Alarm suppression is used to prevent unnecessary alarm activations, annunciations and notifications when the operational environment deems an alarm to be inapplicable. Alarm suppression is applied and removed automatically via a configured expression or tag reference. For example, if a "Low Flow" alarm is configured to detect a low flow rate, but the alarm is meaningless if the pump isn't running, then this alarm should be suppressed when the "Pump Running" tag is FALSE."
By comparison, alarm disabling must be done by an authorized person, directly in the configuration of each alarm. Also, the rule governing the suppression of one alarm can apply to many, whereas the act of disabling an alarm must be done one alarm at a time.
While the result of disabling or suppressing an alarm is the same (no alarm), these are different operations and therefore they are tracked independently. The Alarm Page and the Alarm List Widget provide separate views for disabled and suppressed alarms.
The condition that suppresses an alarm may be independent of whether anyone is signed in, therefore this feature is not protected by a privilege beyond the ability to create or modify tags.
The alarm suppression feature is available in Alarm tags and I/O & Calculation tags. For an I/O tag, there is a single alarm suppression expression that suppresses all the built-in alarms.
This feature does not apply to legacy Status tags.
Each time you toggle suppression on an alarm, an event is recorded. If you must repeat this operation frequently for hundreds of tags, a large number of events can be recorded. In this situation, consider setting the property RecordSuppressionStatus to 1.
Customers who used VTScada prior to the release of this feature might have configured parameter expressions in their I/O & Calculation tags to disable alarms. Those expressions are automatically transferred to alarm suppression as part of the upgrade process.
Comparison: Shelve / Disable / Suppress Alarms
| Feature | Used by | Use to... |
|---|---|---|
| Shelve |
Authorized Operators Available through the user interface. |
Hide and silence an alarm temporarily. |
| Disable |
Developers / Engineers Must be configured in individual alarms. |
Block specific alarms from occurring. For example, the alarm is not currently needed but might become relevant again. |
| Suppress |
Automated Developers set a condition for suppressing one or more alarms using an expression or a tag. If set using a memory tag, authorized operators can suppress the alarms. If set using an expression, alarms can be suppressed automatically. |
Block specific alarms from occurring while a condition is true. For example alarms might be suppressed while related equipment is not running. |
By default, no actions are recorded for an alarm while it is suppressed. You can alter this behavior using configuration properties such that, even though the alarm is suppressed, the occurrence of the activating or the normalizing state will be recorded. These records go directly to the Alarm History and are never part of the active alarm list.
MakeActiveAlarmUnackedWhenUnsuppressed
TRUE to mark an active alarm as unacknowledged when it becomes unsuppressed
RecordSuppressionStatus
TRUE to record the suppression status of an alarm
RecordAlarmStatusWhileSuppressed
TRUE to record the alarm status while an alarm is suppressed
Configure an Alarm for Suppression
Define the condition under which the alarm should be suppressed. It will be suppressed when the condition is TRUE, and unsuppressed when the condition is FALSE
