DNP3 binary outputs (Object group 10) are cross-coupled with the protection relay’s IEC 61850 control data classes SPC and DPC. The DNP3 stack automatically handles the conversion between the two protocols’ control models.
DNP3 control is never done directly to the binary outputs but rather indirectly using the Control Relay Output Block (CROB) function. The CROB function contains some additional information regarding the control sequence, for example, pulse length and number of control pulses. These parameters are intended for RTU type (non-intelligent) DNP3 devices. However, in this protection relay, all the required control parameters are already configured properties of the control object. Therefore most control parameters given in the DNP3 CROB command are ignored by the protection relay. Only the control direction is noticed. Most single point objects, like resets and acknowledgements, can only be controlled using ON. However, there may also be single point objects that have two states, ON or OFF. Double-point objects may be controlled using ON or OFF.