hello all...
i need a little clarification of the subject of pf control...

let us take a hypothetical situation in which there are two generators in a system which is presently islanded. We take both the machines to pf control manually and set at a constant pf ( i.e. the pf of the system). The system is stable. Now, if we switch off certain load (which in effect will vary the system pf), what will be the consequences if:

a) the pf of the system decreases due to load switching
b) the pf of the system increases due to load switching

Kindly help me with this

 

When you're operating as an island, the power factor is what it is. If you try to control power factor with two machines, and the power factor changes then there are going to be issues, probably over- or under-voltage. maybe even some kind of VAr fighting might even happen under worst-case scenario if the regulators aren't tuned very well. But, certainly there will likely be some kind of over- or under-voltage condition on the "island".

Sounds like what you need or want is some kind of VAr sharing scheme.

 

Try to check the basics of Real power, apparent power, and reactive power. If the power factor of the system decreases, definitely your apparent power will increases, which will also increase the current and vise versa.

Check the rating of P.f of your generator. The pf when it is fully loaded (KW rating)should not be less than of that in the nameplate, otherwise it will be overloaded, due your kva is much higher. The one responsible for the pf control is your avr.

 

Thanks CSA and Blackstoneboy for the explanation.. I'll check the ratings of machines..