User's Manual

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REX Meter
2 Product Description Technical Manual
2-4 30 November 2006
■ kWh received
■ kWh sum (kWh delivered + kWh received)
■ kWh net (kWh delivered - kWh received)
The metered quantity is used to calculate total energy, energy on a TOU basis,
demand, and load profiling data.
Note: When the selected metered quantity is kWh net, the meter
calculates demand from kWh-delivered and stores kWh-
delivered pulses for load profiling.
Demand Calculation. Demand is the average value of power over a specified
interval of time. The REX meter supports the block interval method for demand
calculation. The demand interval is specified in minutes and must be 15, 30, or
60 minutes.
The block interval calculates demand using the following equation:
For example, if the demand interval is 15 minutes and the total accumulated
energy is 50 kWh, then the demand is 200 kW.
Maximum Demand. Maximum demand (also referred to as indicating
demand) is the highest demand value that occurs in a billing period. The
demand for each demand interval is calculated and compared to an earlier
maximum demand value. If the new interval value exceeds the previous
maximum demand, then the new demand is stored as the maximum demand
(see Figure 2-3). When a demand reset occurs, the maximum demand is reset
to zero. The demand for the first full interval after the demand reset becomes the
maximum demand.
Figure 2-3. Maximum demand
Demand Forgiveness. Demand forgiveness is the time during which demand
is not calculated or stored after a power failure. The demand forgiveness may be
set to a number between zero (disabled) and 255 minutes.
hours
t
energy daccumulatetotal
D =
kW200
h0.25
kWh50
D ==
Interval 6
demand
(9.2 kW)
Interval 8
demand
(9.5 kW)
Interval 7
demand
(9.9 kW)
New maximum
demand (9.9 kW)
Earlier maximum
demand (9.9 kW)
Earlier maximum
demand (9.7 kW)