Communication Hardware Solutions - ABB REC670 Applications Manual

Section 21
Remote communication
21.1.2.1
596
where the differential current is evaluated. If the evaluation results in a trip, the trip
signal will be sent over the two communication links.
3-end differential protection with two communication links
IED-A
Ldcm312
IEC16000077 V1 EN-US
Figure 229: 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.

Communication hardware solutions

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 230.
The protocol used is IEEE/ANSI C37.94. The distance with this solution is typical 110
km/68 miles.
Ldcm312
IED-B
Ldcm313
1MRK 511 401-UUS A
Ldcm312
IED-C
IEC16000077-1-en.vsd
Bay control REC670 2.2 ANSI
Application manual
M12844-11 v5