1. SCADA Alarming Practices
A Quick Overview
of Some of AECI’s
SCADA Alarming Practices

2. Alarm Philosophy Background

3. requiring a response. (ISA 18.2)
Should an alarm exist?
An audible and/or visible means of indicating
to the operator an
abnormal condition
requiring a response. (ISA 18.2)

4. How long before it happens?
Rationalization
How Severe?
Severity
Priority
High
Medium
Low
Consequence
How long before it happens?
Time to
Respond

5. Severity of Consequence + Time = Priority
Minor Consequence
Major Consequence
Severe Consequence
≈ 30 minutes
Low
Medium
≈ 10 minutes
< 3 minutes
High

6. In the real world… High Medium Low None Priority Color Examples Red
Any alarms involving human safety
(Require individual acknowledgement)
Fire Alarms
Danger to Personnel
Rare occurrences
MVA Limit Exceeded
Medium
Orange
Exception for CBs, CSW, MOS, Disconnect
Any change of state
Yellow
MVA Warning
Voltage Limit Exceeded
Tie shift
Low
White
Voltage Warning
LTC
Reasonability exceeded
Analog Return to Normal
Temporary holding for unrationalized alarms
This makes them easy to find and rationalize later.
 Station Alarms
Green
Default system color for issued control commands
None
Light Blue
External, off-system events.
Do not require acknowledgement. Historical info only.
External CB operations
External MVA and KV Limits
Gray
Deleted "Log Only" events. Never require a response. Appear only when viewed from All/Summary views.
System
Event log
In the real world…

7. MVA Alarms – Line Loading
Event
Class Message / Description
Deadband
Sound
MVA Limit 2
Exceeded Limit
Yes
MVA Limit 1
Near Limit – 90%
Return to Limit 1
Improved to Near Limit
1% and 20s
MVA RTN
Normal
MVA Data Reasonability
Data Unreasonable
12s

8. MVA - Dynamic Limits Temperature data from a weather service
G&Ts associated with a region to determine location temperature
Substation owner associated with lines and transformers
Calculate rating based on most limiting element at the temperature for that region
FAC 008
Conductor ratings
Map temperature adjusted ratings to SCADA points on EMS.

9. Voltage Alarms Event Class Message / Description Deadband Sound
KV Limit 2
Exceeded High/Low Limit
Yes
KV Limit 1
Near High/Low Limit
Return to Limit 1
Improved to Near Limit
1% and 20s
KV RTN
Normal
KV Data Reasonability
Data Unreasonable
12s

10. Voltage Limits 74.5 - 108% 149 - 108% 173.9 - 108% 249 - 108%
High Exceeded Limit 2 % % % % % %
High Warning Limit 1 % % % % % %
Nominal Voltage
69 KV
138 KV
161 KV
230 KV
345 KV
500 KV
Low Warning Limit 1 % % % % % %
Low Exceeded Limit 2 % % % % % %

11. CB, CSW, MOS, Disconnects Event Class Message / Description Deadband
Sound
Change of State
Changed State
Yes
Multiple Operations
Return to Normal
Returned to Normal
Control Failed

12. Fin