Excluding Hidden Alarms from the WinCC AlarmControl Hitlist in SIMATIC PCS 7

In SIMATIC PCS 7 WinCC OS environments, generating alarm management audit reports using the AlarmControl Hitlist often improperly aggregates smart-alarm hidden messages despite selecting 'Only displayed messages'. Because the Hitlist evaluates historical alarm frequencies directly from SQL Server archive tables, excluding hidden alarms requires applying explicit SQL criteria filters targeting the message state and hide attribute (HideState = 0) within the WinCC AlarmControl Hitlist configuration tab.

Role of the WinCC Alarm Hitlist in Alarm Management and Reporting

In compliance with international alarm management standards (such as ISA-18.2 and EEMUA 191), industrial plants must regularly audit alarm frequency to eliminate "bad actors" and nuisance alarms. In SIMATIC PCS 7 WinCC OS:
* The WinCC AlarmControl Hitlist aggregates and sorts alarms by frequency of occurrence, total duration in active state, and average acknowledgment time.
* It enables plant engineers to identify the top 10 or top 20 most frequent alarm tags over a selected reporting window (e.g., past 24 hours or past 7 days).
* However, when Hitlist totals include nuisance alarms that were deliberately suppressed using PCS 7 Alarm Hiding, the reporting metrics become distorted.

Mechanics of Alarm Hiding (Smart Alarm Management) in PCS 7

PCS 7 provides Smart Alarm Management to prevent alarm flooding during major operational state changes (such as plant startup, shutdown, or equipment maintenance):
* Manual Hiding: Operators manually select active alarms and send them to the hidden alarm list.
* Automatic Hiding: The Alarm Hiding logic in CFC evaluates operational modes (e.g., unit offline) and sets the suppression attribute dynamically.
* Internal Database Flag: Hidden alarms are not deleted; they are archived in the SQL message database with a special status bit: HideState = 1 (Active Hidden) or HideState = 2 (Suppressed by Logic).

The Root Cause: Why 'Only Displayed Messages' Fails in Hitlist Views

Engineers frequently configure WinCC AlarmControl under General -> Display Options -> Show messages: 1 - Only displayed messages, expecting hidden alarms to disappear from Hitlist statistics:
* The "Only displayed messages" filter applies strictly to the Message List (active online alarms).
* The Hitlist tab operates on a separate underlying SQL analytical query that evaluates historical archive records (AlgViewEX / MsArcLong).
* Because the Hitlist calculation evaluates all matching message records unless an explicit SQL WHERE filter restricts the query, hidden alarms continue to be tallied in frequency totals.

Step-by-Step Procedure to Filter Hidden Alarms in AlarmControl Properties

To completely purge hidden alarms from Hitlist statistics:
1. Open Graphics Designer on the Engineering Station and open the picture containing the alarm report control (or @AlarmHitlist.pdl).
2. Double-click the WinCC AlarmControl to open its Properties dialog.
3. Select the Hitlist tab in the configuration tree.
4. Navigate to the Selection / Filter section.
5. Click Edit... to open the SQL filter expression builder.
6. Configure the filter condition:
* Select criterion: State / HideState (or State).
* Operator: Equal to (=).
* Value: 0 (where 0 denotes visible / unhidden alarms).
7. If your WinCC version lacks a dedicated HideState drop-down, enter the advanced SQL condition in the Selection criteria:
sql HideState = 0
8. Save the picture, perform an OS compile/download, and activate runtime. The Hitlist query now excludes all records flagged with hidden states.

Verification

In WinCC OS runtime, manually hide a recurring high-frequency test alarm using the Hide Alarm button in the alarm banner.
Trigger several occurrences of the alarm while hidden.
Open the Hitlist display and click Calculate / Refresh.
Confirm that the hidden test alarm does not appear in the top-frequency list.
Open the Hidden Messages list to confirm that the alarm is still actively logged and tracked by the system.

Limitations and Operational Precautions

Applying complex SQL filters to Hitlist queries over massive archive time spans (e.g., several months) can increase SQL query execution times; limit Hitlist evaluation windows to reasonable periods (e.g., 24 to 72 hours).
Ensure standard operational alarms unhide automatically upon unit restart so they resume normal Hitlist auditing.
Never disable alarm logging in an attempt to suppress alarms from Hitlist; always use structured Alarm Hiding and SQL filtering.

Engineer FAQ

What standard does the WinCC Hitlist assist with?
It supports ISA-18.2 and EEMUA 191 alarm management auditing by identifying bad actors and alarm distribution frequencies.
What SQL database table stores WinCC alarm records?
Alarms are stored in segmented SQL tables under the runtime database, accessed via analytical views like AlgViewEX.
What does a HideState value of 0 indicate in WinCC Alarm Logging?
HideState = 0 indicates that the message is normal, visible, and not hidden or suppressed.
What is the difference between Manual Hiding and Automatic Hiding in PCS 7?
Manual hiding is executed by operators via faceplate; automatic hiding is controlled by CFC logic based on plant operating state.
Can I export the filtered Hitlist table to a CSV file?
Yes, the WinCC AlarmControl toolbar includes an Export button that saves current Hitlist records to a .csv or .txt file.
Does filtering hidden alarms from the Hitlist delete them from the archive?
No, filtering alters only the visual analytical query; all alarm transactions remain permanently recorded in the SQL archive.
Where is the system screen @AlarmHitlist.pdl located?
It resides in the WinCC project directory under the GraCS/ folder, generated by the OS Project Editor.
Why do alarms stay hidden after an operator logs out?
Alarm hiding states are system-wide process states tied to the alarm instance, not user session attributes.
Can I filter the Hitlist by specific plant areas?
Yes, the Selection tab supports multi-criteria filtering by plant area, message class, priority, and date/time range.
How does Process Historian handle hidden alarms?
Process Historian archives all alarm records including their complete HideState flags for long-term reporting in Information Server.

Technical References

SIMATIC HMI WinCC V7.4 / V7.5 Alarm Logging System Manual
SIMATIC PCS 7 OS Process Control System Operating Manual
Siemens Industry Online Support Entry: Filtering Hidden Alarms in WinCC Hitlist (Entry ID 298812)
ISA-18.2 Management of Alarm Systems for the Process Industries