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Therefore, it is advisable to install a separate earth-termination for lines from LPZ 0 A to LPZ 1 must have a lightning current
system for every single building or part of an installation and discharge capacity which is described by the 10/350 µs test
to intermesh them. This intermeshing (Figure 9.32.6) reduces wave form. Surge protective devices of different requirement
potential differences between the buildings / parts of the in- classes must be coordinated with one another. This is ensured
stallation and thus conducted partial lightning currents. The by DEHN surge arresters.
closer the mesh of the earth-termination system, the lower the
potential differences between the buildings / parts of the in- Shield treatment in intrinsically safe measuring
stallation in case of a lightning strike. Mesh sizes of 20 x 20 m circuits
(mesh sizes of 10 x 10 m are recommended in potentially ex- The treatment of the cable shield is an important measure to
plosive atmospheres and when using electronic systems) have prevent electromagnetic interference. In this context, the ef-
proven to be economically feasible. When selecting the earth- fects of electromagnetic fields must be reduced to an accept-
ing material, it must be ensured that the buried pipes do not able level to prevent ignition. This is only possible if the shield
corrode. is earthed on both cable ends. Earthing the shield on both ends
is only permitted in hazardous areas if absolutely no potential
Equipotential bonding differences are to be expected between the earthing points (in-
Consistent equipotential bonding must be established in all po- termeshed earth-termination system, mesh size of 10 x 10 m)
tentially explosive atmospheres to prevent potential differen ces and an insulated earthing conductor with a cross-section of
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between different and extraneous conductive parts. Building at least 4 mm (better 16 mm ) is installed in parallel to the
columns and structural parts, pipes, containers, etc. must be in- intrinsically safe cable, is connected to the cable shield at any
tegrated in the equipotential bonding system so that a voltage point and is insulated again. This parallel cable must be con-
difference does not have to expected even under fault condi- nected at the same equipotential bonding bar as the shield of
tions. The connections of the equipotential bonding conductors the intrinsically safe cable (Figure 9.32.6).
must be secured against automatic loosening. According to
IEC 60079-14 (EN 60079-14), supplementary equipoten- Moreover, permanently and continuously connected reinforc-
tial bonding is required which must be properly estab- ing bars can be used as equipotential bonding conductor. These
lished, installed and tested in line with the IEC 60364-4-41 are connected to the equipotential bonding bar on both ends.
(HD 60364-4-41) and IEC 60364-5-54 (HD 60364-5-54) stand-
ard. When using surge protective devices, the cross-section of Summary
the copper earthing conductor for equipotential bonding must The risk of chemical and petrochemical plants due to a light-
be at least 4 mm . ning discharge and the resulting electromagnetic interference
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is described in the relevant standards. When using the light-
Lightning equipotential bonding outside the ning protection zone concept for designing and installing such
hazardous area plants, the risks of sparking in case of a direct lightning strike
The use of surge protective devices in low-voltage consum- or discharge of conducted interference energies must be safely
er’s installations and measuring and control systems outside minimised with economically acceptable efforts. The surge
the hazardous area (e.g. control room) does not differ from arresters used must fulfil explosion protection requirements,
other applications (for more detailed information, please also ensure coordination with terminal equipment and meet the
see brochure DS 649 E “Red/Line Selection Guide”). In this requirements resulting from the operating parameters of the
context, it must be pointed out that surge protective devices measuring and control circuits.

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