The relay can be set to five different states: Local, Remote, Station, All or Off. CB controls from an IEC 60870-5-103 client are possible when the relay is in the Remote, Station or All state. When the relay is in the Local or Off state, the circuit breaker cannot be controlled via IEC 60870-5-103. The IEC 60870-5-103 mapping includes two ASDU1 ON or OFF points dealing with these states.
First, the classic Local or Remote ON or OFF indication, CTRL.LLN0. Loc, is the easiest signal to use on the client side. The indication shows "ON" when the relay is in the Local or Off state, and "OFF" when the relay is in the Remote, Station or All state. Basically, this object tells if control is possible from the IEC 60870-5-103 client at a particular moment. This object is sufficient for most users.
The relay cannot distinguish if the IEC 60870-5-103 client is of the Station or Remote (NCC) type. However, it is possible to locally reject the control operations on the IEC 60870-5-103 client side based on this indication and information about the client type (NCC or Station).