ABB REF542plus Installation And Commissioning Manual page 22

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REF 542plus switchbay protection and control unit
Manual Part 3: Installation and Commissioning
Figure 4: Grounding of the REF542plus Central Unit housing
To ensure the EMC (Electro Magnetic Compatibility) the housing must be grounded
by a low impedance galvanic connection to the grounding system. As it is shown in
the figure, an appropriate cable connection, which is fixed from a specific screw on
the housing to the grounding system in the LV compartment, must be foreseen. That
is why an interweaving cable is used for the grounding connection. If, due to the in-
stallation construction, the low impedance connection from the housing to the ground-
ing system is already given, the additional grounding connection by the interweaving
cable can be abstain from.
The housing of the HMI Local Control Unit must also be grounded too. As can be
seen in the next figure, a specific grounding cable is to be connected from the hous-
ing of the HMI Local Control Unit to the grounding system in the LV compartmen.
DMS,2001-10-04 REF542plus: Installation and Commissioning 22 / 80