pf correction

8/3/2019 PF Correction

1/18

POWER FACTOR IMPROVEMENT

EPM333 APRIL 2011Prof. Hossam Talaat

Electrical Power Eng.

Ain Shams Univ


2/18

POWER FACTOR DEFINITION

S = V I*

PF = Cos()

Q = V I sin()+V

-

Ia Ir

I

R L+V

-

Ia Ir

I

R C

Ir

Ia

I

V

Ir

Ia

I

V

Inductive Load Capacitive Load

Leading Power Factor

Lagging Power Factor

Q

P

S

V

Lagging Q

Q

P

S

V

Lagging Q

Q = S sin() = +vePower factor = P / S (lagging)

Q = S sin() = -vePower factor = P / S (leading)


3/18

PRACTICALVALUESOFPOWERFACTORFORDIFFERENTAPPLICATIONS

Load Type Plant / Appliance PF

Lighting

Incandescent Lamps

Fluorescent Lamps (Uncompensated)

Fluorescent Lamps (Compensated)

1.0

0.5

0.93

Heating

Ovens Using Resistance Elements

Induction Heating Ovens (Compensated)

1.0

0.85

Welding

Fixed 1-Phase Arc-Welding Set

Arc-Welding Transformer-Rectifier Set

0.5

0.7 to 0.8

Induction

Motors

Loaded At 0%

Loaded At 50%

Loaded At 100%

0.17

0.73

0.85

Arc Furn. Arc Furnace 0.8


4/18

RELATIONSHIPBETWEENREACTIVEPOWER

ANDPOWERFACTOR

P = 1000 kW

S = P/PF

= 1000/PF


5/18

RELATIONSHIPBETWEENSYSTEMLOSSESAND

POWERFACTOR

Ploss = |I|2 r = [Ia /PF]

2 r

Ploss-normalized = Ploss / Ploss-min = 1 / PF2


6/18

CONCEPTOF PF IMPROVEMENT

PL

QL

SL Qc

QTSTT

L

PL

QL

SL

Qc

QT PL,ST


7/18

ADVANTAGESOF PF IMPROVEMENT

1- Reduce Electricity Billl (customer)

2- Reduction of cable size (Customer)

Multiplying factor for the cross-sectional

area of the cable core

1 1.25 1.67 2.5

Power Factor 1 0.8 0.6 0.4

3- Reduction of Losses (Utility + Customer)

4- Reduction of Voltage Drop (Utility)

5- Increase Equipment Capacity (utility)

Transformers, Feeders, T.L.,


8/18

TYPICAL EXAMPLE


9/18

POWERWORLD SIMULATOR MODEL(WWW.POWERWORLD.COM)

slack

Line Losses =

Line Loading Transformer Loading

12

3

11.31 kV 11.31 kV 0.391 kV

0%

A

Amps

0%

A

MVA

0.00 AMP

0.000 MW

0.000 Mvar

0.000 MW0.000 MW

0.000 Mvar

0.000 Mvar


10/18

UNCOMPENSTED LOAD

slack

Line Losses =


12

3

11.31 kV 10.71 kV 0.349 kV

39%

A

Amps

40.45 AMP

0.500 MW

0.500 Mvar

0.030 MW0.530 MW

0.589 Mvar

0.000 Mvar

94%

A

MVA


11/18

COMPENSATED LOAD

slack

Line Losses =


12

3

11.31 kV 11.02 kV 0.380 kV

25%

A

Amps

63%

A

MVA

26.23 AMP

0.500 MW

0.500 Mvar

0.012 MW0.512 MW

0.037 Mvar

0.500 Mvar


12/18

COMPARISON

CaseVL (V) ILine (A)

Ploss

(kW)

Trans

Load %

Feeder

Load %

Pgenerated

MW

No-Load 391 0 0 0 0 0

Uncomp.

Load 349 40.45 30 94 39 0.530Compens.

Load 380 26.23 12 63 25 0.512


13/18

PRACTICAL MEASUREMENTOF PF

Average tan()= Annual kVArh / Annual kWh

Cos() = ..


14/18

CREATINGCUSTOMERMOTIVATION

(PENALTYINEGYPT)

Penalty = (0.9-PF) * kWh charges(0.7 < PF < 0.9)

When the average annual PFis less than 0.7, thepenalty is:

Penalty= [ (0.9-0.7) + 3(0.7-PF)/2 ] * kWh charges(PF < 0.7)

If the consumer does not correct the PF, the penaltyincreases after three months to:

Penalty= 2 * (0.9-PF) * kWh charges

The utility also has the right to discontinue service ifthe consumer does not correct the PFwithin anothersix months.


15/18

FIXED VS VARIABLE CAPACITOR BANKS

Fixed capacitors This arrangement employs one or more capacitor(s) to

form a constant level of compensation.

This configuration is usually applied in cases where the

level of load is almost constant. Automatic capacitor banks

This kind of equipment provides a fast adaptation ofcompensation to match the level of load such that aselected level of power factor is maintained within a

tolerated limit. Such equipment is applied at points in an installation

where the active-power and/or reactive-power variationsare relatively large, e.g., at the busbars of a generalpower distribution board, at the terminals of aheavily-loaded feeder cable,


16/18

AUTOMATIC CAPACITORBANK

A bank of capacitors is divided into a number ofsections, each of which is controlled by a contactor.

The size of the bank increased or decreased in steps,

A regulator monitors the power factor of the controlledcircuit(s) and is arranged to close and openappropriate contactors to maintain a reasonablyconstant system power factor.


17/18

AUTOMATIC CAPACITORBANK (CONT.)

Regulator

CT


18/18

AUTOMATIC CAPACITORBANK (CONT.)
http://www.alibaba.com/product-gs/200385441/220V_380V_400V_415V_550V_TBB/showimage.html

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