Alarms, Conditions, and Events

The AVEVA Adapter for OPC UA provides support for alarms, conditions, and events by implementing the Information Model for Alarms and Conditions described in Part 9 of the OPC UA Specification.

OPC UA servers generate events based on the alarms and conditions defined that can be consumed by OPC UA clients.

Users can configure the OPC UA adapter to perform a discovery of data items or event types that persist in the data source (the OPC UA server). With Alarms and Conditions, users can perform a discovery of only event types and use the results as the data selection configuration to collect alarms and conditions data.

The DiscoveryType enumeration type can be used within a Discovery query to find Event Types available on the adapter's server. DiscoveryType has three allowed values:

• Data - Only data items are retrieved in the discovery results.

• Event - Only event types are retrieved in the discovery results.

• DataAndEvents - Both event types and data items are retrieved in the discovery results.

Subscriptions to event types are maintained within the Data selection configuration.

General limitations and restrictions

Alarms, conditions, and events have limitations or restrictions with regards to subtype properties, polling, event types and the string character limit for PI Web API and PI Data Archive.

• Subtype properties - Subtype inherit the properties of their base and have access to all properties starting with BaseEventType until it reaches its level. In the address space, a few subtypes, such as TripAlarmType, do not have any properties exposed. If no properties are exposed, the discovery results list all inherited properties by default.

• Polling - Since Alarms and Condition event notifications are generated in real-time, polling for alarms and conditions is not available.

• Event types - The event types presented in Discovery are limited to the Alarm and Condition types and their subtypes supported by the server. Other event types, such as system event or audit types, are suppressed from the discovery response to avoid unwanted event notifications triggering to the adapter. However, users are permitted to manually configure any event type as desired.

  Suppressed event types include:

  • AuditEventType

  • SystemEventType

  • BaseModelChangeEventType

  • EventQueueOverflowEventType

  • ProgressEventType

  • TransitionEventType

  • SemanticChangeEventType

  • StateMachineType

• String data limit for PI Web API and PI Data Archive - PI Data Archive has a limit for string data of up to 972 characters if annotated, 976 otherwise. If the adapter with PI Web API as OMF Egress Data endpoint has an egress string with a length greater than 972 characters, PI Web API returns an Internal Server Error 500. This is tracked under PI Web API product as a bug.

Quick Start

These steps guide you through the set-up for alarms and conditions. Perform each required configuration to establish an event type.

1. Configure the data source.

2. Optional: Update the Configure client settings to include property names for the event type properties.

3. Perform discovery for event types.

4. Modify the discovery results to collect data for specific event types.

5. Configure data selection using the modified event types list.