ABB Relion 670 Series Applications Manual page 576

Section 22
Remote communication
Link forwarding
If it is not possible to have a communication link between each station, the solution has been
to set the protection up in a slave-master-slave configuration. This means that in Figure 276,
only IED-B has access to all currents and, therefore, this is the only place where the differential
current is evaluated. If the evaluation results in a trip, the trip signal will be sent over the two
communication links.
IEC16000077 V1 EN-US
Figure 276: 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.
22.1.2.1 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 277. The protocol used is
IEEE/ANSI C37.94. The distance with this solution is typical 110 km.
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Doing so will affect all protections for the connected cycle time.
LDCM 64kbit will increase trip time about 5 - 15 ms during normal conditions.
LDCM 2Mbit will increase trip time about 2-3 ms during normal conditions.
In addition IED can get transmission delay from communication either from
direct fiber or other equipment such as MUXs etc. Maximum supported
communication delay is 40 ms.
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.
B, it is set to
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Ldcm312
IED-B
Ldcm313
LinkForwarded should be defined. In IED-
1MRK 511 401-UEN Rev. K
GUID-DD3CF47C-A202-4416-954A-EFC0F8BEBCB7 v1
IED-C
IEC16000077-1-en.vsd
M12844-11 v7
Bay control REC670
Application manual