakloadwouldremainidleformajorportionofyear.
•Hencesuchapowerplantloadshouldnotbesuppliedfromsingle
powerplant.
•Thereshouldbesomepowerstationssupplyingthebaseloadand
somepowerplantswhichshouldbesupplyingpeakloadpower
demand.

39. 39
Important Definitions related with Load curves & Load
Factors :
1. Connected Load
It is the sum of continuous ratings of all the equipments connected to
supply system.
2. Maximum Demand
It is the greatest demand of load on the power station during a given
period.
3. Demand Factor
It is the ratio of maximum demand on the power station to its
connected load.
4.Average Load
It is the average of loads occurring on the power station in a given
period (day or month or year) is known as average load or average
demand.
Demand Factor = Maximum Demand/Connected Load

40. 40
Important Definitions related with Load curves :
5. Load factor :
The ratio of average load to the maximum demand during a given period is
known as Load Factor

41. Prof. Y. M. Khedkar
41
6. Diversity Factor :
It is the ratio of sum of individual maximum demands to the maximum
demand on the power Station.
7. Capacity Factor
It is the ratio of actual energy produced to the maximum possible
energy that could have been produced during a given period.

42. 42
8. Plant Use Factor
It is the ratio of KWhr generated to the product of plant capacity and the
number of hours for which the plant was in operation
9. Units generated/annum = Average load (in kW) ×Hours in a year
= Max. demand (in kW) ×L.F. ×8760
10. Reserve capacity = Plant capacity − Max. demand