ABB AC500 PLC Hardware Manual page 1184

System Assembly, Construction and Connection
Overall Information (valid for complete AC500 Product Family) > Earthing Concept (Block Diagrams)
For CS31 fieldbus modules:
2.4.3 Earthing Concept (Block Diagrams)
1184
NOTICE!
PLC Damage due to missing Earthing
– Ensure to earth the devices.
– The earthing (switch cabinet earthing, PE) is supplied both by the mains
connection (or 24 V supply voltage) and via DIN rail. The DIN rail must be
connected to the earth before the device is subjected to any power. The
earthing may be removed only if it is certain that no more power is being
supplied to the control system.
3ADR010121, 13, en_US 2019/04/17