Operation: CP1SD/T/L Version
38
CENTRON® Polyphase Meter Technical Reference Guide
Power Down Procedures
To de-energize all electronics, remove power from the meter.
A power outage is recognized any time the line voltage drops 20 percent below the lowest
nominal point of the voltage range. With a standard single phase power supply, a power
outage occurs when line voltage drops below 96 volts; with a polyphase power supply, a
power outage occurs when line voltage drops below 45 volts. When a power outage is
recognized, the D/T/L Register saves all billing values to non-volatile Flash memory.
Demand Meter
Restoration of AC power energizes the electronics and causes the meter to perform self-
diagnostic check procedures. The meter then retrieves all billing data from non-volatile
memory, begins measuring energy, and starts the process of calculating any demand values.
TOU/Load Profile Meters
All TOU/Load Profile meters have a battery installed. The battery allows the TOU and Load
Profile data in RAM to be maintained during a power outage. The battery also allows the
timekeeping circuitry in the meter to maintain the meter's clock during an outage. If a
battery is removed on a TOU/Load Profile meter during an outage, then the meter's clock
will be off by the duration of the outage and the TOU data and some Load Profile data will
be lost. Load Profile data is periodically committed to flash as described in the Load Profile
section.
Upon the return of AC power, the register undergoes a procedure similar to the initial
power-up. The meter performs self-diagnostic checks, data is retrieved from non-volatile
memory, and normal operation is resumed. The number of minutes of power outage
maintained while the meter was in carry-over operation, is added to the Time on Battery
register. Since the demand interval is synchronized to the top of the hour, the first demand
interval after a power outage may be shorter than the programmed interval value.
Cold Load Pickup
Normally, when power is restored to the meter after an outage, a new demand interval is
started and demand calculations begin immediately. The meter can be configured to
recognize a demand delay or cold load pickup (CLPU) time. If a CLPU is configured in the
meter, the meter will delay demand calculations for the configured amount of time—0 to
255 minutes in one-minute increments. For example, if a CLPU time of five minutes is
programmed into the meter, a power outage will cause the meter to wait five minutes after
power restoration before resuming demand calculations.
Defining CLPU as zero will cause demand calculations to restart immediately after
any recognized power outage.
