power quality

[jackbenny]

has anyone had experienses with capacitors installed at a panel to correct power factor and reduce electrical bills

 

[StephenSDH]

Yeah. You don't really want to go down that road unless you are forced to. There isn't any real money savings and you don't know what you are in for. I did alot of research to try and talk my customer out of it.

1.) You only save in I2R losses. Unless you are being penitalized
2.) It can improve PF, but it can also increase Harmonics
3.) If harmonics are present care has to be given to protect the Caps
4.) Switching Caps can cause causes Capacitive Ringing around 200% V
5.) Contactors for switching capacitors often prematurely fail because they don't like an instantaneous change in voltage.
6.) Transients from Utility Capacitor Switching can be amplified by customer capacitors causes voltages excesses of 200%
7.) Under no-load conditions if capacitors are not switched off they can cause an over voltage.
8.) When they fail you hope you are not near them.

 

[chevyx92]

has anyone had experienses with capacitors installed at a panel to correct power factor and reduce electrical bills

Depends on what application you are wanting to do this in. I assume commercial application with lots of HID, motors, transformers etc.. The key to capacitors is sizing them correctly. If sized correctly they create equal and opposite capacitive reactive currents to the inductive reactive currents. That power factor correction will create substantial savings.

 

[ptonsparky]

For commercial or industrial applications where the customer is charged for poor PF there can be a substantial savings. Lots of things to consider before hooking one, or more, up.

Some of the Ag customers in this area are penalized if they do not have PF correction installed on 3 phase motors 10hp & above. No one checks to see if they are working units, they just have to be there.

 

[StephenSDH]

That power factor correction will create substantial savings.

Tell me how? Where is the savings?

 

[brian john]

Tell me how? Where is the savings?

What he said was:

For commercial or industrial applications where the customer is charged for poor PF there can be a substantial savings. Lots of things to consider before hooking one, or more, up.

Some of the Ag customers in this area are penalized if they do not have PF correction installed on 3 phase motors 10hp & above. No one checks to see if they are working units, they just have to be there.

If the utility has a PF penalty the savings is in improving the PF.

 

[StephenSDH]

What he said

You got the wrong he. I was quoting chevyx92. I understand everyone wants to save money, but there are a lot of adverse effects to capacitors and you don't want to go there unless the utility financially forces you.

 

[iwire]

You got the wrong he. I was quoting chevyx92. I understand everyone wants to save money, but there are a lot of adverse effects to capacitors and you don't want to go there unless the utility financially forces you.

I don't know of any power company in this area that does not penalize commercial customers with poor PF.

 

[PowerQualityDoctor]

Concerning post #2:

1.) You only save in I2R losses. Unless you are being penitalized
Correct, but most utilities do penalize...
2.) It can improve PF, but it can also increase Harmonics
Correct if capacitors are alone. It is highly recommended to use detuned reactors.
3.) If harmonics are present care has to be given to protect the Caps
Again, reactors should be added (for my opinion - at any case regardless of the current harmonics situation as it may change).
4.) Switching Caps can cause causes Capacitive Ringing around 200% V
Many PF systems today use electronic switching which prevents this issue.
5.) Contactors for switching capacitors often prematurely fail because they don't like an instantaneous change in voltage.
See reply #4.
6.) Transients from Utility Capacitor Switching can be amplified by customer capacitors causes voltages excesses of 200%
Reactors will solve this as well
7.) Under no-load conditions if capacitors are not switched off they can cause an over voltage.
Use automatic system or verify that capacitors are turned off during no load conditions. 5% of the transformer power is recommended for no load transformer compensation
8.) When they fail you hope you are not near them.
Use self-healing with internal fuses.

 

[don_resqcapt19]

1.) You only save in I2R losses. Unless you are being penitalized
Correct, but most utilities do penalize...
...

Around here that would be correct only for industrial customers. Residential and commercial customers do not have a power factor penalty.

 

[brian john]

Concerning post #2:

1.) You only save in I2R losses. Unless you are being penitalized
Correct, but most utilities do penalize....[/B]

Around here there are no penalties, that I am aware of. But it should be noted there is very little industrial, unless you count all the BS congress produces.

 

[StephenSDH]

Around here for industrial PPL doesn't, but PECO does charge for bad PF.

 

[Besoeker]

Correct if capacitors are alone. It is highly recommended to use detuned reactors.

I agree. We always fit detuning reactors.

 

[LarryFine]

Residential and commercial customers do not have a power factor penalty.

I'm sure it's taken into consideration in the standard residential rates.

They may not itemize it in in the bill, but I'm sure it's built in.

 

[skeshesh]

The good ol magic capacitor gets brought up again... I agree with most of the posts in that:

1 - It doesnt not redcuce power consumption significantly.
2 - It may provide savings but only through PF correction and avoiding POCO penalties.

Around here there are no penalties, that I am aware of. But it should be noted there is very little industrial, unless you count all the BS congress produces.

Only if we could come up with way to filter some of that product out, but we'd need a really narrow passband!