ABB REL 551 2.3 Series - Installing the Communication Cables

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Installing the communication cables &KDSWHU
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When using galvanic connection between protection terminal and communication
equipment or point to point galvanic connection between two protection terminals it is
essential that the cable installation is carefully done. This is true regardless of type of
module used, G.703, V.36, short range galvanic etc., only the possible length of the ca-
ble differs. The factors that must be taken into account are the susceptibility for noise
disturbance, due to that the levels of the communication signal are very low.
For best result a cable with twisted pairs and double screens should be used, one screen
for each twisted pair and one surrounding all pairs. Each signal shall utilizie its own
twisted pair as in figure 8
. The screen for each separate pair shall be connected to inter-
nal screen or ground connection of equipment in one and the same end only, if avail-
able, or in other case connected to earth close to the equipment.
The outer screen surrounding all pairs shall be connected to a solid earth at HDFK end
close to the equipment.
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Cc Communication cable
Lc Line connector
Rx Receive input
Sc Screen (or earth/ground) connection
Tx Transmit output
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Rx
Tx
Sc
Lc
Tx
Rx
Sc
Lc
Cc
Relay
Terminal
External
Equipment