Operation
25
There are three strategies for receiving power updates over the network. For the first, it is not necessary to
bind the power network variables. Instead, the monitoring node uses polling to retrieve the current power
value. The second technique uses
nciWMaxSendT
to set an interval at which the WattNode will update all
bound power variables. To use this technique,
nciWMinSendT
and
nciWMinDelta
must be set to their
default values (0 seconds and 1.0e38 watts respectively). The third update technique uses all three
configuration variables.
nciWMinDelta
is set to update power when at least
nciWMinSendT
time has
elapsed since the last power update and the power has changed by the specified amount (150 watts for
example). Use
nciWMinSendT
to limit updates if the power is fluctuating rapidly. Finally,
nciWMaxSendT
is set to update the value periodically even if the value does not change enough to trigger an update.
To disable the minimum update interval, set
nciWMinSendT
to zero time. To disable the maximum update
interval, set
nciWMaxSendT
to zero time. These variables are actually elapsed time structures, so each
field in the structure must be zeroed. To disable the send on delta feature, set
nciWMinDelta
to 1.0e38. The
default configuration sets
nciWMaxSendT
to 10 seconds so that the power is updated every 10 seconds;
nciWMinSendT
is set to zero time to disable the minimum update interval and
nciWMinDelta
is set to
1.0e38 to disable send on delta.
4.3.2 Power Alarms
The power object supports alarms which can be tripped for excessive power and/or for insufficient power.
In addition to the high and low alarm levels, hysteresis bands and alarm setting and clearing delays may be
set. The alarm levels are configured in units of floating point watts over the range 0 to 1.0e38 W. The list
of alarm configuration variables follows:
nciPowLimHi – The power value above which the high power alarm is set. This may be used to warn
of overload conditions. The default value of 1.0e38 W disables this alarm.
nciPowLimLo – The power value below which the low power alarm is set. The low alarm can monitor
that critical equipment or machinery is not shut off, or does not fail. The default value of 0.0 W
disables this alarm.
nciPowAlmSetT – This variable delays the activation of the power alarms, by requiring that the trip
condition be met for the specified time interval before the alarm is set. This can be used to prevent
alarms due to turn on surges. The default is zero delay.
nciPowAlmClearT – The variable delays the clearing of power alarms, by requiring that the clearing
condition be met for the specified time interval before the alarm is cleared. The default is zero delay.
nciPowLimHystHi – This adds hysteresis, or deadband, to the high power alarm. To set the alarm, the
power must exceed
nciPowLimHi
+
nciPowLimHystHi
for time
nciPowAlmSetT
. To clear the alarm,
the power must fall below
nciPowLimHi
–
nciPowLimHystHi
for time
nciPowAlmClearT
. This can be
used to prevent repeated alarm set-clear sequences if the power hovers near
nciPowLimHi
. The default
hysteresis is zero, which disables the feature.
nciPowLimHystLo – This adds hysteresis, or deadband, to the low power alarm. To set the alarm, the
power must fall below
nciPowLimLo
–
nciPowLimHystLo
for time
nciPowAlmSetT
. To clear the
alarm, the power must exceed
nciPowLimLo
+
nciPowLimHystLo
for time
nciPowAlmClearT
. The
default hysteresis is zero.
nciPowAlarmInhT – This prevents any alarms from being reported for an interval after the WattNode
comes out of reset, or the power object is enabled. This could be used to allow time for the power to
stabilize after an outage, without causing alarms.
Summary of Contents for WattNode WNA-1P-240-FT10
Page 40: ......
