Fig. 235: Bus line: Correct
Fig. 236: Bus line: Wrong
2.6.4.8.4 Earthing
In order to avoid disturbance, the cable shields must be earthed directly.
Case a:
Multiple switch-gear cabinets: If it can be guaranteed that no potential differences can occur
between the switch-gear cabinets by means of current-carrying metal connections (earthing
bars, steel constructions etc.), the direct earthing is chosen.
CS31
Shield
BUS 2
BUS 1
slave
CS31 system bus
CS31
slave
CS31 system bus
1
2
3
4
120
Ohms
COM1
PE
CS31 bus master
e.g. PM581
Cabinet 1 Cabinet 2
current-carrying connection current-carrying connectio n
direct earthing of shields
when entering the cabinet
Fig. 237: Direct earthing
Case b:
System Assembly, Construction and Connection
AC500 (Standard) > Connection and Wiring
2019/04/17 3ADR010121, 13, en_US 1285
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