Generator Reactive Power and Leading Power Factor

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Thread Starter

Rezaq

Dear Sir/Madam

I got an alarm from my 1000KVA Generator which is Reverse Reactive warning. So when i check the power factor i saw that the power factor is about 0.94 Leading and Reactive power (KVAr) was in negative values.

Is this leading power factor and negative KVAr values normal or it will be serious problems for the Generator?

regards
Rezaq
 
Rezaq,

Every synchronous generator is supplied with what's commonly referred to as its Reactive Capability Curve, or its Capability Cureve. This diagram, which is pretty much unique for every machine, depicts VArs on one axis and Watts on the axis, and shows the limits of the ability of the generator to continuously operate at various real- and reactive power outpust without damaging the insulation of the stator and/or the rotor.

In general, leading VAr or power factor operation capability is much less than lagging VAr or power factor operation. This is likely why the unit has such an alarm setpoint--to protect against overheating the stator windings/end turns due to elevated leading reactive current flow.

You need to locate the generator Reactive Capability Curve for your machine (usually found in the manual supplied by the generator manufacturer) and consult that to determine how many leading VArs the generator can safely handle at any given load (real power output). Most sites keep a copy of the Curve readily available to operators to refer to at any time. It's a very important document to understand and refer to.

Hope this helps.
 
.94 leading is not good, but not the end of the world. If load % is low this is fine. VARs will add additional heating of the windings in addition to the real power they are providing, however. If this gen is in parallel with another source, then raise your voltage setpoint until you get to 1.0 pf. If this is islanded there is not much you can do, just make sure total Amps is less than rated FLA on the nameplate.

>I got an alarm from my 1000KVA Generator which is Reverse
>Reactive warning. So when i check the power factor i saw
>that the power factor is about 0.94 Leading and Reactive
>power (KVAr) was in negative values.
 
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