sending, information on real phase currents from the two local CTs will not beavailable at the remote line end.In 64 kbit mode, the decision on using one communication channel instead of two(as show in Figure 35) must be made case by case. Correct information on biascurrents is always available locally while only distorted information is available atthe end that receives limited information using only one LDCM.6.1.2.6 Configuration of analog signals M12022-86 v5Currents from the local end enter the IED as analog values via the Analog inputmodules. These currents are converted to digital values and then forwarded to theline differential protection function in the local IED. From there, they aretransmitted to remote IEDs via a Line differential communication module(LDCM). Currents coming from a remote IED are received as digital values vialocal IED's LDCM, and they are then forwarded to the protection function in thelocal IED.LDLPSCH acts as the interface to and from the protection function.Configuration of this data flow is made in the SMT tool as shown in Figure 36.Currents fromremote end 1Currents toremote end 1Currents fromremote end 2Currents toremote end 2LDCM 2LDCM 1Currents fromlocal CT A/DSMAIPre-processingblockLine DifferentialfunctionL3DPDIFIEC05000533-2-en.vsdIEC05000533-NEW V2 EN-USFigure 36: Typical configuration of analog signals for a three-terminal lineFigure 36 shows how one IED in a three-terminal line differential protection can beconfigured. There are two LDCMs each supporting a duplex connection with aremote line end. Thus, the same local current is configured to both LDCMs, whilethe received currents from the LDCMs are configured separately to the linedifferential protection function.Section 6 1MRK 505 393-UEN BDifferential protection84 Line differential protection RED650 2.2 IECApplication manual
