Thyristorised Automatic Power Factor

Correction with 7% D‐Tune HarmonicsSuppression(Reactor/Filtering)System

Powerquality?

InthepresentLowvoltage(LV)industrialdistributionsystemthepowerfactormaintenanceandharmonicscontrolarethemostcriticalissuestoensureacceptablepowerquality,andhencedemandsatmostconcernatconsumersendtomaintainastablepowersystemHarmonicsInrecentyears,with increasedusageofAC/DCDrives,UPS,Computers,ArcFurnaces&Weldersetc,Powerharmonics(bothVoltage&Current)havebecomeaseriousprobleminindustriesandcommercialinstallation.The harmonics generated by these Non‐Linear loads are the biggestobstruction in maintaining the power quality and have been a majorreasonforequipmentfailure&manyotherproblemslike..

VoltageHarmonics cancauseadditionalheating in inductionandsynchronousmotorsandgenerators.

Voltage Harmonics with high peak values can weakeninsulationincables,windings,andcapacitors.

- 25 0 0

- 15 0 0

- 5 0 0

5 0 0

1 50 0

2 50 0

0 5 1 0 1 5 2 0 25 3 0 3 5 4 0

I [A ]

Tim e [m s ]

 

Voltage Harmonics can cause malfunction of differentelectronic components and circuits that utilize the voltagewaveformforsynchronizationortiming.

Current Harmonics in motor windings can createElectromagneticInterference(EMI).

Current Harmonics flowing through cables can cause higherheating over and above the heating that is created from thefundamentalcomponent.

CurrentHarmonics flowing througha transformer cancausehigherheatingoverandabovetheheatingthatiscreatedbythefundamentalcomponent.

CurrentHarmonicsflowingthroughcircuitbreakersandswitch‐gearcanincreasetheirheatinglosses.

RESONANT CURRENTS which are created by currentharmonics and the different filtering topologies of the powersystem can cause capacitor failures and/or fuse failures in thecapacitororotherelectricalequipment.

Falsetrippingofcircuitbreakersadprotectiverelays.

Resonance is the most series consequence when connecting a powercapacitorintheLVdistributionsystem.Thecapacitanceofthecapacitorformsaresonantcircuitinconjunctionwiththefeedingtransformersandcables. The self‐resonant frequency of this circuit lies typicallybetween250and600Hzi.e.intheregionofthe5and11harmonicsandleadstothefollowingeffects

Overloading of capacitors, transformers and transmissionequipment's

Interference with metering, control system, computers andelectricalgear.

 

Whyusea7%harmonicfilterreactorinapowerfactorcorrectioncapacitorbank?

1.Capacitorare required to improvepower factor, andpossible systeminteractionmayoccurwiththeinstallationofaplaincapacitorbank.

2. Permissible distortion limits of the local utility or IEEE‐519 areexceeded,andfiltersarerequiredtoreducedthem.

3. A combination of 1 & 2 above, whereby capacitor are required toimprovepowerfactorandwiththeadditionofthecapacitors,permissibledistortionlimitsareexceeded.

To overcome the resonance effect detuned filter reactor isconnected in series with the capacitor and its self‐resonantfrequency is tuned below the lowest line harmonics by varying thechokingfactorofthereactor

 

BenefitofusingDe‐tunedreactor

1.Pro‐longthelifeofpowerfactorcapacitorbyreducingoverheating,orfusefailure.

2.Preventnuisanceinputfuseblowingorcircuitbreakertripping.

3.Reduceoverheatingoftransformer.

4.Reducetheharmoniccurrentintheelectricalsupplysystem.

5.Addressingtheharmonicproblemscreatedbynon‐linearloadsuchasAFD's,AC‐DCconverter,DCdrives,weldingm/cetc

 

High Speed Real Time Automatic Power Factor Correction System with 7% D-Tune Passive Harmonics Filters

State‐of‐theartelectronicswitchingdevicedesignedtoreplacementofelectro‐mechanicallyswitchedequipmentin

powerfactorcorrectionsystems

High Speed power factor correcting systems are designed tocompensatetheReactivepowerofanyloadorequipmentrequiringP.Fcorrectionwithinaveryshorttime.

There is no contactor switching causing high voltage transient.Harmonics and other disturbances. Prevents voltage flickring.Reduces failures in highly sophisticated electronic equipmentslikePLCs.Computerandothercontrolsystems.

 

BENEFITSOFREALTIMEHIGHSPEEDAPFCAGAINSTCONVENTIONALAPFC:

Power Factor will maintain almost near to unity so guaranteed

P.F.bonusof4%to5%everymonth.

Reduction inKVAdemandby15% to20%.Result in saving

inDemandcharges.

Substantial saving in the electricity bill for HTP‐1 & HTP‐2

consumersinMOSTofthestateinIndia.

Enhancethecapacityofdistributiontransformer,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 thecapacitorduringno 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 shiftingresonancefrequencybelow5thharmonics.

 

The load currentwill be approximately reducedby15% to20%

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 correctionofP.F.LargeH.P.motor canbe startedon

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 switchingAPFCSystems.

 

DISADVANTAGEOFCONTACTORSWITHCHINGAPFC

Slowresponsetime.Typically30to120seconds.

Generate electrical noise & spikes, which can be damagingcomputers, CNCMachinesorotherdigitalequipments.

Due to large inrush current, life of capacitor is very less say, 2‐3years.

The contactors get welded based on the frequency ofoperationandneedsreplacement.

NotsuitableforuseonD.G.SETS.

Takes much longer time to correct voltage sag. Hence, startingcurrent is much higher for longer period, requires Highercapacity of switch gears/cables to cope up with high startingcurrent.

Duetohighstartingcurrent,startingtorqueismuchlower.Drivesneed to be of higher rating to compensate for the low startingtorque. Set up will incur more losses because of lower loadefficiency.

Adds wide range of harmonics because of random switchingoperation.

Doesnotincorporateinductor(REACTOR).Henceresonancemayoccur at times,which can damage the switchgears as well asgenerating sets without visiblenotice.

Requiresregularmaintenance.

 

DISADVANTAGESOFDIRECTLYCONNECTEDCAPACITORSTO

THESYSTEM Fixcapacitorsmake thepower factor in leadingcondition,during

noloadandlessloadcondition.Theseovercorrectionleadstoovervoltages, which can damage electrical equipments. This overvoltageappearsacrosstheterminalsofthecapacitoritselfandcanaffectitslifetoo.

With increase in voltage a demand increases proposal to the

square of the voltages in certain cases and it depends on thecharacteristic of the load. As a rule of thumb, the maximumdemandsof load increaseby1.6timesthe increase involtage. i.e.for every 1% increase in voltage the maximum demand willincrease1.6percent.Theaveragedemandwill increaseone thirdtoonepercentvoltagerise.

Watt loss of capacitors varies from.5w to 2.5w per KVAR. So if

capacitorsareconnecteddirectlytothesystem,thereisawattlossduringnoload&lessloadconditions.

Directly connected capacitors are remain permanently in the

systeminchargedconditionallthetime,whichwill leadstotemp.Riseandaffectthelifespanofthecapacitors.

Directlyconnectedcapacitorsrequiredperiodiccheckingfor

verifyingcapacitorrating. If fixed capacitors are directly connected across the motor

terminal exceeds 85%of thenoloadmagnetizingKVAof themotor, then there are chances of resonance, which isundesirable.

 

If fixed capacitors is connected across themotor employing star delta starters, careshouldbetakenthatthereshouldbeno

disconnection of the motor capacitor group from the supplychangeover from star to delta, otherwise these maydamagemotorwinding,becausefullychangescapacitortendstodischargesuddenlywhenthestarterchangesfromstartodelta.

CentralizedMonitoringSystemforAPFC:

 

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. 

 

 

 

 

 

THD Filters with APFC panel

GTCL- Software

 

Parameters: 

o Frequency  o Phase Current o Neutral Current o Phase to Phase Current* o Phase Voltage o Neutral Voltage o Phase to Phase Voltage o Active Power (kW) o Reactive Power (kVAr) o Apparent Power (kVA) o Power Factor o Time of use (TOU) ‐ in, out, net, total: o Active Energy (kWh) o Reactive Energy (kVARh) o THD at Phase Current o THD at Neutral Current o THD at Phase to Phase Current o THD at Phase Voltage o THD at Neutral Voltage o THD at Phase to Phase Voltage o Harmonics of Phase Current o Harmonics of Neutral Current o Harmonics of Phase to Phase Current o Harmonics of Phase Voltage o Harmonics of Neutral Voltage o Harmonics of Phase to Phase Voltage 

12 

QuestionersforHFID

PowerConsumptioninKVA

PowerConsumptioninKW

ExistingPowerFactorCorrectionpanelinKVAR

ExistingPowerFactorwithCapacitorON

ExistingPowerFactorwithCapacitorOFF

%THDforCurrentwithCapacitorON

%THDforCurrentwithCapacitorOFF

TransformerRatinginKVA

TransformerImpedancein%(normallyspecifiedonthenameplateoftransformer)