User's Manual

ANSI Electric Meter v3.1 User’s Guide 57

 Bit 6: Load side voltage status

0 = none

1 = present

 Bits 7..15: Instantaneous Power Level

o Sum of first four registers in ST28 (0 implies no power

consumption measured in last 50 cycles)

Note: Remember that your meter may be configured to use the Load Side Voltage

Detected error to indicate when load side voltage is present, in which case the

values listed above for Argument Format 4 should not be used.

Low Voltage Operation

When operating below certain voltage levels and under different phase combination,

the operation of the load disconnect contactor may become unpredictable. This

section describes how to avoid disconnect operation under these conditions, and

describes how users can be made aware of these conditions.

A manufacturing configurable voltage threshold can also be used to decide if

disconnect operation is safe, as the power fail threshold is configurable and can be

configured to be lower than the safe threshold. The voltage threshold for each phase

is initially established based on the meter’s hardware configuration.

Each active phase voltage in the meter is monitored at all times, including whenever

a disconnect push button action is acknowledged. An internal flag will be set in the

meter whenever the voltage combination is considered unsafe based on the voltage

threshold. The flag will be cleared when the unsafe condition ceases to exists. Until

the condition ceases to exist, all disconnect operations that require pulsing the load

disconnect contactor will trigger the Load Disconnect State Changed event to track

this. In addition, any local operation of the load disconnect contactor, will trigger the

Load Disconnect State Changed event. This includes use of the disconnect push

button, and the load disconnect contactor being turned off due to exhaustion of

prepay credit or maximum power thresholds being reached, You should also note that

if these conditions exist when a remote procedure is called to open or close the load

disconnect contactor, the procedure will fail and an error code will be returned.

However, an event will not be triggered.

If an attempt to manually open or close the load disconnect contactor using the

disconnect push buttons fails because of a low voltage condition, the meter display

will show scrolling text indicating this. The text that is displayed, and the amount of

time that the text will be displayed for, is user-configurable.

Control Relay

One optional control relay can operate an external low current device, such as a

contactor coil, which in turn can control a larger amperage device. The open or closed

state of the control relay is determined by the present tariff level that is in effect. The

tariff period that activates the relay is configurable. The relay can also be set into the

open or closed state remotely by NES System Software, or locally with the Provisioning

Tool.

When a broadcast command is sent to all meters to close the control relay, a user-

configurable maximum random number of seconds can allow the actual

implementation time to vary per meter. This is provided to reduce the possibility of

spikes or sags on the power grid when multiple loads come online at roughly the