P54x/EN SC/La4 SCADA Communications
(SC) 13-16
MiCOM P543, P544, P545 & P546
SC
A message gap setting is provided:
Message Gap
This allows a gap between message frames to be set to enable compatibility with different
master stations.
The setting for enabling/disabling DNP3.0 time synchronization is described above. When
DNP3.0 time sync is enabled, the required rate of synchronization, known as the “need
time”, needs to be set.
A setting allows different “need time” to be set with setting range from 1 - 30 minutes, step of
1 minute and default at 10 minutes:
DNP Need Time
10mins
The transmitted application fragment size can be set to ensure that a Master Station cannot
be held too long before a complete reply is received and allow it to move on to next IED in a
token ring polling setup.
The maximum overall response message length can be configured:
DNP App Fragment
2048
A single fragment size is 249. Depending on circumstances, a user may set the fragment
size as a multiple of 249 in order to optimize segment packing efficiency in fragments.
However it can also be useful to allow "odd" sizes for users to choose under specific
circumstances, such as if sending data inside SMS frames, through packet radios, etc. In
such cases it can be useful to select the fragment size such that each packet occupies a
single "transmission media frame".
In some cases, communication to the outstation is made over slow, packet-switched
networks which can add seconds to the communication latency.
A setting is provided to allow the application layer timeout to be set:
DNP App Timeout
2s
Select Before Operate (SBO) timeouts can be set.
If the DNP3.0 “Select a trip command” causes the relay’s internal logic to block automatic
tripping, then a corruption of the DNP3.0 “Operate” message could delay the trip. The delay
of tripping can be set:
DNP SBO Timeout
10s
The DNP link timeout can be set:
DNP Link Timeout
10s
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