6.1.2.2 Analog signal transfer for line differential protection
M13647-3 v8
The line differential protection function can be arranged as a master-master system
or a master-slave system alternatively. In the former, current samples are
exchanged between all IEDs, and an evaluation is made in each IED. This means
that a 64 kbits/s communication channel is needed between every IED included in
the same line differential protection zone. In the latter, current samples are sent
from all slave IEDs to one master IED where the evaluation is made, and trip
signals are sent to the remote ends when needed. In this system, a 64 kbit/s
communication channel is only needed between the master and each one of the
slave IEDs. The Master-Slave condition for the differential function appears
automatically when the setting Operation for the differential function is set to Off.
For line differential protection we recommend that all feeder ends
use the same version of RED650 or RED670 and the line data
communication module LDCM. The line differential protection in
the latest version of RED650 is compatible with older versions of
RED670 and RED650. Older versions than RED670 1.2.3 must be
verified with ABB.
Current samples from IEDs located geographically apart from each other, must be
time coordinated so that the current differential algorithm can be executed
correctly, this is done with the echo method.
The communication link is continuously monitored, and an automatic switchover
to a standby link is possible after a preset time.
Section 6 1MRK 505 394-UEN A
Differential protection
86 Line differential protection RED650 2.2 IEC
Technical manual
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