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Applying Harmonic Solutions to Commercial and Industrial Power Systems David G. Loucks, P.E. [email protected] Moon Township, PA © 2005 Eaton Corporation. All rights reserved. Overview Introduction Harmonic Sources Harmonic Symptoms/Concerns (Problems) IEEE 519-1992 Standard Harmonic Solutions Harmonic Solutions for Correcting Power Factor Drive and Rectifier Solutions Solutions for Commercial Power Systems Avoiding Harmonic Resonance Low Voltage Vs. Medium Voltage Solutions The Economics of Harmonic Reduction Summary Tables and Cost Comparisons “Harmonics are not a problem unless they are a problem!” Harmonics 100%, 60 Hz 20%, 180 Hz 12%, 300 Hz 4%, 420 Hz I 2 I 3 I 4 ... 2 %THD I 2 I1 2%, 660 Hz 2 100% 2%, 780 Hz Harmonic Sources Harmonic Sources Power Electronic Equipment (drives, rectifiers (UPS), computers, etc.) Arcing Devices (welders, arc furnaces, fluorescent lights, etc.) Rotating Machines (generators) Most Common Variable Frequency Drives UPS Computer Power Supplies Fluorescent Lighting Voltage Distortion When current flows from other than an infinite source, the source voltage drops The higher the source impedance or the higher the load current, the greater the drop Non-Linear Load Example: 1 switched mode power supply 1 Switched Mode Power Supply Current Harmonics 40A 30A peak 6x 5A rms 0A -40A 0s 0.1s RMS(I(L4)) 60 Hz 4.0A3.6A 0.2s I(L4) 0.3s 0.4s 0.5s 0.6s Time 180 Hz – 3rd 3.1A 300 Hz – 5th 2.25A Isc =0.7s 22000 0.8s IL = 5A 0.9s Isc/IL = 4400 2.0A 420 Hz – 7th 540 Hz – 9th 1.38A 0.74A 0A 0Hz 0.2KHz 0.4KHz 0.6KHz I(L4) Frequency 0.8KHz 1.0KHz 1.2KHz 1 1 Switched Mode Power Supply Current Harmonics THD % I2 I3 I 4 I5 I6 I7 I8 I9 I1 100 0 3.12 0 2.25 2 0 1.38 2 0 0.74 2 4.14 100 3.6 3.6 115 % 60 Hz 4.0A3.6A 180 Hz – 3rd 3.1A 300 Hz – 5th 2.25A 2.0A 420 Hz – 7th 540 Hz – 9th 1.38A 0.74A 0A 0Hz 0.2KHz 0.4KHz 0.6KHz I(L4) Frequency 0.8KHz 1.0KHz 1.2KHz 1 Switched Mode Power Supply Current Harmonics 0 3.35 2 0 2.67 2 0 1.88 2 0 1.22 2 100 3.79 11 .22 7.13 3.53 1.49 4.83 128 % 3.79 3.79 4.0A 60 Hz 3.79A 2.0A This is with 65 kA available 180 Hz – 3rd 3.35A 300 Hz – 5th 2.67A 420 Hz – 7th 540 Hz – 9th 1.88A 1.22A 0A 0Hz 0.2KHz 0.4KHz 0.6KHz I(L4) Frequency 0.8KHz 1.0KHz 1. Current Distortion vs Available Fault Current 22 kA 115% 65 kA 128% Why is the current distortion higher with higher available fault current? Is that the same situation with voltage distortion? Let’s increase the source impedance Remember, our power supply was drawing 5A rms On a 22 kA source, the ratio of Isc/IL= 4400… essentially an infinite source Keeping the same load impedance, let’s drop the source short current down (Isc/IL= 20) 100 A rms Source Voltage Distortion Isc/IL = 4400 THD % V2 V3 V4 V5 V6 V7 V8 V9 V1 100 0 5.4 2 0 0.9 2 0 0 0 0 5.47 100 1.44 % 381 381 20V 22 kA source 1st = 381 V 3rd = 5.4 V 5th = 0.9 V 10V 0V 52Hz 100Hz V(L4:2) 150Hz 200Hz 250Hz Frequency 300Hz 350Hz 400Hz 450Hz Voltage Distortion Isc/IL = 20 THD % V2 V3 V4 V5 V6 V7 V8 V9 V1 100 0 9.12 0 7.8 2 0 4.12 0 1.7 2 12 .78 100 3.4% 377 377 15V Isc/IL = 20 1st = 377 V 3rd = 9.1 V 5th = 7.8 V 7th = 4.1 V 9th = 1.7 V 10V 5V 0V 0Hz 100Hz 200Hz 300Hz 400Hz V(L5:2) Frequency 500Hz 600Hz 70 Harmonic Distortion Standards Harmonic Voltage Distortion Limits IEEE Standard 519 – 1992 Maximum Voltage Distortion in % at PCC* Below 69kV 69-138kV >138kV Maximum for Individual Harmonic 3.0 1.5 1.0 Total Harmonic Distortion (THD) 5.0 2.5 1.5 * % of Nominal Fundamental Frequency Voltage Harmonic Distortion Standards Maximum Harmonic Current Distortion IEEE Standard 519 – 1992 Harmonic Order (Odd Harmonics) Isc/IL <11 11<h<17 17<h<23 23<h<35 35<h %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 2.0 1.0 15.0 >1000 15.0 7.0 6.0 2.5 1.4 20.0 In Percent of Fundamental Harmonic Limits •PCC (Point of Common Coupling) is defined as the point where another customer can be served From IEEE519A Draft Harmonic Limits Update for IEEE 519 The Point of Common Coupling (PCC) with the consumer/utility interface is the closest point on the utility side of the customer's service where another utility customer is or could be supplied. The ownership of any apparatus such as a transformer that the utility might provide in the customers system is immaterial to the definition of the PCC. Note: This definition has been approved by the 519 Working Group. http://home.nas.net/~ludbrook/519error.html From IEEE519A Draft Harmonic Symptoms/Concerns Equipment Failure and Misoperation Economic Considerations Notching Overheating/Failure Nuisance Operation Communication / control interference Oversizing Losses/Inefficiencies/PF Penalties Application of Power Factor Correction Capacitors Other Issues Metering – do you really have a problem? Marketing hype – buy my product! Specmanship - Misinterpretation of the IEEE-519 Standard IEEE 519-1992 Standard MAXIMUM HARMONIC CURRENT DISTORTION IN PERCENT OF IL Individual Harmonic Order (Odd Harmonics) I SC /IL 11 11h17 17h23 23h35 35 h % 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 2.0 1.0 15.0 1000 15.0 7.0 6.0 2.5 1.4 20.0 Even harmonics are limited to 25% of the odd harmonic limits above. Current distortions that result in a dc offset, e.g., half-wave converters, are not allowed. * All power generation equipment is limited to these values of current distortion, regardless of actual ISC / IL. Where, ISC = Maximum Short Circuit at PCC. IL = Maximum Load Current (Fundamental Frequency) at PCC. >> than 519 recommendations especially in specs (drives for example) Voltage or current harmonics ?? PCC?? 102% Current MAXIMUM VOLTAGE DISTORTION IN % AT PCC < 69 kV 69 kV – 161 kV 161 kV Maximum for Individual Harmonic 3.0 1.5 1.0 Total Harmonic Distortion (THD) % 5.0 2.5 1.5 Reduce Harmonics – Save Money??? Aside from the “power quality” issues (misoperation, damage, etc), harmonics also “cost” you in other ways…. Cost of oversized neutrals (2x), transformers (1.25-2x), generators (1.4-2x), UPS (1.5-2x), k-factor transformers, etc. kW losses in cables, transformers and other power system components (1-8% losses). VTHD = 2.3% Utility Source VTHD = 5.8% Generator Source Symmetrical Components Harmonic Sequence Harmonic Sequence 1 + 10 + 2 11 3 0 12 0 4 + 13 + 5 14 6 0 15 0 7 + 16 + 8 17 9 0 18 0 Reduce Harmonics – Save Money??? • • Motor damage, losses (heating) from “negative sequence currents”. High harmonics = low total power factor (utility penalties). “Negative Sequence Current” • Tries to Rotate Motor in Opposite Direction • Causes Motor Losses, Heating and Vibrations 60 Hz Rotation 5th Harmonic Rotation Drive and Rectifier Solutions Line Reactors • K-Rated/Drive Isolation Transformers • DC Choke • 12-Pulse Converter • Harmonic Mitigating Transformers/Phase Shifting • Tuned Filters • Broadband Filters • 18-Pulse Converter • Active Filters Solutions for Commercial Power Systems • Neutral Blocking Filter • Harmonic Mitigating Transformers/Phase Shifting Oversized Neutrals • K-Rated/Drive Isolation Transformers • Tuned Filters • Broadband Filters • Active Filters • Low Distortion Loads (Lighting Ballasts, Drives, etc.) LEGEND PFC K Incoming Utility Service - Power Factor Correction MV Switchgear - K Factor Transformer - Tuned Filters MV Power Factor (optional harmonic filter) PFC Active - Active Filters - Blocking Filter for 3rd Harmonic - Blocking Filter for Drives HMT LV Secondary Unit Substation - Harmonic Mitigating Transformer Bus Voltage without Correction - Multi-pulse Drives (12/18/24) Active Transformer w/Neutral Blocker HMT Bus Voltage with Correction Control/Sensing for Active or Switched Filter K PFC MCC Active PFC Panelboard Feeding Computers (3rd harmonics) Panelboard Feeding 120/208V Harmonic Loads Electronic Ballasts LV Switchboard With Harmonic Loads HMT HMT AFD AFD AFD M M M Free Standing PF Correction and/or Harmonic Filter (AFD) Adjustable Frequency Drive (12/18/24 pulse) Expected Harmonics Source Typical Harmonics* 6 Pulse Drive/Rectifier 5, 7, 11, 13, 17, 19… 12 Pulse Drive 11, 13, 23, 25… /Rectifier 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 H = NP+/-1 i.e. 6 Pulse Drive - 5, 7, 11, 13, 17, 19,… Harmonic Solutions Oversized Generator XT Active Filter G Xs 480 V Low Distortion Electronic Ballast Blocking Filter 12 Pulse M Welder M Filter K-Rated UPS w/Filter M + - Effect of Drive Line Reactors (IEEE519A) Phase Shifting – 12 Pulse From IEEE519A Draft CP9000 - 18 Pulse++ Passive Filters (Parallel / Tuned) Passive Filters (Series / Broadband) 18-Pulse Equivalent From IEEE519A Draft 6-Pulse Drive Active Filters From IEEE519A Draft Harmonic Solutions for PF Application of Harmonic Solutions for PF Correction • Reduce Utility Penalties – Most Common Reason Today • Resonance Issues • Reduce Harmonic = Reduce Vars • LV/MV? Harmonic Resonance The “Self Correcting” Problem - Blow Fuses - Fail Capacitors - Damage Transformer hR kVA kvar SC CAP Harmonic Resonance - Solutions • Apply another method of kvar compensation (harmonic filter, active filter, synchronous condenser, etc) Change the size of the capacitor bank to over-compensate or under-compensate for the required kvar and live with the ramifications. Harmonic Correction Selection for Drives in MCC’s Parallel / Passive Filter 125 Hp and up (10-20% Distortion) Series Passive Filter (8-12% Distortion*) Active Correction (5-20% Distortion) 50 Hp 18 Pulse Drive (5% Distortion*) 30 Hp * per Drive 10 Hp 5 Recommendation based on price and MCC integration 10 15 Drive Quantity 20 Fundamental Neutral Summation Harmonic Summation in Neutral Neutral Heating – Oversize Equipment 10A at 180 Hz 10A at 60 Hz A B C N 10A at 180 Hz 10A at 60 Hz 10A at 180 Hz 10A at 60 Hz 0A at 60 Hz 30A at 180 Hz Neutral Blocking Filter - Blockade TRANSFORMER ENCLOSURE PHASE C 60Hz CURRENT & NON TRIPLEN HARMONIC CURRENT 60Hz AND NON-TRIPLEN HARMONIC CURRENTS PHASE B Neutral Blocking Filter NO 3rd HARMONIC CURRENTS CIRCULATE IN DELTA WINDING TO BUILDING STEEL PHASE A SAFETY GROUND COMPUTER COMPUTER COMPUTER 60Hz IMBALANCE CURRENT ONLY Individual Phase Currents Neutral Harmonic Currents Solution Summary Tables Type 2 – Comparison of Solution Options (and Effectiveness) by CORRECTIVE EQUIPMENT • • • • Shunt/Parallel Filters Series Filters/Reactors Transformer Solutions Other Table 3 – Comparison of Solution Options by LOAD TYPE • • • • • Drives, Rectifiers, 3-Phase UPS Computers Fluorescent Lighting Welding/Arcing Loads System Solutions Cost of Harmonic Correction Description K-Factor Reactor Capacitors (LV) Switched Capacitors (LV) Single-Tuned Fixed Filter (LV) Single-Tuned Switched Filter (LV) Single-Tuned Fixed Filter (MV) Single-Tuned Switched Filter (MV) Blocking Filter (3rd's) Blocking Filter (Drives) Active Harmonic Filter Phase-Shifting Transformers Typical $/kVA* 20 3-4 12 25 35 40-50 12 15 100 100 150 50 Note that prices are generalized for comparison only but not absolute. Some equipment must be fully rated for loads - others can be partially rated Capacitors are shown for reference only. Solutions: AF Drives Pros Drives and Rectifiers – Includes 3-Phase UPS Loads Cons Inexpensive For 6-pulse standard May require additional drive/rectifier, can reduce Line Reactors compensation harmonic current distortion from 80% down to about 35-40% Offers series reactance No advantage over K-rated/Drive (similar to line reactors) reactors for reducing Isolation and provides isolation for harmonics unless in pairs transformer some transients for shifting phases Not always an option Slightly better than AC for drives DC Choke line reactors for 5th and 7th Less protection for harmonics input semiconductors Cost difference approaches 18-pulse 85% reduction versus 12-Pulse Convertor drive and blocking standard 6-pulse drives filters, which guarantee IEE 519 compliance Harmonic cancellation Harmonic highly dependent on load Substantial (50%-80%) Mitigating balance reduction in harmonics Transformers/Phase Must have even when used in tandem Shifting multiples of matched loads Solutions: AF Drives (continued) Pros Cons Drives and Rectifiers – Includes 3-Phase UPS Loads (continued) Tuned Filters Bus connected – accommodates load diversity Provides PF correction Broadband Filters Makes 6-pulse into the equivalent of 18-pulse Excellent harmonic control for drives above 18 Pulse Converter 100HP IEEE 519 compliant Handles load/harmonic diversity Active Filters Complete solution up to 50th harmonic Requires allocation anaylysy Sized only to the requirements of that system Higher cost Requires one filter per drive High Cost High cost Solutions: 1 Power Supplies Pros Cons Neutral Blocking Filter Computers/ Switch-mode Power Supplies Harmonic Mitigating Transformers Oversized Neutral/Derated Transformer K-Rated Transformer Eliminates the 3rd harmonic from load Relieves system capacity Possible energy savings 3rd harmonic recalculated back to the load When used as phaseshifted transformers, reduces other harmonics Reduces voltage “flattopping” Tolerate harmonics rather than correct Typically leased expensive Tolerate harmonics rather than correct High Cost May increase voltage distortion Requires fully rated circuits and over sized neutrals to the loads Upstream and downstream equipment fully rated for harmonics Does not reduce system harmonics Solutions: Fluorescent Lighting Pros Cons K-Rated Transformer 3rd harmonic recalculated back to the load When used as phaseshifted transformers, reduces other harmonics Reduces voltage “flattopping” Tolerate harmonics rather than correct Low Distortion Ballasts Reduce harmonics at the source Harmonic Mitigating Transformers Fluorescent Lighting Requires fully rated circuits and over sized neutrals to the loads Does not reduce system harmonics Additional cost and typically more expensive than “system” solutions Solutions: Welding, Etc. Pros Cons Active Filters Welding/ Arcing Loads Tuned Filters Tuned Filters System Solutions Fast response and broadband harmonic corrention Reduces voltage flicker SCR controlled tuned filters simulates an active filter response Provides PF correction Lower cost compared to other systems High cost SCR controlled units are high cost but fixed filters are reasonable System analysis required to verify application Harmonic Mitigating Transformers Excellent choice for new design or upgrade No PF correction benefit Active Filters Ideal solution and handles system diversity Highest cost Review of Solutions SOLUTION Shunt/Parallel Filter Solution Passive Harmonic Filters Active Harmonic Filter ADVANTAGES DISADVANTAGES Typically sized to reduce the most prevalent harmonics to an acceptable level Requires system Provides PF correction knowledge and analysis Avoids resonance by selecting “tuned” frequency Excellent cancellation for 2nd through 50th harmonic currents Highest cost Cannot be overloaded Handle diversity of loads Review of Solutions - 2 SOLUTION Series Filters/Reactors ADVANTAGES Active Harmonic Filter Excellent power conditioning for removing source voltage harmonics Neutral Blocking Filters Eliminated 3rd harmonic current from load Broadband Blocking Filters Makes 6-pulse into 18pulse equivalent AC Line Reactors DC Reactors for Drives DISADVANTAGES Highest cost High cost May increase voltage distortion loads High cost Requires one filter per drive Inexpensive For 6-pulse standard drive/rectifier can reduce harmonic distortion from 80% to 35% to 40% May require additional compensation Better than AC line reactors for 5th and 7th harmonics Not always an option for drives Less protection for input semiconductors SOLUTION Transformer Solutions Isolation Transformers Transformer Derating Harmonic Mitigating Transformers/Phase Shifting ADVANTAGES Neutral Cancellation Transformer – Zero sequence Trap 18 Pulse Drive Systems K-Factor Transformers DISADVANTAGES No advantage over reactors Offers series reactance and for reducing harmonics provides electrical isolation unless used in pairs for phase shifting Does not remove the Lowest cost solution harmonics Harmonic cancellation highly dependent on load Substantial (50% to 80%) balance reduction in harmonics when used in tandem Must have even multiples of unmatched loads 3rd harmonic recalculated back to the load Can reduce the 5th and 7th Requires fully rated harmonics when used as circuits downstream to the phase shifting pairs loads Reduces voltage “flattopping” Excellent harmonic control for drives above 100HP Higher Cost IEEE 519 compliant Tolerate harmonics rather Does not reduce system than correct harmonics Review of Solutions - 4 SOLUTION ADVANTAGES DISADVANTAGES Other Live with high 3rd harmonics Oversized Neutrals Downstream panels and shared neutrals must be oversized Transformer windings and neutral must be sized for high harmonics Wrap-up Power quality problems are costly ($$$) Energy management considerations should include power factor analysis Power factor correction capacitors are typically cost effective solutions to energy management Harmonics must be considered when applying capacitors Harmonics problems are increasing with the addition of power electronic loads on the power system Model the power system based on typical data or measurements Verify computer model with measurements Let’s Be Careful Out There!!! Thank You! Questions?