ABB RELION REB670, Applications Manual

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where the differential current is evaluated. If the evaluation results in a trip, the trip
signal will be sent over the two communication links.
IED-A IED-B IED-C
IEC16000077-1-en.vsd
3-end differential protection with two communication links
Ldcm312
Ldcm312
Ldcm313
Ldcm312
IEC16000077 V1 EN-US
Figure 208: Three-end differential protection with two communication links
If the LDCM is in 2Mbit mode, you can send the three local currents as well as the
three remote currents from the other links by configuring the transmitters in IED-B:
1. Ldcm312 transmitter sends the local currents and the three currents received by
Ldcm313.
2. Ldcm313 transmitter sends the three local currents and the three currents received
from Ldcm312.
As a result, six currents are received in IED-A and IED-C. These currents can be
connected to the protection function together with the local three currents.
In order to forward the logic signals (for example, inter-trip or inter-
block) between IED-A and IED-C, the setting
LinkForwarded should
be defined. In IED-B, it is set to LDCM313 for Ldcm312 and to
LDCM312 for ldcm313.
This setup results in a master-master-master configuration, but without the benefit of
reverting to a slave-master-slave configuration in case of a communication link
interruption. In case of a communication link interruption, all three IEDs would be
blocked.
18.1.2.1 Communication hardware solutions
M12844-11 v5
The LDCM (Line Data Communication Module) has an optical connection such that
two IEDs can be connected over a direct fibre (multimode), as shown in figure
209 .
The protocol used is IEEE/ANSI C37.94. The distance with this solution is typical 110
km/68 miles.
Section 18
1MRK 505 370-UUS A
Remote communication
492 Busbar protection REB670 2.2 ANSI
Application manual