IED-A IED-B IED-CIEC16000077-1-en.vsd3-end differential protection with two communication linksLdcm312Ldcm312Ldcm313Ldcm312IEC16000077 V1 EN-USFigure 114: Three-end differential protection with two communication linksIf the LDCM is in 2Mbit mode, you can send the three local currents as well as thethree remote currents from the other links by configuring the transmitters in IED-B:1. Ldcm312 transmitter sends the local currents and the three currents receivedby Ldcm313.2. Ldcm313 transmitter sends the three local currents and the three currentsreceived from Ldcm312.As a result, six currents are received in IED-A and IED-C. These currents can beconnected 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 LinkForwardedshould be defined. In IED-B, it is set to LDCM313 for Ldcm312and to LDCM312 for ldcm313.This setup results in a master-master-master configuration, but without the benefitof reverting to a slave-master-slave configuration in case of a communication linkinterruption. In case of a communication link interruption, all three IEDs would beblocked.20.1.2.1 Communication hardware solutions M12844-11 v7The LDCM (Line Data Communication Module) has an optical connection suchthat two IEDs can be connected over a direct fiber (multimode), as shown in figure115. The protocol used is IEEE/ANSI C37.94. The distance with this solution istypical 110 km.Section 20 1MRK 511 407-UEN CRemote communication324 Phasor measurement unit RES670 2.2 IECApplication manual
