ABB REB670 Applications Manual page 465

1MRK 505 337-UUS -
Application manual
• Slot 302: Main channel
• Slot 303: Redundant channel
The same is applicable for slot 312-313 and slot 322-323.
DiffSync: Here the method of time synchronization, Echo or GPS, for the line differential
function is selected.
Using Echo in this situation is safe only as long as there is no risk of
varying transmission asymmetry.
GPSSyncErr: If GPS synchronization is lost, the synchronization of the line differential
function will continue during 16 s. based on the stability in the local IED clocks.
Thereafter the setting Block will block the line differential function or the setting Echo will
make it continue by using the Echo synchronization method. It shall be noticed that using
Echo in this situation is only safe as long as there is no risk of varying transmission
asymmetry.
CommSync: This setting decides the Master or Slave relation in the communication
system and shall not be mistaken for the synchronization of line differential current
samples. When direct fibre is used, one LDCM is set as Master and the other one as Slave.
When a modem and multiplexer is used, the IED is always set as Slave, as the
telecommunication system will provide the clock master.
OptoPower: The setting LowPower is used for fibres 0 – 1 km (0.6 mile) and HighPower
for fibres >1 km (>0.6 mile).
TransmCurr: This setting decides which of 2 possible local currents that shall be
transmitted, or if and how the sum of 2 local currents shall be transmitted, or finally if the
channel shall be used as a redundant channel.
In a breaker-and-a-half arrangement, there will be 2 local currents, and the grounding on
the CTs can be different for these. CT-SUM will transmit the sum of the 2 CT groups. CT-
DIFF1 will transmit CT group 1 minus CT group 2 and CT-DIFF2 will transmit CT group
2 minus CT group 1.
CT-GRP1 or CT-GRP2 will transmit the respective CT group, and the setting
RedundantChannel makes the channel be used as a backup channel.
ComFailAlrmDel: Time delay of communication failure alarm. In communication
systems, route switching can sometimes cause interruptions with a duration up to 50 ms.
Thus, a too short time delay setting might cause nuisance alarms in these situations.
ComFailResDel: Time delay of communication failure alarm reset.
Section 17
Remote communication
459