3.5.2.1 Direct operation
Direct operation is possible for the double command if the controllable object has
been configured to "Direct control" mode. If attempting to perform direct control
for a controllable object in SBO mode, command is rejected and an error response is
generated.
3.5.2.2 Select-execute operation
A two-step select-and-execute operation is possible only if the target DPC object’s
control model is configured as select-before-operate (SBO). For most target DPC
objects, the default control model setting mode is SBO.
IEC 60870-5-104 selection timeout is defined by the protocol instance’s
Selection
Timeout
setting parameter. When a command is performed from the IEC
60870-5-104 instance, the selection timeout setting configured for the IEC 61850
DPC target object is overridden.
3.5.2.3 Cause of transmission and selected status
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.
3.6 Integrated totals objects
Integrated totals objects M_IT_NA_1 (IT objects) are mainly cross-referenced from
IEC 61850 binary counter (BCR) type objects. Forward or reverse energy is typically
measured in these object types. The IT objects' time-tagged change reporting
M_IT_TB_1 is optional and triggered by a freeze operation.
2NGA001859 A
Vendor-specific implementation
REX615
IEC 60870-5-104 Communication Protocol Manual
21
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