Siemens S7-400 installation manual Lightning Protection Element for the 24 VDC Supply

Assembling and Installing Systems

A.9.3 Rules for the Transitions between Lightning Protection Zones 1 <-> 2 and Greater

Rules for Transitions 1 <->2 and Above (Local Equipotential Bonding)

for all lightning protection zone transitions 1 <->2 and greater:

•Set up local equipotential bonding at each subsequent lightning protection zone transition.

•Include all cables (also metal pipelines, for example) in the local equipotential bonding at all subsequent lightning protection zone transitions.

•Include all metal installations located within the lightning protection zone in the local equipotential bonding (for example, metal part within lightning protection zone 2 at transition 1 <-> 2).

Additional Measures

We recommend you ensure low-voltage protection for the following elements

•for all lightning protection zone transitions 1 <->2 and greater and

•for all cables that run within a lightning protection zone and are longer than 100 m.

Lightning Protection Element for the 24 VDC Supply

You should only use the lightning conductor KT, type 24 VAD SIMATIC for the

24 VDC power supply of the S7-400. All other surge protection components do not meet the required tolerance range of 20.4 V to 28.8 V of the S7-400’s power supply.

Lightning Protection Element for Signal Modules

You can use standard overvoltage protection components for the digital I/O modules. However, please note that these only permit a maximum of 1.15 x VNom =

27.6V for 24 VDC nominal voltage. If the tolerance of your 24 VDC power supply is higher, use the surge protection components for 30 VDC nominal voltage.

You can also use the VT lightning conductor, Type AD 24 V SIMATIC. However, this can result in the following restrictions:

•Digital inputs: An increased input current can flow in the case of negative input voltages.

•Digital outputs: Dropout time of contactors can increase significantly.

Automation System S7-400	Hardware and Installation	A-25
A5E00850741-01