ABB AC 800M User Manual page 81

Section 3 Fieldbus Topologies
If a sufficient potential equalization between the hazardous area and the safe area
cannot be guaranteed, the cable shield shall be directly connected to the
equipotential bonding earth only in the hazardous area. In the safe area the shield
shall be connected to earth through a capacitor. The impedance of the connection
should be minimized for high frequencies. However, the need for an electric
envelope as complete as possible cannot be entirely fulfilled.
Figure 30.
The connection between both groundings through a capacitor may also be placed at
an other position between power supply and the hazardous area (or between
different hazardous areas), but it has always to be in a safe area.
3BDS009029R5001 B
Capacitive grounding
Shielding and data line connection
81