McGill Power Sales & Engineering, INC.

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© 2007 Eaton Corporation. All rights reserved.

Power Factor Correction

Terry McGill President McGill Power Sales & Engineering Inc.

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Agenda

• What is power factor? • What are the costs of low power factor? • What are the solutions to low power factor? • Power factor correction selection considerations • Design considerations and pitfalls

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Power factor definition

• “Real” power = working power = kW • “Apparent” power = Volts x Amps = kVA • “Reactive” power = magnetizing power = kVAR

φ

kVA kVAr

kW

• Power factor is the ratio between the “real” power and the “apparent” power of an electrical system

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Is the Glass Half Empty or Half Full?

Full Capacity

(KVA)

Foam/Fizz Capacity (KVAR)

Liquid (KW)

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Utility must generate, transmit, and distribute active AND reactive power

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If reactive power could come from another source – utility can reduce

© 2007 Eaton Corporation. All rights reserved.

Demonstration

Power Factor Demonstration Unit

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Why Consider PFC? PF correction provides many benefits: • Primary Benefit:

• Reduced electric utility bill if there is a penalty (a typical payback period is less than two years)

• Other Benefits: • Increased system capacity • Improved voltage regulation • Reduced losses in transformers and cables • May reduce harmonics on the power system (with

harmonic filters)

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Where has all the money gone?

+

Energy (kWh)

Demand (kW)

PF Charges

Taxes

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Typical Uncorrected Power Factor

Low PF typically results from unloaded or lightly loaded motors Unloaded motor – PF = .20 Loaded motor – “rated PF” = .85

Industry Percent Uncorrected PF

Brewery 76-80

Cement 80-85

Chemical 65-75

Coal Mine 65-80

Clothing 35-60

Electroplating 65-70

Foundry 75-80

Forge 70-80

Hospital 75-80

Machine manufacturing 60-65

Metal working 65-70

Office building 80-90

Oil-field pumping 40-60

Paint manufacturing 55-65

Plastic 75-80

Stamping 60-70

Steelworks 65-80

Textile 65-75

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Typical Sources of Low Power Factor

• Reactive power is required by many loads to provide magnetizing current for: • Motors • Power transformers • Welding machines • Electric arc furnaces • Inductors • Lighting ballasts

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Cost to end user or consumer- Utility fees and surcharges

• There is no free lunch!! • Many utilities pass on

the extra costs they incur through penalties, surcharges or other methods

• Methods of recovering these costs vary with each utility and can be confusing to customers

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Where do PF charges appear on a bill?

• Explicit • Power Factor Penalty • Power Factor Adjustment • Power Factor Multiplier • Reactive Demand Charge • Calculated Demand • Billed Demand

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Where do PF charges appear on a bill?

• Shift to Temp 624 Model

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Escalation in Electrical Energy Cost

• Electrical Energy cost has increased nearly 50% over the last 10 years.

• The rate of increase has accelerated in the past few years.

• Currently the PF adjustment is being increased.

Industrial Electrical Energy Cost by Year

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4.5

5

5.5

6

6.5

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Pric

e/KW

H (c

ents

)

Source Energy Information Administration

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Cost savings due to increased capacity

• Correcting poor power factor can significantly reduce the load on transformers and conductors and allow for facility expansion • Transformers are rated

by kVA and must be sized accordingly

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Example – increase capacity with new transformer • Existing plant has a

power factor of 0.80 or 80% PF

• Existing transformer is 500kVA

• Plant needs to add new production line of 75kW

kVA = 500

kVAr

=30

0

kW = 400

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Example – increase capacity with new transformer

• Cost to increase capacity to accommodate new production • New transformer

• next standard size 750kVA • Long lead-time

• Plant shut down to add new transformer – days? • Labor and materials to install new transformer

• Upsize conductors for 750kVA transformer

• Disposal of old transformer

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Example – increase capacity by adding PFCC • Correct power factor

from 80% PF to 97% PF by adding 200kVAR power factor correction capacitor

• Keep existing 500kVA • Add 75kW of new load • Existing 500kVA

transformer actually runs cooler than before!!!!

kVA = 412

kVAr

= 1

00

kW =400

kVA = 485

kVAr

= 1

00

kW =475

Power Factor Correction

Power Factor Correction and addition of 75kW

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Example – increase capacity by adding PFCC

• Cost to increase capacity to accommodate new production • New power factor correction capacitor • Minimal interruption to energize and start up new

capacitor system

© 2007 Eaton Corporation. All rights reserved.

How to correct poor power factor

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Capacitor Selection Capacitor selection issues (besides size) • Utility penalties • Installed cost, payback of equipment, and NPV • Load variability • Voltage regulation • Load requirements (Speed of changing PF) • Harmonic resonance

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Effect of Location

R2 R1

Motor Load

Resistive Load

Place here for utility PF penalty

Place here for utility PF penalty (utility owned transformer)

or

Place here to reduce losses in transformer or free capacity

Place here for line loss reduction and voltage

improvement

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LV Fixed Capacitor Banks • Designed for industrial and

commercial power systems • Lowest installed cost • var Range: 1 kvar to 400 kvar • 208 Volts through 600 Volts AC • Must be harmonic free

environment

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LV Switched (Automatic) PFC Capacitors Banks • Automatically sense changes in load

• Automatic Controller • Steps of 50 kvar standard

Smaller wall mounted units are available, and can be a real cost savings!

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• Provides similar PF correction (as caps)

• Avoid harmonic capacitor interaction problems

• “Filter” harmonics to reduce voltage and current distortion

LV Harmonic Filtering Equipment

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MV Capacitors

• Pole Mounted • These banks have exposed live parts and

are typically supported on a wood power pole.

• Rack Mounted • These banks have exposed live parts and

are supported on a steel structure. These banks are usually located in fenced-in substations.

• Metal Enclosed or Pad Mounted • These banks are typically enclosed in a

steel enclosure and are usually located within a fenced-in substation or switchgear room.

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Cost of Power Factor Correction

TABLE 4 INSTALLED COST COMPARISON

OF POWER FACTOR CORRECTION EQUIPMENT

TYPE OF CORRECTION INSTALLED COST, $/KVAR

Fixed (LV – motor applied) $15

Fixed (LV) $25

Fixed (MV) $30

Switched (LV) $50

Switched (MV) $50

Static Switched (LV) $75

Switched Harmonic Filter (LV) $75

Switched Harmonic Filter (MV) $60

Active Harmonic Filter (LV) $150

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Additional Application considerations

• Switching transients • Potential resonance

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Capacitor switching transients

• Capacitor energization (common event) • Voltage difference between system and capacitor • Capacitor voltage cannot change instantaneously • System voltage pulled nearly to initial capacitor

voltage • Inrush current as capacitor charges • Voltage overshoots and oscillation occurs

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Definition • Steady state components of voltage and current at

higher frequencies than 60 Hz (or fundamental frequency)

Causes • ‘Nonlinear’ loads, normally electronic loads • In industrial facility, predominately motor drives (AC

or DC), also large UPSs, computer loads, rectifiers • These electronic loads draw non-sinusoidal current • All load current (particularly transformers and motors)

has some amount of harmonic content

Harmonics

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H = NP+/-1

i.e. 6 Pulse Drive - 5, 7, 11, 13, 17, 19,…

Source Typical Harmonics* 6 Pulse Drive/Rectifier 5, 7, 11, 13, 17, 19… 12 Pulse Drive /Rectifier 11, 13, 23, 25… 18 Pulse Drive 17, 19, 35, 37… Switch-Mode Power Supply 3, 5, 7, 9, 11, 13… Fluorescent Lights 3, 5, 7, 9, 11, 13… Arcing Devices 2, 3, 4, 5, 7... Transformer Energization 2, 3, 4 * Generally, magnitude decreases as harmonic order increases

Expected Harmonics

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If a capacitor exists on the power system

AND

Harmonic producing loads are in use

You MUST check for harmonic resonance.

(Series and Parallel)

Harmonic Resonance

The “Self Correcting” Problem •Blown Fuses •Failed Capacitor

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Harmonic Resonance - Solutions 1. Change the method of kvar compensation (harmonic

filter, active filter, etc.) 2. Change the size of the capacitor bank to over-

compensate or under-compensate for the required kvar and live with the ramifications (i.e. overvoltage or PF penalty).

Natural System frequency of oscillation typically at 5th to 13th harmonic

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Several factors must converge simultaneously for resonance to be a potential problem

1) P.F. correction kVAr >25% of xfmr kVA 2) Nonlinear load > 25% of xfmr kVA 3) Larger, fixed capacitance Often, resonance effects exist to some degree, but is not

severe enough to cause problems

When is resonance a concern ?

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Resonance not generally a concern when: • Total kVAR <15% system kVA • Total nonlinear load <25% of system kVA • Adding capacitors to individual motors

When is resonance not a concern ?

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Resonance will happen when: Ht = (Sqrt ((xfmer kva / z)/kvar)) Ht = (Sqrt((1000/.058)/300) Ht = (Sqrt(17,241/300)) Ht = (Sqrt (57.47)) Ht = 7.58 • Record harmonic data. • Determine resonance points. • Compare to required kVAr.

How to know for sure?

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?

Questions

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Power Quality Experience Center and Lab • Overview of Lab and Capabilities

• Purpose • To demonstrate and Test PQ

Problems and Solutions • Power Quality solutions, especially

harmonic solutions, are difficult to understand

• Demystify solutions – mis-information and confusion regarding PQ and energy savings

• Equipment (Harmonic Related) • 18 Pulse Drives

• HMT’s • Active Filters • Broadband Filters

• Link:http://www.eaton.com/EatonCom/Markets/Electrical/ServicesSupport/Experience/index.htm – Simply search on Google for Eaton Experience Center

• Passive (Fixed) Filters • Passive (Switched) Filters • Active Rectifier (UPS) • Reactors

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Thank You.