Power factor correction (PFC): energy optimization

DAMASCUS,DAMASCUS,Ministry of ElectricityMinistry of Electricity2424thth November 2009November 2009

Export Manager Capacitors and Export Manager Capacitors and SystemsSystems Div. Div. –– DUCATI ENERGIADUCATI ENERGIA

Pier Luigi FarinaPier Luigi Farina

In electrical circuits the current is in phase with the voltage in case of resistiveresistiveloads, whereas the current is lagging when the load is inductiveinductive (motors, transformers with no load conditions) and leading when the load is capacitivecapacitive(capacitors).

AP cos =ϕ

The reactive powerreactive power (QQ) doesn't produce mechanical work and it is an additional load for the energy supplier.The parameter defining the absorption of reactive power is the power factorpower factor.

Cos Cos φφ

A power factor correctionpower factor correction system, connected in parallel with the other loads, will reduce the amount of reactive inductive power to be supplied by the electricity supply companies, thus reducing or eliminating the overchargesovercharges for excessive reactive power absorption.

PFC PFC mainmain targettarget

In addition to the immediately profitableimmediately profitable effect, power factor correction also offers important technical advantages.An increaseincrease of coscosϕϕ considerably reduces Power Lossesreduces Power Losses (heat) in power transmission lines, thus slowing down the ageing process.

PFC PFC advantagesadvantages

IncreasingIncreasing cos cos φφfrom 0,7 to 1 means:

• around 50% lesslesscostscosts due to network resistive losses.

• around 50% extra extra currentcurrent availabilityavailabilityin the network.

An increaseincrease of coscosϕϕ will reduce onreduce on--line Voltage Dropline Voltage Drop, thus ensuring better user performance, the line voltage along the line being closer to its rated power.

To properly size a PFCsize a PFC system both its quantitativequantitative and qualitativequalitative aspects of the load power factor have to be taken into due consideration:1) the power factor correction rate (kVAr) to be installed to avoid surcharges, by means of the analysis of consumption.2) the expected capacitor working conditions (environment and power mains), which must be evaluated particularly as far as the presence of harmonics in the line is concerned.

TypeType of PFCof PFCThe choice of the correct power factor correction equipment depends on the type of loads present and by their way of working.

PFC PFC sizesize and and choicechoice

Individual Individual compensationcompensation

Central Central compensationcompensation

Individual compensation is most effective if the majority of the reactive power is concentrated on few loads with high power and that work for long period of time.

Central compensation is best suited for systems where the load fluctuates through out the day.If the absorption of reactive power is variable, it is advisable the use of automatic regulation than fixed capacitors.

The distortions of the current waveforms are generated by nonnon--linear loadslinear loads (inverter, saturated transformers, rectifier, etc.) and produce the following problems:- mechanical vibration on the A.C. motors that can reduce the life. The increase of the losses creates overheating and damaging of the insulating materials;- increasing the copper and iron losses of transformers with possible damaging of the windings and increasing of magnetizing currents;- capacitors suffer from the increasing of the voltage that reduce the life.- flickersflickers in the network.

PFC PFC withwith harmonicharmonic distortiondistortion

The dimensioning of PFC systems with tuned or detuned filtersPFC systems with tuned or detuned filters is linked to:- impedance of the network.- presence of possible and further loads that generate harmonics linked to other nodes on the network.- capacitor types: the eventual capacitance decrease varies the series resonance frequency and this inconvenient could be very dangerous because the system could have parallel resonance. To have the guarantee of a constant capacitance during the time it is necessary to use durable capacitors.

Besides the tuned filter made of capacitors and reactors (passive filter) it is possible, to remove the harmonics in the network (Power QualityPower Quality), to use another type of construction of tuned filter: the Active FilterActive Filter. The working is based on the injection in the network of the same current harmonics created by the non-linear loads but with inverted angle phase.

Power Power capacitorscapacitors forfor LV/MVLV/MVLV SINGLELV SINGLE--PHASE CYL.PHASE CYL.

POWER: 0.5kvar to 10kvarPOWER: 0.5kvar to 10kvar

VOLTAGE: 230V to 690VVOLTAGE: 230V to 690V

LV THREELV THREE--PHASE CYL.PHASE CYL.

POWER: 1kvar to 30kvarPOWER: 1kvar to 30kvar

VOLTAGE: 230V to 1000VVOLTAGE: 230V to 1000V

MV SINGLEMV SINGLE--PHASEPHASE

POWER: 25kvar to 800kvarPOWER: 25kvar to 800kvar

VOLTAGE: 1kV to 36kVVOLTAGE: 1kV to 36kV

MV THREEMV THREE--PHASEPHASE

POWER: 25kvar to 700kvarPOWER: 25kvar to 700kvar

VOLTAGE: 3kV to 12kVVOLTAGE: 3kV to 12kVLV THREELV THREE--PHASE MODULARPHASE MODULAR

POWER: 2,5kvar to 60kvarPOWER: 2,5kvar to 60kvar

The most important materials in power capacitors are dielectricdielectric filmfilm (metallizedpolypropilene or polypropilene/aluminum used to manufacture the capacitive element) and impregnatingimpregnating materialmaterial (resin or oil used to wrap, protect and insulate the capacitive element).The metallized PP film, used in LV LV applicationapplication, is selfself--healinghealing and the metalization iscomposed by zinc and aluminium. Self-healing means that in case of a localized short circuit (or break down) in a single layer of film, this results in a small arc that evaporatesthe metallization in the local region of the short circuit (in a matter of microseconds). This means that a non-conducting isolation region free of metalization is formed therewithout discontinuing the capacitor operation.

Power Power capacitorscapacitors technologytechnology

LV PFC capacitors are manufactured according to IEC831MV PFC capacitors are manufactured according to IEC871

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1 1,05 1,1 1,15 1,2 1,25 1,3 1,35 1,4 1,45 1,5

Un/U

Life

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LV PFC LV PFC systemssystems

- wall mounted up to 200kVAR200kVAR, - natural cooled, - cable inlet from the top,- modular structure.

- on the floor up to 400kVAR400kVAR, - forced cooling, - cable inlet from the top,- modular structure.

LV PFC LV PFC systemssystems ““modularmodular””

- on the floor up to 1600kVAR1600kVAR, - forced cooling, - cable inlet from the top,- rack structure.

LV PFC LV PFC systemssystems ““racksracks””

• Thanks to the use of electronic controllers and switching devices, realreal--timetime power factor correction systems can compensate reactive power within one cycle of the network (20ms) by means of “soft” switching in and out of capacitor banks. This makes it possible to “tracktrack” the Power Factor, so as to optimize the efficiency of the distribution network.

• Both in industry and the public sector, we are witnessing a growing use of equipment incorporating AC DC conversion systems: this has resulted in an increased need for harmonic compensation and fast power factor correctionfast power factor correction solutions. Active filtersActive filters and realreal--timetime power factor correction systems may successfully compete with current systems in terms of cost while offering all the advantages of the new technology.

PFC realPFC real--time & time & activeactive filtersfilters

Vol

tage

[V

]C

urr

ent

[A]

Senza “real time”:Avviamento fallito

Con “real time”:Avviamento OK

Induction motor starting with/without Induction motor starting with/without ““realreal--timetime””

Arc welder operating cycle without/with Arc welder operating cycle without/with ““realreal--timetime””• Capacitor switching “zero-crossing” voltage peaks

• Complete compensation of inductive reactive power absorption within one network period (20 ms)

• Energy savings, they are more efficient than traditional power factor correction systems

• Increase in the active power transmission capability within the network

• Drastic reduction in voltage drops and flickering

• Reduction in circulating currents

• Prevention of costly downtimes caused by the tripping of automatic cutout devices due to excessive voltage and current drops.

• Prevention of wear (on contacts and capacitors).

• They eliminate the need to install starter devices (soft starters, inverters) for each individual unit of equipment.

• They enhance the delivery capacity of any local generators.

AdvantagesAdvantages of of ““realreal--timetime””

MV/HV PFC MV/HV PFC systemssystems

MV MV capacitorcapacitor banksbanks 2424--36kV36kV

MV MV capacitorcapacitor banksbanks up 230kVup 230kV

MV/HV MV/HV harmonicharmonic filtersfilters

MV PFC MV PFC panelspanels up up toto IP55IP55

PFC IP55 panel PFC IP55 panel withwith detuneddetuned reactorsreactors and and switch forswitch for outdoor outdoor desert installationdesert installation

PFC IP30 panel PFC IP30 panel withwith contactor contactor inrush currentinrush current limitinglimiting reactorsreactors

PFC IP30 panel PFC IP30 panel withwith nono--load load switchswitch and and detuneddetuned reactorsreactors

INDUCTION FURNACE CAPACITORSINDUCTION FURNACE CAPACITORS

POWER: 25kvar to 700kvarPOWER: 25kvar to 700kvar

VOLTAGE: 600V to 3kVVOLTAGE: 600V to 3kV

FREQUENCY: 50Hz FREQUENCY: 50Hz toto 500Hz500Hz

RC FILTERSRC FILTERS

forfor primaryprimary & & secondarysecondary ofof

ElectricElectric ArcArc FurnaceFurnace TransformersTransformers

RC RC filtersfilters & & InductionInduction furnacefurnace

MV/HV PFC MV/HV PFC protectionprotection

ExpulsionExpulsion fusesfuses and HRC and HRC fusesfuses

UnbalanceUnbalance relaysrelays forfor YY--Y Y banksbanks

UnbalanceUnbalance CT CT forfor YY--Y Y banksbanks

ThankThank youyou