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 fiber 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 and HighPower.
Short-range LDCM: Use LowPower for fibres 0 – 1 km and HighPower for fibers
greater than 1 km.
Medium-range LDCM: Typical distance 80 km for both LowPower and
HighPower.
Long-range LDCM: Typical distance 120 km for both LowPower and HighPower.
An optical budget calculation should be made for the actual case. For medium
range LDCM and long range LDCM the recommendation is to use the LowPower
setting to minimize the power consumption and keep the heat dissipation at
minimum.
The HighPower setting adds 3 dBm extra optical power and can be used to increase
the margin at distances close to maximum.
Table 62: Optical budgets with C37.94 protocol
Type of LDCM
Short range (SR) Short range (SR) Medium range
(MR)
Long range (LR)
Type of fibre Multi-mode fiber
glass 50/125 μm
Multi-mode fiber
glass 62.5/125
μm
Single-mode fiber
glass 9/125 μm
Single-mode fiber
glass 9/125 μm
Modem type 1MRK0002122-
AB
1MRK0002122-
AB
1MRK002311-AA 1MRK002311-BA
Contact type ST ST FC/PC FC/PC
Table continues on next page
1MRK 506 369-UEN B Section 22
Remote communication
Line distance protection REL670 2.2 IEC 847
Application manual
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