Thyristorised Automatic Power Factor Correction with 7% D

Thyristorised Automatic Power Factor Correction with 7% D
Thyristorised
Automatic Power Factor
Correction with 7% D‐Tune Harmonics
Suppression(Reactor/Filtering)System
Powerquality?
InthepresentLowvoltage(LV)industrialdistributionsystemthepower
factormaintenanceandharmonicscontrolarethemostcriticalissuesto
ensureacceptablepowerquality,andhencedemandsatmostconcernat
consumersendtomaintainastablepowersystem
Harmonics
In recent years, with increased usage of AC/DC Drives, UPS, Computers,
ArcFurnaces&Weldersetc,Powerharmonics(bothVoltage&Current)
havebecomeaseriousprobleminindustriesandcommercialinstallation.
The harmonics generated by these Non‐Linear loads are the biggest
obstruction in maintaining the power quality and have been a major
reasonforequipmentfailure&manyotherproblemslike..
2 50 0
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 Voltage Harmonics can cause additional heating in induction
andsynchronousmotorsandgenerators.
 Voltage Harmonics with high peak values can weaken
insulationincables,windings,andcapacitors.
 Voltage Harmonics can cause malfunction of different
electronic components and circuits that utilize the voltage
waveformforsynchronizationortiming.
 Current Harmonics in motor windings
ElectromagneticInterference(EMI).
can
create
 Current Harmonics flowing through cables can cause higher
heating over and above the heating that is created from the
fundamentalcomponent.
 Current Harmonics flowing through a transformer can cause
higherheatingoverandabovetheheatingthatiscreatedbythe
fundamentalcomponent.
 CurrentHarmonicsflowingthroughcircuitbreakersandswitch‐
gearcanincreasetheirheatinglosses.
 RESONANT CURRENTS which are created by current
harmonics and the different filtering topologies of the power
system can cause capacitor failures and/or fuse failures in the
capacitororotherelectricalequipment.
 Falsetrippingofcircuitbreakersadprotectiverelays.
Resonance is the most series consequence when connecting a power
capacitorintheLVdistributionsystem.Thecapacitanceofthecapacitor
formsaresonantcircuitinconjunctionwiththefeedingtransformersand
cables. The self‐resonant frequency of this circuit lies typically
between250and600Hzi.e.intheregionofthe5and11harmonicsand
leadstothefollowingeffects
 Overloading of capacitors, transformers and transmission
equipment's
 Interference with metering, control system, computers and
electricalgear.
Whyusea7%harmonicfilterreactorinapowerfactorcorrection
capacitorbank?
1. Capacitor are required to improve power factor, and possible system
interactionmayoccurwiththeinstallationofaplaincapacitorbank.
2. Permissible distortion limits of the local utility or IEEE‐519 are
exceeded,andfiltersarerequiredtoreducedthem.
3. A combination of 1 & 2 above, whereby capacitor are required to
improvepowerfactorandwiththeadditionofthecapacitors,permissible
distortionlimitsareexceeded.
To overcome the resonance effect detuned filter reactor is
connected in series with the capacitor and its self‐resonant
frequency is tuned below the lowest line harmonics by varying the
chokingfactorofthereactor
BenefitofusingDe‐tunedreactor
1.Pro‐longthelifeofpowerfactorcapacitorbyreducingoverheating,or
fusefailure.
2.Preventnuisanceinputfuseblowingorcircuitbreakertripping.
3.Reduceoverheatingoftransformer.
4.Reducetheharmoniccurrentintheelectricalsupplysystem.
5.Addressingtheharmonicproblemscreatedbynon‐linearloadsuchas
AFD's,AC‐DCconverter,DCdrives,weldingm/cetc
High Speed Real Time Automatic Power Factor Correction System
with 7% D-Tune Passive Harmonics Filters
State‐of‐theartelectronicswitchingdevicedesignedto
replacementofelectro‐mechanicallyswitchedequipmentin
powerfactorcorrectionsystems
High Speed power factor correcting systems are designed to
compensatetheReactivepowerofanyloadorequipmentrequiring
P.Fcorrectionwithinaveryshorttime.
There is no contactor switching causing high voltage transient.
Harmonics and other disturbances. Prevents voltage flickring.
Reduces failures in highly sophisticated electronic equipments
likePLCs.Computerandothercontrolsystems.
BENEFITSOFREALTIMEHIGHSPEEDAPFCAGAINST
CONVENTIONALAPFC:
Power Factor will maintain almost near to unity so guaranteed
P.F.bonusof4%to5%everymonth.
Reduction in KVA demand by 15% to 20%.Resultin saving
inDemandcharges.
Substantial saving in the electricity bill for HTP‐1 & HTP‐2
consumersinMOSTofthestateinIndia.
Enhancethe capacity of distributiontransformer,switchgearand
HTcable.
Eliminate high voltage condition during no load. [i.e. vacation,
recess,shiftchange,strikes,offloadetc.]
Saving in manpower for switching on & off the
capacitors.
Eliminatefixed lossesof the capacitor duringno load & less load
condition.
Thesystemismaintenancefreebecauseitdoesnotusecontactors
forswitchingthecapacitors.
Capacitors life is enhance minimum 3 to 4 times. Due to
electronics switching & rectors available in the system. The
reactorswillfiltertheharmonics& prevents the possibility of
resonanceby shiftingresonancefrequencybelow5th harmonics.
The load current will be approximately reduced by 15% to 20%
which in turn will reduce fluctuation in voltage and improve
voltage quality and prevents damaged to sensitive electronics
equipment.
IfusedwithD.G.sets,Itcanbeadditionallyloadedby15%to20%
&Correspondingincreaseinfuelefficiency.WhenrunningonD.G.
setthefluctuationinvoltageissubstantiallyreduce.
Capacitor connection is through Thyristor and at zero current
Crossing,thisdoesn’tgeneratetransient.
Due to fast correction of P.F. Large H.P. motor can be started on
generators already running near full load capacity. Large HP
motors Do not require soft start starters if connected through
FRPFC.
Renders the distribution network stable & helps in improving
system PF to 0.99 plus, without causing any problem to
sophisticated electronics equipment & other loads of variable
nature.
Cost is comparable with conventional contactors switching
APFCSystems.
DISADVANTAGEOFCONTACTORSWITHCHINGAPFC
Slowresponsetime.Typically30to120seconds.
Generate electrical noise & spikes, which can be damaging
computers, CNCMachinesorotherdigitalequipments.
Due to large inrush current, life of capacitor is very less say, 2‐3
years.
The contactors get welded based on the frequency of
operationandneedsreplacement.
NotsuitableforuseonD.G.SETS.
Takes much longer time to correct voltage sag. Hence, starting
current is much higher for longer period, requires Higher
capacity of switch gears/cables to cope up with high starting
current.
Duetohighstartingcurrent,startingtorqueismuchlower.Drives
need to be of higher rating to compensate for the low starting
torque. Set up will incur more losses because of lower load
efficiency.
Adds wide range of harmonics because of random switching
operation.
Doesnotincorporateinductor(REACTOR).Henceresonancemay
occur at times, which can damage the switchgears as well as
generating sets without visiblenotice.
Requiresregularmaintenance.
DISADVANTAGESOFDIRECTLYCONNECTEDCAPACITORSTO
THESYSTEM
 Fix capacitors make the power factor in leading condition, during
noloadandlessloadcondition.Theseovercorrectionleadstoover
voltages, which can damage electrical equipments. This over
voltageappearsacrosstheterminalsofthecapacitoritselfandcan
affectitslifetoo.
 With increase in voltage a demand increases proposal to the
square of the voltages in certain cases and it depends on the
characteristic of the load. As a rule of thumb, the maximum
demands of loadincrease by1.6times the increase involtage. i.e.
for every 1% increase in voltage the maximum demand will
increase 1.6 percent. The average demand will increase one third
toonepercentvoltagerise.
 Watt loss of capacitors varies from.5w to 2.5w per KVAR. So if
capacitorsareconnecteddirectlytothesystem,thereisawattloss
duringnoload&lessloadconditions.
 Directly connected capacitors are remain permanently in the
systeminchargedconditionallthetime,whichwillleadstotemp.
Riseandaffectthelifespanofthecapacitors.
 Directlyconnectedcapacitors requiredperiodiccheckingfor
verifyingcapacitorrating.
 If fixed capacitors are directly connected across the motor
terminal exceeds 85%ofthenoloadmagnetizingKVAofthe
motor, then there are chances of resonance, which is
undesirable.
 If fixed capacitors is connected across the
motor employing star delta starters, care
shouldbetakenthatthereshouldbeno
disconnection of the motor capacitor group from the supply
changeover from star to delta, otherwise these may damage
motorwinding,becausefullychangescapacitortendstodischarge
suddenlywhenthestarterchangesfromstartodelta.
CentralizedMonitoringSystemforAPFC:
GTCL- Software
THD Filters with APFC panel
All or single APFC System over plant network can be interconnected through communication wire to transfer the following data from system to Gloabtel Software. Where it can be viewed & recorded in graphical & tabular format. It offers complete control and power quality management of the plant. Parameters: o
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Frequency Phase Current Neutral Current Phase to Phase Current* Phase Voltage Neutral Voltage Phase to Phase Voltage Active Power (kW) Reactive Power (kVAr) Apparent Power (kVA) Power Factor Time of use (TOU) ‐ in, out, net, total: Active Energy (kWh) Reactive Energy (kVARh) THD at Phase Current THD at Neutral Current THD at Phase to Phase Current THD at Phase Voltage THD at Neutral Voltage THD at Phase to Phase Voltage Harmonics of Phase Current Harmonics of Neutral Current Harmonics of Phase to Phase Current Harmonics of Phase Voltage Harmonics of Neutral Voltage Harmonics of Phase to Phase Voltage QuestionersforHFID
 PowerConsumptioninKVA
 PowerConsumptioninKW
 ExistingPowerFactorCorrectionpanelinKVAR
 ExistingPowerFactorwithCapacitorON
 ExistingPowerFactorwithCapacitorOFF
 %THDforCurrentwithCapacitorON
 %THDforCurrentwithCapacitorOFF
 TransformerRatinginKVA
 TransformerImpedancein%(normallyspecifiedonthenameplateof
transformer)
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