IEC 62541-9:2026 ED4

OPC unified architecture - Part 9: Alarms and Conditions

Scope

IEC 62541-9:2026 specifies the representation of Alarms and Conditions in the OPC Unified Architecture. Included is the Information Model representation of Alarms and Conditions in the OPC UA address space. Other aspects of alarm systems like alarm philosophy, life cycle, alarm response times, alarm types and many other details are captured in standards such as IEC 62682 and ISA 18.2. The Alarms and Conditions Information Model in this document, is designed in accordance with IEC 62682 and ISA 18.2. Annex C specifies a recommended mapping between OPC Classic Alarm & Events (A&E) servers to the model described in this document. Annex A describes recommended localized names for Alarm states. Annex B describes examples (e.g. Event sequences, Alarm areas in AddressSpace). This fourth edition cancels and replaces the third edition published in 2020. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) addition of "Comment" parameter to Alarm shelving methods;
b) addition of method that allows a client to get the members of a group, since it is possible that the AddressSpace does not expose instances of alarms;
c) addition of deadband properties for all limits in the limit AlarmType (from which all other types described in this issue are derived);
d) addition of text explaining the disabling of alarms is no longer supported in ISA 18.2 and that it is maintained in this document for backward compatibility, but that it is recommended that Alarm not be disabled;
e) addition of optional severities for limit alarms;
f) addition of new AlarmState variable type that can be used to collect alarm information for displays on graphics;
g) addition of SupportsFilterRetain property to improve Client filtering;
h) removal of ConditionSubClassId and ConditionSubClassNames from the conditiontype definition since they are now defined in BaseEventType.