Demand Pulse Meter
- Thread starter VIC1958
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Here is a brief explanation.
http://openenergymonitor.org/emon/node/79
Some utilities will supply them for billing purposes on large accounts. They look just like a regular power meter with a pulse module added. Some companies sell units that can be installed to monitor usage behind the utility billing meter. These come in handy if a parent company wants to keep track of individual stores. We supply pulse metering for all the Wal-marts on our system. It allows the Bentonville office to monitor power and remotely turn off devices when a certain threshold is reached. This saves a tremendous amount on the bill as they would have to pay for their maximum power all month, plus energy, even if they used a lot of power for 15 minutes only.
http://openenergymonitor.org/emon/node/79
Some utilities will supply them for billing purposes on large accounts. They look just like a regular power meter with a pulse module added. Some companies sell units that can be installed to monitor usage behind the utility billing meter. These come in handy if a parent company wants to keep track of individual stores. We supply pulse metering for all the Wal-marts on our system. It allows the Bentonville office to monitor power and remotely turn off devices when a certain threshold is reached. This saves a tremendous amount on the bill as they would have to pay for their maximum power all month, plus energy, even if they used a lot of power for 15 minutes only.
rcwilson
Senior Member
- Location
- Redmond, WA
A Demand meter measures kWH use in a demand interval, usually 15, 30 or 60 minutes, and records the maximum value measured during a billing period.
A meter with a pulse attachment or function outputs a pulse (contact closure) for every "x" kWH used.
Counting the pulses measures the energy (kWH) used. It is real time instead of waiting for a meter reading and subtracting the previous reading It is cheaper and more accurate than using a kW transducer to send a signal to a control or accounting system.
Old analog meters had a gearing attachment that switched a form C contact every few disk revolutions. A pulse accumulator could take pulses from several meters, total them and record the result. The contacts were wired out to a device that registered each pulse on a mechanical counter that reset at the end of the interval and printed the interval's total on a paper tape. Each billing period, the utility meter reader removed the tape and looked for the largest recorded demand.
Most modern meters can do this with communications instead of the pulse contacts.
Our aluminum plant meters had 1 pulse = 400 kWH. Meters for the four utility feeders fed pulses to an accumulator with a dipaly and papaer tape recorder. We bought power strictly by demand, no kwh charges. Each month, we contracted for delivery of a set MW, always in units of 400 kwh, like 150.40 MW ( =376 pulses). If we went over in any one hour, we got charged that higher demand for the next 6-10 months. By monitoring the rate of power use and controlling the high current DC process we could squeeze an extra "free" 350 kwh out of each hour by getting the meter to reset before it hit pulse 377.
A meter with a pulse attachment or function outputs a pulse (contact closure) for every "x" kWH used.
Counting the pulses measures the energy (kWH) used. It is real time instead of waiting for a meter reading and subtracting the previous reading It is cheaper and more accurate than using a kW transducer to send a signal to a control or accounting system.
Old analog meters had a gearing attachment that switched a form C contact every few disk revolutions. A pulse accumulator could take pulses from several meters, total them and record the result. The contacts were wired out to a device that registered each pulse on a mechanical counter that reset at the end of the interval and printed the interval's total on a paper tape. Each billing period, the utility meter reader removed the tape and looked for the largest recorded demand.
Most modern meters can do this with communications instead of the pulse contacts.
Our aluminum plant meters had 1 pulse = 400 kWH. Meters for the four utility feeders fed pulses to an accumulator with a dipaly and papaer tape recorder. We bought power strictly by demand, no kwh charges. Each month, we contracted for delivery of a set MW, always in units of 400 kwh, like 150.40 MW ( =376 pulses). If we went over in any one hour, we got charged that higher demand for the next 6-10 months. By monitoring the rate of power use and controlling the high current DC process we could squeeze an extra "free" 350 kwh out of each hour by getting the meter to reset before it hit pulse 377.
T
T.M.Haja Sahib
Guest
I am unable to believe this.Once the meter recorded the contracted 376 pulses,even a momentary increase in load will be reflected in the recorded pulses beyond 376 and so you will be penalized for it.............
rcwilson
Senior Member
- Location
- Redmond, WA
Our billing was strictly based on demand and power factor penalties, not kwh. The counter would not increment until the full 400 kwh for the next step was consumed. An extra 300 kWH in this hour was not carried over to the next, due to the reset of the old style counters.
By monitoring the pulse counts and the kW rate we would get very close each hour without going over, even though the usage rate it was one pulse every 9-12 seconds. The control system that adjusted the potlines' DC voltage and current could quickly change load enough to hit our target. Load was very steady so it was easy to predict where the demand would be at the end of the hour. Only a utility voltage jump would increase the power usage, most process upsets reduced the kW. It was relatively easy to shoot for 200-300 kwh over our contracted target and not go over.
That type of a power purchase contract disappeared years ago. (So did the aluminum plants when power was no longer $0.003/kwh).
By monitoring the pulse counts and the kW rate we would get very close each hour without going over, even though the usage rate it was one pulse every 9-12 seconds. The control system that adjusted the potlines' DC voltage and current could quickly change load enough to hit our target. Load was very steady so it was easy to predict where the demand would be at the end of the hour. Only a utility voltage jump would increase the power usage, most process upsets reduced the kW. It was relatively easy to shoot for 200-300 kwh over our contracted target and not go over.
That type of a power purchase contract disappeared years ago. (So did the aluminum plants when power was no longer $0.003/kwh).
T
T.M.Haja Sahib
Guest
Sorry,this is not possible.You can not use extra 300KWH without corresponding excess demand recording in the demand meter.In that case the reset of the meter will not be back to the original contract demand value but be correspondingly increased.
mivey
Senior Member
You would not be able to squeeze every hour because you are robbing Peter to pay Paul. In the susequent hour, you start the hour being "shorted" from the game in the previous hour. I do not believe the energy accumulator gets dumped but is rolled to the next hour. In other words, the 300 you garnered in the prior hour essentially results in a 100 kWh pulse at the first of the next hour.
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