power factor of steam turbine generator

[insinyur02]

good morning,

i am a new graduate working in cogen power plant.

- i want to know, can i increase power factor to 1.0 from the steam turbine generator by increasing voltage from voltage regulator.

- in our plant, power factor is 0.82 from generator.... if i increase voltage from voltage regulator to have power factor to 0.95 , is it possible?, what will happen to the generator and the system?

- why my bos never increase power factor to 0.95, as i know higher PF means reactive power lower and it is good.

please explain.... thank you

 

[ScottyUK]

You can increase the field current to bring the PF to unity, but only if the generator is under-excited. More likely is that the generator is over-excited and the field current would have to reduce to bring the power factor to unity.

Normally you would be correct that higher PF is better, but real world loads such as induction motors consume vars and this requirement for reactive power has to be met from somewhere. Normally the generator is best able to supply reactive power. If the load consumes lagging vars, as an induction motor does, then the system has to supply lagging vars. An over-excited generator is one source of lagging vars.


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If we learn from our mistakes I'm getting a great education!

 

[davidbeach]

And if you don't supply enough reactive power for system stability that is bad.

 

[insinyur02]

okay, we have 7 steam turbines each 100 MWe. only one turbine runs with PF 0.93 while others is 0.82, why they dont like to increase the power factor? what are d possible reasons?

- why increasing voltage generator, can increase power factor?
- what is the best PF for 100 MWe generator, if you say we need VAR?

 

[slavag]

Hi.
It's not clear.
I think "standard" PF is about 0.93-0.96 for the big size of generator.
Why 0.82? don't know, may be it feeding some auluminium plant or loads are request more reactive energy.
More information needed.
What is a plant, utilities or industrial ( for example I've seen in inustrial steam turbines PF=0.73-0.77, used for change common factory PF).
Regards.
Slava

 

[GTstartup]

Could be that you have a requirement to supply a specific power factor to the utility, either by contract or just by request. It could be done with just one turbine or a combination of all. Not all the units need to have the same power factor

Why don't you just ask your boss?

 

[cranky108]

Or could it be that the field voltage effects the GSU primary voltage, and they are trying to keep the primary voltage stable.

It's just better to supply some vars (VArs) from the generator in place of transmission capacitors.

 

[waross]

The system demands VARs for inductive loads. That's a fact of life. A single generator running islanded runs at the same power factor as the system. When you have two or more generators in parallel you can adjust how many VARs each generator supplies but the total VARs will be what the system demands. When you increase the VAR output of one generator the other paralleled generators will drop their VAR production to compensate so that the total VARs remains what the system demands.
If one generator is running at a lower power factor than the other generators, the field current will be less than normal. There may be some problem or weakness in your machine that has led to the decision to run at a lower power factor.

Bill
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"Why not the best?"
Jimmy Carter

 

[jghrist]

Are the generators running in parallel with the utility?

 

[QBplanner]

Davidbeach:
Strictly speaking, there is no such an issue "system stability" when we talk about stability it is only machine stability. Unless voltage stability but that is loads driven mostly.
Generator can run into even leading power factor within certain range.

Lagging power factor is good for the system voltage support or your own small system .

It will depned if your generator is pf controlled or voltage controlled. Normally ultility company will specify a terminal voltage for you to run your machine at lagging power factor unless it is a islaned or no net input generators. The pf required by NERC or WECC is 0.9 lagging to 0.95 leading. Your generator shall be capable to run at least in between. But in some special cases that say for the local generator I saw generator run at 0.8 lagging to provide system Var support. In the company I work we will not requiring IPP run at 0.82. In your case,I guess unless you have your own loads which require high dynamic Var supportslike induction motor loads. you should not operate at 0.82lagging pf. If you connect to the system then I will be so surprise. you may have to charge them for the Var support