Dear Sir,

I am working in 3 MW power plant for capital use (Exporting to our Chemical division). presently we have not any capacitor bank for power plant auxiliaries and we are maintaining pf 0.85 lag. Is there any losses for operation with less pf..?

reg,
Javali

 

Javali,

There are more losses associated with operating at a reduced power factor. You also need to be cognizant of the generator's capability curve, sometimes called D-curve, or reactive capability curve. Your generator nameplate may provide more information--the VA rating is usually expressed at some power factor, but most generators are slightly over-rated for the prime mover (turbine). But by far the best reference is the generator manufacturer's capability curve which should always be readily available to any power plant operator.

Reducing the power factor in the lagging direction requires increased excitation current which increases the heating of the generator rotor windings. This additional heat must be removed to prevent damage to the generator rotor winding insulation and this is generally the limiting factor for reduced power factor operation.

Finally, the power for the excitation current has to come from somewhere--for many smaller generators the exciter is "brushless" which means some of the torque being applied to the generator by the prime mover is used to produce the exciter current--which means less torque is available for real power (watts). Use your preferred World Wide Web search engine to research "power triangle " for more information.

But do use the capability curve provided by the generator manufacturer to be certain you are operating your generator within its design guidelines to avoid damage when operating at reduced power factor (lagging or leading).

 

Sir, Thank you for your valuable replay.

Our generator output is 3750 KVA with 0.8 Pf as per name plate. Presently our generator is isolated with grid, and generator running with 0.95 pf lagging (As per pf meter in AVR panel) with help of capacitor bank which was installed in our chemical plant. I cannot understanding that after switched on the capacitor bank in downstream (in Chemical Plant) how pf was increased for generator from 0.8 to 0.95 lag. And the power factor for power plant downstream (Aux load) is remain same i.e. 0.85 lag. How we can increase pf in power plant aux load from 0.85 to 0.95 lag without any additional capacitor panel?

Please explain briefly.

Reg,
Javali

 

Javali,

Please have a re-read of both of your posts--there are some serious contradictions, as well as some difficult-to-understand statements. It's likely that English is not your first language and that accounts for some of the inconsistencies and choice of words. However, this is a technical forum (and, admittedly, I do make more than my share of punctuation and typographical errors) and it's very important that you be as precise as possible for the best answer.

As for answering your queries, as I know, increased reactive current has an effect on efficiency--that's what power factor measures: the amount of real power versus the total power (real power component plus reactive power component). I can always learn a thing or two, and am keen to do so; so I'll let someone else take a swing at providing a better answer.