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Chapter 8—Measurements and calculations PowerLogic™ PM5100 series user guide
The following illustration shows the different ways power demand is calculated using
the block interval method. In this example, the interval is set to 15 minutes.
Synchronized demand
You can configure the demand calculations to be synchronized using an external pulse
input, a command sent over communications, or the device’s internal real-time clock.
• Command synchronized demand: This method allows you to synchronize the
demand intervals of multiple meters on a communications network. For example, if
a programmable logic controller (PLC) input is monitoring a pulse at the end of a
demand interval on a utility revenue meter, you can program the PLC to issue a
command to multiple meters whenever the utility meter starts a new demand
interval. Each time the command is issued, the demand readings of each meter are
calculated for the same interval. When setting up this type of demand, you can
choose Cmd Sync Block (command-synchronized block demand) or Cmd Sync
Roll Block (command-synchronized rolling block demand). Cmd Sync Roll Blk
requires that you specify a subinterval.
• Clock synchronized demand: This method allows you to synchronize the demand
interval to the power meter’s internal real-time clock. This helps you synchronize the
demand to a particular time, typically on the hour (for example, at 12:00 am). If you
select another time of day when the demand intervals are to be synchronized, the
time must be specified in minutes from midnight. For example, to synchronize at
Block interval demand example
15 30 45
15 30 45
60 . . .
15
30 45
20 35 4025
Demand value is the
average for the last
completed interval
Demand value is
the average for
the last
completed
interval
Demand value is
the average for
the last
completed
interval
Time
(sec)
Time
(min)
Time
(min)
Calculation updates
every 15 seconds
Calculation updates at
the end of the interval
Calculation updates at the end of
the subinterval (5 minutes)
Timed Sliding Block
Timed Block
Timed Rolling Block
15-minute interval
15-minute interval
15-minute interval 15-min
15-minute interval