Submeter design and calculations

Dovid

Joined Jul 6, 2022
6
We are designing an electric submeter. We are looking for the calculations with the exact variables that we can collect from the voltage taps and current transformers to generate the kW used. For instance, if the CT gives us only amps, how do know how out of phase it is with the voltage to calculate power factor, etc.?

Thank you.

ericgibbs

Joined Jan 29, 2010
15,743
Hi Dovid.
Welcome to AAC.
Is this a college assignment.?
E

Dovid

Joined Jul 6, 2022
6
Hi Dovid.
Welcome to AAC.
Is this a college assignment.?
E
Hi Eric. No, this is for a commercial application.
Thank you. Dovid

Papabravo

Joined Feb 24, 2006
18,839
Ummm. What exactly is a submeter?

Dovid

Joined Jul 6, 2022
6
Ummm. What exactly is a submeter?
It is really like a regular electric meter, just measuring sub-loads.

Jon Chandler

Joined Jun 12, 2008
261
Microchip and others have dedicated chips to so this that measure all the required parameters and calculate the resultant values. That's probably a good place to start.

Dovid

Joined Jul 6, 2022
6
Microchip and others have dedicated chips to so this that measure all the required parameters and calculate the resultant values. That's probably a good place to start.
Yes, thank you. We want to build the the calculation/programming itself without using chips.

Ian0

Joined Aug 7, 2020
5,571
Yes, thank you. We want to build the the calculation/programming itself without using chips.
Without chips? That's ambitious.
To get the power you need to multiply the instantaneous voltage by the instantaneous current, then average the result.
"Without chips" would imply you are building a Gilbert cell out of transistors to do the multiplication, and I doubt you could meet the required standards for accuracy without a lot of adjustment.
If you mean "without microprocessors", then an analogue multiplier ICs don't come much cheaper than the AD633 at £15, and you can buy a handful of microprocessors for that price.
Microchip's dedicated electricity meter IC ATM90E26 will cost you £1.25

Dovid

Joined Jul 6, 2022
6
Without chips? That's ambitious.
To get the power you need to multiply the instantaneous voltage by the instantaneous current, then average the result.
"Without chips" would imply you are building a Gilbert cell out of transistors to do the multiplication, and I doubt you could meet the required standards for accuracy without a lot of adjustment.
If you mean "without microprocessors", then an analogue multiplier ICs don't come much cheaper than the AD633 at £15, and you can buy a handful of microprocessors for that price.
Microchip's dedicated electricity meter IC ATM90E26 will cost you £1.25
We want to do it centralized, not in the field.

Papabravo

Joined Feb 24, 2006
18,839
Yes, thank you. We want to build the the calculation/programming itself without using chips.
That is going to be a tall order. Were you planning to resurrect the vacuum tube!!?
Sounds like what you have in mind is something to log the data and transmit it over some kind of data link.

Ian0

Joined Aug 7, 2020
5,571
We want to do it centralized, not in the field.
What do you mean? Please explain.

Ian0

Joined Aug 7, 2020
5,571
That is going to be a tall order. Were you planning to resurrect the vacuum tube!!?
6HZ6 Dual-control pentode?

Dovid

Joined Jul 6, 2022
6
The following is the data from a meter in the field. We are looking for how they came up with (what is the equation/calculation) the kVA and PF which generated the kW.

 No. Date/Time V1 V2 V3 I1 I2 I3 KW L1 KW L2 KW L3 Kvar L1 Kvar L2 Kvar L3 kVA L1 kVA L2 kVA L3 PF L1 PF L2 PF L3 kW kvar kVA PF PF LAG PD LEAD In FREQ V UNB% I UNB% 1​ 6/22/2022 16:34​ 268​ 270.3​ 268.3​ 4.17​ 2.63​ 3.95​ 0.731​ 0.616​ 0.758​ 0.503​ 0.294​ 0.283​ 0.887​ 0.683​ 0.809​ 0.824​ 0.902​ 0.937​ 2.162​ 1.1​ 2.426​ 0.891​ 0.891​ 1​ 1.54​ 60.02​ 0.5​ 28.6​ 2​ 6/22/2022 16:34​ 268.3​ 270.5​ 268.6​ 4.03​ 2.53​ 4.05​ 0.732​ 0.593​ 0.834​ 0.457​ 0.3​ 0.253​ 0.863​ 0.665​ 0.872​ 0.848​ 0.892​ 0.957​ 2.094​ 1.011​ 2.325​ 0.901​ 0.901​ 1​ 1.36​ 60.01​ 0.5​ 21.2​ 3​ 6/22/2022 16:34​ 268.5​ 270.5​ 268.6​ 4.09​ 2.59​ 3.89​ 0.7​ 0.622​ 0.778​ 0.484​ 0.284​ 0.226​ 0.851​ 0.684​ 0.81​ 0.822​ 0.91​ 0.96​ 2.064​ 1.038​ 2.31​ 0.894​ 0.894​ 1​ 1.22​ 60.01​ 0.5​ 26.2​ 4​ 6/22/2022 16:35​ 268​ 270.1​ 268.3​ 4.24​ 2.71​ 3.93​ 0.737​ 0.614​ 0.758​ 0.478​ 0.33​ 0.229​ 0.878​ 0.697​ 0.792​ 0.839​ 0.881​ 0.957​ 2.193​ 1.065​ 2.438​ 0.9​ 0.9​ 1​ 1.3​ 60.01​ 0.5​ 27​ 5​ 6/22/2022 16:35​ 268​ 270.3​ 268.1​ 4.05​ 2.65​ 3.89​ 0.741​ 0.614​ 0.775​ 0.483​ 0.312​ 0.273​ 0.884​ 0.689​ 0.822​ 0.838​ 0.892​ 0.943​ 2.112​ 1.066​ 2.366​ 0.893​ 0.893​ 1​ 1.56​ 60.01​ 0.5​ 24.1​ 6​ 6/22/2022 16:35​ 268​ 270.1​ 268.3​ 4.26​ 2.71​ 4.03​ 0.714​ 0.639​ 0.791​ 0.506​ 0.268​ 0.268​ 0.875​ 0.693​ 0.835​ 0.816​ 0.922​ 0.947​ 2.111​ 0.974​ 2.325​ 0.908​ 0.908​ 1​ 1.54​ 60.01​ 0.5​ 28​ 7​ 6/22/2022 16:35​ 268​ 270.3​ 268.3​ 4.07​ 2.59​ 4.01​ 0.726​ 0.599​ 0.785​ 0.499​ 0.313​ 0.249​ 0.881​ 0.676​ 0.823​ 0.824​ 0.886​ 0.953​ 2.022​ 1.169​ 2.336​ 0.866​ 0.866​ 1​ 1.61​ 60.01​ 0.5​ 24.5​ 8​ 6/22/2022 16:35​ 268​ 270.1​ 268.3​ 4.09​ 2.69​ 3.91​ 0.7​ 0.608​ 0.754​ 0.458​ 0.288​ 0.307​ 0.836​ 0.673​ 0.804​ 0.84​ 0.905​ 0.952​ 2.111​ 1.023​ 2.346​ 0.9​ 0.9​ 1​ 1.5​ 60.01​ 0.5​ 26.7​ 9​ 6/22/2022 16:35​ 268​ 270.3​ 268.3​ 4.19​ 2.53​ 3.89​ 0.717​ 0.614​ 0.778​ 0.505​ 0.264​ 0.239​ 0.877​ 0.668​ 0.813​ 0.818​ 0.919​ 0.956​ 2.049​ 1.01​ 2.284​ 0.897​ 0.897​ 1​ 1.28​ 60.02​ 0.5​ 26.5​ 10​ 6/22/2022 16:35​ 268​ 270.1​ 268.3​ 4.2​ 2.53​ 3.89​ 0.686​ 0.586​ 0.74​ 0.443​ 0.303​ 0.271​ 0.816​ 0.66​ 0.788​ 0.84​ 0.888​ 0.939​ 2.109​ 0.996​ 2.332​ 0.904​ 0.904​ 1​ 1.38​ 60​ 0.5​ 30​

Papabravo

Joined Feb 24, 2006
18,839
6HZ6 Dual-control pentode?
Can you get a quantity discount on them?

Jon Chandler

Joined Jun 12, 2008
261
Yes, thank you. We want to build the the calculation/programming itself without using chips.
Since you seem to be a bit short of understanding what needs to be done, reading the datasheets for some of the power meter chips would help build that understanding. If you're trying to "roll your own", a thorough understanding of the principles involved will be needed.

Ian0

Joined Aug 7, 2020
5,571
Can you get a quantity discount on them?
I got them from ESRC vacuum tubes, who were in your neck of the woods (Orlando, to be precise) for $1 each. Sadly the firm no longer exist after the proprietor died. I wonder who bought all theirs stock Ian0 Joined Aug 7, 2020 5,571 The following is the data from a meter in the field. We are looking for how they came up with (what is the equation/calculation) the kVA and PF which generated the kW.  No. Date/Time V1 V2 V3 I1 I2 I3 KW L1 KW L2 KW L3 Kvar L1 Kvar L2 Kvar L3 kVA L1 kVA L2 kVA L3 PF L1 PF L2 PF L3 kW kvar kVA PF PF LAG PD LEAD In FREQ V UNB% I UNB% 1​ 6/22/2022 16:34​ 268​ 270.3​ 268.3​ 4.17​ 2.63​ 3.95​ 0.731​ 0.616​ 0.758​ 0.503​ 0.294​ 0.283​ 0.887​ 0.683​ 0.809​ 0.824​ 0.902​ 0.937​ 2.162​ 1.1​ 2.426​ 0.891​ 0.891​ 1​ 1.54​ 60.02​ 0.5​ 28.6​ 2​ 6/22/2022 16:34​ 268.3​ 270.5​ 268.6​ 4.03​ 2.53​ 4.05​ 0.732​ 0.593​ 0.834​ 0.457​ 0.3​ 0.253​ 0.863​ 0.665​ 0.872​ 0.848​ 0.892​ 0.957​ 2.094​ 1.011​ 2.325​ 0.901​ 0.901​ 1​ 1.36​ 60.01​ 0.5​ 21.2​ 3​ 6/22/2022 16:34​ 268.5​ 270.5​ 268.6​ 4.09​ 2.59​ 3.89​ 0.7​ 0.622​ 0.778​ 0.484​ 0.284​ 0.226​ 0.851​ 0.684​ 0.81​ 0.822​ 0.91​ 0.96​ 2.064​ 1.038​ 2.31​ 0.894​ 0.894​ 1​ 1.22​ 60.01​ 0.5​ 26.2​ 4​ 6/22/2022 16:35​ 268​ 270.1​ 268.3​ 4.24​ 2.71​ 3.93​ 0.737​ 0.614​ 0.758​ 0.478​ 0.33​ 0.229​ 0.878​ 0.697​ 0.792​ 0.839​ 0.881​ 0.957​ 2.193​ 1.065​ 2.438​ 0.9​ 0.9​ 1​ 1.3​ 60.01​ 0.5​ 27​ 5​ 6/22/2022 16:35​ 268​ 270.3​ 268.1​ 4.05​ 2.65​ 3.89​ 0.741​ 0.614​ 0.775​ 0.483​ 0.312​ 0.273​ 0.884​ 0.689​ 0.822​ 0.838​ 0.892​ 0.943​ 2.112​ 1.066​ 2.366​ 0.893​ 0.893​ 1​ 1.56​ 60.01​ 0.5​ 24.1​ 6​ 6/22/2022 16:35​ 268​ 270.1​ 268.3​ 4.26​ 2.71​ 4.03​ 0.714​ 0.639​ 0.791​ 0.506​ 0.268​ 0.268​ 0.875​ 0.693​ 0.835​ 0.816​ 0.922​ 0.947​ 2.111​ 0.974​ 2.325​ 0.908​ 0.908​ 1​ 1.54​ 60.01​ 0.5​ 28​ 7​ 6/22/2022 16:35​ 268​ 270.3​ 268.3​ 4.07​ 2.59​ 4.01​ 0.726​ 0.599​ 0.785​ 0.499​ 0.313​ 0.249​ 0.881​ 0.676​ 0.823​ 0.824​ 0.886​ 0.953​ 2.022​ 1.169​ 2.336​ 0.866​ 0.866​ 1​ 1.61​ 60.01​ 0.5​ 24.5​ 8​ 6/22/2022 16:35​ 268​ 270.1​ 268.3​ 4.09​ 2.69​ 3.91​ 0.7​ 0.608​ 0.754​ 0.458​ 0.288​ 0.307​ 0.836​ 0.673​ 0.804​ 0.84​ 0.905​ 0.952​ 2.111​ 1.023​ 2.346​ 0.9​ 0.9​ 1​ 1.5​ 60.01​ 0.5​ 26.7​ 9​ 6/22/2022 16:35​ 268​ 270.3​ 268.3​ 4.19​ 2.53​ 3.89​ 0.717​ 0.614​ 0.778​ 0.505​ 0.264​ 0.239​ 0.877​ 0.668​ 0.813​ 0.818​ 0.919​ 0.956​ 2.049​ 1.01​ 2.284​ 0.897​ 0.897​ 1​ 1.28​ 60.02​ 0.5​ 26.5​ 10​ 6/22/2022 16:35​ 268​ 270.1​ 268.3​ 4.2​ 2.53​ 3.89​ 0.686​ 0.586​ 0.74​ 0.443​ 0.303​ 0.271​ 0.816​ 0.66​ 0.788​ 0.84​ 0.888​ 0.939​ 2.109​ 0.996​ 2.332​ 0.904​ 0.904​ 1​ 1.38​ 60​ 0.5​ 30​ To get power you multiply instantaneous voltage by instantaneous current and average the result. To get VA you multiply average current by average voltage. To get power factor you divide power by VA. Papabravo Joined Feb 24, 2006 18,839 I got them from ESRC vacuum tubes, who were in your neck of the woods (Orlando, to be precise) for$1 each. Sadly the firm no longer exist after the proprietor died. I wonder who bought all theirs stock
Some guy with an 8' table at a hamfest – no doubt