The relay’s native IEC 61850 data model does not include any cause of transmission (COT) information data. Therefore, monitoring object transmissions from the IEC 60870-5-104 stack can only include the following cause of transmission values.
- 1 = Cyclical
- 3 = Spontaneous
- 20 = General interrogation
- 21...36 = Group 1...16 interrogation
The control command’s response message returned to the controlling client includes COT value 11 = Remote command, but the controlled object value change in monitoring direction is always COT=3 (Spontaneous). While this information is not so important for the controlling client, it can be for another client in a multiple-client environment.
In IEC 61850, it is thought that the other client should monitor the DPC .stSeld (selected status) indication object. If the object goes ON, the DPC object has been selected for control operation. Based on the Local/Remote setting, this control selection is done either locally or remotely. The .stSeld indication object is activated only if the DPC object’s control model is configured as SBO.