Telecom. Network
*) *)
Multiplexer Multiplexer
en05000527-2.vsd
*) Converting optical to galvanic G.703
IEC05000527 V2 EN-US
Figure 226: LDCM with an external optical to galvanic converter and a multiplexer
When an external modem G.703 or X.21 is used, the connection between LDCM and the modem
is made with a multimode fiber of max. 3 km length. The IEEE/ANSI C37.94 protocol is always
used between LDCM and the modem.
Alternatively, a LDCM with X.21 built-in converter and micro D-sub 15-pole connector output
can be used.
18.1.2.2 Application possibility with one-phase REB670
M12844-20 v4
For busbar protection applications in substations where dynamic zone selection is required, it
is typically necessary to wire the normally open and normally closed auxiliary contacts from
every monitored disconnector and/or circuit breaker to the optocoupler inputs of the busbar
protection. When one phase version of REB670 is used, then six optocoupler inputs (that is,
two in each phase/IED) are required for every primary switchgear object. For big stations (for
example, with 24 bays) this will require quite a lot of binary inputs into every IED. To limit the
number of required optocoupler inputs into every IED it is possible to use LDCM
communication modules to effectively share the binary Ios between three units, as shown in
figure
227227.
1MRK 505 370-UEN D Section 18
Remote communication
Busbar protection REB670 421
Application manual
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