Meter Constant / Billing

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iplay1515

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I am a Progress Energy North Carolina customer.
My billing rate is Residential Time of Use Demand rate.

My electric meter is a GE IRM 70-S.

The meter is both electronic and mechanical and uses a current transformer.

My electric service is 400 amps using 2, 200 amp panels mounted side by side on the opposite side of the wall from the exterior meter can/housing.

The meter's digital display continueously cycles displaying a register number and the value associated with that register.

Register 18 contains the value of 000.050, which according to the documents supplied by Progress Energy, is the "Watt Hour Constant". Customer service reps. have refered to this register as the Kh and also as the "meter constant".

My monthly bill indicates that a constant of 60 is used to calculate the actual KWH.

A meter technician from Progress Energy recently inspected my equipment and advised that the CT / Current Transformer had a ratio of 600:5.

The meter's digital display shows values for registers 1 - 23 except for registers 3,7,10,14,17, and 19.

My monthly bill indicates both the highest KW for on peak and off peak showing the KW, time, and date. Looking at several years of bill, the times shown are always on 15 minute boundaries either on the hour, 15 minutes past the hour, 30 minutes past the hour or 45 minutes past the hour.

Progress Energy Customer Service representatives are not trained to answer technical questions about their demand and time of use billing or measurement techniques and are reluctant to allow me to talk to more knowledgable individuals in the company, so I am posting my questions here seeking advice from members.

Given the above information:

1. What is the relationship to the value in register 18 "watt hour constant" which is currently 000.050 and the "meter constant" of 60 as indicated on my monthly bill?

2. What is the relevance of the CT ratio with respect to question 1 above?

3. What is the significance of the 15 minute interval with respect to demand billing, and does the meter record average demand over the 15 minute interval or peak demand.

4. PE customer service advised that the 15 minute interval was a moving window. If this is correct, why are all readings for the past 6 years on one of 4 times at fixed intervals?

5. PE indicates date and time for off peak KW on their bill, however none of the registers display the date and time for off peak. Where do they get this information?

6. Meter registers 22 and 23 indicate the date and time for the highest on peak KW for the current month. Does the time value indicate the beginning of the 15 minute interval or the end of the interval?

7. The definition for on peak times for Progress Energy changes twice a year. How does the meter programed with the correct times?

8. Are there registers that aren't displayed by the meter but are downloaded into the data collection device used by the meter reader each month?

Thanks in advance for your assistance and information.
 
090415-0846 EST

You have presented some good questions. I have no answers for you.

I believe we are entering an era where it is going to be become very necessary to have our own monitoring equipment to verify the correctness of meters such as you are describing. This means we must know how those meters work in great detail.

"1984" has come to be. If you have not read "1984" here is one reference:
http://www.online-literature.com/orwell/1984/

.
 
iplay1515 said:
I am a Progress Energy North Carolina customer.
My billing rate is Residential Time of Use Demand rate.

My electric meter is a GE IRM 70-S.

The meter is both electronic and mechanical and uses a current transformer.

My electric service is 400 amps using 2, 200 amp panels mounted side by side on the opposite side of the wall from the exterior meter can/housing.

The meter's digital display continueously cycles displaying a register number and the value associated with that register.

Register 18 contains the value of 000.050, which according to the documents supplied by Progress Energy, is the "Watt Hour Constant". Customer service reps. have refered to this register as the Kh and also as the "meter constant".

My monthly bill indicates that a constant of 60 is used to calculate the actual KWH.

A meter technician from Progress Energy recently inspected my equipment and advised that the CT / Current Transformer had a ratio of 600:5.

The meter's digital display shows values for registers 1 - 23 except for registers 3,7,10,14,17, and 19.

My monthly bill indicates both the highest KW for on peak and off peak showing the KW, time, and date. Looking at several years of bill, the times shown are always on 15 minute boundaries either on the hour, 15 minutes past the hour, 30 minutes past the hour or 45 minutes past the hour.

Progress Energy Customer Service representatives are not trained to answer technical questions about their demand and time of use billing or measurement techniques and are reluctant to allow me to talk to more knowledgable individuals in the company, so I am posting my questions here seeking advice from members.

Given the above information:

1. What is the relationship to the value in register 18 "watt hour constant" which is currently 000.050 and the "meter constant" of 60 as indicated on my monthly bill?

2. What is the relevance of the CT ratio with respect to question 1 above?

3. What is the significance of the 15 minute interval with respect to demand billing, and does the meter record average demand over the 15 minute interval or peak demand.

4. PE customer service advised that the 15 minute interval was a moving window. If this is correct, why are all readings for the past 6 years on one of 4 times at fixed intervals?

5. PE indicates date and time for off peak KW on their bill, however none of the registers display the date and time for off peak. Where do they get this information?

6. Meter registers 22 and 23 indicate the date and time for the highest on peak KW for the current month. Does the time value indicate the beginning of the 15 minute interval or the end of the interval?

7. The definition for on peak times for Progress Energy changes twice a year. How does the meter programed with the correct times?

8. Are there registers that aren't displayed by the meter but are downloaded into the data collection device used by the meter reader each month?

Thanks in advance for your assistance and information.
Click to expand...
Given the info:
1. Wh is the watt-hours for each disk revolution. In your example, 20 revolutions equals one watt-hour on the meter. The watt-hours recorded by the meter would need to be multiplied by the meter multiplier (the constant) to get the actual watt-hours consumed.

2. The meter multiplier is the PT ratio times the CT ratio. With a 600:5 CT, I would have expected your multiplier to be 120, not 60. I would guess that you are only being charged for 1/2 of you actual usage or the 600:5 is really 300:5.

3. The 15 minute interval takes the average demand over the 15 minutes.

4. It resets every 15 minutes, so it does move, but it is not a sliding window.

5. From the time stamp on the 15 minute readings. This data is stored in the meter and downloaded as 15 minute interval data when the meter is read.

6. I don't know for your meter.

7. It probably isn't. I suspect it does not care. The data is processed back at PE using the time stamps on the data.

8. There are certainly other registers. These can be downloaded by the meter reader. There could be things like tamper indicators, test codes, etc. These are normally of no interest to the customer or even most of the people at PE.
 
1. Wh is the watt-hours for each disk revolution. In your example, 20 revolutions equals one watt-hour on the meter. The watt-hours recorded by the meter would need to be multiplied by the meter multiplier (the constant) to get the actual watt-hours consumed.

If 20 revolutions = 1 watt-hour, is it correct then that 1KWH would require 20,000 revolutions of the disk?

If the meter/CT multiplier really is 60, then is it correct that 1KWH of actual usage would equal 20,000/60 or 333.33 revolutions?

Thanks for you input on this matter.
 
I wrote this for a training manual some time ago. This may be of value. :smile:​

INSTANTANIOUS kW DEMAND
​
If you want the total instantaneous demand while in the field, this method will work. This method will give you the instantaneous demand for only that point in time and will not give any unbalance. In other words, if a service has three-fourths of the load on one leg and one-fourth on the other, you would not be able to tell that.

This method will work on any meter, including a primary meter.

1. Look at the meter for a Kh (secondary watt-hour constant) number, this is the meter constant and indicates the energy used by the load for each revolution of the disk. If you are looking at a CT cabinet, someone will have marked a multiplier and is used to increase the Kh value for the CT ratio.

2. Count the revolutions of the disk for one minute, if you want a little more accuracy, use a little more time.

3. Multiply the number of revolutions in one minute by the Kh, and then by 60. Divide the resultant by 1000.

Example:

You are at a service that has a meter with a Kh of 3.6 and time the turns at 68 per minute.
(68)(3.6)(60) / 1000 = 14.688 kW​

If this is a single phase service, the load in amperes is
14.688 / 0.24 = 61.2 amperes​

This is just an instant in time and is of no use for any kind of load study. However, it may prove useful if you want a quick approximation of the load.
 
iplay1515 said:
1. Wh is the watt-hours for each disk revolution. In your example, 20 revolutions equals one watt-hour on the meter. The watt-hours recorded by the meter would need to be multiplied by the meter multiplier (the constant) to get the actual watt-hours consumed.

If 20 revolutions = 1 watt-hour, is it correct then that 1KWH would require 20,000 revolutions of the disk?

If the meter/CT multiplier really is 60, then is it correct that 1KWH of actual usage would equal 20,000/60 or 333.33 revolutions?

Thanks for you input on this matter.
Click to expand...
correct .
 
charlie said:
I wrote this for a training manual some time ago...​
Click to expand...
That's the same as mine except I used a whole number for the revolution count:​

kW = 3600 x Pri Kh const x # disc revs / (1000 x seconds for disc revs)

where Pri Kh const = Sec Kh const x C.T. Ratio x P.T. Ratio
 
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charlie said:
My intent was to make the whole thing a bit easier to understand (I don' t know if I actually did that though). :)
Click to expand...
It was easy enough but people usually find a formula easier than text. The formula I gave flows with what you do when you use a stopwatch (works good with slow revs too).
 
iplay1515 said:
If the fifteen minute interval is an average kw usage demand, how many sample readings are made during any given interval that are used to compute the average?
Click to expand...
It varies among meters, but it can be from tens to hundreds of samples per cycle. So we are talking about millions of samples in a 15 minute interval, and that is just for one reading, like a current or voltage.
 
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