ABB REF 54 Series Technical Reference Manual, General page 82

REF 54_
Feeder Terminal 1MRS750527-MUM
Technical Reference Manual, General
In case of LON communication, the command time-out parameter has to be longer
than or equal to 1.5 sec. A longer time-out is needed because the time for horizontal
communication to take place needs to be taken into account.
Normally the time-out parameter of the client must always be adjusted in accordance
with the IED command time-out parameter (longer time-out on the client side). At
all times there shall be only one communication port from which secured object
control is possible.
The command time-out parameter is located in MAIN MENU/Communication/
General.
For more information about secured object control, refer to the control function
block manuals.
Setting the command time-out parameter for LON
communication
The correct command time-out parameter value depends on how many LON
communication inputs are in use (COMM_INx variables). If no horizontal
communication is used, 1.5 seconds shall be used as time-out.
In order to take full advantage of the secured command handling procedure, the
complete scenario must be known.
There are two scenarios:
1. Confirmed command handling with NV poll support: NV poll selected by the
LNT tool.
2. Command handling with asynchronous blockings.
Confirmed command handling with NV poll support
If LON NV polling is used for communication inputs, the time-out must be based on
the minimum time-out, and is calculated from:
amount_of_polled_inputs*poll_timeout*(retries+1)
which gives a typical minimum value of:
amount_of_polled_inputs*128ms...256ms*5
(see the LN settings and refer to the instructions given for default time-outs).
An over dimensioned longer time-out will not cause any harm, because the operation
will always be faster in real life than the maximum time-out.
On application side, the comm_in and comm_outs need to be used systematically to
ensure that exceptions to the normal operation are handled correctly (for example
handling of the live bits).
Command handling with asynchronous blockings
Fig. 5.1.13.10.-1 shows the asynchronous blocking principle of sending the reserve-
output state to the block-inputs of other bays. As horizontal communication is
trusted directly, 1.5 seconds shall be used as command time-out.
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