Rules For The Transition Point Between Lightning Protection Zones 1 - Siemens SIMATIC S7-300 Hardware And Installation Manual

Principle of the transition points between lightning protection zones
At the transitions points between lightning protection zones, you must take
measures to prevent surges being conducted downstream.
The principle of the lightning protection zone concept also specifies that all cables
which are capable of carrying lightning current (!) and installed at the transition
points of lightning protection zones must be included in the equipotential bonding
system.
Conductors and cables capable of carrying lightning current are:
• Metal pipes (e.g. water, gas and heat)
• Power cables (for example, mains voltage, 24 V supply)
• Data cables (for example, bus cable).

12.3.2 Rules for the transition point between lightning protection zones 1

Rules for transition point 0 <-> 1 (Lightning protection equipotential bonding)
The following measures are suitable for lightning protection equipotential bonding
at the transition between lightning protection zones 0 <-> 1:
• Use grounded, spiraled, current-conducting metal straps or metal braiding as a
cable shield at both ends, for example, NYCY or A2Y(K)Y.
• Install cables in one of the following media:
in continuous metal pipes that are grounded at both ends, or
–
in continuously armored concrete ducts or
–
on closed metal cable trays grounded at both ends.
–
Use optical waveguides instead of metal conductors.
–
Additional Measures
If you cannot take measures as described above, you must install a high-voltage
protection for your system between the 0 <-> 1 transition points with a lightning
conductor. The table below contains the components you can use for high-voltage
protection of your plant.
S7-300 Programmable Controller Hardware and Installation
A5E00105492-02
Appendix
12-21