OPC Alarms and Events Area Space
Section 3 Features
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The generated event type for a signal is always a condition event. The event categories
used by the SPA OPC Server are listed in Table 3-5. They are described more precisely in
sections 3.3.1 and 3.3.2.
The event definitions for the Discrete event categories must be defined in the
configuration so that they can be used. The other event types do not need any
configuration.
In each condition event notification the vendor specific attribute CV (current value) is
included. This attribute holds the current value of the signal that generated the event.
3.3.1 System message events
The SPA OPC Server generates system message events for some notifications from the
devices or lines. The notifications may be
device_started
,
device_suspended
,
etc.
The source of such an event is the node name of the device or line from which the
notification originates. The message is "Operation failed (status code number)". For
information on status codes, see
.
System message events may also be generated to inform about internal problems in the
SPA OPC Server, e.g. communication queues filling up.
3.3.2 Discrete (Indication) events
Discrete events describe a state change in a signal that can be a single or double
indication, for example a signal that represents the position of a breaker. Discrete events
have multiple sub-conditions depending on the signal type. Events for single indications
have two sub-conditions, and events for double indications have four sub-conditions, see
Table 3-5: Event categories and event types
Event category
Event type
System Message
simple
Discrete
condition
