II - DCE FEL ČVUT v Praze

Mechanical Configuration of an Automation System with SIMATIC S7 Ex Modules
1.9.7 Lightning Strike
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04
When lightning strikes an explosive atmosphere it always ignites. There is
also a risk of ignition by excessive temperature raise in the lightning
discharge paths. In order to prevent, at Zones 0, 1 and 10 themselves, the
harmful effects of lightning strikes occurring outside the zones, surge
diverters, for example, must be fitted at suitable points. Tank insulation
covered with earth and made of metal materials with electrical equipment or
electrically conductive system sections, which are electrically insulated with
respect to the tank, require equipotential bonding; for example, in the case of
measurement and control systems and filling pipes.
Note
Lightning protection equipment and grounding systems must be tested by an
expert upon their completion and at regular intervals. Based on ElexV, the
testing interval for electrical systems and lightning protection systems for
hazardous areas is three years.
Summary:
Enhanced external lightning protection (reduced mesh size, increased
number of down conductors) on all buildings and systems.
Meshing of grounding systems in the building to create area grounding.
Meshing of equipotential bonding.
Fitting of lightning conductors and surge diverters in the power system.
Fitting of overvoltage fine-protection devices at both ends of
measurement and control cables.
Shielding of measurement and control cables.
Measurement and control cables with twisted pairs of cores.
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