ABB Relion 670 Series Applications Manual page 318

Section 20
Remote communication
Table 35:
Type of LDCM
Type of fibre
Modem type
Maximum distance
Attenuation in fibre-
optic cables
2 contacts
Factory splice
attenuation
Repair splices
Fiber margin for
aging
Total attenuation
Optical link budget
Link margin
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,
properly set. From the definition follows that asymmetry is always positive at one end and
negative at the other end.
MaxTransmDelay indicates maximum transmission delay. Data for maximum 40 ms transmission
delay can be buffered up. Delay times in the range of some ms are common. If data arrive in wrong
order, the oldest data is disregarded.
MaxtDiffLevel indicates the maximum time difference allowed between internal clocks in
respective line ends.
64 kbit mode specific settings
TransmCurr is used to select among the following:
• one of the two possible local currents is transmitted
• sum of the two local currents is transmitted
• channel is used as a redundant backup channel
312
Example of calculating the optical budget (maximum distance)
Short range (SR)
Multi-mode fiber
glass 50/125 μm
1MRK0002122-AB
2 km
6 dB
2 dB
0.3 dB
0.1 dB
0.2 dB
8.6 dB
9 dB
0.4 dB
Echo synchronization method can be used, provided that AsymDelay is
© Copyright 2017 Hitachi Power Grids. All rights reserved
Short range (SR) Medium range (MR)
Multi-mode fiber Single-mode fiber
glass 62.5/125 μm glass 9/125 μm
1MRK0002122-AB 1MRK002311-AA
3 km 80 km
9 dB 25.6 dB
3 dB 0.6 dB
0.45 dB 0.64 dB
0.3 dB 0.8 dB
0.3 dB 0.8 dB
12.05 dB 26.04 dB
13 dB 26.8 dB
0.95 dB 0.76 dB
1MRK 511 407-UUS Rev. J
Long range (LR)
Single-mode fiber
glass 9/125 μm
1MRK002311-BA
120 km
25.2 dB
0.6 dB
0.96 dB
1.2 dB
1.2 dB
28.56 dB
28.7 dB
0.14 dB
Phasor measurement unit RES670
Application manual