ABB Relion 670 Series Applications Manual page 554

Section 21
Remote communication
IEC16000077 V1 EN-US
Figure 246: 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.
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.
21.1.2.1 Communication hardware solutions
The LDCM (Line Data Communication Module) has an optical connection such that two IEDs can be
connected over a direct fiber (multimode), as shown in figure 247. The protocol used is IEEE/ANSI
C37.94. The distance with this solution is typical 110 km/68 miles.
IEC06000519 V2 EN-US
Figure 247: Direct fiber optical connection between two IEDs with LDCM
The LDCM can also be used together with an external optical to galvanic G.703 converter or with
an alternative external optical to galvanic X.21 as shown in figure 248. These solutions are aimed
548
3-end differential protection with two communication links
Ldcm312
IED-A
Ldcm312
In order to forward the logic signals (for example, inter-trip or inter-block) between
IED-A and IED-C, the setting
LDCM313 for Ldcm312 and to LDCM312 for ldcm313.
© Copyright 2017 ABB. All rights reserved
Ldcm312
IED-B
Ldcm313
LinkForwarded should be defined. In IED-B, it is set to
1MRK 511 401-UUS F
IED-C
IEC16000077-1-en.vsd
en06000519-2.vsd
Bay control REC670
Application manual
M12844-11 v7