Alarm suppression behavior

Alarm suppression behaviors are additive, and to determine if an alarm should be generated, the system compares the alarm state when the first suppression is triggered to the state when the last suppression timeout ends.

The comparison of alarm states is important since a child record can be configured for parent control, parent alarm, and transient alarm suppression thereby activating the timers for all the configured suppression types.

If, for instance, (a) a control suppression event is followed by a parent alarm suppression event, and (b) the child record’s state changes, then after the control suppression timeout expires, the system does not generate an alarm because the child is still suppressed by parent alarm suppression. In the event that the parent alarm suppression timeout expires, and no suppression timeout exists for the child, then the child point’s current state is compared to the state when the control suppression trigger occurred. If it is different, then the system generates an alarm.

In addition, easy eXtended Operator Station (ezXOS) summaries and annotated displays show the alarm icon next to the child data whenever the child is in the alarm state, regardless of alarm suppression. The suppression only applies to the alarm summary displays.

The alarm event is also recorded within the event summary. If the child record’s alarm state changes during the suppression timeout, the summary shows when the system triggers and cancels alarm suppression.

The analog and status summaries can show filtered lists of records that are currently in alarm suppression. The summaries show child records actively suppressed if they have undergone an alarm state change since alarm suppression was triggered.