power factor penalty

[psozot]

we have two power factor improvement plants of 300 kvar & six stage each. Transformers are of 2000 kva (two Nos each). available load is 1900kw. presently we are facing power factor penalty. we are bound to have power factor of 0.9 by supply company. is it because of tranformer coil inductance. as whole 1900 kw is not operative all time. please advise the solution

 

[BigWallyB]

I beleive poor pf is mostly caused by motor inductances, but I think I'm lost with "power factor improvement plants." These are what exactly? You do not mention any pf correction capacitors? Generally caps are used to correct pf. Need more input!!!

Life is what happens while we're making other plans.

Wally

 

[psozot]

Power factor improvement plants are capacitor banks

 

[Skogsgurra]

The reactive power consumed MAY in part be the idling transformer. If there are taps on the primary to select voltage, select the highest possible primary voltage (equal to lowest possible secondary voltage). That CAN bring your pf up marginally. But perhaps enough to avoid penalty.

Doing the same on both transformers will also decrease voltage to induction motors and reduce reactive power consumption. This is especially effective if you are running them with above rated voltage.

If that isnt possible, or if it doesn't help, then you need more capacitors.

Gunnar Englund

http://www.gke.org

 

[BigWallyB]

Okie dokie. Wait, gotta wipe egg from face. Ok, I can see now. Still need input. Is your pf correction system automatic?

Ahhh, found what I wanted. Knew I could count on Eng-tips. Marke, a common contributor here has some good info at - [link]http://www.lmphotonics.com/pwrfact.html[/url]

I can't explain it any better, thats for sure.
If you still have questions, someone else can chime in.


Life is what happens while we're making other plans.

Wally

 

[vtpower]

We currently enforce a .9 pf penalty for all of our C&I customers but will soon be upping this to .95 due to ISO requirments.
I have met with multiple industrial customers on this issue to provide support to correct and the most commmon solution is power factor controlled multiple stage cap banks (or power factor improvement plants). Often thse are on the LV (480V) and have high voltage overrides to avoid over voltages during light load times. It sounds like you have the equipment and just need to have the proper switching incorporated. With two seperate banks, if I understand you correctly, you will need to be sure to utilize your delay times for switching as to avoid hunting of the two banks. Basically choose which bank will be first in and last switched out.

 

[Bung]

If my sums are right, 600kVAr (2x300 banks) of capacitors will only correct 1992kVA at 1900kW, ie bring a 1900kW at 0.95 pf up to unity pf. Do you mean 2 sets of 6x 300kVAr steps? What is your pf with the capacitors out of service (ie your load pf)? And don't forget that your transformer (if you are being metered on the HV side) is contributing around 200kVAr to your inductive load at full power.

I think you may just need some more capacitors.


Bung
Life is non-linear...

 

[buckman]

I good place to start would be your utility, many times they will offer some design services for you. While they don't really advertise that they do this, they certainly do this only regular basis with their on systems, and can often provide you with what you need.