Role of Control of Power Factor

8/9/2019 Role of Control of Power Factor

1/37


2/37

How Do You Get Low PF?

VARs.


3/37

Whats Wron With Low PF?

Overloads E ui ment

Costs Money Uses Up Natural Resources


4/37

Active Power (W) is required toperform useful work.

Reactive ower VAR is re uiredfor the generation of magnetic field ininductive loads.

Vresultant of above two powers.

Power Factor is the cosine of theR

.

All these powers can be representedW

w e e p o power r ang e.


5/37

m l x P w r

= =


6/37

Sin le Phase Power

= =

kVA = kV I

kW = kVA PF


7/37

= . = .

=

kW = kVA PF

Note: kV is the phase-to-phase voltage


8/37

PF Exam le Correction

ac y as pea eman o oa

.

.

needed to correct to a 0.9 PF

How much is ca acitance in microfarads?


9/37


10/37


11/37

PF Ex m l n in


12/37

Power Factor Correction Maintain the high power factor above 0.9 lagging with

automatic power factor improvement plant at WAPDAsupply. Because low power factor results in:

Increased current in lines

Increased line losses

Increased voltage drop in lines Reduced equipment life

More investment on transformers

Decreased enerator efficienc


13/37

Power Factor can be improved with the help of capacitors.

The capacitors are installed parallel to the load.


14/37

Benefits of Power Factor

Cost Reduction

Better Voltage Regulation

Increased Equipment Life

Improved Motor Performance

Increased System Capacity


15/37

7800 hours per year

415Volt, 3 phase

Assumed System losses = 5%

Existing Power Factor = 0.75

.


16/37

2 1 2

= 1 (0.75/0.95)2 = 0.38

System loss reduction = (loss reduction) x(Sys. Loss)

= 0.38 x 0.05= 0.019

Total kW load will be reduced = 1000 x 0.019 = 19 kW

Total kWh/Season = 7800 x 19 kW = 148,200 kWh

Total Amount @ Rs. 8/kWh = 1,185,600 / Annum


17/37

Correction Factor Table

kVAR = kW x k-factor


18/37

Power

Quality

kVAr = kW x CF

kVAr = 10 x 0.692

.

.Optimum


19/37

reducing the angle of lag betweensupply voltage and supply current.


20/37

Location of power-factor

Induction motors of all types (which from byf r h r in ri l l n . .mains).

. .control and electro-chemical processes).

. Welding machines Electric-arc and induction furnaces.

Choke coils and ma netic s stem. Neon sins and fluorescent lighting.


21/37

Consider Harmonics When A l in Ca acitors

System harmonics should be considered when applying

power factor correction capacitors. Although capacitors do not generate harmonics, under

. Harmonics are generated when non-linear loads are

applied to power systems. These non-linear loads include: adjustable speed drives, programmable controllers,

induction furnaces, computers and uninterruptible power

Capacitors can be used successfully with nonlinear loadswhen harmonic resonant conditions are avoided.


22/37

To minimize the occurrence of harmonic resonance, the

resonant harmonic of the system including the capacitorshould be estimated.

Where: h = calculated system harmonic kVAsc = short circuit power of the system kVAR = rating of the capacitor


23/37

, , ,should be avoided as they correspondto the characteristic harmonics of non-

. The harmonic value of 3 should also be

avoided as it coincides with harmonics

energization and/or operation of thetransformer above rated voltage.


24/37

Harmonics can be avoided in several wa s

Change the applied kVAR to avoid unwanted harmonics.

harmonics, it is not always successful because typically someportion of the applied kVAR is switched on and off as load

conditions re uire.

The calculation of system harmonics should be repeated for each.

Adjusting the size of the capacitor(s) may be necessary to avoid thearmonic va ues.


25/37

Add harmonic filters

n or er o er armon cs a a spec csite, tuned harmonic filters can bea lied.

A capacitor is connected in series with

an inductor such that the resonantfrequency of the filter equals theharmonic to be eliminated.

without a detailed analysis of thes stem.

The currents expected to flow in thefilter are difficult to predict and are a

comp ex unction o t e system anload characteristics.


26/37

feeding the capacitor can be

harmonic currents.

capacitor from the harmonics

harmonics from the system.

determine correct ratings for

.


27/37

1,2,4,4

1,2,2,4,4

FIFO

Reconnect TimeC/K settings


28/37

Power losses in ca acitors The dielectric loss

In ractice ever dielectric exce tin vacuum has some resistance

which allows a small current in phase with the supply voltage passthrough, and consume power, this is known as dielectric loss

,it, and the current taken by a capacitor leads the applied voltage by

exactly 90o

, the power being zero. With any other dielectric, however, there is a loss, known as the

dielectric loss, which has the result that the current does not lead thevolta e b the full 90o.

The phase angle by which the lead falls short 90o

is called the lossangle. If this angle is represented by the sign , then the phase angle . - ,

equals tan g.

Because of the small value of the angle g, the loss factor is normallyreferred to as tan . The current taken by a capacitor is equal to l = sCV, and the power absorbed by a capacitor is equal to VI cos .


29/37

Effect of Power Factor on Generator

Source: Rated power factor tests and installation acceptance of emergency and standby power systems

White paper By Jim Iverson, Senior Applications Engineer, Cummins Power Generation


30/37

Effect of Power Factor on Generator

R

FACT

O

WE

DING

L

E

A generator set can carry up to 10 percent of its rated kVAR capability in

ea ing power actor oa s wit out eing amage or osing contro ooutput voltage.


31/37

Advanta es of Power Factor Im rovement

Better voltage regulation

ecrease oa ng on rans ormers an genera ors

No penalty charges in utility bills

Exam le:

If power factor of a 1 MW gas generator running at 80% load

saved per annum.

.


32/37

Unwise wastage of money

kWh MDI Penalty Total Bill Rs./

kWh P.F

.

Jan.10 780 40 14 2 1,036.1 14,769 18.01 0.79

Feb.10 1,340 0 16 3 1,324.1 21,411 15.98 0.77

Mar.10 1,580 0 18 4 667.8 23,558 14.91 0.84

May.10 1,640 0 20 4 3,176.3 27,823 16.97 0.65

Jun.10 2,020 0 19 3 3,203.6 30,956 15.32 0.63

Aug.10 1,800 40 19 4 4,793.7 33,417 18.16 0.57Sep.10 1,800 20 17 3 4,725.7 30,886 16.97 0.49

18,927.1 182,820 16.62

kWh MDI Penalty Bill Rs./

Amount kWh .

Off Peak Peak Off Peak Peak Low P.F

Dec.09 360 20 15 0 2,721 12,500 32.89 0.61

Jan.10 961 7 18 0 2,048 18,213 18.82 0.72

Feb.10 1,498 23 25 0 2,090 25,825 16.98 0.77

ar. , , , . .

Apr.10 1,360 40 16 1 2,790 23,493 16.78 0.64

May.10 949 43 13 1 2,404 18,560 18.71 0.63

Jun.10 1,350 20 15 1 2,289 22,059 16.1 0.67

. , , , . .Aug.10 2,220 120 16 2 2,563 32,649 13.95 0.7

Sep.10 1,300 70 16 3 2,712 24,915 18.19 0.67

22,859 22,084 18.01


33/37

Power

Quality


34/37

Power

Quality

Power

Quality

au y apac ors an s raw more power an e oss urnout to be more as compared to the savings they provide.

Check the kW drawn by the capacitor banks periodically.

If i t draws more power, then its replacement with new ones ene c a .

calculate the power factor to avoid the LPF penalty at theend of the month, in case of capacitor banks failure.

This check will help you the timely replacement of faulty

.


35/37

Power

Quality

Power

Quality

Bank Volts Amp. Power

FactorMeasured

kWkVAr

Status

Capacitor

415v

5kVAr

. . . .

OK417.7584 7 0 1.69

, . .

15 kVAr

394.90 20.7 0.07

Replace it.395.59 15.8 0.64

. . .

10 kVAr407.37 8.1 2.76 1- leg off

Extra loss406.33 8 2.7

. -


36/37

PFI, Panel #

Capacitor

Bank # Phase Volts Ampare

Measured

kW

Measured

kVAr

Rated

kVAr

R 234.00 74.40 0.01 16.29

01 50.00Y 234.70 74.60 0.08 16.42

B 231.30 73.20 0.07 15.99

0.16 48.70

R 234.10 57.90 0.09 12.74

02

50.00Y 234.20 49.80 1.05 11.03

B 231.70 48.60 0.90 10.642.04 34.41

R 234.20 51.20 2.04 11.00

03 50.00Y 234.40 58.20 1.08 12.86

B 231.60 41.20 0.99 9.00

4.11 32.86

R 234.00 76.70 0.00 16.8204

.. . . .

B 231.40 71.40 0.36 15.58

0.85 48.11

R 233.90 54.50 1.50 11.88

05 .. . . .

B 231.20 61.40 0.47 13.46

2.92 36.37

R 234.00 58.90 0.02 12.90

06 .. . . .

B 231.30 55.80 0.15 12.22

0.41 37.81

R 233.90 53.30 0.45 11.71

07 .. . . .B 231.70 49.10 0.00 10.74

0.93 34.25


37/37

Thank You & Warm Regards

e nergy en er-----------------------------------------------------------------------------

nd ,e-mail:[email protected], [email protected] http://www.hec.net.pk

Please consider your environmental responsibility before printing this document

Date post:	01-Jun-2018
Category:	Documents
Upload:	abbasabbasi
View:	214 times
Download:	0 times

Role of Control of Power Factor

Documents