Siemens SCALANCE W788C-2 Series Operating Instructions Manual page 31

Supply voltage
Safety extra low voltage
The equipment is designed for operation with Safety Extra-Low Voltage (SELV) by a
Limited Power Source (LPS).
This means that only SELV / LPS (Limited Power Source) complying with IEC 60950-1 / EN
60950-1 / VDE 0805-1 must be connected to the power supply terminals or the power
supply unit for the equipment power supply must comply with NEC Class 2, as described by
the National Electrical Code (r) (ANSI / NFPA 70).
If the equipment is connected to a redundant power supply (two separate power supplies),
both must meet these requirements.
Transient overvoltages
Take measures to prevent transient voltage surges of more than 40% of the rated voltage.
This is the case if you only operate devices with SELV (safety extra-low voltage).
SCALANCE W788C-2
Operating Instructions, 01/2017, A5E03692120-11
WARNING
WARNING
5.2 Lightning protection, power supply and grounding
Connection
31