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#209844 - 05/06/13 10:13 AM General question about meters - Peak demand vs KWh
WD_Electrical Offline
New Member
Registered: 04/10/13
Posts: 8
Loc: USA
Hi all,

For existing electrical services, some utilities seem to be able to provide peak demand info in KW or KVA (useful for our trade) and other times they can only provide info in KWh (useless for our trade). Does anyone know if this difference in data is due to meter types? For example, are certain types of meters incapable of providing peak demand info?

Thanks for any info/clarification.
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#209845 - 05/06/13 12:06 PM Re: General question about meters - Peak demand vs KWh [Re: WD_Electrical]
HotLine1 Offline


Member
Registered: 04/03/02
Posts: 6776
Loc: Brick, NJ USA
The 'basic' meter for resi/small comm only records KWHr here.

Demand meters are usually installed on larger comm/industrial sites. That was 'how it was'.

The new smart meters have an abundance of info available, that's what my POCO meter tech explained to me last week. However, that info cannot be 'read' by everyone.

One facility I worked at had 'older' demand meters that provided peak, off peak, and 'night' demands.

_________________________
John
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#209863 - 05/08/13 08:40 AM Re: General question about meters - Peak demand vs KWh [Re: WD_Electrical]
Scott35 Offline

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Member
Registered: 10/19/00
Posts: 2707
Loc: Anaheim, CA. USA
To expand more on John's Post ("John = HotLine1)...

1.: In the case of "Standard Mechanical Readout" KWH Meters; the types with a rotating Register and "0-9 Pointer" Dial Indicators:

Poco's obtain Peak Records within Billing Cycles, per the readout tally of the "Demand Register", typically an added set of Register Dials with Pointers, which is separate from the KWH Tally Register, however, the Demand Register may be a single Pin-Type Pointer, with a scaled Graph behind.

In either case, the Demand Register has a Mechanical "Reset" handle, which is meant for the Meter Reader to use after each Monthly reading, so as to reset the Demand Register back to "Zero".
Only the highest Demand level will be indicated.

The most basic of these Demand Meters will indicate Peak Kilo Watts, in addition to the Standard KWH Tally.

Where KVAR is measured (in addition to KWH / Peak KW), a separate Meter is included, which measures KVARH (KVAR-Hours), and will include Peak Demand KVAR.
BTW: Some may be Totalizing Meters, where all is compiled within a single Meter base

The Peak KVA is found by applying the following formula:

C^2 = A^2 + B^2

"A" = Peak Demand KW (True Power),
"B" = Peak Demand KVAR (Reactive Power),
"C" = Peak Demand KVA (Apparent Power).

Very Basic Example:

If the Reactive Power Demand ("B") equals 3.0 KVAR,
and the True Power Demand ("A") equals 4.0KW,
the Apparent Power Demand ("C") will be 5.0 KVA.

Meters with KWH Measurements only will not read Peak Demands; they only record consumption over time.
These are the Meters with only one Register Set available; the KWH Registers.

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2: In the case of a "Digital Recording" type Meter; with or without a rotating Register, there are multiple recording 'Sections" available, which allow for a single based Meter to tally total Consumption, and Peak Demands as well.

Most likely, if the Poco supplies Peak KW, KVA and/or KVAR Demand levels of some accuracy (typically with a Peak Power Factor included), the readings were obtained from a Digital Recording type Meter.

Let me know if this was helpful.

--Scott (EE)
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
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#209864 - 05/08/13 09:40 AM Re: General question about meters - Peak demand vs KWh [Re: WD_Electrical]
gfretwell Offline


Member
Registered: 07/20/04
Posts: 9038
Loc: Estero,Fl,usa
The system they just installed here sends the meter readings in real time but I am not sure what the sample rate is. Hardware wise I doubt it has to be more than a few seconds to scan the whole county. I am not sure what the server topology is on the PoCo end. The WiFi concentrators are on poles about one a block.
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Greg Fretwell
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#209868 - 05/08/13 07:51 PM Re: General question about meters - Peak demand vs KWh [Re: WD_Electrical]
HotLine1 Offline


Member
Registered: 04/03/02
Posts: 6776
Loc: Brick, NJ USA
Just an additional view. The first generation of digital meters had/have a digital readout that cycles thru KWHr, Voltage (phase-phase) & phase to N, Amperage on each leg, TOD, and KW demand. These are 3 phase, 277/480 and 120/208.

This is probably what Scott said above, in his usual eloquent fashion.

I have a POCO meter tech supervisor going to be at a job on Saturday, he may educate me on the 'smart' meters that they are installing.

BTW, the EMon-DMon check (submeters) provide a lot of info also.
_________________________
John
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