#778 Proposal for electric meters: power vs. demand

Stephen Frank Mon 13 Jan 2020

So back when we (that's an inclusive "we") worked on the elec meter tagging standard, we decided not to include a special tag for demand, vs. power. However, since then, I've realized that most power quality meters include both:

  • Power: "instantaneous" reading of active power (actually, an average over a few cycles)
  • Demand: average reading of active power over the utility billing demand interval (typically 15 minutes)

I've now realized that it would be best to have both power and demand tags defined, where demand is specifically defined as active power averaged over the billing demand interval. This is what we're doing now with our own meters.

I would post this in the electric meter working group, but I think when we had that working group it pre-dated the WG section of the forum and I can't find it. (Well, I'm sure I could but it would take me a while digging through forum history.)

Keith Bishoρ Tue 14 Jan 2020

Completely agree with adding demand.

The only change I would recommend is removing "utility" and "billing" from the definition. With submeters, these reading may have no association with with those 2 concepts but simply serve as a rolling average of power over a period of time.

Chad Ruch Tue 28 Jan 2020

I would keep in mind that demand can be used to describe heating, cooling, airflow, etc. demand from an airHandlingEquip and/or airTerminalUnit when discussing this.

  1. JCI has points called PI Cooling Demand, PI Heating Demand, Cooling Required, and Heating Required.
  2. Distech, Honeywell, and Trane have points called Terminal Load.

Also, demand control ventilation (DCV) should be considered as well.

Hans Langels Sun 2 Feb 2020

If power is understood as "electrical power" then the definitions of power, input power ("demand" or "consumption") and output power ("generation") per IEV (International Electrotechnical Vocabulary) are given as:

IEC DD 113-03-52 power power

derivative with respect to time t of energy E being transferred or transformed, thus P=dEdt

NOTE 1 For power in electric circuits, see IEC 60050-131.

NOTE 2 The coherent SI unit of power is watt, W.

IEC DD 113-03-53 input power input power

for a given system, power transferred to that system from an external system 

IEC DD 113-03-54 output power output power

for a given system, power transferred from that system to an external system 

It would be beneficial to use these standard terms and definitions.

Brian Frank Tue 24 Mar 2020

We have added elec-demand to Haystack 4 preview 3.9.8.

I made it a subtype of active-power

I added the following as a child point of ac-elec-meter

total ac elec demand sensor point

Feedback on the points listed under elec meter?

Also as part of this change I added ac to all the ac-elec-meter points

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