Power Factor Improvement

Can your prime mover deliver the required power at 0.95pf?.

In some cases, improving PF can keep you from "bumping up" against the kva rating of the generator. This may allow you to use extra kw capacity from the prime mover.

However, in your case, you seem to be exceeding the kw capacity already. I don't see how further PF correction can help.

[This just rephrases or supplements pnaban's GA (or GQ).]

I have put it Off topic but why the other two added up I wonder _{when all the following posts have repeated the statement of para 1}.

The second para was of course not On Topic, i was interested since the google search had shown the TGs of 135MW in the OP's zone. In fact 100MW turbines are not that common around it is usually 110MW or 120MW.

Hello..Greetings.. I am from Pune and would like to help you get answer and solution to your query. Please send me more details at . I can also be reached at . I am based in Pune,Maharashtra. If you provide me your contact details, I can also connect to get more details from you. I will then forward them to a company in UK which is world known for the PF improvement technique and products. Kindly send the details. Regards... SANJAY JAGTAP

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OK I WILL BT HOW?

Your first paragraph is okay, but not the second. The load characteristic can be changed by putting capacitors in parallel with it.

Leading or lagging reactive power can and is provided by another generator. That gets close to optimum, resistive power at the generator's site. Does not improve the transmission or the user. A capacitor bank at the user's end brings the load closer to resistive, improving the situation overall.

It depends, who is willing, or capable of controlling the nonresistive power causing circulating, unsaleable reactive currents.

Your plant is currently "rated" at 100 MW because 0.8 pf is the industry "standard" for generators.

As you have already seen, increasing your pf "slightly" will allow higher output.

The key is what is being "controlled"- IF your plant is "in-house" and only supplying YOUR equipment, then- by adding the appropriately-sized capacitor banks- typically including controls to switch parts of the bank ON or OFF as required to maintain the desired pf "visible" to the generator system- just past the generator input to your distribution switchgear will allow the generator to "see" the higher pf and perform as it should.

However- an even "better" solution would be to install "approximately" sized fixed capacitors at the power input to each MAJOR motor and fluorescent lighting bank (test them to determine a "reasonable" fixed adjustment and then install the "adjustable" capacitor bank (now MUCH smaller) at the generator input to your primary power distribution plant.

The reason for the fixed capacitors is to minimize the impact of the lower pf on the wiring feeding each of those systems. Generally, electrical code allowable wiring ampacity tables for each insulation type and wire size are based on a 0.8 pf. Lower pf will generate higher wire temperatures due to the higher NET power flow, putting cables at risk of early failure due to thermal breakdown of the insulation. By raising the "local" pf to "near-unity" with the fixed capacitors, you eliminate that "risk" and at the same time seriously offset the size of the primary power supply capacitor bank.

AS AN ADDED VALUE- if you have installed "local" capacitors that might be "too big", all that will happen is that the local system will go into "leading" pf rather than the more-common "lagging". If this happens, it will negate some other minor lagging pf's somewhere else on site, further reducing the required size for the primary capacitor bank.

Get a competent electrical engineer on-site to test your main loads as well as your total site load, then size the capacitors as needed. It is a relatively small investment with HUGE returns.

I am a process engineer. I've learnt a great deal of electrical and other engineering by following Cr4 and a bit of private study. It's great when subjects like Power Factor raise their heads from time to time as it gives non-specialists a time to catch up and it gives specialists a time to reflect. Do keep on reviving well known concepts from time to time. Great also to see rapid responses from a predictable few. On certain subjects one can almost be sure tornado will get in there with a choppy response.

thank you

Sir,first i would like to thank u for ur valuable information.

i m doing training for power plant operation and maintenance. i want to get some clear knowledge regarding this pf at which alternator operate. so far as i know most of the TG are rated for around pf 8.5(lagging). so all the TG operate on lagging pf. if we r generating power for transmission purpose than we need some reactive power to transmit that power to long distance. also since most of the loads are reactive in nature so they also need reactive power. so we will have to generate reactive power as well as active power. By changing the excitation we can control the pf till we don't reach the limit of excitation. Now i would like to ask some question:

1. what would be the effect if i increase the excitation to make pf unity if my TG is connected to grid?

2. why we always go for lagging pf operation?

3. I studied when we change power factor from leading to lagging, by keeping load current excitation and speed unchanged, terminal voltage decreases. It means when power factor is leading armature flux support main flux and we get more emf and in case of lagging power factor it is reverse. Why not we go for leading power factor operation?

4. Is it advisable to operate TG on different pf than rated? (suppose it is rated for .85 lagging but what will be happen if i operate it at .9 lagging).

may be these questions are silly but it would we very help full for me to get some clear concept regarding these things.

thank usir for ur positive response....but sir i have one doubt i.e. how can i calculate the maximum capacity of capacitor to be add in any system.

actualy sir i know that if we added any capacitor in parallel then it will generate reactive power & sypply to system or load & improve pf, & also changes in generator characterstics but how many capacitor?

That is why I recommended that you hire an experienced electrical engineer. This forum is not to be used for providing absolute answers- only guidance.

IF you can measure the pf of each major motor- there are relatively inexpensive testing tools to do this- then you can go to a variety of resources- including the Engineering Toolbar from CR4- to get a reasonable idea of the amount of "local" capacitance you will need for each of those loads.

Do the same with electrical load banks the feed the majority of your fluorescent lighting loads.

Then, measure- or have measured due to the risk related to high energy electrical systems- the resulting power factor of your primary input system. Again- you can get fairly close to selecting the appropriate size of capacitor to get your site's power factor to near unity (100%).

The use of electrical engineers will make this much easier and generate a "final" solution that will allow your 125 MVA generator system to produce nearly 125 MW of power- lowering your operating costs and reducing the CO2 and NOx that your and your generating system are responsible for.

By the way- if you get the site power factor to near-unity, no matter WHAT the power usage is, you will see reduced costs, and reduced environmental releases due to the fact that you are only making the amount of energy you are using, NOT phantom energy that has a cost- economically and environmentally- but no value.

I agree with energygod (GA by the way). It will be a little more expensive, but installing capacitance at the individual loads is more effective overall then a single capacitance ahead of your load system. A single capacitor for the entire load will improve the PF the generating system sees, but it won't help individual PF loads in consuming part of the system. This would mean that things such as motors and florescent lighting will still have their respective PF contributing to power loss and potentially excessive heating of those respective conductors. Uncorrected local PF can also contribute to a shorter life cycle for the equipment itself (due to higher internal heat generated by a lower PF).

Also mentioned by a number of posters here, pushing your PF to 1 (i.e., unity) or higher is not ideal. Posters with more knowledgeable than I have gone into why this is true, so I won't get into the gritty details, but suffice it to say a leading power factor is not efficient and will cause a lot of problems, and you will lose on the generating side. With a leading PF it will cost you more energy to generate the same power out of the generator (if it will work at all). Again, keep in mind your load system will have some loads with a higher PF and some with a lower PF, so even if you got a leading power factor out of the gen set it could screw up some of your equipment on the load side. From what I have seen, best practices suggest a PF of .9 - .95.

yes we can , where are you located?

Sir We have been taking company's with PF s from .35 to .85 we always bring them up to .98, .99 and 1. What we have been able to do is, hold those numbers ( .98 & .99 ) regardless what the load is. Cost is minimal ROI less than 24 months. If you are serious about fixing your problem email us. Regards

Is it economical to correct pf to 0.98 or 0.99,have you done an analysis?.

Yes, we found out that the percentage of power factor correction related directly to the amount of savings on the utility bill.

economical study is not savings in energy bill. It is a comparison of savings with that invested in purchasing,installing,maintaining capacitor banks and interest on capital invested,depreciation etc

Based on an "in-house" generator-

Assuming an AVERAGE load of 1500 kW with a thermal-to-electric efficiency of 35% using natural gas at a relatively "cheap" $8.00 per MMBTU and a "normal" site power factor of 80%, the generator needs to produce 1875 kVA of power, which will cost $1,280,962 a year ((((1875 x 3412 / 0.35) x 8760) / 1,000 000) x 8.00).

Increasing the pf to 95% will reduce the required generator output to 1579 kVA (84.2% of the BASE) so the new cost will be $1,078,570, with total savings of $202,392. Using a 2-year payback scenario, you can spend up to $404,784 on this installation- should NOT be a problem.

Bumping the pf to 99% will cut the required generator output to 1515 kVA (96% of the 95% pf value) so the NOW new cost will be $1,035,427 with additional savings of $43,143. Using the same 2-year payback scenario, that means you can spend another $86,286 for the relatively small added capacitance. Since just MORE capacitors are required- you already have the controls, wiring, etc., the extra capacitor capacity should DEFINITELY cost a LOT less than $86,286 so raising the pf to 99% makes economic sense.

The efficiencies are always related to KW (actual power) and not KVA (apparent power)

The conversion of 1500/0.8 Vs 1500/0.95 hence is not valid.

The only difference in the extra KVA are in losses (and associated effects like voltage drops etc)

Anonymous Poster- It is VERY CLEAR why your post was "anonymous". I sure as hell would not want to be linked to such a ridiculous statement.

kVA is ACTUAL POWER produced by the generator.

kW is POWER USED by the system.

POWER FACTOR is, essentially, the relationship between POWER USED and POWER PRODUCED.

At a Unity power factor (100%) ALL of the POWER PRODUCED is POWER USED.

At ANYTHING LESS THAN UNITY, some of the power produced was negated by reactive power created from one or more of the USERS.

WHOEVER OWNS THE GENERATOR PAYS FOR THE POWER PRODUCED. That is why utilities charge commercial and industrial USERS a penalty if their power factor falls below an arbitrary value set by the Utility that it has used in its rate base.

If YOU own the generator and find a way to USE virtually all of the power PRODUCED, then it will COST YOU LESS than if you "waste" some of the power you produced which will be designated by a less than unity power factor. The closer to unity power factor you can get at your generator- the more money you save.

IT REALLY IS THAT SIMPLE !!!!!

You got it basically right the first time in post 27; now you seem to be growing confused.

Fuel consumption is most closely related to kw (actual power); not as closely to kva (apparent power).

Low pf leads to higher current and thus increased I²R losses and heating of conductors, but only to slightly increased fuel consumption.

You shouldn't have self-voted this post as OT; once again you are right.

[Sometimes I miss the satire....]

Cost of increasing kVAr include fuse/cb,contactor as well as enclosure. They say increasing pf beyond 0.8 need more capacitors than that required from 0.6 to 0.8. In your analysis include the actual cost of additional capacitors,contactor,fuse/cb and enclosure.

that is correct. that is a turn key price. Our PMU box has a control has a pcb board that controls the each capacitor`s usage.

i am confused through reading all comments, just i want to know is that possibale in economical way? could u tell me what will be the cost of instalation & what will be saving of cost by using this......also want know that for 125mva generator at 0.8pf lag for (100mw+45mvr) laod what capacity of capacitor will be install to bring pf of generator up to .90 to .95 lag