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Harmonic Distortion in Drives

Variable-frequency-drive- (VFD-) generated harmonics largely is a perceived, rather than real, issue. In 27 years of applying VFDs in HVAC and other applications, this author has experienced only a handful of actual harmonics problems, with all but one stemming from high levels of voltage distortion, not the current distortion that has been getting so much attention lately.

Most of the VFD-interference problems this author has encountered have been the result of poor installation — particularly, poor wiring and grounding. In the majority of cases, radio-frequency interference (RFI) or electromagnetic interference (EMI), not harmonics, was the culprit. RFI/EMI issues stem from noise in the 50-Khz-to-low-megahertz range, not the 300-Hz fifth or 420-Hz seventh harmonic range.

HISTORY

In 1981, ANSI/IEEE Standard 519, IEEE Guide for Harmonic Control and Reactive Compensation of Static Power Converters, was published. It included maximum total-harmonic-voltage-distortion (THDV) recommendations.

In the extreme, voltage distortion can cause flat-topping of power-system voltage waveforms (Figure 1), which can cause sensitive electronic processors to become confused and malfunction.

In 1992, ANSI/IEEE Standard 519 was revised. Renamed IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems, it now concentrates more on total harmonic current distortion (THD1) than voltage distortion.

THD1 can propagate through utility step-down/step-up transformers and make its way from one facility to another. For example, several years ago, a VFD manufacturer was creating high amounts of current distortion during its burn-in testing operation. The current distortion traveled through the utility transformers at the VFD manufacturer’s plant to the utility feed at a neighboring printing plant, corrupting the logic circuits in the controls and direct-current (DC) drives running the printing plant’s printing press and causing the printing-press registration to malfunction.

THD1 results in additional heat in the distribution transformers typically provided by utilities, as well as the power-feeder cables of the equipment from which it originates. Basically, THD1 is current that a utility has to generate and source to a facility, but that brings no revenue to the utility. While it is a real issue for utilities, THDI largely is a perceived problem from a facility manager’s point of view.

ANSI/IEEE Standard 519-1992 addresses the system-issue nature of THD1 by introducing total demand distortion (TDD), which can be calculated as follows:

where:

Ihe = total harmonic current as measured by system

Ihc = total harmonic current contributed by VFDs

IL = maximum demand-load current (fundamental frequency component) (15- or 30-min demand) at utility point of common coupling (PCC) as measured in system

IC = fundamental frequency component contributed by vfds (included only if vfds are an addition to existing loads)

(All quantities are in amperes root mean square.)

ANSI/IEEE Standard 519-1992 states, “Within an industrial plant, the PCC is the point between the nonlinear load and other loads.” Many consulting engineers have interpreted this to mean that THD1 is to be measured at VFD input-power connections (PCC2, instead of PCC1, in Figure 2). This misapplication of ANSI/IEEE Standard 519-1992 has contributed to the overuse of multipulse drives in the HVAC industry. Many millions of facility-equipment dollars have been squandered through the specification and installation of 12- and 18-pulse drives in commercial office buildings and other environments in which a standard six-pulse drive would have done the same job for substantially less upfront cost.

Also unfortunate is the fact ANSI/IEEE Standard 519-1992 has five different levels of acceptable maximum TDD, which depend on the ratio of maximum short-circuit current (ISC) to maximum IL at a PCC. The ISC-to-IL ratios in Table 1 are functions of the strength of a utility’s feed to a facility and the size of the substation transformer.

CURRENT SITUATION

Many specifications simply state, “VFDs shall meet ANSI/IEEE Standard 519.” Such a statement is meaningless without the information needed to perform harmonic calculations:

  • Transformer kilovolt-amperes and percent impedance.
  • Total linear connected-load amperage or total expected linear connected amperage.
  • The number and sizes of VFDs.
  • Utility ISC available.

Calculations are even more accurate when manufacturers have additional information, such as facility total current, existing harmonic content, and wire sizes and lengths.

Some engineers have taken to writing hardware specifications based on horsepower size requirements. For example: “All VFDs 100 hp and up shall be 18-pulse designs.” At 100 hp, an 18-pulse drive easily can cost four times as much as a six-pulse drive with no improvement in energy savings.

That is not to say there are no applications for which a 12- or 18-pulse drive is appropriate. Take, for instance, a cinderblock pump station in a residential neighborhood. This author observed one in which there were three 300-hp VFDs, overhead fluorescent lighting, and a wall-mounted programmable logic controller (PLC). The pump station was fed by a dedicated 480-v transformer. Virtually the entire load on the transformer was non-linear. The VFD non-linear load represented approximately 1,100 amps. The PLC and fluorescent-light loads totaled a couple of amps. That was an ideal application for 18-pulse or other ultralow-harmonic VFD technology.

In a commercial office building, if VFDs are installed on every fan and pump, they typically will use less than 20 percent of the electrical demand load. In almost all such cases, standard six-pulse drives are a good choice.

Contrary to popular belief, ANSI/IEEE Standard 519 is not a law or government/utility regulation; it is a “recommended practice.” It states that strict adherence to its recommended harmonic limits “will not always prevent problems from arising.” The contrary also is true: A facility may have harmonics in excess of the standard’s maximum recommended limits and not experience difficulties.

TECHNOLOGIES

The simplest and least-expensive method of mitigating VFD-generated harmonics is adding impedance at a VFD. This can be accomplished with an input line reactor (Figure 3) or a DC link reactor (bus choke) (Figure 4). In a 1-percent-source-impedance system, a 3-percent line reactor can reduce harmonic-current content at the input to a VFD to about 40 percent at full-load output.

The next-most-common type of harmonic-mitigation technology is the 12-pulse VFD (Figure 5). A 12-pulse VFD reduces harmonic-current content to about 10 percent.

Also common are broad-band and passive filters (Figure 6). These hybrid filters reduce harmonic-current content to approximately 7 percent.

The next-most-effective technology is the 18-pulse drive (Figure 7), which typically presents approximately 5-percent current distortion at VFD inputs. Compared with a VFD with no impedance, total harmonic reduction is in the range of 93 percent.

Relatively new technologies are the active harmonic filter (Figure 8) and the active-front-end VFD (Figure 9). A single active filter can filter the harmonics of several VFDs or an entire facility. Meanwhile, the THDI content of a VFD with an active front end — measured at the VFD input — typically is less than 4 percent, while the total-harmonic-current-content reduction is 95 percent.

Table 2 lists the expected current distortion, percent current-distortion reduction, and relative cost of the various harmonic-reduction technologies. The estimates are based on a 1-percent-source-impedance system and a perfectly balanced voltage supply.

All hardware-based, “brute-force” methods of harmonic reduction are affected negatively by input-power-system voltage imbalances. Most VFD manufacturers have computer programs that can be used to estimate harmonic distortion from VFDs.

The greater the base load on a substation transformer, the lesser the current distortion at a PCC. Because harmonic-current distortion causes additional transformer heating, utilities often oversize substation transformers relative to the loading expected from a facility. As a result, having the correct maximum transformer load (estimated or measured) is vital. Otherwise, maximum transformer IL must be assumed.

THE DIRTY LITTLE SECRET

Most harmonic-analysis programs assume available power is a balanced voltage — for example, 480 v each on Phase A, Phase B, and Phase C. In the real world, however, no matter how well-designed a building distribution system is, perfect balance is unobtainable. The best one can hope for is a slight imbalance, such as 478:480:482 v. Most utilities allow power-voltage imbalances of up to 3 percent.

Many years ago, at a large university in the Midwest, the VFDs provided in an energy-saving retrofit project were being blamed for buildings exceeding the distortion levels recommended in ANSI/IEEE Standard 519. Harmonic analysis showed substantial third-harmonic content. In a perfect world, VFDs do not create third harmonics, as third and other triplen harmonics cancel because of the three-phase nature of VFDs. If, however, the voltage relationship between phases A, B, and C is unbalanced, cancelation cannot occur completely, and VFDs can create triplen harmonics. In this case, Phase A was approximately 450 v, while phases B and C were close to 480 v. The university was asked to move loads to get the input voltage to a more balanced condition. Once that was done, the VFDs stopped causing elevated levels of harmonic distortion.

During the mid-1990s, the Power Electronics Applications Center, a subsidiary of the Electric Power Research Institute, tested the drives of 17 manufacturers.1 A 0.2-percent voltage imbalance at the input lugs of a VFD with no input line reactor or DC-bus choke was found to cause up to a 17-percent current imbalance.

With an unbalanced input-power system, all hardware-based harmonic-mitigation technologies are subject to detrimental harmonic-cancelation effects. For example, a 12-pulse phase-shifting transformer has three input leads and six output leads and two components: a delta/delta winding set and a delta-wye winding set (Figure 10). This configuration causes a 30-degree electrical-phase shift in the power being fed into one of the drive’s two diode bridges, causing, in a perfect world, fifth and seventh harmonics to be canceled. If input power is unbalanced, however, cancelation will not occur completely.

Some VFD manufacturers supply 18-pulse drives with an additional 5-percent impedance reactor in front of the auto transformer. This helps balance the current draw into the auto transformer’s three sets of windings and helps to minimize the effects of unbalanced voltage and source feeds.

SO IT IS NOT A PERFECT WORLD — WHAT NOW?

The most effective means of obtaining ultralow harmonics at VFD inputs is an active filter or an active front end. An active filter works like an active noise-reduction headset. If, for example, it detects a 30-amp fifth harmonic in Phase A of a power supply, it injects 30-amp fifth harmonic 180 degrees out of phase with the VFD-created harmonic, creating a cancelation effect. This technology is less susceptible to incoming-voltage imbalances because it measures and injects corrective harmonic content automatically.

A few manufacturers make ultralow-harmonic VFD technologies. An ultralow-harmonic VFD has six insulated-gate bipolar transistors (IGBTs), rather than passive diode-bridge components, in its convertor section (Figure 11). These IGBTs control the harmonic current drawn by a VFD. With no harmonic current drawn, no cancelation is required. Ultralow-harmonic technology typically reduces input harmonic currents to 4 percent or less at a VFD input (Table 2).

In one test, a 3-percent voltage imbalance on the input of an 18-pulse transformer/drive caused a 1.5-percent-per-unit increase in current distortion. Thus, if the computer harmonic-analysis estimate had been 4 percent, actual THDI would have been 5.5 percent.

With an ultralow-harmonic or active-filter system, a 3-percent voltage imbalance increases harmonic-current distortion by less than 0.5 percent per unit.

CONCLUSION

A harmonic analysis should be performed before a design is finalized. The analysis should be conducted at the PCC to determine current distortion at the main utility service entrance to a building. Hardware-based specifications dictating that any drives over a certain horsepower shall be a certain technology should not be utilized.

REFERENCE

1) Mansoor, A., Phipps, K., & Ferro, R. (1996). System compatibility research: Five horsepower pwm adjustable-speed drives. Knoxville, TN: Power Electronics Applications Center.

For past HPAC Engineering feature articles, visit www.hpac.com.

The manager of HVAC applications for ABB Inc. Power & Control Sales, Michael R. Olson has extensive experience in the HVAC, water/wastewater-treatment, and chemical industries. He has written numerous trade-journal articles discussing the application of adjustable-speed drives and been a contributing editor to several books on the subject. He has a bachelor’s degree in electrical engineering from the University of Illinois and a master’s degree in engineering management from the Milwaukee School of Engineering. He is a member of the American Society of Heating, Refrigerating and Air-Conditioning Engineers and BACnet International. He can be contacted at mike.olson@us.abb.com.

Electric Power Quality and Lighting (part 2)

Posted May 29 2012 by Sufi Shah Hamid Jalali in Energy Efficiency, Lighting on Electrical Engineering Portal

Original Source: Wolsey, Robert, Power Quality, Volume 2, Number 2, February 1995 (Lighting Research Center (LRC) and Power Quality),

What is power factor?

Power factor is a measure of how effectively a device converts input current and voltage into useful electric power. Mathematically it is defined as follows:power-factor-triangle-explained

Power factor triangle

power-factor-formula

 

 

Where P is active power and S is the apparent power.

It is often confused with: Continue reading

Electric Power Quality and Lighting (part 1)

Posted May 26 2012 by Sufi Shah Hamid Jalali in Energy Efficiency, Lighting with 2 Comments
on Electrical Engineering Portal
Original Source: Wolsey, Robert, Power Quality, Volume 2, Number 2, February 1995 (Lighting Research Center (LRC) and Power Quality)

Introduction

Concerns about the effects of lighting products on power distribution systems have focused attention on power quality. Poor power quality can waste energy and the capacity of an electrical system; it can harm both the electrical distribution system and devices operating on the system.

There are many elements in a power system that affects two major parameters; power factor and harmonics. Electric motors, some lighting fixtures, transformers and other inductive and capacitive appliances introduce reactive power to the system, and thus involved in damaging the power factor. These components need reactive power to work.

Nonlinear loads like UPS, computer systems, fluorescent fixtures, CFLs, digital electronics, etc. are distorting current waveforms and introducing harmonics to the power system.

This technical article will help lighting specifiers and consumers better understand power quality, so that they can more confidently select energy-efficient lighting products. Continue reading

Take another look at your drives!

vacon

Source : mepca Engineering

Vacon UK – Using variable speed drives (VSDs) is a great way of saving energy but, if your VSDs are more than five years old, it’s time to take another look at them, says Stephen Takhar, Managing Director of ac variable speed drive expert, Vacon UK.

For the last decade, the technical press has been awash with stories about the energy savings that can be made by fitting VSDs. The stories are true, which is why many companies have already installed VSDs. When engineers in these companies see the VSD energy saving stories, they probably think they’ve been there and done that, but are they justified in sitting back and enjoying the glow of a job well done? That depends on the age of their VSDs. If they’re just a few years old, it’s unlikely that further action is needed. But if the VSDs are over five years old, it’s a different story. Continue reading

Guidelines for producing Power Quality case studies for the web

Here are some guidelines to produce an informative Power Quality case studies that will help to sell your skills or mitigating solutions. These sections should be covered:

  • Introduction – The problem statement and the consequences
  • Analysis – what are the steps taken to analyze the problem
  • Solution – what solution has been chosen to mitigate the problem
  • Conclusion – show how effective is the solution Continue reading

International Frequency and Voltage Levels

 

Country Frequency (Hz) and tolerance (%) Household voltage (V) Commercial voltage   (V) Industrialv oltage(V) Voltage tolerance(%)
Albania 50 + 0.5 220/380 220/380 220/380 • 6 kV – 10 kV +5
Algeria 50 ±1 220 380/220 380/220 • 30 kV (rural)10 kV (urban) ±10
Andorra 50 +1 230400 230400 230 • 400 +6/-10
Angola 50 ±5 380/220 • 220 380/220 400/231 ±10
Antigua and Barbuda 60 400/230 • 120/208 400/230 • 120/208
Argentina 50 ±2 220 380/220220 380/220 ±8
Armenia 50 ±0.4 380/220 • 220 380/220 • 220 • 110 kV35 kV/6 kV •10 kV 380/220 • 220 • 110 kV35 kV/6 kV • 10000 kV ±5
Australia 50 ±0.1 400/230 400/230 400/230 +10/-6
Austria 50 ±1 230 400/230 400/230 ±10(400/230)
Azerbaijan 50 ±0.4 380/220 • 220 380/220220 380/220 ±5
Barhain 50 ±2 415/240 • 240400/230 415/240 • 240400/230 11 kV • 415/240240 • 400/230 ±6
Bangladesh 50 ±2 400/230 400/230 11 kV • 400/230 ±10
Belarus 50 ±0.8 380/220 • 220220/127 • 127 380/220 • 220 380/220 Normally ±5Maxi 10
Belgium 50 ±3 230 • 400/230 230 • 400/230 From 3 to 15.5 kV +6/-10
Benin 50 ±5 220 220 to 380 15 kV/380V ±10
Bolivia 50 ±5 230 400/230 • 230 400/230 +5/-10
Bosnia Herzergovina 50±0.2 380/220 • 220 380/220 • 220 10 kV • 6.6 kV380/220 ±8±5
Brazil 60 220/127 380/220 • 220-127 380/220 • 440/254 +5/-7.5
Bulgaria 50 ±0.1 220/230 220/230 380 ±10
Burkina faso 50 ±10 230 400 400 ±10
Burundi 50 ±1 380/220 400/230 400/230 • 66 kV/400-23010 kV/400-23030 kV/400-230 ±10
Cambodia 50 ±0.5 220 380/220 380/220 ±5
Cameroun 50 ±1 220-260 260-220 380/220 +5/-10
Canada 60 ±2 240/120240 347/600 • 416/240208/120 • 600 46 kV • 34.5 kV/20 kV24.94 kV/14.4 kV 13.8 kV/8 kV12.47 kV/7.2 kV

4.16 kV/2.4 kV • 600/347

+4/-8.3
Canary island 50 ±5 220 220/380 380/220 ±5
Cape Verde 50 220 220/380 380/400 • 20 kV • 6 kV15 kV • 13 kV • 10 kV ±5
Central African Republic 50 ±4 220/380 15 kV • 220/380 15 kV • 220/380 ±10
Chad 50 ±1 220 220 380/220 Not available
Chile 50 ±0.2 220 380 13.8 kV • 13.2 kV12 kV • 440 • 380 ±3.5
China 50 ±0.2 220 380220 380220 ±7+7/-10
Colombia 60 ±0.2 240/120 • 208/120 240/120 • 208/120 44 kV • 34.5 kV • 13.8 kV(11.4 kV Bogota only) +5/-10
Congo (Democratic Republic) 50 220/240 380/220 380/220 • 6.6 kV20 kV • 30 kV ±10
Costa Rica 60 240/120 240/120 • 208/120 240/120 • 208/120400/277 ±5
Cote d’Ivorie 50 ±2 230/400 15 kV • 19 kV • 43 kV 15 kV • 19 kV • 43 kV +6/-10
Crotia 50 400/230 • 230 400/230 • 230 400/230 ±10
Cuba 60 ±1 115/230 230/400 230/400 ±10
Cyprus 50 ±2.5 230/400 230/400 22/11 kV • 230/440 ±10
Czech republic 50 ±1 230/400 230/400 • 500690 400 kV • 220 kV • 110 kV35 kV • 22 kV • 10 kV6 kV • 3 kV +6/-10
Denmark 50 ±1 400/230 400/230 400/230 +6/-10
Djibouti 50 220 400/230 400/230 • 20 kV ±10
Dominican republic 60 240 240/120 7.2 kV • 480 • 220/110208 • 115 ±3
Ecuador 60 ±1 110 110 440/220 ±5
Egypt 50 ±0.5 380/220 • 220 380/220 • 220 132 kV • 66 kV • 33 kV20 kV • 22 kV • 11 kV6.6 kV • 380/220 ±10
Estonia 50 ±1 380/220 • 220 380/220 • 220 380/220 ±10
Ethiopia 50 ±2.5 220 380/230 15 kV • 45 kV • 132 kV230 kV • 380/230 ±10
Fiji 50 ±2 415/240 • 240 415/240 • 240 11 kV • 415/240 ±6
Finland 50 +/0.1 230 • 400 400/230 400/230 • 690/400 • 690/40010 kV • 20 kV • 110 kV +6/-10
France 50 ±1 400/230 • 230 400/230 • 690/400 20 kV • 10 kV • 400/230 +6/-10
French Guiana 50 220 230/ 400 15 kV • 20 kV • 30 kV • 400 Not available
Georgia 50 ±0.5 380/220 380/220 380 • 6 kV • 10 kV ±10
Germany 50 ±0.5 400/230 • 230 400/230 • 230 20 kV • 10 kV • 6 kV690/400 • 400/230 +6/-10
Ghana 50 ±5 240-220 240-220 415-240 ±10
Greece 50 230 230/400 400 +6/-10
Grenada 50 230 400/230 400/230 +4/-8
Guadeloupe 50 and 60 220 380/220 20 kV • 380/220 Not available
Honduras 60 ±3 220/110 480/277 • 240/120 69 kV • 34.5 kV • 13.8 kV480/277 • 240/120 + ou-5
Hong Kong 50 ±2 380/220 380/220 11 kV • 380/220 ±6
Hungary 50 ±1 230/400 230/440 230/400 ±10
Iceland 50 ±0.1 230 400/230 400/230 +6/-10
India 50 ±3 440 • 230 400 • 230 11 kV • 440/250 ±10
Indonesia 50 220 • 220/380 220/380 150 kV • 70 kV • 20 kV ±5
Iran 50 ±5 220 380/220 20 kV • 400/230 • 380/220 ±5
Iraq 50 220 380/220 11 kV • 6.6 kV3 kV • 380/220 ±5
Ireland 50 ±2 230 400/230 10 kV • 20 kV • 38 kV110 kV • 400/230 +6/-10
Israel 50 +0.5/-0.6 400/230 400/230 For above 630 kVA:12.6 kV/22 kV/33 kV/110 kV/161 kV ±10
Italy 50 ±2 400/230 • 230 400/230 20 kV • 15 kV10 kV • 400/230 ±10
Japan 50 (east) / 60 (west) 200/100 200/100(up to 50 kW) 140 kV • 60 kV • 20 kV6 kV • 200/100 ±6V(101V)±20V(202V)6-140 kV
Jordan 50 230 400/230 415/240 • 3.3 • 6.6 • 11 kV ±7
Kenya 50 ±2.5 240 415/240 415/240 ±6
Korea republic of south 60 ±0.2 220 ±13 • 110 ±10 380 ±38V • 220 ±13 20.8 kV • 23.8 kV380 ±38V • 380/220 Not available
Kuwait 50 ±4 230 400/230 400/230 +10/-10
Latvia 50 ±0.4 380/220 • 220 380/220 • 220 380/220 +10/-15
Lebanon 50 220 380/220 380/220 ±10
Lybian 50 ±1 220 220/380 38011 kV ±10
Lithuania 50 ±1 400/230 400/230 400/230 ±10
Luxembourg 50 ±0.0 400/230 400/230 65 kV • 20 kV +6/-10
Macedonia 50 380/220 • 220 380/220 • 220 10 kV • 6.6 kV • 380/220 Not available
Madagascar 50 ±2 220/110 • 380/220 220/110 • 380/220 63 kV • 35 kV • 30 kV20 kV • 15 kV5.5 kV • 380/220 Low voltage: ±7Hight voltage: ±5
Malaysia 50 ±1 240415/240 415/240 415/240 +5/-10
Mali 50 220380/220 220 • 380/220 Not available Not available
Malta 50 ±2 230 400/230 11 kV • 400/230 +10/-6
Martinique 50 230 230/400V • 230 230/400 • 20 kV -10/+6
Mauritania 50 380/220 380/220 15 kV • 380/220 ±10
Mauritius 50 ±1 230 400/230 400/230 ±6
Mexico 60 ±0.2 220/127 • 220 • 120 220/127 • 220 • 120 13.8 kV • 13.2 kV480/277 • 220/127 ±10
Morocco 50 ±5 380/220 380/220 225 kV • 150 kV60 kV • 22 kV ±10
Netherlands 50 ±10 400/230 • 230 400/230 25 kV • 20 kV • 12 kV10 kV • 230/400 ±10
New Zealand 50 ±1.5 400/230 • 230 400/230 • 230 11 kV • 400/230 ±6
Nigeria 50 ±1 230 • 220 400/230 • 380/220 15 kV • 11 kV400/230 • 380/220 ±5
Norway 50 ±1 400/230 400/230 400/230 • 690 ±10
Pakistan 50 230 400/230 • 230 400/230 ±5
Paraguay 50 ±5 220 380/220 • 220 22 kV • 380/220 ±5
Peru 60 ±6 220 220 20 kV • 10 kV • 220 ±5
Poland 50 +0.2/-0.550 +0.4/-1 230 400/230 1 kV • 690/400400/230 • 6.3 kV +6/-10
Portugal 50 ±1 400/230 • 230 60 kV • 30 kV • 15 kV10 kV • 400/230 • 230 60 kV • 30 kV • 15 kV10 kV • 400/230 • 230 60 ±10
Qatar 50 ±1 240 415/240 33 kV • 66 kV • 132 kV ±5
Romania 50 ±0.5 230 440/230 660/380400/230 ±10
Russia 50 ±0.2 380/220 • 220 660/380/220380/220/127 660/380/220380/220/127 +10/-20
Rwanda 50 ±1 220 380/220 15 kV • 6.6 kV • 380/220 ±5
Saudi Arabia 60 ±0.3 220/127 220/127 13.8 kV • 380/220 ±5
Senegal 50 ±5 220 380/220 • 220/127 90 kV • 30 kV • 6.6 kV ±10
Serbia 50 230/400230 230/440230 10 kV • 6.6 kV • 230/400 ±10
Singapore 50 ±1 400/230 • 230 400/230 22 kV • 6.6 kV • 400/230 ±6
Slovakia 50 ±0.5 230/030 230/400 230/400 ±10
Slovenia 50 ±0.1 230/400 230/400 35 kV • 20 kV • 10 kV • 6 kV3.3 kV • 1000V • 660V500V • 400/230 +6/-10 for 400/230
Somalia 50 230 • 220 • 110 440/220 • 220/110230 440/220 • 220/110 ±10
South Africa 50 ±2.5 433/250 • 400/230380/220 • 220 11 kV • 6.6 kV • 3.3 kV433/250 • 400/230380/220 11 kV • 6.6 kV • 3.3 kV500 • 380/220 ±10
Spain 50 ±0.5 380/220 • 220220/127 • 127 380/220 • 220/127 25 kV • 20 kV • 15 kV11 kV • 10 kV • 6 kV3 kV • 380/220 ±7
Sudan 50 240 415/240 • 240 415/240 Not available
Sweden 50 ±0.5 400/230 • 230 400/230 • 230 6 kV • 10 kV • 20 kV400/230 +6/-10
Switzerland 50 ±2 400/230 400/230 20 kV • 16 kV • 10 kV • 3 kV1 kV • 690/400 • 950/400 ±10
Syrian Arab Republic 50 380/220 • 220 380/220 • 220220/115 380/220 ±5
Thailand 50 ±5 220 380/220220 380/220 Not available
Tunisia 50 ±2 380/220 • 231/400242/420 380/220 • 231/400242/420 30 kV • 15 kV • 10 kV ±10
Turkey 50 ±1 380/220 380/220 36 kV • 15 kV6.3 kV • 380/220 ±10
Ukraine 50 +0.2/-0.4 380/220 • 220 380/220 • 220 380/220220 +5/-10
United Arab Emirates(ADWEA) 50 ±0.5 415/240 415/240 11 kV • 415/240 ±5
United Arab Emirates(DEWA) 50 ±1 380/220 380/220 11 kV • 6.6 kV • 380/220 ±3
United Arab Emirates(SEWA) 50 ±1 415/240 415/240 11 kV • 6.6 kV • 415/240 ±5
United Arab Emirates(FEWA) 50±1 415/240 415/240 11 kV • 415/240 ±5
United KingdomExcluding Northern Ireland 50±1 230 400/230 22 kV • 11 kV • 6.6 kV3.3 kV • 400/230 +10/-6
UK Northern Ireland 50±0.4 230 • 220 400/230 • 380/220 400/230 • 380/220 ±6
(USA) North Carolina 60 ±0.06 240/120 • 208/120 ±10%240 • 480/277460/265 • 240/120

208/120

±10%24 kV • 14.4 kV • 7.2 kV2.4 kV • 575 • 460 • 240

460/265 • 240/120 • 208/120

+5/-2.5
(USA) Michigan 60 ±0.2 240/120 • 208/120 480 • 240/120208/120 13.2 kV • 4.8 kV • 4.16 kV480 • 240/120 • 208/120 +4/-6.6
(USA) California 60 ±0.2 240/120 4.8 kV • 240/120 4.8 kV • 240/120 ±5
(USA) Miami 60 ±0.3 240/120 • 208/120 240/120 • 208/120 13.2 kV • 2.4 kV480/277 • 240/120 ±5
(USA) New York 60 240/120 • 208/120 240/120 • 208/120240 27.6 kV • 13.8 kV • 12.47 kV4.16 kV • 480/277 • 480 Not available
(USA) Pittsburgh 60 ±0.3 240/120 460/265 • 240/120208/120 • 460 • 230 13.2 kV • 11.5 kV • 2.4 kV460/265 • 208/120460 • 230 ±5 (ligthning)±10 (power)
(USA) Portland 60 240/120 480/277 • 240/120208/120 • 480 • 240 19.9 kV • 12 kV • 7.2 kV2.4 kV • 480/277208/120 • 480 • 240 Not available
(USA) San Francisco 60 ±0.08 240/120 • 208/120 480/277 • 240/120 20.8 kV • 12 kV • 4.16 kV480 • 480/277 • 240/120 ±5
(USA) Ohio 60 ±0.08 240/120 • 208/120 480/277 • 240/120208/120 12.47 kV • 7.2 kV • 4.8 kV4.16 kV • 480480/277 • 208/120 ±5
Uruguay 50 ±1 220 220 • 3×220/380 15 kV • 6 kV • 2203×220/380 ±6
Venezuela 60 120 480/277 • 208/120 13.8 kV • 12.47 kV4.8 kV • 2.4 kV Not available
Vietnam 50 ±0.1 220 380/220 500 kV • 220 kV • 110 kV35 kV • 22 kV • 15 kV10 kV • 6 kV • 3 kV

Source : W orld Headquarters and International Department 87045 Limoges Cedex - France

Harmonic Mitigation Techniques Applied to Power Distribution Networks

Source: Advances in Power Electronics
Volume 2013 (2013), Article ID 591680, 10 pages
http://dx.doi.org/10.1155/2013/591680

Faculty of Engineering, Sohar University, P.O. Box 44, 311 Sohar, Oman

Academic Editor: Hadi Y. Kanaan

Abstract

A growing number of harmonic mitigation techniques are now available including active and passive methods, and the selection of the best-suited technique for a particular case can be a complicated decision-making process. The performance of some of these techniques is largely dependent on system conditions, while others require extensive system analysis to prevent resonance problems and capacitor failure. A classification of the various available harmonic mitigation techniques is presented in this paper aimed at presenting a review of harmonic mitigation methods to researchers, designers, and engineers dealing with power distribution systems. Continue reading