#
Parameter
Range
Notes
11
Inhibit(s) #1 to #32
Varies
Inhibit(s), that if active, can inhibit the alarm from becoming active.
Note that there are only four fields for inhibits in PICUS.
12
Action
Varies
Action to be taken.
*Note:
Trigger level
is typically fixed and cannot be changed. However, the set point for
Directional over-current
determines the
Trigger level
. In addition, you can configure I/O alarms with a
High
or
Low Trigger level
.
4.2.2 Set point
The
Set point
is the reference value that is compared by the controller to decide whether the
Alarm condition
is present in the
system.
When the operating value, that the alarm is based on, reaches the
Set point
, the controller starts the
Time delay
(if applicable) for
the alarm. The
Set point
is often a percentage of the controller's nominal setting.
INFO
Most alarms require a
Set point
to be configured.
For example, the
Set point
for the
Over-current 1
alarm can be 100 %. This means that the current from the equipment must be 100
% (or more) of the nominal current to activate the alarm.
4.2.3 Reset hysteresis
The
Reset hysteresis
prevents the operating value from being too close to the alarm
Set point
when the alarm is reset. The
Reset
hysteresis
makes the system more stable by imposing hysteresis on the alarm
Set point
. The
Reset hysteresis
is a value that is
subtracted from the set point of high alarms (and added to the
Set point
of low alarms).
A
Reset hysteresis
can only be used where the alarm is based on an analogue value.
Overspeed example
Consider an
Overspeed
alarm with a
Set point
of 110 % of nominal speed and a
Reset hysteresis
of 10 %. The overspeed alarm cannot be reset until the operating
value falls below 100 % of nominal speed. The red line in the following figure shows
that the alarm is activated when the value exceeds the
Set point
. The alarm is only
deactivated when the value drops below the reset value.
0
Set
point
Value
time
Reset
Under-speed example
Consider an
Under-speed
alarm with a
Set point
of 80 % of the nominal speed and
a
Reset hysteresis
of 5.0 %. The alarm is only reset when the operating value is
above 85.0 % of the nominal speed.
Set
point
Value
time
Reset
4.2.4 Action
The alarm
Action
is the response that you allocate to the
Alarm condition
. Each alarm can only be assigned one alarm
Action
. The
controllers are delivered with pre-defined alarm actions. You can change the alarm
Action
for most alarms.
DESIGNER'S HANDBOOK 4189340911K UK
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