Bulk/Static correction and billing.

[Electrical guy]

Need help with this,

In speaking with some engineers, this still seems to be a grey area, could someone please clarify. We all agree KW stays the same and in fact may go up due to introduction of caps.

Putting power factor penalty aside.
If a business has a .90PF or more with caps at the mains and I install caps at a load, lets say reduce the KVA at load by 100KVA. Will this have an effect at the utility meter (metered secondary side of transformer) or am I just obtaining magnetising loss, and will it depend on load distance from Utility meter. If it does make a difference at the meter do I just subtract the 100KVA from the KVA billing portion of the bill to get an ROI. Will it effect the KWH portion of the bill.

Thanks,

 

[bob]

Need help with this,

In speaking with some engineers, this still seems to be a grey area, could someone please clarify. We all agree KW stays the same and in fact may go up due to introduction of caps.

That would not be correct. Adding caps does not change the kw demand.

Putting power factor penalty aside.
If a business has a .90PF or more with caps at the mains and I install caps at a load, lets say reduce the KVA at load by 100KVA. Will this have an effect at the utility meter (metered secondary side of transformer) or am I just obtaining magnetising loss, and will it depend on load distance from Utility meter. If it does make a difference at the meter do I just subtract the 100KVA from the KVA billing portion of the bill to get an ROI. Will it effect the KWH portion of the bill.
Thanks,

If you are being billed on a KVA basis, adding caps may reduce the KVA demand and reduce the billing. I say may because if you already have a high PF the caps will not help the billing. If you are being billed on a KW basis, adding caps will do nothing to reduce the bill. Ask the utility if you are being billed for KVA or KW demand and get the PF.

 

[Electrical guy]

That would not be correct. Adding caps does not change the kw demand.


If you are being billed on a KVA basis, adding caps may reduce the KVA demand and reduce the billing. I say may because if you already have a high PF the caps will not help the billing. If you are being billed on a KW basis, adding caps will do nothing to reduce the bill. Ask the utility if you are being billed for KVA or KW demand and get the PF.

I agree the kw is negligible.

Would distance play a role in your opinion.

 

[bob]

I agree the kw is negligible.

Would distance play a role in your opinion.

Not sure what you mean.

 

[Electrical guy]

Not sure what you mean.

I have used a data logger on the load I am not to concearned about the KW increase. By introducing caps there is a slight increase in kw but is negligible even on 125HP motor its not enough of an issue. As far as distance, if I lower the KVA by 100KVA would it show the same reduction on the utility meter if I was 10 feet away or 100 feet away or more (if theoretically I was being billed pure KVA)

Thanks,

 

[bob]

I have used a data logger on the load I am not to concearned about the KW increase. By introducing caps there is a slight increase in kw but is negligible even on 125HP motor its not enough of an issue. As far as distance, if I lower the KVA by 100KVA would it show the same reduction on the utility meter if I was 10 feet away or 100 feet away or more (if theoretically I was being billed pure KVA)

Thanks,

Distance has nothing to do with it. If you are on a KVA demand billing and you add caps the KVA demand will be reduced assuming that your PF is not 1.0. The meter does not care where the caps are located. They can be at the main sw or at the motor. If you add caps to the motor you will reduce the I?R losses. That's I? x the resistance of the conductor. If the conductor distance is very long and the motor runs a lot of hours then you would see a reduction in the kwh's associated with this loss. Eg. If the distance was 400ft and the motor ran 24/7 then you would likely see a reduction in kwh's.

 

[Electrical guy]

Distance has nothing to do with it. If you are on a KVA demand billing and you add caps the KVA demand will be reduced assuming that your PF is not 1.0. The meter does not care where the caps are located. They can be at the main sw or at the motor. If you add caps to the motor you will reduce the I?R losses. That's I? x the resistance of the conductor. If the conductor distance is very long and the motor runs a lot of hours then you would see a reduction in the kwh's associated with this loss. Eg. If the distance was 400ft and the motor ran 24/7 then you would likely see a reduction in kwh's.

Thanks Bob for the clarfication on distance, much appreciated. You bring up an intresting point though. You are suggesting that IR losses are related to KWH Billed, if I am not mistaken.
Are you refering to a KW reduction or KVA reduction in KWH calculation. How would you calculate this type of reduction if (I will use rounded numbers and back to my original question). A Utility supplies 4000KVA and 3500KW I reduce at load 100KVA will this be directly subtracted from the 4000KVA supplied if you say the meter does not care where the caps are located.

 

[bob]

A Utility supplies 4000KVA and 3500KW I reduce at load 100KVA will this be directly subtracted from the 4000KVA supplied if you say the meter does not care where the caps are located.

If your demand is 4000 kva and 3500 kw , you Pf = 0.875. If you were to add about 750 kvar capacitors and improve it to 0.95, your KVA demand would drop to 3800 kva. At $5.00/kva, that reduction would amount to about $1000 per month saved. Check with the utiity on the figures shown.

 

[mivey]

If your demand is 4000 kva and 3500 kw , you Pf = 0.875. If you were to add about 750 kvar capacitors and improve it to 0.95, your KVA demand would drop to 3800 kva. At $5.00/kva, that reduction would amount to about $1000 per month saved. Check with the utiity on the figures shown.

That would drop to about 3700 kVA and would be worth about $1500/mo at $5/kVA.

 

[mivey]

If you add caps to the motor you will reduce the I?R losses. That's I? x the resistance of the conductor. If the conductor distance is very long and the motor runs a lot of hours then you would see a reduction in the kwh's associated with this loss. Eg. If the distance was 400ft and the motor ran 24/7 then you would likely see a reduction in kwh's.

About 50 kWh/month or so.

But if the uncorrected p.f. is very low, it could be to the tune of several hundred or so kWh/mo.

The biggest $ factor will be the kVA charge or excess kvar penalty, and what you could save in reduced size feeder equipment (or released feeder capacity).

 

[Electrical guy]

If your demand is 4000 kva and 3500 kw , you Pf = 0.875. If you were to add about 750 kvar capacitors and improve it to 0.95, your KVA demand would drop to 3800 kva. At $5.00/kva, that reduction would amount to about $1000 per month saved. Check with the utiity on the figures shown.

Thanks Bob,
I understand how to calculate PF correction but it still does not answer my question. If I drop 100KVA at load anywhere in a plant will that be directly subtracted from my 4000KVA supplied by utility? If not, is there a calculation or software that can calculate all variables?

 

[bob]

Thanks Bob,
I understand how to calculate PF correction but it still does not answer my question. If I drop 100KVA at load anywhere in a plant will that be directly subtracted from my 4000KVA supplied by utility? If not, is there a calculation or software that can calculate all variables?

Very likely or something close to it. If you have already established the 4000 kva peak demand, dropping a 100 kva would not alter the bill.

 

[Electrical guy]

Ok, lets see what we get, let me post some statements, let me know if they are true or false, if false please explain. If true, no explanation needed.

PART 1
Assume PF is at .70 and will not go over .80PF ever, by installing caps in the scenarios below, are the following statements ture or false?

1.Power factor correction introduced at the main only, lowers your KVA demand.
2.Power factor correction introduced at the load only, lowers your KVA demand.
3.Power factor correction introduced at the main only, lowers your Utility bill.
4.Power factor correction introduced at the load only, lowers your Utility bill.
5.Power factor correction introduced at the main only, lowers your KWH.
6.Power factor correction introduced at the load only, lowers your KWH.
7.Power factor correction introduced anywhere, does not alter KW.
8.By lowering 100KVA (introducing caps) introduced at load only, you reduce 100KVA demand.
9.Assuming we do not go over .80PF ever. By putting caps at load, PF correction introduced at load will have negligble effect, except for IR loss if there is existing PF correction at the main.

PART 2
Assume a .90PF corrected to .95 by installing caps in the scenarios below, are the following statements true or false?

1.Power factor correction introduced at the main only, lowers your KVA demand.
2.Power factor correction introduced at the load only, lowers your KVA demand.
3.Power factor correction introduced at the main only lowers your utility bill.
4.Power factor correction introduced at the load only, lowers your utility bill.
5.Power factor correction introduced at the main only, lowers your KWH.
6.Power factor correction introduced at the load only, lowers your KWH.
7.Power factor correction introduced anywhere does not alter KW.
8.By lowering 100KVA PF introduced at the load only, demand stays the same.
9.Assuming we are corrected over PF penalty .90PF plus at main (existing). Power factor correction introduced at load will have no effect on anything.

Can we all agree????

 

[bob]

PART 1
Assume PF is at .70 and will not go over .80PF ever, by installing caps in the scenarios below, are the following statements true or false? Also assume that You are being billed on a KVA basis
1.Power factor correction introduced at the main only, lowers your KVA demand. T
2.Power factor correction introduced at the load only, lowers your KVA demand.T
3.Power factor correction introduced at the main only, lowers your Utility bill.T. Because it lowers your KVA billed
4.Power factor correction introduced at the load only, lowers your Utility bill.T same as 3
5.Power factor correction introduced at the main only, lowers your KWH.F Caps have no affect on KWH's
6.Power factor correction introduced at the load only, lowers your KWH.T I?R loss is reduced
7.Power factor correction introduced anywhere, does not alter KW DEMAND T.
8.By lowering 100KVA (introducing caps) introduced at load only, you reduce 100KVA demand.T that is approximately correct
9.Assuming we do not go over .80PF ever. By putting caps at load, PF correction introduced at load will have negligble effect, except for IR loss if there is existing PF correction at the main.F. See 1 - 4

PART 2These answers are the same as above. The correction of the high power factor to a higher PF is no different than the correction of a low power factor as stated above. You just do not see as large a saving. Going from 0.90 to 0.95 may not be cost justified because the savings is small.
Assume a .90PF corrected to .95 by installing caps in the scenarios below, are the following statements true or false?

1.Power factor correction introduced at the main only, lowers your KVA demand.
2.Power factor correction introduced at the load only, lowers your KVA demand.
3.Power factor correction introduced at the main only lowers your utility bill.
4.Power factor correction introduced at the load only, lowers your utility bill.
5.Power factor correction introduced at the main only, lowers your KWH.
6.Power factor correction introduced at the load only, lowers your KWH.
7.Power factor correction introduced anywhere does not alter KW.
8.By lowering 100KVA PF introduced at the load only, demand stays the same. F. See 8 above
9.Assuming we are corrected over PF penalty .90PF plus at main (existing). Power factor correction introduced at load will have no effect on anything. F Adding Caps will have an affect any time you add more.

 

[bob]

That would drop to about 3700 kVA and would be worth about $1500/mo at $5/kVA.

Last night is was $1000/mo I swear.

 

[beanland]

Reduce Losses - maybe

Reduce Losses - maybe

Improving power factor may slightly reduce power distribution losses in a facility. But, your total power distribution losses may only be 5% of power consumed. So if you lower losses by 5%, your total bill will drop by 0.25%. Not enough to measure.

However, if the power factor improvement is on the secondary of a transformer, the reduced losses may be more. You need to examine the "lossiness" of the transformers. Only copper losses, not iron losses, are reduced. Reduced losses may also reduce A/C loads by lessening heat loads inside a building.

Utilities use power factor correction to reduce line current, reduce voltage drop, reduce losses, and increase available transformer capacity.

 

[VoltzElectric]

I was just talking with a Rep. from MERIT (who sells CAL's) yesterday, and he was looking at our molding machines for helping us with poor PF. By installing the CAL after the motor starter, we can reduce our KVA, but obvously not our true power. Our machines are pretty bad at around .5 - .6 PF. So, By reducing the KVA, we will see less current used at the meter, and make our savings on the I2R losses. We can hope to gain aprox. 3 -6% off our electric bill. I still havent gotten in touch with the POCO to figure exactly how they are charging us on our Peak Demand, and how that plays in yet, but we could end up saving more than that in the long run. I beleive that with A CAL type system, you as the consumer will see the cost benefits vs. using a large auto switching bank at the transformer, that only helps the POCO out.

 

[bob]

Voltz
How long is the cable run from the starter to the motor? If it is short it would not make any difference if the caps were ahead of the starter. Utilities bill for the max KVA demand during the month at about $5.00 per kva. It does not take much to save a lot of money. The the I2R saving are usually small unless the motor is use for many hours. Most designers place the caps at the motor. You need to make sure you don't have any VFD on the motors. Capacitors and VFD do not play well together.

 

[Electrical guy]

Improving power factor may slightly reduce power distribution losses in a facility. But, your total power distribution losses may only be 5% of power consumed. So if you lower losses by 5%, your total bill will drop by 0.25%. Not enough to measure. Acknowledge and agree with you.

However, if the power factor improvement is on the secondary of a transformer, the reduced losses may be more. You need to examine the "lossiness" of the transformers. Only copper losses, not iron losses, are reduced. Reduced losses may also reduce A/C loads by lessening heat loads inside a building. When you say more do you mean 10%,20% or higher?

Utilities use power factor correction to reduce line current, reduce voltage drop, reduce losses, and increase available transformer capacity. Acknowledge.

For billing purposes, I was under the assumption Static control (caps at load) do not lower the customers bill at all, if a well installed PF correction switching bank (.95) was present at the main. The assumption was, static control as you stated reduces demand and increases efficiency internally only. Correct me if I am wrong.

Thanks for your input.

 

[VoltzElectric]

The caps being after the starter help from the standpoint that when the machine is down or pumps off, you are not feeding the capacitor back onto the feeders and putting too much capacitance into the system. Also, we have some equipment with VFD's that we are looking at putting filters on. THe length from the starter to the motor is less then 10 feet.
Most of our machines run 24/5. I know that every area has the power company charging different ways. We have a line item on our bill that we pay for poor PF. I have tried now to get ahold of the POCO for a couple of weeks now, but the guy hasnt returned my calls. Our peak Demand is $8.85/KW. What Im not sure on is exactly how they come up with that. THey would have to add the apparent power usage in there some how, they're not just gonna give it to me for free.