This section explains the effect that alarm suppression has on ClearSCADA.
In the bullet list below, parent alarm refers to an alarm that meets the Parent Alarm Condition criteria and is raised on the item that is configured as a Parent Alarm Object. Child alarm refers to an alarm that is raised on a database item on which the above Parent Alarm Object is specified. For more information, see Configure any Alarm Suppression Requirements.
When alarm suppression is configured:
- Should the parent alarm go active:
- ClearSCADA will suppress any new child alarms (see The Effects of Suppression on Alarm Displays)
- An event will be logged for each suppressed alarm. The event record will indicate whether each alarm is suppressed due to Maintenance, or Consequential, alarm suppression
- Each child item’s State Alarm status attribute will indicate whether its alarms are suppressed
- Any existing ‘child’ alarms will remain active
- The parent alarm’s Suppressed Alarm Count (displayed, for example, on Alarms Lists and the Alarm Banner) will indicate how many child alarms are suppressed
- The parent item’s Suppressed Alarm Objects pick action will provide access to a list of the child database item(s) for which alarms might be suppressed due to the parent alarm being active.
- Whenever the parent alarm ceases to become active:
- ClearSCADA will automatically activate any existing suppressed child alarms (see The Effects of Suppression on Alarm Displays). The newly activated alarm entries will be time stamped with their occurrence time (or, on systems on which the Use Visible Time As Alarm Active Time feature is enabled, their unsuppressed time)
- An event will be logged for each existing child alarm that is unsuppressed, indicating the time that the alarm became unsuppressed
- Any Alarm Redirection activity that applies to the child alarms will come into effect (for instance, ClearSCADA will start any redirection timers).
The parent-child alarm relationship can be cascaded, so that a top level parent alarm will disable the alarms of its child items, and of the children of those child items, and so on.
For an example that demonstrates the effects of alarm suppression in ClearSCADA, see Example Configuration.