Beckhoff EL2904 Operating Instructions Manual page 21

PE power contact
The power contact labelled PE can be used as a protective earth. For safety reasons this contact mates
first when plugging together, and can ground short-circuit currents of up to 125 A.
Insulation tests
Note that, for reasons of electromagnetic compatibility, the PE contacts are
CAUTION
capacitatively coupled to the mounting rail. This may lead to incorrect results during
insulation testing or to damage on the terminal (e.g. disruptive discharge to the PE line
during insulation testing of a consumer with a rated voltage of 230 V).
For insulation testing, disconnect the PE supply line at the Bus Coupler or the Power
Feed Terminal! In order to decouple further feed points for testing, these Power Feed
Terminals can be released and pulled at least 10 mm from the group of terminals.
Serious risk of injury!
The PE power contact must not be used for other potentials!
DANGER
4.1.4.2 Overvoltage protection
If protection against overvoltage is necessary in your plant, provide a surge filter for the voltage supply to
the Bus Terminal blocks and the TwinSAFE terminals.
EL2904
Operation
19