powerfactor correction model

8/13/2019 Powerfactor Correction Model

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POWER FACTOR CORRECTION

CH.V.SESHA GIRIRAO

Associate ProfessorEEE Department


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OUTLINE

DEFINITION

CAUSES OF LOW POWER FACTOR

DISADVANTAGES OF LOW POWER FACTOR

POWER FACTOR CORRECTION METHODS

ADVANTAGES OF POWER FACTOR CORRECTION

CONCLUSION


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DEFINITION

Power factor (P.F) is the ratio between actual power to the

apparent power.Power factor=Actual power/Apparent power.

P.F=Kw /Kva.

Inductive loads cause the current to lag behind the

voltage. The wave forms of voltage and current are then

"out of phase" with each other. The more out of phase

they become then the lower the Power Factor. PowerFactor is usually expressed as Cos Phi.()

For a purely resistive load the power factor is unity.


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Active Power:

Also known as real power or simply power. The

average power in a circuit is called active power . It ismeasured in watts and often expressed in kilowatts (KW)

or megawatts (MW). The terms activeor realpower

are used in place of the term power alone to

differentiate it from reactivepower.

Reactive Power:

The power that supplies the stored energy in reactiveelements is called reactive power. It is measured in vars

and often expressed in kilovars (KVAR) or megavars

(MVAR).


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Apparent Power:

The product of the voltage (in volts) and the current (in

amperes). It comprises both active and reactive power .It is measured in volt-amperesand often expressed in

kilovolt-amperes (KVA) or megavolt-amperes

(MVA).


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CAUSES OF LOW POWER FACTOR

A poor power factor can be the result of either asignificant phase difference between the voltage andcurrent at the load terminals or it can be due to a highharmonic content or distorted/discontinuous currentwaveform.

Large phase angle of load current is generally the resultof an inductive load such as an induction motor, powertransformer, lighting ballasts, welding equipments,induction furnace, Induction generators, Wind millgenerators and high intensity discharge lightings.

A distorted current waveform can be the result of arectifier variable speed drive, switched mode

power

supply, discharge lighting or other electronic load

.


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DISADVANTAGES OF LOW POWER

FACTOR

Increases heating losses in the transformers and

distribution equipments.

Reduce plant life.

Unstabilise voltage levels.

Increase power losses. (I=P/V Cos )

Decrease energy efficiency.

Increase electricity costs by paying power factorsurcharges.


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POWER FACTOR CORRECTIONLoads on an electrical distribution system fall into one of threecategories: resistive, inductive or capacitive.

The most common is likely to be inductive. Typical examples aretransformers, fluorescent lighting and AC induction motors.

All inductive loads require two kinds of power to operate:Active power(KW) - to produce the motive force

Reactive power(KVAR) - to energize the magnetic field

The operating power from the distribution system is composed ofboth active (working) and reactive (non-working) elements. Theactive power does useful work in driving the motor whereas thereactive power only provides the magnetic field.


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POWER FACTOR CORRECTION

The amount of Power Capacitor KVAR required tocorrect a system to a desired Power Factor level is thedifference between the amount of KVAR in theuncorrected system and the amount of desired KVAR inthe corrected system.

Themost efficient location for power factor capacitors isat the load. Capacitors work from the point ofinstallation back to the generating source.

Individual motor correction is not always practical, it ismore practical to connect larger capacitors on thedistribution bus or install an automatic system at theincoming service along with fixed capacitors at the load.


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KVAR CORRECTION

Capacitive Power Factor correction (PFC) is applied to electriccircuits as a means of minimising the inductive component of the

current and thereby reducing the losses in the supply.

The introduction of Power Factor Correction capacitors is a widelyrecognised method of reducing an electrical load, thus minimising

wasted energy and hence improving the efficiency of a plant andreducing the electricity bill.

It is not usually necessary to reach unity, i.e. Power Factor 1, sincemost supply companies are happy with a PF of 0.95 to 0.98.

By installing suitably sized capacitors into the circuit, the PowerFactor is improved and the value becomes nearer to 1 thusminimising wasted energy and improving the efficiency of a plant.


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POWER FACTOR CORRECTION METHODS

Fixed Capcitors

Switch Capacitors

Synchronous Condensers

Static Var Compensator (SVC)

Static Synchronous Compensator (STATCOM)

Modulated power filter capacitor compensator


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FIXED CAPACITOR

The fixed capacitor are used for power factor correction

where the load does not change.

It is suitable for locations where induction motors are

used, like food processing plants or where small multiple

loads require reactive power compensation.

Each Fixed Capacitor Bank is designed for high

reliability and long life. These products are designed forapplications that do not contain harmonic generating

distortions.


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POWER CAPACITORS

Power Factor correction on site with

Pole Cap


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SWITCHED CAPACITOR

It is suited for centralized power factor correction in

applications where plant loading is constantly changing,resulting in the need for varying amounts of reactivepower.

An advanced microprocessor-based reactive powercontroller measures plant power factor via a singleremote current transformer and switches capacitormodules in and out of service to maintain a user-selected

target power factor.Typically applied at service entranceor near fluctuating loads.


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SYNCHRONOUS CONDENSER

Synchronous condenser is a salient pole synchronous

motor with no load condition.

Synchronous condenser stabilizes power system

voltage by supplying reactive power to the power

system and use for power factor correction.

It is more economical than capacitors.


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SYNCHRONOUS CONDENSER


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POWER FACTOR MEASUREMENT

Power factor can measure by using power factor meter

which is well known in power industry.

Power factor can also be calculated by installing watt

meter along with the Ampere meter and volt meter byusing the power factor basic formula.

Power factor=Actual Power/ Apparent power


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POWER FACTOR MEASUREMENT


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ADVANTAGES OF POWER FACTOR

CORRECTION

Eliminate Power Factor PenaltiesIncrease System Capacity

Reduce Line Losses in distribution systems

Conserve EnergyImprove voltage stability

Less total plant KVA for the same KW working power

Improved voltage regulation due to reduced line voltagedrop

Reduction in size of transformers, cables and switchgear

in new installations


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Increase equipment life

Save on utility cost

Enhance equipment operation by improving voltage

Improve energy efficiency


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POWER COST REDUCTION

Utility companies in many areas include a penalty charge

in the electrical rate for low power factor.

The installation of power factor capacitors on the user's

electrical distribution system eliminates the necessity ofpaying premium rates to the utility company for poor

power factor.

The savings of the utility company derives in reducedgeneration, transmission and distribution costs are passed

on to the user in the form of lower electrical charges.


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Common ways a utility charges a user for poorpower factor are:

KVA demand

KVAR demand

When the utility uses either KVA demand orKVAR demand as the basis for its penaltystructure, all users pay a penalty, but those withhigh power factor pay a much lower penalty ornone at all.


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SYSTEM CAPACITY INCREASEBy adding capacitors to the system, the power factor isimproved and the KW capacity of the system isincreased.

For example, a 1,000 KVA transformer with a 70%power factor provides 700 KW of power to the main bus.With the installation of capacitors so that the powerfactor is improved, say, to 90%, the KW capacity of thesystem is increased to 900 KW.

When a system power factor is improved, the amount ofreactive current flowing is lowered thus reducingtransformer and distribution circuit loads, and releasingsystem capacity.


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VOLTAGE IMPROVEMENT AND POWER

LOSS REDUCTION

System losses are also reduced through power factorcorrection by reducing the total current and power in the

system.

A 20% reduction in current will yield a 36% reduction

in distribution system losses. In this situation, an energy

savings of as much as 50% will be realized with the

installation of power factor capacitors.

In addition, power factor capacitors decrease the

distribution system voltage drops and fluctuations.


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CONCLUSION

By observing all aspects of the power factor it is clear

that power factor is the most significant part for theutility company as well as for the consumer.

Utility company will reduce the power losses while theconsumer free from low power factor penalty charges.

By installing suitably sized power capacitors into the

circuit the Power Factor is improved and the valuebecomes nearer to 1 thus minimising line losses and

improving the efficiency of a plant.


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REFERENCES

Electrical Power System Design and Analysis by M.E.EI-

Hawary.

Power System Operations by Robert H Miller.

IEEE papers

www.ABB.com

BC Hydro (www.bchydro.ca)
http://www.bchydro.ca/http://www.bchydro.ca/

powerfactor correction model

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