ABB REC670 Applications Manual page 605

1MRK 511 401-UUS A
Bay control REC670 2.2 ANSI
Application manual
The same is applicable for slot 312-313 and slot 322-323.
DiffSync defines the method of time synchronization for the line differential function:
Echo or GPS.
Using Echo in this case is safe only if there is no risk of varying
transmission asymmetry.
GPSSyncErr: when GPS synchronization is lost, synchronization of the line differential
function continues for 16 s based on the stability in the local IED clocks. After that,
setting Block blocks the line differential function or setting Echo keeps it on by using
the Echo synchronization method.
Using Echo in this case is safe only if there is no risk of varying
transmission asymmetry.
CommSync defines the Master and Slave relation in the communication system, and
should 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 as Slave. When a
modem and multiplexer is used, the IED is always set as Slave because the
telecommunication system provides the clock master.
OptoPower has two settings: LowPower is used for fibres 0 – 1 km (0.6 mile) and
HighPower for fibres >1 km (>0.6 mile).
ComAlarmDel defines the time delay for communication failure alarm. In
communication systems, route switching can sometimes cause interruptions with a
duration of up to 50 ms. Too short a time delay can thus cause nuisance alarms.
ComAlrmResDel defines the time delay for communication failure alarm reset.
RedChSwTime defines the time delay before switching over to a redundant channel in
case of primary channel failure.
RedChRturnTime defines the time delay before switching back to the primary channel
after channel failure.
AsymDelay denotes asymmetry which is defined as transmission delay minus receive
delay. If fixed asymmetry is known, Echo synchronization method can be used,
provided that AsymDelay is properly set. From the definition follows that asymmetry is
always positive at one end and negative at the other end.
Section 21
Remote communication
599