Leading Power Factor Problem

If you over compensate the PF you will be charged at the same rate as not compensating. Usually between .9 lag or lead will not be penalised.

Plus there is the added factor of the cost of the equipment to over compensate!

The electrical problems are the same ether side PF of 1. But you will make the local power company happy for a leading PF. Normally Lagging PF is produce by most electrical motor and most power company fine you if you are to far from PF of 1 and some will reduce you bill for a leading PF!

William Benson

I have never seen a utility that will reduce your tariffs for presenting a leading pf. As I said, my experience is that they fine you equally either way, leading or lagging. If your plant supplys kVARs into a grid that does not need them, it starts to affect your neighbors, who will blame the utility, not you.

Many yeas ago when I was In South Caroline we ran large Synchro motors and found out if lift them on we would generate a leading power PF. With about 75% of grid load is non-synchro motors causing Lagging PF which power company had to add very expenses CAPS to compensate. They were very happy to see us with the Leading PF!

Did they give you any money back?

Or did they play both ends against the middle, charging for both leading and lagging PF, even though the two cancel out?

Leading power factor operation results in increased heating in areas of the generator stator (leading power factor operation requires reduced excitation power to the generator rotor, so heating of the rotor because of current flowing in the rotor isn't so much of a problem)..

http://www.cumminspower.com/www/literature/technicalpapers/PT-6001-ImpactofPowerFactorLoads-en.pdf

http://www.chloridepower.com/Documents/Protected-downloads/White-papers/English-US/Leading-power-factor-loads.pdf

http://cliffordpower.com/wp/wp-content/uploads/2010/08/CPS_info_sheet_40_PF_relating-to-gensets1.pdf

A system load with a low P.F. will draw more current than a system with a higher P.F.. A system designer considers the following:
• A Low P.F. draws a higher internal current and the excessive heat generated will damage and/or shorten equipment life
• Increased reactive loads can reduce output voltage and damage equipment sensitive to reduced voltage
• Low P.F. requires equipment to be constructed heavier to absorb internal energy requirements
• Low P.F. will result in a more expensive system with equipment able to absorb internal loads and larger load requirements
• A system designer looks to increase P.F. to lower system costs, increase reliability and increase the system's life cycle
• Utilities will charge a higher cost to industrial and commercial clients having a low P.F.

Dear Forum,

We are at load end, we have no control on generating side, as customer i would like to know what are the benefits and dis advantages of leading power factor.

I am from India, will there be any advantages of maintaining leading power factor in terms of power consumption or power bill.

TonyS gave you the answer as best we can, the only possible difference might be related to the penalties imposed by your LOCAL utility. What he is telling you is that from their perspective, you presenting a leading power factor is just as bad as a lagging one. So when they do their determination, they in effect square the kVAR so that the value is always factored as a positive number. Or...Let's try this. You get zero benefit from presenting a leading power factor.

Keep in mind that harmonics too should be controlled in addition to pf as it increases the kwh consumption as well as the heat generated in the equipment

In Simple terms:

Any time your p.f. is different from 1, you are having your kVAH > kWH. The useful power you can convert to mechanical is the kWH.

Therefore, you should try to keep the p.f. as near as possible to 1 since you are billed on the kVAH.

If your installation is having a power factor correction panel with capacitor banks, then the best setting should be to keep the p.f. at ~ 0.95 and not more.

Leading p.f. can create a lot of harmonics which could be damaging to some equipment (Electronics etc...). Therefore, unless your installation is naturally having a leading p.f. without the capacitor banks, try not to get it into leading p.f.

Normally, all installations will be in the lagging p.f. range. Sometimes, an installed p.f. meter could be wrongly installed or damaged for it to show leading values. Please Check the connections of any p.f. correction equipment in relation to the measuring CT. If placed in the wrong place (in the supply lines), you could be reading a wrong p.f.

In pf meters if the pf in each phase is different,what will be the indication?.

It is normal to have different p.f. when the load is not balanced in all its aspect: Inductive, capacitive and resistive.

This will usually happen when the load is mainly between phases and the neutral (Single phase loads). The p.f. control panel (if installed) will usually take care of it as long as the difference is not too big. You must balance the loads as much as possible in medium to big installations.

Instead of having a single ammeter/voltmeter with selector switch,3 ammeters, 3 voltmeters and 3 pf meters would be more useful to see at one glance which phase has low pf/voltage or high current.

LAA Lucke - "Leading p.f. can create a lot of harmonics" . . . tell us more ? ? ?

Why? are doubting this fact?

In any case, if you are correcting a p.f. without properly investigating your installation in depth, you might endup with an increase in harmonics.

For the leading p.f., please consult some educative references or your old books. I am not a teacher here (unless I so wish with my time).

with all respect.

LAA Lucke - with due respect to you, Sir . . i submit . . .

(1) i don't doubt without reason . . . and i doubt everything . . . doubting leads to closer examination and expansion of knowledge . . .

(2) "facts" are many . . . many "facts" get replaced by new "facts" as human knowledge increases . . .

(3) the question if increase in harmonics by insufficient examination of the case before applying pf correction is substantial reason to substantiate (1) and (2) above . . .

(4) even lagging pf can in cases lead to harmonic generation . . . so why single out leading pf in a presumptive and incomplete / hanging statement?

(5) i believe that one of the most common reasons for generation of harmonics is unbalance of either voltage or load (current is a consequence of the two) . . . any unbalance creates "shifted zero" in a neutral (or a non-equilateral delta) resulting in a negative sequence component . . . this phenomenon does not have anything to do with absence or presence pf correction as a cause . . if i am missing a "fact" then i will appreciate help to know more . . .

(6) i do not believe that a question on CR4 has ever surfaced for which the answer may not be available in some educative reference books . . . the essence of any internet based discussion board is to focus an on-line discussion towards the sharing of knowledge . . . which incidentally also helps the grow the knowledge . . . however if you do not have the time (or inclination) to share, then your position is definitely worthy of respect, Sir!

i sincerely hope that this six pointer explains that there was absolutely no intent to doubt your knowledge, experience or intention . . . only intended to bring back focus on the directness of the basic question and also help the original poster to not get into what can be side issues for his particular concern . . . .

To soebfatehi -

It is a pleasure to read your input. I also was wondering what specific reason(s) were present for LAA Lucke to single out problems with harmonics as characteristic of a leading power factor. Are there known specific negative harmonic interactions that present themselves in significant number in power systems connected to leading power factor users, or is this a general theoretical supposition? If so, what are they? I am currently disposing of many old textbooks, so I may have already disposed of the hard copy answer - there does seem to be an understandable prejudice for nearly balanced with slight lag - isn't that what mostly is out there?

Thank you for your reply.

The subject is very complex as it is allways with harmonics related situations. In fact, the p.f. by itself in a nice clean environment will not cause harmonics. It is the presence of harminics generated by electronic switching devices and, as the op seem to have, single phase loading and unbalanced loading...that will be exacerbated by overcorrection to leading p.f.

google search "leading power factor and harmonics" and download the pdf file [PDF]

[PDF]

- 1 - HARMONICS AND HOW THEY RELATE TO POWER FACTOR ...

citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.130.3182...

or even this:

http://www.reo.co.uk/files/power_factor_correction_engl_02-08_1.pdf

you might even find better articles and will realise the complexity.(i suspect that you might have an insight already...)

thanks you for suspecting right!

so having concluded that pf is not the root cause of harmonics i can safely pray that the original question asker be deconfused back into his state of bewilderment and subsequent enlightenment about whether to lag or to lead . . . was that the question?

The OP is worried and seem to believe that a leading p.f. might be advantageous to reduce his billing (being billed on total KVAh).

In the 1st place, there is no advantage to have a leading p.f. since it might worsen any TDs due to harmonics, while his billing will remain the same for the same p.f. leading or lagging.(Sending reactive power back to the utility will not reverse the billing).

therefore, unless his system is naturally in the leading p.f., he should keep it in the lagging area and avoid worsening his TDs. He is not competent enough to handle the whole system complexity and should consult if in the leading zone.

Thank you LAA Lucke. I have been enlightened.

You may like to get the tariff from your power supplier company for the type of connection you have (commercial, domestic, High Voltage, Low voltage etc.). I have found in India two electric companies impose penalty for power factor below 0.9 (lagging or leading). Even incentive is offered for power factor between 0.95 and unity (again for lagging as well for leading). If you try to maintain power factor on leading side, this means that you are over compensating (assuming that your base load is lagging, which is the case with most of the customers). By over compensating you are increasing the cost of compensation by using more capacitors for the purpose without getting any return for the same. You have not given information about you uncompensated power factor and compensated power values.

same as lagging pf

If you associated with the leading power factor in a power system, then there will be lagging power factor for your average energy consumption based on the energy meter reading.

If Power Factor is leading, the Terminal Voltage will be more than the Induced Voltage. You can verify this by drawing a Vector Diagram. That is the problem for the Operator. The Power Supply Agency will be happy since you are sharing their problem of low power factor and compensate.

DHAYANANDHAN.S

Electricity board installed a new energy Meter secure make premier 300 in our company. Now kvah is increasing very high at no load or at leading P.f. resulting low P.f. 0.25

This problem was never faced in old energy Meter at leading P.f. or no load.

Any solution?

maybe . . the problem was not observed (ie not recorded / measured) when the old energy meter was used . . . . it is best if you point this out to your supply company and request them to investigate as at site . . . . if you share their findings / report here, a more reasonable insight may emerge . .