800xa Alarm Hiding -What is the mask scanning frequency? Is it dependent on the number of masks/rules setu
I'm not sure there is a thing such as scanning frequency inside the alarm hiding.
Hiding Masks and Hiding Rules accept enabling via OPC DA, e.g. by writing an expression pointing out some property that shall trigger hiding.
In practice when using OPC DA delivered activation of hiding, it will typically take an additional second before the hiding is activated in the Alarm Manager. Only alarms arriving AFTER the enabling will become hidden.
Hence, triggering of hiding of "own" alarms from Alarm Global Properties:IsAlarmActive on the local object will not work.
There exist a Feature Addon pack for System 800xA 5.1 Feature Pack 4. This Addon pack contain, amonst other functions, something called Retroactive Alarm Hiding. With this enabled, also alarms arriving BEFORE the mask/rule activation will become hidden.
Please ask your regional ABB sales representative if you are eligible to purchase the Feature AddOn pack.