Hitachi Relion 670 Series Product Manual page 35

Line differential protection RED670
Version 2.2
automatically when the setting Operation for the differential
function is set to Off.
IED
IED
IEC05000043 V2 EN-US
Figure 9. Five terminal lines with master-master system
IED
Comm. Channels
IED
IEC05000044 V2 EN-US
Figure 10. Five terminal line with master-slave system
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.
Networks with fixed routes where symmetric time delay is
applied, or networks with fixed route switching where both
directions have the symmetric time delay even after route
switching has been performed. In these types of networks,
different channel delay times are automatically
compensated for, and echo timing can be used.
Additional security logic for differential protection LDRGFC
Additional security logic for differential protection (LDRGFC)
can help the security of the protection especially when the
communication system is in abnormal status or for example
when there is unspecified asymmetry in the communication
link. It helps to reduce the probability for mal-operation of
the protection. LDRGFC is more sensitive than the main
protection logic to always release operation for all faults
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Protected zone
IED IED
Protected zone
IED IED IED
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For line differential protection we
recommend that all feeder ends use the
same version of RED670 and the line data
communication module LDCM. The line
differential protection in the latest version of
RED670 is compatible with older versions of
RED670. Older versions than 670 1.2.3
must be verified with Hitachi Power Grids.
IED
Comm.
Channels
IEC0500043_2_en.vsd
IED
IEC050000 44-2-
en.vsd
Networks with unspecified route switching require that the
line differential protection IED's built-in GPS receiver, PTP
or IRIG-B is used. This way the protection function can
operate correctly independent of the symmetric delays in
communication channels.
The communication link is continuously monitored, and an
automatic switchover to a standby link is possible after a
preset time.
detected by the differential function. LDRGFC consists of
four sub functions:
• Phase-to-phase current variation
• Zero sequence current criterion
• Low voltage criterion
• Low current criterion
1MRK 505 379-BEN R
GUID-8F918A08-E50E-4E7B-BDCA-FF0B5534B289 v3
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