Immediate Energy Efficiency with Power Factor Correction
Power Quality Clean power, Efficient business
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Outline
Power Factor:
●Definition & Examples
●Cost Savings
●Power Factor Correction Equipment
Harmonics:
●Introduction
●Harmonics and Power Factor Correction Capacitors
●IEEE 519 Standard
●Traditional Harmonic Mitigation Methods
●Active Filter Technology & Applications
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Definitions: ●kW = Active Power: It does the "work" for the system - providing the
motion, heat, or whatever else is required.
●kVAR = Reactive Power: It doesn't do useful "work." It simply sustains the electromagnetic field.
●kVA = Apparent Power: It is the vector addition of Working Power and Reactive Power.
●Power Factor : The ratio of Active Power (output) to Total Power (input). It is a measure of efficiency.
What is Power Factor?
Total Power (kVA)
θ
Active Power (kW)
Power Factor = Active (Real) Power Total Power = kW kVA = Cosine (θ)
Reactive Power (kVAR)
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Power Factor:The Beer Analogy
Mug Capacity = Apparent Power (kVA)
Foam = Reactive Power (kVAR)
Beer = Real Power (kW)
Power Factor = Beer (kW)
Mug Capacity (kVA)
Capacitors provide the Foam (kVAR), freeing up Mug Capacity so you don’t have to buy a bigger mug and/or so you can pay less for your beer !
kVAR Reactive Power
kW Active Power
kVA Apparent Power
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Why is Power Factor Important? ●Low power factor results in:
●Poor electrical efficiency ●Lower system capacity ●Higher utility bills
●Most utilities have power factor penalties to encourage power factor correction. Otherwise the utility may have to:
– Build more power plants – Purchase new transformers – Use larger cables
●Power factor correction ●Reduces power cost ●Releases system capacity ●Reduces power losses ● Improves voltage
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● The easiest solution to improve power factor is to add power factor correction capacitors to your electrical distribution system.
A2
Power Factor Correction
M
The Capacitor Supplies Reactive Current
Current that is drawn from the voltage source is then only used to do real work (kW) and not to create a magnetic field (kVAR). The source current is then minimized
» The customer only pays for the capacitor » Since the utility doesn’t supply the kVAR, the customer doesn’t
pay for it » In short, capacitors save money
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In this example, demand is reduced from 100 kVA to 80 kVA by installing a 60 kVAR capacitor.
Before: PF = kW/kVA = 80%
After: PF = kW/kVA = 100%
Transformer loading is reduced
Power Factor Correction
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● Reduced Power Costs: lower utility bills since utility no longer supplies the reactive current.
● Released System Capacity
●Capacitors off-load transformers and cables
● Improved Voltage
● Reduced losses
kW 100
kVAR 100
kW 100
kVAR 75
kW 100
kVA = 141 PF = 70%
kVA = 125 PF = 80%
kVA = 100 PF = 100%
Benefits of Power Factor Correction
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How do utilities charge for Power Factor?
Billing Actual Actual Possible Required Required % ReductionService Demand Power Demand Demand Cost Capacitor kVAR Capacitor kVAR of Transformer
Month kW Factor kVA kW Savings for 0.92 pf for 1.0 pf kVA Load05/14/11 900.0 0.8000 1,000.0 800.0 $550.00 259 600 20% 06/14/11 800.0 0.7950 888.9 706.7 $513.33 238 539 21% 07/16/11 850.0 0.7625 944.4 720.1 $714.24 304 611 24% 08/15/11 875.0 0.7511 972.2 730.2 $796.20 331 642 25% 09/16/11 910.0 0.7574 1,011.1 765.8 $793.01 334 660 24% 10/16/11 780.0 0.7722 866.7 669.2 $609.18 266 551 23% 11/16/11 890.0 0.7950 988.9 786.2 $571.08 265 600 21% 12/16/11 870.0 0.7950 966.7 768.5 $558.25 259 586 21% 01/16/12 760.0 0.7625 844.4 643.9 $638.61 272 546 24% 02/16/12 750.0 0.7511 833.3 625.9 $682.46 284 550 25% 03/16/12 690.0 0.7574 766.7 580.7 $601.30 253 501 24% 04/16/12 870.0 0.7722 966.7 746.5 $679.47 296 614 23%
0.0 0.0 Savings 2012 $7,707.13
Approximate cost of standard power factor correction equipment $12 to $15K === Payback about 2 years.
Approximate cost of filtered power factor correction equipment $18 to $21K === Payback about 3 years.
●Example with $5.50 per demand kW
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Power Factor Correction
●Capacitors: ● Low Voltage Power Factor Correction Capacitor Banks
●Fixed
●Standard Automatic
●Detuned
●Transient Free
●Medium Voltage Power Factor Correction Capacitor Banks
●Fixed
●Standard Automatic
●Detuned
●Active Filters ● LV and MV Hybrid VAR Compensation Products
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Outline
Power Factor:
●Definition & Examples
●Cost Savings
●Power Factor Correction Equipment
Harmonics:
●Introduction
●Harmonics and Power Factor Correction Capacitors
●IEEE 519 Standard
●Traditional Harmonic Mitigation Methods
●Active Filter Technology & Applications
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Harmonic Basics ● What are harmonics?
●A harmonic is a component of a periodic wave with a frequency that is an integer multiple of the fundamental frequency
●Created by power semiconductor devices ●Converts power (AC to DC)
●Characteristic harmonics are the predominate harmonics seen by the power distribution system
●Predicted by the following equation:
– HC = characteristic harmonics to be expected
– n = an integer from 1,2,3,4,5, etc.
– p = number of pulses or rectifiers in circuit
Harmonic Frequency Sequence 1 60Hz + 2 120Hz - 3 180Hz 0 4 240Hz + 5 300Hz - 6 360Hz 0 7 420Hz + : : 19 1140Hz +
Fundamental
3 rd Harmonic
5 t1h Harmonic
7 th Harmonic
Waveform seen with oscilloscope
1±= npHc
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Harmonic Filtering
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Multi-pulse Converters
Harmonic Orders Present
Hn1 phase 4-pulse
2 phase 4-pulse
3 phase 6-pulse
3 phase 12-pulse
3 phase 18-pulse
3 x x5 x x x7 x x x9 x x11 x x x x13 x x x x15 x x17 x x x x19 x x x x21 x x23 x x x x25 x x x x27 x x29 x x x31 x x x33 x x35 x x x x x37 x x x x x39 x x41 x x x43 x x x45 x x47 x x x x49 x x x x
Harmonics present by rectifier designType of rectifier
Hn = np +/- 1
Hn = characteristic harmonic order present
n = an integer
p = number of pulses
Elimination of lower orders removes largest amplitude harmonics
AccuSine SWP
AccuSine PCS
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Harmonic Basics ●Nonlinear loads draw harmonic current from source
● Does no work
Inverter Converter
DC bus
M
A B C
Current: high TDD between 90-120%
Voltage: flat topping of waveform
Basic PWM VFD
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Harmonic Basics
●Why the concern? ●Current distortion
●Added heating = reduced capacity
●Equipment failures
– Transformers
– Conductors and cables
– Nuisance tripping of electronic circuit breakers (thermal overloads)
●Heating proportional to harmonic order in cables & bus bars ●Squared effect on transformers & AC
motors
Loads
Ih
hhh ZIV ×=
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Harmonic Basics
Voltage distortion
●Created as current harmonics flow
through the system
● Interference with other electronic loads ●Malfunctions to failure
● Induces harmonic currents in linear loads ●AC motor winding over heating & bearing failures
Loads
Ih
hhh ZIV ×=
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M M M
Utility
VFD
Harmonics and Standard Capacitors
●Capacitors absorb harmonics ●Overheating of PFC capacitors
●Tripping of PF protection devices
●Reduced life expectancy
●Magnification of harmonics by resonance ●Amplification of current between
capacitor and transformer
●Current distortion rises
●Voltage distortion rises
●Main transformer &/or capacitor fuses blow
●Equipment damage
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Capacitor Resonance
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Detuned Capacitors
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Conventional Switch Structure
HRC Fuses
Contactors
Optional De-tuned Inductor
L1 L2 L3 Electro- mechanical switching elements (contactors) are used to connect a capacitor group.
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IEEE 519-1992
●Defines current distortion as TDD (Total Demand Distortion) ● Largest amplitude of harmonic current occurs at maximum load of
nonlinear device – if electrical system can handle this it can handle all lower levels of amplitudes
● Always referenced to full load current ● Effective meaning for current distortion
●Defines voltage distortion as THD ● Total harmonic voltage distortion
●Does not use THD(I) ● Total harmonic current distortion ● Instrument measurement (instantaneous values) ● Uses measured load current to calculate THD(I)
fII
THDi h∑=2
)(
2
FLAfII
TDD h∑=fVV
THDv h∑=2
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IEEE 519-1992 ● Issues addressed:
● THD(V) delivered by utility to user (Chapter 11)
●THD(V) must be < 5% [< 69 KV systems]
●Defines the amount of TDD a user can cause (Chapter 10)
●Based upon size of user in relation to power source
●Table 10.3 for systems < 69 kV
●Defines limits for voltage notches caused by SCR rectifiers – Table 10.2
●Defines PCC (point of common coupling)
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IEEE 519-1992
Total I, rms
Fund I, rms
Harm I, rms THD(I) TDD
Full load 936.68 936.00 35.57 3.8% 3.8%836.70 836.00 34.28 4.1% 3.7%767.68 767.00 32.21 4.2% 3.4%592.63 592.00 27.23 4.6% 2.9%424.53 424.00 21.20 5.0% 2.3%246.58 246.00 16.97 6.9% 1.8%111.80 111.00 13.32 12.0% 1.4%
Measured
• TDD and THD(I) are not the same except at 100% load
• As load decreases, TDD decreases while THD(I) increases.
• Example:
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IEEE 519-1992 Table 10.3 Current Distortion Limits for General Distribution Systems (<69 kV)
Isc/Iload <11 11<=h<17 17<=h<23 23<=h<35 h>=35 TDD<20 4.0% 2.0% 1.5% 0.6% 0.3% 5.0%
20<50 7.0% 3.5% 2.5% 1.0% 0.5% 8.0%50<100 10.0% 4.5% 4.0% 1.5% 0.7% 12.0%
100<1000 12.0% 5.5% 5.0% 0.2% 1.0% 15.0%>1000 15.0% 7.0% 6.0% 2.5% 1.4% 20.0%
Isc = short circuit current capacity of sourceIload = demand load current (fundamental)
(TDD = Total harmonic current distortion measured against fundamental current at demand load.)
TDD = Total Demand Distortion
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•Designed to protect utility •Most harmonic problems are not at PCC with utility
•Occur inside the plant •Occur where nonlinear loads are concentrated •Occur with generators & UPS (high probability of problems) •Need to protect the user from self by moving the PCC to where harmonic loads are located.
•Apply principals of IEEE 519-1992 Table 10.3 inside the plant
•Assures trouble free operations •Assures compliance to standard
•We have the products to meet 5% TDD inside the plant
Harmonic Standards
Harmonic mitigation methods - (Applied per VFD)
Solution Advantage Disadvantage Typical %
TDD Typical Price
Multiplier* Increase short circuit capacity Reduces THD(V)
●Increases TDD ●Not likely to occur**
Dependent upon SCR***
Cost of transformer and installation change out
C-Less Technology
●Lower TDD ●Simplified design ●Less cost
●Compliance is limited ●Application limited ●Size limited 30 - 50% TDD 0.90 - 0.95
Impedance (3% LR or 3% DC choke)
●Low cost adder ●Simple ●Compliance difficult 30 - 40% TDD 1.05 - 1.15
5th Harmonic filter
Reduces 5th & total TDD
●Does not meet harmonic levels at higher orders^ 18 - 22% TDD 1.20 - 1.45
Broadband filter Reduces TDD (thru 13th)
●Large heat losses ●Application limited 8 - 15% TDD 1.25 - 1.50
12-pulse rectifiers ●Reduces TDD ●Reliable
●Large footprint/heavy ●Good for >100 HP 8 - 15 % TDD 1.65 - 1.85
18-pulse rectifiers ●Reduces TDD ●Reliable
●Large footprint/heavy ●Good for >100 HP 5 - 8% TDD 1.65 - 1.85
Active front end converter
●Very good TDD ●Regeneration possible
●Large footprint/heavy ●Very high cost per unit ●High heat losses < 5% TDD 2.0 - 2.5
* Price compared to a standard 6-pulse VFD. ** Utilities and users are not likely to change their distribution systems. *** Increasing short circuit capacity (lower impedance source or larger KVA capacity) raises TDD but lowers THD(V). ^ Can be said for all methods listed.
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Active Filter Concept
Source XFMR
Load(s)
Is
Ia
Il
Optional CT location
•Parallel connected
• includes 2nd to 50th harmonic current
• <5% TDD
las III
=+aI
sI
LOAD Sense
SOURCE Sense
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●Price (first cost) ●Footprint required ●Heat losses ●Cost to operate
●Site cooling required ●Net Present Value (NPV)
System solution Comparison of 18-P VFD to AccuSine PCS + standard VFD
Harmonic Mitigation Solutions
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Solutions by AccuSine Model
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Schneider Electric Offer
●AccuSine SWP ●20-120 Amps
●400 VAC
●Neutral correction
●AccuSine PCS ●50-300 Amps
●208-480 VAC/600 VAC/690 VAC
●AccuSine PFV ●50-300 Amps
●208-480 VAC/600 VAC/690 VAC
●No harmonics
●Use customized transformers for higher voltages (to 15 kV for harmonics & 35 kV for non-harmonic modes)
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AccuSine SWP
●The Schneider Electric solution for harmonic filtering in buildings.
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AccuSine PCS
●The Schneider Electric solution for active harmonic filtering in industrial installations.
● Most common – VFD sites ●Centrifugal pumps and fans
●Pumping Stations
– Potable
– Wastewater
●Wastewater Plants
●Water Purification (potable)
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AccuSine® PCS/PFV Power Diagram
+ C
E
C
E
C
E
C
E
C
E
C
E
C
Line Inductor
Filter Board
Pre-charge Contactor
Inductor
Fuse
Fuse
Fuse
AC Lines
S4
S5
S6
S1
S2
S3 DC Bus Capacitors
IGBT Module
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AccuSine® PCS Performance Summary - Harmonics ●Discrete Spectrum Logic (DSL)
●TDD <= 5%, if loads have =>3% Z installed ● 2nd to 50th orders, discrete ● <2 cycle response ●Resonance avoidance logic ●Adjustable trip limits per harmonic order ●On-board commissioning program
●Phase rotation (clockwise required) ●Automatic CT orientation (phase rotation/polarity/calibration) ●Run lockout if not possible to re-orient
●Oscilloscope feature built into HMI ● Load/source bar graphs
●Load balancing ●Can parallel up to 99 units of each size and mix sizes
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System Solution
AccuSine® PCS Sizing Example ●A 125 HP variable torque 6-pulse VFD with 3% LR
● Required AHF filtering capability = 47.5 amperes ●Two 125 HP VT 6-pulse VFD w/3% LR
● Required AHF size = 84.4 amps ●Three 125 HP VT 6-pulse VFD w/3% LR
● Required AHF size = 113.5 amps ●Six 125 HP VT VFD w/3% LR
● Required AHF size = 157.6 amps ● (not 6 x 47.5 = 285 amps)
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Product Package ●Standard (UL/CSA, ABS) ● Three current ratings ●Enclosed – NEMA 1/IP20
● 50 amp – 52”(1321mm) x 21”(533mm) x 19”(483mm)
●Weight – 250#(114 K\kg) ● 100 amp – 69”(1753mm) x 21”(533mm) x
19”(483mm) ●Weight – 350#(159 kg)
● 300 amp – 75”(1905mm) x 32”(813mm) x 20”(508mm)
●Weight – 775#(352 kg) ●Wall mount – 50 & 100 amp ● Free standing – 300 amp with disconnect
AccuSine® PCS/PFV
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Product Package
●Other enclosures (380 - 480VAC) ●NEMA 12, IP30, IP54
●50 amp – 75”(1905mm) x 31.5”(800mm) x 23.62”(600mm)
– Weight – 661Ib(300 kg) ●100 amp – 75”(1905mm) x 31.5”(800mm) x 23.62”(600mm)
– Weight – 771Ib(350 kg) ●300 amp – 75”(1905mm) x 39.37”(1000mm) x 31.5”(800mm)
– Weight – 1012Ib(460 kg) ●Free standing with door interlocked
disconnect ●CE Certified, C-Tick, ABS, UL, CUL
AccuSine® PCS/PFV
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AccuSine PCS 600/690 VAC
● Includes autotransformer & input fused disconnect
●Simple installation ● 600 VAC: UL/cUL/CE ● 690 VAC: CE ●Ratings: PCS 600V 690V 50 A 39 A 33 A 100 A 78 A 67 A 300 A 235 A 200 A
300A
50/100A
Height
Height
1000 mm
800 mm
800 mm
600 mm
1900 mm
1972 mm
Depth 800 mm
600 mm
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AS off AS on Order % I fund % I fund Fund 100.000%100.000% 3 0.038% 0.478% 5 31.660% 0.674% 7 11.480% 0.679% 9 0.435% 0.297% 11 7.068% 0.710% 13 4.267% 0.521% 15 0.367% 0.052% 17 3.438% 0.464% 19 2.904% 0.639% 21 0.284% 0.263% 23 2.042% 0.409% 25 2.177% 0.489% 27 0.293% 0.170% 29 1.238% 0.397% 31 1.740% 0.243% 33 0.261% 0.325% 35 0.800% 0.279% 37 1.420% 0.815% 39 0.282% 0.240% 41 0.588% 0.120% 43 1.281% 0.337% 45 0.259% 0.347% 47 0.427% 0.769% 49 1.348% 0.590% TDD 35.28% 2.67%
AccuSine Performance
AccuSine injection
Source current
At VFD Terminals
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700 HP Drive – AccuSine ON – OFF
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700 HP Drive – AccuSine ON – OFF
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700 HP Drive – AccuSine ON – OFF
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Ias = rms output current of AccuSine PCS
Ih = rms harmonic current
If = rms fundamental current
Ias Ih If100.0 10.0 99.5100.0 20.0 98.0100.0 30.0 95.4100.0 40.0 91.7100.0 50.0 86.6100.0 60.0 80.0100.0 70.0 71.4100.0 80.0 60.0100.0 90.0 43.6100.0 95.0 31.2
Examples
AccuSine® PCS Dual Mode Operation 22
fhas III +=
● Assignment of capacity ● Assign priority to Harmonic or PF/LB
(fundamental) modes ● Use % of harmonic mode to set split
●100% means capacity utilized for harmonic correction, then left over can be used for PF/LB ●0% assigns fundamental (PF correction/LB) current as primary mode, left over used for harmonic correction ●Can split to limit harmonic mode capacity, left over to PF correction/LB
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Power Factor & VAR Compensation
●HVC (AccuSine PFV + PF caps) ●Larger systems approach
●HVC is Hybrid VAR Control
– Combines AccuSine PFV with PF caps – Caps on line all the time
●AccuSine adjusts fundamental current to attain unity DPF ●Cycle-by-cycle response ●Voltages to 33 kV (6.6 kV shredder in France, 12.47 kV in US
automotive, 13.8 kV steel mill in Colombia) ●Fundamental current balancing (optional since 1 Nov 10))
●Sometimes critical – i.e. two phase loads
AccuSine® PFV
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Thank You
Questions?