Alarm Handling

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Introduction

An Alarm is an indication of an abnormal condition. Examples of Alarms include:

In Fernhill SCADA some tag types automatically generate alarms when an abnormal condition occurs. The Channel Tag will raise an alarm if the communication channel fails.

You can also define your own alarms using these tags:

Alarm Lifecycle

An alarm has four main states: Normal, Active, Acknowledged, and Cleared.

Alarm Lifecycle

Normal: There is no abnormal condition and the alarm is not active.

Active Alarm: The abnormal condition has been detected.

Acknowledged Alarm: The alarm has been acknowledged by a user (the abnormal condition is still present).

Cleared Alarm: The abnormal condition is no longer present, but the previous abnormal condition has not yet been acknowledged.

Once an alarm is detected, the alarm can not return to normal until both of the following occur:

Disabling Alarms

Sometimes a nuisance alarm occurs where the abnormal condition is detected and cleared repeatedly. This might be caused by a faulty sensor, or intermittent connection, or a deadband that is too narrow. In such situations is may be appropriate to disable the alarm to prevent user distraction.

Fernhill SCADA allows alarms to be disabled. Use the Disable Alarms Tag Command to disable alarms. Use the Enable Alarms Tag Command to enable alarms.

Alarm Severity

Each alarm is assigned a severity value that ranges from 1 to 1000. The lowest severity is 1 and the highest severity is 1000.

Fernhill SCADA assigns a color indicating the relative severity of the alarm. The default severity mapping is:

SeverityPropertyDefault Color
750 - 1000P1AlarmColor
500 - 749P2AlarmColor
250 - 499P3AlarmColor
1 - 249P4AlarmColor

Note: The alarm color assignment can be changed by editing the properties of the Database Root Tag.

Forwarding Alarms using Email

You can configure Fernhill SCADA to automatically send alarms using email with the Alarm Router Tag.

The Alarm Router Tag supports:

Managing Alarms in Fernhill SCADA

You can access the alarm list using:

All options allow you to view the active alarms and optionally acknowledge alarms.

Accessing Alarm Data From Other Programs

You can access alarm data from other programs using any of these methods:

Running an SQL Query to Access Alarm Data

You can use this type of SQL query to query alarms:

SELECT 
    SourceName,ConditionName,UpdateTime,Message,Severity,StateAsText AS "State"
FROM 
    Alarms
WHERE
    State = 1		-- Enabled, inactive, not acknowledged
	OR State = 3	-- Enabled, active, not acknowledged
	OR State = 7 	-- Enabled, active and acknowledged

The above query can be used with these data access interfaces:

Connecting an OPC AE client

The Fernhill SCADA OPC Server supports these OPC AE Interfaces:

Using these interfaces, an OPC AE client applications can browse, query, and acknowledge alarms.

Further Information

Fernhill SCADA Concepts

To learn about other Fernhill SCADA Concepts.

Configuration Tool

To learn about the tool to configure Fernhill SCADA.

Drivers

To learn about the different drivers available in Fernhill SCADA.

Fernhill SCADA Server

To learn about the SCADA Server.

Data Access

To learn about integrating data into third party applications.

Glossary

For the meaning of terms used in Fernhill SCADA.