03-25-2011 07:01 AM
we have three cat G3520 C with rated power of 1950 KW.From the last two days power factor of one generator is low.Details are
G# P.F Load (amps)
01 0.91-0.93 78
02 0.82-0.84 90
03 0.91-0.93 78
although generator is in operation but i am worried ,so plz reply what will be its effects on generator performance in the future?
03-25-2011 10:47 AM
Okay, so the Gen 2 is supplying more reactive power to the system. What kind of system is this? Is this three units paralleled in an island mode? Paralleled to a grid? How do you do VAR sharing or VAR load control? And is the information below indicating a lagging or leading power factor
If you're in parallel to a grid, then whatever controls your power factor/VAR's is not adjusted or working the same as the other two units.
If you're in an island mode, then how you are doing your VAR share is important. Are you in droop, cross current compensation or using an active VAR controller of some type?
This appears to be a 12kV system, so a few more details would help in providing you a better answer. The quick reply to your basic question is that no, running the generator at a 0.80 lagging power factor should not be a concern if the tail end is properly sized and cooled. You mention a power rating of 1950 ekW, what is the kVA rating of the tail end? If the power factor indicated is actually leading, then you could be close to the limits of the tail end based on the reactive capability curve for that machine.
03-25-2011 11:50 PM
well all three gensets are paralled in island mode.System is not ye parralled to grid.We have PF controller units in the system to compensate reactive power.It should be noted that 5 other cat genstes are attached to the same bus bar and power factor of all 5 + 2 gensets is Ok i,e 0.91-0.93.Only there is problem with gen#02,it is really unstable,sometimes it is between 0.82-0.85 and some times close to 0.88. Now plz clear the following
1)Now where is the fault basically? ??The capacitors attached to PMG are weak?
2) what will be its effect if it remain for long time as more amps are generated for the same KW.
3) More reactive Power effect generator efficiency?
03-27-2011 06:58 PM
Sorry, a little confused by the information provided. You said you're using PF controllers on an island system, is this correct? Are you assuming the other units on line will take the VAR swings? Who makes the PF controllers? How are they installed, and what mode are they operating in?
Back to your #2 gen, it is putting out more VAR's than the other units, so it is unlikely anything is "weak". So it is either being told to take a greater portion of the VAR load by the controller, it has less droop than the other units, or it is adjusted to a higher nominal voltage and it's grabbing more of the VAR load.
What kind of AVR's do you have, CAT CDVR's, VR6's or something else?
Based on your numbers you're still a good bit away from your maximum kVA on your tail end, so this really doesn't look like a big issue, but if you want ot get it fixed please answer the questions and provide as much detail as you can.
03-27-2011 11:03 PM
Three G3520 C are running in island mode and all other cat G3516 A are sync to the same busbar but with fix mode operation.By PF controller i mean these are installed at Distributioion side .These is cat CDVR.