ABB Relion 615 series, Manual

3.3.3 

Controls

The IEC 60870-5-103 standard defines remote control of indications or control of
objects without corresponding indication. Example of a controllable indication
could be circuit breaker ON/OFF whose position can be monitored as a normal
ASDU 1 indication, and which also can be controlled ON or OFF by the IEC
60870-5-103 client. Example of a control object without corresponding indication
could be an acknowledge object, for example LED Reset.

According to the standard the remote control operations are performed using the
ASDU 20 object type. Controllable indications usually can be controlled into two
positions, ON or OFF. Acknowledge points can only be controlled ON. If the IED
is in local mode, the remote CB controls are rejected.

3.3.3.1 

Circuit breaker control model

Circuit breaker can only be controlled with DIRECT ON/OFF commands. This is
due to the limitations in the IEC 60870-5-103 standard. In case the IED’s internal
(IEC 61850) circuit breaker control model is set to Select-Before-Operate, the IEC
60870-5-103 stack will internally emulate both SELECT and OPERATE
commands toward the circuit breaker. To the IEC 60870-5-103 client the control
operation always appears to be DIRECT.

3.3.3.2 

Control operation rejections

The IEC 60870-5-103 standard does not take into account that the IED could have
several remote client connections. It should be noticed that a remote control
operation could also be rejected if another remote client is performing a control
operation at the same time. The IED handles the remote command rejection in
three different ways.

•

Remote command to an existing object, while the IED is in Local mode or the
IED is in Remote mode, but control operation is blocked for some reason
(Blocking reasons include simultaneous control being performed by another
remote client):
•

The command is accepted on link level (Link ACK)

•

The command is rejected on application level (Negative response,
COT=21)

•

Remote command while the IED is still performing the previous command of
the same client:
•

The command is rejected on link level (Link NAK, DFC=1)

•

Remote command performed on a non-existing object:
•

The command is rejected on link level (Link NAK, DFC=0)

In the last two cases the DFC flag is used to distinguish the faults.

1MRS756710 C

Section 3

Vendor-specific implementation

615 series

17

Communication Protocol Manual