DNP3 objects that are not of “Static-only” type can be assigned by the Communication Management tool in PCM600 into DNP3 event classes 1...3. Event buffering is defined per DNP3 object type and not by DNP3 event class.
The DNP3 standard does not define or suggest any specific usage of the different classes. In polled mode, the controlling station could prioritize the polling of a specific class. However, this is not used very often, since the chronology of events is considered more important than the prioritization of certain objects.
Different DNP3 object types are often assigned to different DNP3 event classes. This has no meaning if the client performs class polling simultaneously to all the three classes. Outstation still responds to the events in chronological order. However, there are some advantages.
- The event buffering is handled by DNP3 object type, but a possible event overflow signal is in turn given from the DNP3 event class. If a class only contains a particular object type, the overflow occurs for that DNP3 object type.
- In unsolicited reporting mode, the controlling station enables the classes that should start the spontaneous event reporting. One or some of the classes could then be left disabled.