LV reactive power compensation

[rzgpp]

Hi,all!There is power factor controller on LV network.A group of outputs...which control contactor for stages of capacitor banks...is not working...the reason is not interesting...loose connection somwhere inside the controller...Is there any technical reasons...not to connect 2 contactors...with two capacitor bank groups on same output of controller?Becouse...there is half of outputs....which are in work.It is clear..that with this kind of grouping...tunning will not be so fine....like with double outputs...but for a period of time..is it possible to work on half of controller outputs?

 

[jghrist]

The devil is in the details. Sometimes other things get connected together inadvertently and cause problems.

 

[rzgpp]

It is right....this kind of connection is against something in me....but I can't find technical reason....

 

[waross]

You may have to re-tune the controller if that is possible.
What may happen is that the power factor drops, the controller pulls in two steps instead of one step of correction and over corrects.
The controller detects the over correction and drops the two contactors back out.
Rinse and repeat until a contactor fails.
You may be able to simply skip a step, so that as the power factor drops and a capacitor bank fails to connect the controller eventually detects enough PF drop to call in the next step which would include the missed step.
as jghrist said, "The devil is in the Details".
Another solution would be to simply connect the failed bank permanently across the line.
Another detail that you have not mentioned is your billing tariffs (And I am glad, I don't feel like wading through a lot of technical documents written by lawyers.)
The best solution is to fix the controller.
If the issue is a failed contactor, paralleling it to another output won't help and may do further damage to the controller.


Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[rzgpp]

Thank you all!Controller have self recognizing function.....so.. will recognize that...on this step there is 20KVAr...instead of 10KVAr,the output power is enought to switch 2 contactors....but I am not sure.....if there is some interval....in miliseconds time deviation between contactors..if one output control 2 contactors...is there a problem....or some other technical problem....controller is out of care....it is clear to me...but it is not clear...is it possible to control 2 contactors....by one output...any suggestions?Controller will not overcompensate.....becouse all steps are not enought to compensate more than 0.96 ind..at every moment

 

[Parchie]

@rzgpp,
If your contactor is capable of carrying two of your capacitors, why use two contactors to handle the two capacitors? Distribute your capacitors on every step. Maker sure your switching logic switches enough capacitance to correct the power factor and not over-correct.

 

[che12345]

Dear Mr rzgpp
R1. [highlight #729FCF][highlight #729FCF][highlight #729FCF]"...if one output control 2 cont[/highlight]actors...is there a problem....or some other technical problem.,
.."[highlight #3465A4][/highlight][/highlight][/highlight]
C1. There is no problem one output control 2 contactors. Even the contactors may close at a slightly difference in time, which are beyond our control. The important thing is to ensure that the controller contact output current rating is sufficient to switch on two contactor coils.
C2. To avoid complication, set equal kvar rating for each step i.e. 1:1:1:1:1.....
C3. Don't understand/unable to answer the other questions.
Che Kuan Yau (Singapore)

 

[waross]

It depends:
We don't know the output capabilities of your controller.
Putting two sets of capacitors on one contactor is easy in the office, just a couple of lines changed on the drawing.
In the field, it may entail quite a bit more work, it depends.
Will one contactor handle two sets of capacitors? It depends.
Timing of two contactors on one output: Consider using an auxilliary contact on one contactor to pull in the second contactor. That will avoid simultaneous inrush on the controller.
This is relatively easy, just requires a couple of control circuit jumpers.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[rzgpp]

Parchie,
Becouse half of outputs of controller were broken....i.e. now there is 6 steps instead of 12 and use the same contactors.
Thanks all!Thanks Che12345....yes there is no problem..the controller is working now...of course the power of output is enought for 2 contactors,also there is no problem to control by 6 steps 12 contactors....for now...there is no problem...I am waiting the new one controller!Thanks!