87946469 Reactive Power Compensation

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REACTIVE POWERCOMPENSATION

Prepared By :-Shashikant ramEN 3rd year


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CONTENTSINTRODUCTIONDEFINITIONNEED FOR REACTIVE POWER COMPENSATIONMETHOD OF COMPENSATIONTYPES OF COMPENSATION

FIXED COMPENSATION vs. DYNAMIC COMPENSATIONINFORMATION REQUIRED FOR DESIGNING RPCCAPACITOR IN RPC

AUTOMATIC POWER FACTOR CORRECTIONBENEFITS OF RPCCONCLUSIONREFERENCE


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INTRODUCTION

Major industrial loads e.g. induction motors,furnaces, transformers, etc. need reactive power for sustaining the magnetic field.As in case of inductionmachine the reactive power is needed just to

create air gap magnetic field.Series inductance intransmission lines implies consumption of reactivepower. Reactors, fluorescent lamps and allinductive circuits on the whole require a certain

amount of reactive power to work. Thus reactivepower is not delivered as effective mechanicalpower output of motor unlike the real power whichis effectively converted as mechanical output.


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DEFINITION : Any device which is connected inshunt or series with the load and

which is capable of supplying thereactive power demanded by theload is called a Reactive power compensation device.


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NEED FOR REACTIVE POWERCOMPENSATION

The power supplier charges penalty for excessive consumption of reactive power.Reduced energy losses make reactive

power profitable.Additional machines are to be connected toalready fully loaded substations, cables or transformer.

The power transmission for a new plant canbe planned more economically if power factor correction is taken into consideration.


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METHODS OF COMPENSATION

There are two major ways of reactive compensation1. Shunt compensation:

Shunt capacitors are connected inparallel in the system and are usedmainly for power factor improvementand in harmonic filters. It also booststhe voltage of the bus. This also

known as load compensation.


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2. S ERIES COMPENSATION Series capacitor are connected in series in thelines and are used mainly for boosting thereceiving end voltage, increase in transmissioncapacity and reduction in losses in the lines.

It also improve power factor at the sending endof the line.Unlike shunt capacitor whose output depends

on the voltage, the voltage improvement byseries capacitors increase with increase in loadcurrent.In other word the series capacitor is a self regulating type. Series compensation is alsoknown as live compensation.


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TYPES OF COMPENSATION

There are different types of compensation:(1)Individual compensation:

Advantage:-Additional control and protectionequipments not required.

Overcompensation are avoided.

limitation:-compensation value limited by the noload KVA of the motor.

Risk of the high inrush currents due to parallelswitching.

Not feasible to design an effective harmonic filter.


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2)Group compensation: Advantage:-Proper protection scheme can be

provided. It can be used aseffective harmonic filters.

limitation:-compensation value limited by the noload KVA of the motor.Risk of the high inrush currents due to parallel

switching.Not feasible to design an effective harmonic

filter.(3)Central compensation: Advantage:-This could be most economical.

if single large bank has to be used

for improvement of P.F. only to avoid the penaltyLimitation:- Cannot unburden the transformer from reactive power load .Can not reduce systemloss.


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FIXED COMPENSATION VS DYNAMIC COMPENSATION

FIXED COMPENSATION:-Here the reactivepower fed by the capacitors to the system isfixed. These are basically breaker controlledcapacitors and are used in system which hasconstant load having a set pattern of operation.

DYNAMIC COMPENSATION:-Here the reactivepower fed by the capacitors to the system isdynamic. This is done using thyristor controlled

capacitors. These are used in systems where theloads are fluctuating in nature like arc furnaceloads.


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INFORMATION REQUIRED FORDESIGNING R.P.C

SHUNT COMPENSATION:-1. System voltage with variation2. System frequency with variation3. Actual system fault level4. Uncompensated power factor 5. Harmonic generating loads or harmonic current

generated in the systemSERIES COMPENSATION:-

1. Load details at each bus2. Line parameters3. Voltage improvement required4. Maximum and Minimum load


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CAPACITOR IN REACTIVE POWERCOMPENSATIONCapacitor can be viewed as generator of reactivepower When a capacitor connected across the load ,thecapacitor supplies reactive power to the load,there by relieving the transmission networkwhich can carry only the active power.

As opposed to the rotating machines, thecapacitor is a device with no moving parts, whichgenerates reactive power.High voltage capacitors are built up a singlephase capacitor units.


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AUTOMATIC POWER FACTORCORRECTION(APFC)

If the capacitor output is fixed when theload decreases, total load will be capacitiveat low active load.

Thus depending on the actual short circuitcapacity of the bus, the additional reactivepower will cause a rise in the voltage on thatbus.In order to avoid the disadvantage ,plantswith fluctuating loads are often provided withautomatic regulation.


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BENEFITS OF REACTIVE POWERCOMPENSATION

Better efficiency of power generation, transmissionand distributionImprovement in voltage

Reduced KVA demandHigher load capability.Reduced system losses.


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The figure show the relation between apparent (S),

active (P), and reactive power (Q) at a certain power factor of the load.The load is uncompensated and if the conductor or the transformer is fully loaded the arc of the circle

defines the maximum power output.


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CONCLUSION

When a capacitor connected across theload,the capacitor supplies reactive power to the load, thereby network carry only theactive power.By reducing the negative impact of reactivepower in high voltage AC networks, thecapacity of transmission systems can bedramatically increased. This means greater reliability and better use of existing lines.RPC reduce energy loss.


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REFERENCE

>Elements of power system analysis byW.D.Stevenson,TMH

>Element of power system by

C.L.Wadhwa,NEW AGE


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T H A N K Y O U

Date post:	14-Apr-2018
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87946469 Reactive Power Compensation

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