Power Factor On DG

G

Thread Starter

GGN

Alternator rating is 500kva, 385a, pf: 0.8, 750v

Actual load current is now 200a, and p.f 0.81

Want to improve power factor to 0.95.

We understand we can use more load by improving powerfactor and diesel consumption also will reduce. Can we quantify the saving?

Regards
 
GGN,

Is the DG supplying a load independent of a grid or other generators?

If so, it's not really possible to change the power factor at the generator--the power factor is a function of the characteristic of the load (motors; lights; televisions; computers; computer monitors; etc.).

Also, if the DG is supplying a load independent of a grid or other generators then the load can't be changed at the generator, either. The load is a function of the current required by the motors and lights and other devices the DG is powering.

And, if it's a single DG then the DG governor is likely operating in what's called Isochronous Speed Control mode and is adjusting the fuel flow-rate to the diesel to maintain the generator frequency as load changes. If the load is relatively stable then the fuel flow-rate will be relatively stable, and you can't "improve the load" (by which I assume you mean <i>increase</i> the load), you can only increase the frequency of the generator--which isn't desirable.

If the DG is supplying a load in parallel with (synchronized to) other generators, then if the DG governor is operating in Droop Speed Control mode then it should be possible to increase the load AND increase the power factor. (This presumes you are connected to a grid, or that this particular DG is not being used to maintain frequency for the other generators it is synchronized to.)

As for quantifying the fuel savings, well, that really depends on how the DG is being operated and what the load characteristic is. <i>In general,</i> the power factor is a measurement of the efficiency of the machine in converting the energy to real power (watts, KW).

If the power factor is 1.0, then the efficiency is 100%, and if the power factor is 0.85 then the efficiency is 85%, and so on. This is a rough (very rough) way to quantify how efficient the generator is at converting the diesel fuel flowing into the diesel engine to real power (watts) at the output of the generator. And since most generators get paid only for real power, the more efficient (the higher the power factor) the more money they are making for the fuel they are consuming.

The paragraph above really presumes the operator has the ability to change the power factor (in other words, it's paralleled to (synchronized with) other generators and that it can vary its reactive current flow without affecting grid stability. You haven't told us how the DG is being used, and so we can't say too much more than what was said above. Again, <i>in general,</i> power factor is a measure of efficiency (the efficiency of converting torque to watts when talking about a generator). And that can be used to <b>estimate</b> revenue improvement for the same fuel flow rate.

Changing the load of a generator which is solely supplying a load isn't possible--the load is a function of the number and type of motors and lights and televisions and computers and computer monitors, etc. You can't make a generator produce 450 KW if the load is only 200 KW. If you want the generator in this case to produce more power--you need to increase the number of motors and lights and televisions and computers and computer monitors. But you can't just increase the fuel flowing into the diesel driving the generator and increase the power produced by the generator. All that will happen (in this case) is that the frequency will increase--and that's not increasing load.

Remember, generators are devices for converting torque into amperes, just like motors are devices for converting amperes into torque to do useful work. There's also the reactive power component that has to be considered, and <i>when possible</i> if the power factor can be increased to be as close to 1.0 as possible then that means the generator is nearly 100% efficient at converting the torque being provided to it by the prime mover (the diesel engine in your case) to real power (watts, KW). And that means you will receive the most revenue for the watts/KW you are producing--which is saying you are more efficient.

Some DG manufacturers provide curves and/or graphs which tell you how much fuel will be flowing (consumed) for various conditions (watts/KW; and possibly power factor). You could also use this to estimate your revenue for watts versus fuel consumption knowing the cost of fuel for various outputs. If you have such charts, it would be interesting to know how your calculations compare to estimates using power factor percentages.

Hope this helps!
 
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