Low PF Value of Generator

I haven't run a DG powerhouse in quite a while, so some of my ideas may be rusty.

If one of your genset governors is in isochronous mode, and the others in droop (all of which is normal), there could be PF differences.

Your AVRs may appear to be adjusted the same, but there could be instrument inaccuracies, for instance.

You could try small adjustments to AVR and/or governor settings, and simply observe whether the PF readings improve. Such tweaking may work at one level of loading, but not necessarily at all levels.

The overall PF depends on the load characteristics (inductive, resistive, capacitive). If all the gensets are equal, any further improvement must come from the nature of the loads.

Are the kW equal on all gensets, even if the PFs are not?

By the way, welcome to CR4. Your question is good, and there are some better and more up-to-date experts here who can help you out.

Basic knowledge on power factor http://www.psa-outline.com/power-factor/

it might be useful for you!

Thank you Anonymous for your information.

Tornado: Thank you very much for your reply. The kW shared on all 3 set is equal (occasional difference of 0.1kW) and voltage is the same.

Am suspecting it is caused by difference in phase but I'm not sure how to check since I did not see any physical capacitor in the genset. Using Deepsea AVR

Participated in the load test today and discovered that the PF becomes normal after load exceeds 20%. So i guess I wasted half a day trying to figure out the issue with low PF.

But the problem with the readings of the fan is still unresolved.

Situation: Manually measured each of the two fans to be drawing over 20A. Two of the genset shows 47-50A current on the display but the one particular genset shows 0A and 0kW load.

I suspect that for the particular genset, the current produced by the two fans cancelled off each other and resulted in the reading.

What is your take on the matter? Would love to receive alternate views or confirmation on this issue. Appreciate the help.

PF of gensets in parallel is controlled by the AVR in term of excitation to the generator or exciter of the generator. It may be by the voltage droop or cross-compensating of the AVR.

You did not mention the voltage of the generators, what is the hp or kW rating of the fans?

Did the two gensets with 47-50A have the same kW? How far the fans over 20A? Any other load on these gensets

For the genset, 440 V/60 Hz.

I didn't note down the power rating of the fans.

The other 2 gensets have the same kW. No other load on the genset.

Not too sure with regards to the question of "How far the fans over 20A?"

Thank you for your reply franksun

The gensets are 1100kVA each, or 1443A each @ 440V 3 ph.

The genset of 0.38 pf lagging may be underexcited. The current on this unit should be lower then the other two units with same kW load across all three gensets.

With light load on the gensets in parallel, the sharing on the reactive current will not be easily rectified due the the slight different on the output of the AVR. The cooling fans are taking totally over 40A. This load of over 40A in compare with the total generators capacity of 4330A is so light. The AVRs may not able to share the reactive current. The 47-50A current of the two generators would be the load of the fans and the circulating current between these two generators. I think these slightly different betwen the generators on the light load is acceptable. Try to load up the generators to above 25% to check if the AVR is set properly for current sharing.

Instruction from Deepsea for the AVR setup will help.