Alarm Conditions

Introduction

An Alarm Condition is an indication of an abnormal state. Examples of Alarm Condition include:

A piece of equipment fails to operate. For example, a pump does not run when required.
A measured value is outside a defined range. For example, a temperature is too high, or a pressure is too low.
There is a communication failure.
A PLC or RTU is offline.

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:

Use the Digital Alarm Tag to raise an alarm from a digital source.
Use the Analog Level Alarm Tag to raise an alarm from an analog source.

Alarm Condition Lifecycle

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

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 Condition becomes active, the alarm cannot return to normal until both of the following occur:

The Alarm Condition has been acknowledged by an operator.
The condition that caused the alarm has cleared.

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 operators to disable alarms. 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:

Severity	Property	Default Color
750 - 1000	P1AlarmColor
500 - 749	P2AlarmColor
250 - 499	P3AlarmColor
1 - 249	P4AlarmColor

Note: Edit the properties of the Database Root Tag to change the colors assigned to alarms.

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:

An alarm filter to select which alarms are sent using email.
A condition to define which alarm states are reported.

Managing Alarms in Fernhill SCADA

You can access the alarm list using:

The Alarm List in the Operator Interface.
The View Alarms option in the Tag Window Menu of the Configuration Tool.
The All Alarms predefined query in the SQL Test Tool.

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:

Run an SQL Query on the Fernhill SCADA Database.
Connect an OPC AE Client to the OPC Server.

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: