power factor penalty 3

[furm]

How the electric companies calculate the power factor penalty?

 

[davidbeach]

It will be spelled out in the applicable rate schedule. Different utilities do it differently.

 

[itsmoked]

Anyway they want to...

Seriously though they measure your facility's PF and then apply 'their' markup to that. Sometimes a flat rate sometimes they adjust a multiplier in your meter which just ups the kw-hrs from what you really consume.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[furm]

Thank you for answering my question.
Do you have some detail/contacts names about the subject?

 

[jraef]

Your friendly neighborhood power company! Really, how someone else does it has no relevance to how yours does it. There is no universal governing body who sets up rules or methods.

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> faq731-376

 

[mohpower]

you might find some information in this link

http://www.progress-energy.com/custservice/carcig/resourcectr/presentations/power_factor_final.pdf

thanks

 

[waross]

A formula that was used by some utilities for many years was 1% surcharge for every percent that the PF dropped below 90%.
Many utilities now use a much more punitive formula. I understand that India penalises for any power factor below 100%, both lagging and leading.
Many power bills have the power factor calculation on the bill. On some bills it is in "Adding Machine" language. A call to the billing department of your local utility should get an answer. Although there may not be much restriction on how punitive a penalty may be, whatever formula the utility charges will be included in their tariffs.
On the old rate of penalty equals 90% minus the percent power factor, I have seen a penalty of 90%. This was a large transformer that was energised but which had no load connected. Sure, there were some real power losses, but the magnetizing current was so great in realation to the loss current that in the real world, rounding took the power factor to zero.
As an excercise, I took a very low power factor, that would have resulted in a penalty of 80% or 90% on the old formula. I applied one of the more punitive formulas and the calculated penalty was 800%.
respectfully

 

[oldfieldguy]

I just had a discussion over the electrical power ocntract for a facility we're upgrading.

It presently uses 300 kVA to run mostly inductive lads, and the power factor is in the .80-.85 range, lagging.

Our upgrade installs a 9000 horsepower electrci motor with a variable frequency drive. It will run at essentially unity power factor to the utility.

The utility wanted to put us on a power factor penalty schedule. I doubt a power factor problem will exist while we're running the 9000-HP motor, but when we're back down to the old load level, we'd be hitting the penalty schedule.

I requested and received a change to the schedule based on the total station load, basically a kVAR penalty schedule.

old field guy

 

[gobblerhuntr]

We penalize customers that fall below 85% on peak for the month. They basically pay twice the demand charge for all kw that is used by not keeping above the 85%.

 

[dpc]

It is likely that your utility will have its tariffs (rates) somwhere on their website. The pf penalty will be described there. If you can give us the description for your utility, we can probably give you more help.

There are many ways that pf penalty is computed and billed.

 

[furm]

Thank you all for answering
First of all I’m not from USA and it is not so simple to get information from the utility’s web. Because they “force” you some personal details like: customer name address etc. my purpose for asking this question is to get information about more methods other than what I know.
The PF used in billing is generally an average figure for the entire month, the typical procedure for determining the PF is to measure the kilovarhours (kVARh) as well as the kilowatthours (kWh). This is usually done with two separate induction disk-type meters or with an electronic meter. The kVARh and the kWh are then combined.
This method can’t give a solution in case the consumption, during the night for 8 hours for example, will be[COLOR=red yellow] – KVARh (cap)[/color]. Is anyone can tell me what methods will overcome this problem?

 

[davidbeach]

The utility won't want a capacitive load any more than they want an inductive load; power factor correction caps need to be controlled to react to changing load power factor.

Utilities can also, either in addition to kVArh or instead of, use kVAr-demand against kW-demand to calculate the power factor penalty.

You really need to find someone locally who can answer the specifics of your question, or post your locality and hope that someone is familiar with that location, but this is one question for which there are no general answers.

 

[dpc]

That's a common method computing pf penalty. I doubt if the leading pf is even being metered if you have electro-mechanical metering. Leading pf was historically not penalized, although that is becoming more common, at least in the US.

When you say "This method can't give a solution", I'm not sure what you mean. You may not like the method, but it can be used regardless of what your night time power factor is.

The best solution used to be to install capacitors that were switched on and off with individual motors. With the increased use of adjustable frequency drives, this solution has become another problem.

Best approach might be to install a bank of switched capacitors with automatic pf controller. Static var compensation is also available, but will be more expensive.

 

[waross]

Back in the days when power factor correction was an art we often used the following method.
First, the power companies historically penalised you if your consumption of VARHrs in a month exceeded a percentage of the KWHrs in the same period. The percentage usually worked out to 90% PF.
We would calculate the number of VARs required to raise the PF to 90%.
Here's where the art came in. We would then consider the system loads and their characteristics. Does the plant operate 5 days a week or 7 days a week? Does it run 1, 2, or 3 shifts?
How many VARs will it take, if they are connected for 24 Hrs. a day, and will this be excessive for the system?
We often were able to justify adding capacitors that were permanently connected.
If we could not justify adding a fixed capacitor bank, we would then start looking at creative switching.
I did some work in sawmills. The typical mill had several large motors, 75Hp. to 300 Hp. and scores of smaller motors.
We would first calculate the correction needed for the largest motors and see if correcting the largest motors to 100% would bring the overall average up to 90%.
The next step would be to use a large motor to close a contactor on a bank of capacitors of the approximate same rating as the correction on the motor. The normal startup sequences would usually result in enough small motors being on-line as each large motor started that the power factor never went dangerously leading.
Although the VARHr meters normal were fitted with a ratchet device to prevent them from crediting us with leading VARHrs, during the off hours, we would benefit from the difference between 90% PF. and 100% PF.
There was a significant cost advantage to using a few large capacitor banks rather than small capacitors at each individual small motor, both in the cost per VAR and the labour to install.
We had a few opther tricks as well, sometimes we would push a large transformer up to 90% leading PF. to compensate for other loads.
If we sometimes went leading in the small hours of the morning, the utilities didn't seem to mind. At that time, the residential loads would be predominantly motors, freezers, refrigerators, furnace fans, and the distribution system would benefit from a few extra VARs.
respectfully

 

[DanDel]

It is common in my part of the USA for the Utilities to charge for Demand kVA instead of Demand kW, including the PF penalty in the Demand charge, and penalizing the customer for any PF above or below 100%.

 

[jraef]

...and penalizing the customer for any PF above or below 100%.

±100%? That seema a bit draconian!

furm,
You might also consider that if you have a large motor that runs continuously, put a synchronous motor on it and use it to automatically maintain the plant's overall pf within the acceptable range by operating it in a leading pf mode.

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> faq731-376

 

[DanDel]

Not Draconian, just a good way to maximize profits...

 

[CJCPE]

The Springfield Missouri City Utility Co. has the following pf charge:

A Power Factor charge of $0.025 per kW of billing demand will be made for each whole percent by which the monthly power factor is less than 100%.

The power factor shall be the kW demand divided by the coincident kVA demand expressed as a percentage, for the peak 30-minute interval during the billing month.

In other words, the charge is $0.025 for pf=.99, $0.05 for pf=.98, $0.075 for pf=.97 etc.