182 • SMP Gateway User Manual
and SMP 8-40, also supports redundancy and can therefore be used to connect serial devices to 2
redundant SMP 4-20s or SMP 8-40s.
19.1.1 Redundant IEDs
When needed, breakers can be monitored and controlled by multiple protection relays to make
sure that a fault is always detected; normally different relays from different manufactures are used.
To report only one data set to the control center the SMP Gateway has the “best of” automation
function (see “The SMP Gateway Automation Functions Module” o
n page 163).
COMMUNICATION
FAILURE
COMMUNICATION
RESTORE
ACQUISITION OVER TWO
LINKS TO TWO DEVICES.
INFORMATION FROM
PRIMARY SOURCE IS
PREFERED.
SECONDARY SOURCE
INFORMATION IS USED.
TRYING TO RESTORE COMM.
WITH PRIMARY SOURCE.
INFORMATION FROM
PRIMARY SOURCE IS
PREFERED.
You should know that:
The “best of” automation function is protocol independent.
It is a per-point redundancy, allowing any failure in the acquisition path.
Connection with two links to the same device can also be done. However, this achieves
almost the same as the Master link redundancy but with more configuration effort.
When both IEDs have the same data map, a redundant master can be used instead of a
“best of” configuration.
The main advantage of the “best of” function over master link redundancy is that the “best of”
allows the mixing of different devices. On the other hand, the disadvantage is the size of the
configuration, as 3 points are needed to get the data from a single input/output: 2 master points
and 1 best of point.
19.1.2 Giving Priority to an SMP Gateway of the Group
It is possible to give one of the SMP Gateways the priority; the SMP Gateway that has priority
will become active when there are no error conditions. This setting will cause an additional
failover when the SMP Gateway that has priority recovers from a fault. This is explained in the
following sections.
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