Alarm acknowledgment workflow in SCADA systems - Step-by-Step Execution

Process Flow - Alarm acknowledgment workflow

Alarm Triggered

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Alarm Displayed on HMI

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Operator Reviews Alarm

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Operator Acknowledges Alarm

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System Logs Acknowledgment

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Alarm State Changes to Acknowledged

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Alarm Cleared or Resolved

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Alarm Removed from Active List

This flow shows how an alarm is triggered, displayed, acknowledged by the operator, logged, and finally cleared.

Execution Sample

SCADA systems

1. Alarm triggers
2. Display alarm on HMI
3. Operator clicks acknowledge
4. System logs acknowledgment
5. Alarm state updates

This sequence simulates the steps from alarm triggering to acknowledgment and state update.

Process Table

Step	Event	Condition/Action	System State	Output
1	Alarm Triggered	Alarm condition detected	Alarm state: Active	Alarm shown on HMI
2	Alarm Displayed	Operator sees alarm	Alarm state: Active	Waiting for acknowledgment
3	Operator Acknowledges	Operator clicks acknowledge button	Alarm state: Active	Acknowledgment logged
4	System Logs	Record acknowledgment time and user	Alarm state: Acknowledged	Alarm state updated
5	Alarm Cleared	Alarm condition resolved	Alarm state: Cleared	Alarm removed from active list
6	End	No active alarms	Alarm state: None	System idle

💡 Alarm condition resolved and acknowledged, system returns to idle state

Status Tracker

Variable	Start	After Step 1	After Step 3	After Step 4	After Step 5	Final
Alarm State	None	Active	Active	Acknowledged	Cleared	None
Acknowledgment Logged	No	No	Yes	Yes	Yes	Yes
Alarm Displayed on HMI	No	Yes	Yes	Yes	No	No

Key Moments - 3 Insights

Why does the alarm state remain 'Active' after operator acknowledgment in step 3?

Because step 3 is the operator clicking the acknowledge button (logging the response); the system processes it and changes the state to 'Acknowledged' in step 4, before the condition is resolved in step 5.

What happens if the operator does not acknowledge the alarm?

The alarm stays in 'Active' state and remains displayed on the HMI, waiting for acknowledgment, as seen in steps 2 and 3.

When is the alarm removed from the active list?

Only after the alarm condition is resolved and the state changes to 'Cleared' in step 5, then the system removes it from the active list.

Visual Quiz - 3 Questions

Look at the execution table, what is the alarm state immediately after the operator acknowledges the alarm (step 3)?

A Cleared

B Acknowledged

C Active

D None

💡 Hint

Check the 'System State' column for step 3 in the execution table.

At which step does the system log the acknowledgment?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look for the 'System Logs' event in the execution table.

If the alarm condition is not resolved, what will be the final alarm state?

A Cleared

B Acknowledged

C Active

D None

💡 Hint

Refer to the variable_tracker for 'Alarm State' after Step 4 (system logs), since Step 5 requires condition resolution.

Concept Snapshot

Alarm acknowledgment workflow:
1. Alarm triggers and shows on HMI.
2. Operator reviews and acknowledges alarm.
3. System logs acknowledgment.
4. Alarm state updates to 'Acknowledged'.
5. Alarm clears when resolved and is removed from active list.

Full Transcript

The alarm acknowledgment workflow starts when an alarm triggers due to a condition. The alarm is displayed on the Human Machine Interface (HMI) for the operator to see. The operator reviews the alarm and clicks the acknowledge button. The system then logs the acknowledgment and updates the alarm state to 'Acknowledged'. The alarm remains in 'Acknowledged' state (condition still active) until resolved. Once resolved, the system changes the state to 'Cleared' and removes it from the active list. This process ensures operators respond to alarms and the system tracks their acknowledgment and resolution.