Both direct operate and select before operate DNP3 control functions are supported for binary outputs.
In the native IED IEC 61850 data, these control operation differences are referred to as the control model. The control model is in turn configured as a property of the control object. Thus an IEC 61850 control object can be either in “Direct” or “SBO” mode. This is applicable for double-point control objects. Single point control objects in the protection relay always work in “Direct” mode. Depending on the control model setting of the native IEC 61850 control object, various DNP3 control functions can be performed.
| IEC 61850 control model | Supported DNP3 control function |
|---|---|
| Direct | Direct only |
| SBO | Direct or SBO |
When making a DNP3 direct command to a SBO configured object, the desired behavior can be defined in the Communication Management tool. In case the direct control mode property is set to “Always allowed”, the DNP3 stack automatically performs the two needed commands to the native control object. Direct control is always allowed. In case the direct control mode property is set to “Control model”, the DNP3 control command must follow the native 61850 objects control model. SBO control must be used in the SBO mode.
The DNP3 stack has a protocol dependent parameter setting for the timeout between Select and Operate commands. The default value is “10 seconds” but it can be changed via CROB select timeout parameter. Also the native control object have a configured timeout for the SBO operation. Since the control object may also be available for Local (manual) control, a longer timeout is often required. The DNP3 timeout should be set lower than the native control object timeout.