recommended as it reduces information about bias currents. Bias current is considered the
greatest phase current at any line end, and it is common for all three phases. When sending full
information from both local CTs to the remote end, the principle works, but when the two local
currents are summed up before sending, information on real phase currents from the two local
CTs will not be available at the remote line end.
In 64 kbit mode, the decision on using one communication channel instead of two (as show in
Figure
) must be made case by case. Correct information on bias currents is always available
locally while only distorted information is available at the end that receives limited information
using only one LDCM.
In 2 Mbit mode, it is possible to send up to 9 different analog signals from each LDCM;
therefore only one LDCM can be used.
4.2
Communication between channels via Line data
communication module
GUID-1F6C28EF-26C8-4305-832C-B8CC8225DCC1 v1
Communication between two IEDs requires that each IED is equipped with a Line Data
Communication Module (LCDM). The LDCM then acts as an interface to 64 kbit/s and 2Mbit/s
communication channels for duplex communication between the IEDs.
IEC10000229 V1 EN-US
Figure 15: Selection of LDCM for analog or binary signal transfer
4.3
Configuration of analog signals
M12022-86 v5
Currents from the local end enter the IED as analog values via the Analog input modules. These
currents are converted to digital values and then forwarded to the line differential protection
function in the local IED. From there, they are transmitted to remote IEDs via a Line differential
communication module (LDCM). Currents coming from a remote IED are received as digital
values via local IED's LDCM, and they are then forwarded to the protection function in the local
IED.
LDLPSCH acts as the interface to and from the protection function.
Section 4
1MRK 505 382-UEN E
Analog and binary signal transfer for line differential protection
22
Communication set-up, 670/650 series
Application Guide
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Summary of Contents for Relion 670 series
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