By Francisco Boshell / Published on Wed, 2007-11-21 18:45
Dear Colleagues,
I’ve heard that introducing massively high efficiency lamps like CFL may produce a quite negative effect on the public grid and power quality due to the reactive power increase, and the dropping of the power factor below 0.8.
I’d like to ask you whether this is correct, and, if so, how to avoid such problems without impacting incentives for the implementation of high efficiency lamps?
Regards,
I would appreciate information on the use of Switch Mode Power Supplies and their effectiveness to ride through voltage sags ›
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Reactive power due to CFL lighting
By Shah Haider / Published on Thu, 2007-11-22 6:46 CFL normally available in the markets have Power factor as low as 50-60%, and High Harmonic distortion. With normal lighting load more than 40%, this is going to have negative impact on distribution system. The Power factor will be lower and Total harmonic distortion will be high. As a result losses will increase and equipment life will also decrease. Again savings in demand of electricity and Utilization of Transformer capacity will not be fully achieved. The mercury content in CFL is a problem unless it is safely desposed. This require special recycling. Many countries have opted for Eco bulbs having Power factor more than 90% and low harmonic distortion. Their mercury content is very low. We should rember there is no alternate to Energy saving lamps, but they should be of good quality.
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Reactive power due to CFL lighting
By Francisco Celaya / Published on Thu, 2007-11-22 11:59
Fco. Celaya Gómez
I supposse you must put in balance the advantages and disadvantages of this type of very efficient lighting. More, as said before, looking for the quality of integrated electronic CFLs could be a solution in power factor improving.
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papers related
By Francisco Boshell / Published on Thu, 2007-11-22 21:24
Dear Shah,
Thanks for your constructive reply. Do you have some literature (paper) to share which discuss the factors that you mentioned?
Francisco Boshell, MSc.
Sustainable Energy Technology
Reply
Dear Francisco,unfortunately
By Stefan Fassbinder / Published on Thu, 2007-11-22 21:55
Dear Francisco,
Unfortunately it is true that CFLs have poor power factors, resulting not from displacement power factor DFP, also addressed as cosφ, but from the harmonic reactive power, also called wattles power in English, which is much worse and represents the harmonic distortion you mention. Now personally I assume that the problem with the CFLs is often exaggerated in the discussion. A few cases have been reported where problems arose (in hotels). But let me tell you one thing: If problems arise then it is not due to the nature of the lamps but due to inadequate electrical installation! At least this is a viewpoint which can – and I think should – be taken upon the problem. So if you have a TN-C or TN-C-S configuration of distribution, then problems are integrated already in the planning phase. You should have a clean TN-S network. Clean means that many of them are not clean, and this again means they have more than one connection between the N conductor and the earthing system. This makes most of the advantages of a TN-S system void.
As for the transformer and the cabling, it should be selected with a considerable reserve, then you won’t get into trouble. But note that CFLs are 4 times more efficient than incandescent light bulbs, so despite the terrible distortion they do cause you get a reduction in TRMS current when you replace accordingly. The load on your lines and your transformer is not any greater, it is reduced. If the transformer still overheats because the harmonics cause (in part extremely) higher losses than the fundamental current, which unfortunately they do, certain filtering techniques will see to that. Normally a fairly cheap passive filter will do the job (see this application note). This is much more cost efficient than integrating mitigation measures in each and every one of the little lamps, which on top of that makes them sensitive to network disturbances or turns them into high frequency disturbers themselves.
Note that also the very popular halogen lamps are incandescent lamps and their efficiencies are hardly any better than those of ordinary incandescent lamps. Halogen lamps are often addressed as energy saving lamps but this is a pure lie.
Also note that you compare a 75% energy saving in the lighting to an increase of network losses, say, from 2% to 3%, if any at all.
As for literature, I am just writing a detailed article on exactly this topic for a German magazine, to be published in December. When it is out we will have an English translation made and post it here, so please have a few month patience! Regarding the nasty load on transformers, such a translation is presently under commission, but our translator is very busy these days!
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Expecting the article
By Francisco Boshell / Published on Thu, 2007-11-22 23:22
Dear Stefan,
Thanks and I really look forward to read you article as soon as it's published in english.
Please, let me know when it is available.
Best regards,
Francisco Boshell, MSc.
Sustainable Energy Technology
Reply
Effect of CFLs
By Emmanuel Amankwah / Published on Mon, 2008-01-28 9:50
Dear Sir,
My country went into a power crises and in the process replaced some six million incandescent lamps with CFLs.
Could you please help analyse how this exercise will affect the national electricity grid
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Effects of CFL
By Shah Haider / Published on Wed, 2008-02-13 16:47
Apparently there should be saving of 35+ MW considering Diversity factor, Low Power factor CFL etc. Actual savings will depend on quality of CFL, Power factor; Harmonics, Consumer electricity usage pattern etc. Can I know your Country name, Total Peak demand, effects due to change of 6 million incandescent lamps to CFL etc.
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what is meant by CFL
By N.K.Namboothiri / Published on Sat, 2008-03-15 17:06
what is meant by CFL Harmonics?
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CFL = Compact Fluorescent
By Hans De Keulenaer / Published on Sun, 2008-03-16 12:19
CFL = Compact Fluorescent Light Bulb (or Lamp)
CFL harmonics refers to the harmonic currents generated by such lamps, as described in application note 3.1 of our power quality application guide:
www.leonardo-energy.org/drupal/apguide
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Chasing the elusive power factor
By nicoduka / Published on Mon, 2008-04-07 20:40
Source:
http://www.homepower.com/article/?file=HP96_pg128_Letters_1
I’m writing to defend Carol Montheim (HP92, page 48), who had it exactly right until the powerfactor nitpickers descended upon her with such a clatter that she was forced to recant half of her evidence for the virtue of compact fluorescent lightbulbs (CFLs).
The nitpickers were right to say that power companies supply power in volt-amperes (VA). And they were right to say that most CFLs have a power factor rating of about 0.5, which means that a 25 watt CFL takes 50 VA to run (25 watts divided by 0.5). But it is not true that utilities must therefore burn twice as much coal or cook twice as many atoms in order to supply twice as much energy to run Carol’s CFLs. Power factor does not affect the energy consumption of homes either on or off the grid.
Volt-amperes are a measure of apparent power (as in false and tricky). Watts are a measure of true power (as in honest and upright, like Carol). When AC power hits reactive loads like CFLs or TVs or air conditioners or surge protectors or computers, electrical current and voltage tend to get jostled out of phase with each other, causing voltamperes (sneaky false power) to rise above watts (foursquare honest power).
So our reactive 25 watt CFL still uses an honest 25 watts, even though amps and volts go out of phase and the sneaky VA rise to 50, making energy consumption appear to double. The extra 25 volt-amperes is not lost or consumed, just stored or borrowed. It goes to work somewhere else. It may offset the power factor of another appliance or it may go back out to the utility line where industrial capacitors tweak it back into phase. Utility meters may not read the extra volt-amperes that CFLs suck into the house, but neither do they read the extra voltamperes that blow back into the grid from Carol’s house. Everything gets canceled out, and the only thing actually consumed is the 25 watts.
Inductors (which cause current to lag voltage) and capacitors (which cause current to lead voltage) store or borrow volt-amperes that are not consumed as watts. They return those unused volt-amperes to the circuit later. For example, pure inductance does not consume energy; it stores it as a magnetic field. When that magnetic field collapses, the energy is returned to the circuit.
Utilities like the power factor of loads to be close to 1.0 (unity) because that makes it cheapest to distribute energy. These companies constantly adjust loads to bring current and voltage back into phase without using significant extra power. Commercial fluorescent lights usually have power factors of 0.9 or higher. Utilities lobbied to get residential CFLs to have similar power factors, but bulb manufacturers revolted because high power factor bulbs are more expensive to make. But the issue was power management, not energy consumption.
To prove this point, I set up an experiment with CFLs vs. incandescent lights (resistive loads with a power factor of 1.0), and measured watts and volt-amperes delivered by my inverter. Then I measured the amps from my power source, a bank of L-16 batteries, which are DC sources wise to the tricks of reactive power.
A 75 watt incandescent bulb measured 70 watts and 70 volt-amperes out of the inverter, which is what you would expect with a power factor of 1.0. The TriMetric meter measuring true power from the batteries measured 71.8 watts (volts times amps). The slightly higher wattage was due to inefficiency in converting 12 volt DC to 120 volt AC.
Then I lit a 25 watt CFL. It measured 25 watts and 52 volt-amperes out of the inverter, which indicated a power factor of about 0.5. The TriMetric, however, showed the true power needed by the batteries was 26.5 watts. The low power factor did not require the batteries (or the utility) to produce any extra energy.
This is not to say that volt-amperes are not important. Household wiring must be sized for the highest volt-ampere load it will carry, not for the highest watt load. Inverters, too, must be able to handle the highest volt-ampere load thrown at them, not the highest watt load.
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I disagree with some of your
By Nathan Campbell / Published on Wed, 2008-05-14 8:24
I disagree with some of your comments. The power station supplies VA from the generators, thus once the VA limit of the generators is reached, they can supply no more. Transformers are rated in VA, thus no matter what the load they can only go to their VA limit. Lines are a fixed size, they have a current limit, higher VA = more current= i^2r losses. If voltage inside the house stays constant eg 240 V, then if you have a higher VA this equals a higher current draw.
So if I have a 20W incandescent (PF 1)= 20VA and 20W CFL (PF 0.5) = 40VA. Wouldn't it be reasonable to say that i would need double the generation capacity, double the transformer capacity, larger conductor size. Especially when looking from the power companies point of view a lot more capacity is required. This does not take into account that a 20W CFL is as bright as a 100W incandescent.
However if these are used in large numbers they will degrade the power factor and correction will be required. This correction equipment doesn't grow on trees for the power company - it costs lots of money, capacitors, inductors etc. If low power factor CFLs stay around I'm sure we will be seeing the costs in rising electricity prices.
This also does not take into account the terrible harmonics created by CFLs.
So in summary if we have a better power factor this will reduce loads on the system and PFC costs.
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CFL's
By juliotamu / Published on Fri, 2009-03-13 12:43
Fortunately they are starting to make high PF CFL's.
I've had permanent metering equipment in my house (with 16 power channels for the various circuits) for the last ten years. I've retrofitted magnetic ballast CFL's with a 5uf capacitor (capacitor required depends on the wattage and Volt Amps) which correct the power factor to near 1 from 0.5 (Lights of America w 22w lamp and GE biax design). Haven't been able to do the same with electronic ballasted models (typically reduces the power factor from 0.45 to 0.3). Seems to work great. All other lighting uses T8 fluorescent lamps with electronic ballasts and electronic ballasts with the power factor near 1. In one case using an older magnetic ballast (not a CFL) I've documented an actual wattage reduction by adding a capacitor however can't claim the same with compact fluorescents (reduces VA while improving PF while wattage is same). I've also applied correction capacitors to the refrigerator, washing machine, and dishwasher using my power meter to determine the appropriate size capacitor (and making sure the main electric panel doesn't see the capacitor except when the motor/compressor is on as overcorrection when there is no load reduces power factor and increases the VA.
In 1995 I retrofitted a Torchierre with 500 watt quartz to a fluorescent lamp prior to the same thing being proclaimed 'invention of the year' by Popular Science magazine and the Department of energy in 1997.
In summary, power factor can be improved either by retrofit or if the manufacturer is required to produce a high power factor product.
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No, power engineers not actually wrong abt. power.
By Steve Nordquist / Published on Tue, 2009-04-14 8:02
No, the extra 25W is not actually borrowed, and a TriMetric used in innocence is not scientific measurement. You may enjoy fun surprise blackouts more than I. The VA thing is something of a ruse; volts x amps = watts, the issue is not the maximum rating (which one wants to stay well under, natch) but that suddenly drawing several amps for 2milliseconds out of 50 is no favor to people trying to power your fishtank light. If everyone got the same Brand C CFL, more consistent than well-designed, and it therefore picked about the same moments to draw, we would would get some flickering incandecents, some blackouts, fires and other damage from burnt out neutrals; (and then things would be fine because coping mechanisms put the remaining well-pruned AC system back into stable operation. Many trucks will be rolling!) So; maybe a power factor around .86 (and not all the same make; though no, they are not (so far) complementary types sharing powerline cultures and love) suggests more like 0 added blackouts. Reactive power (those 26W) is not dissipated at the bulb, which is fine for A/C savings. Since lots of CFLs suck power spikes instead of a constant draw (unfortunately paralleled in automotive MPG by good drivers) line and transformer losses of yes, 26W happen. You pay for about 26W of that. Great solar inverters can just supply the power without any transformer or transmission issues (unless they have big output inductors,) but they too are harder used and more radio noise (EMI) is made, so a price is paid. Power Factor closer to 1 means your CFL ballast has closer to 0 reactive power.
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I disagree as well
By 5-String / Published on Sat, 2009-04-25 18:11
Never underestimate the power of pure math and a trusty old TI-83 Plus graphing calculator. If you work through the math and come up with the actual functions representing the power absorbed by the load (which equals the power supplied by the source, in this case) for each load tested (i.e. the incandescent bulb and the CFL) Here is what you should come up with provided that the bulbs are both rated for the same wattage.
For the CFL:
You will arrive at a cosine function with an average value greater than zero, an amplitude, a frequency equal to twice the frequency of the voltage or current, and a phase shift.
For the Incandescent:
You will arrive at a cosine function with the same average value as with the CFL, an amplitude less than the amplitude with the CFL, the same frequency as with the CFL, and no phase shift.
You can graph the functions to compare.
What all this means:
The true power that was measured with the TriMetric meter is equal to the average value of either of the functions described above. It will be the same for both cases. This is the power you get billed for. You are correct to a certain extent. The power company will have to produce the same average power for either case. However, the company will have to produce a higher peak power for the CFL in order to achieve the same average power (because of the higher amplitude).
What happens to the extra power?
The extra power is stored in either a magnetic or a electric field or possibly both (depending on whether it's a capacitive reactance or inductive reactance or both). It is later released when the field or fields collapse. What happens after that depends on the circuit. It could be used to offset some other power factor. It could be converted to heat loss in the transformer or wires or whatever."
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