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Requirements for External Lightning Protection Components

Tests based on the example of an MV clamp electrical test the specimens have to be fixed on an insulating plate
At first, the number of test combinations has to be determined. The MV (Figure 5).
clamp used is made of stainless steel (StSt) and hence can be combined Three lightning current impulses of 10/350 μs wave form with 50 kA (nor-
with steel, aluminium, StSt and copper conductors as stated in Table 1. mal duty) and 100 kA (heavy duty) are applied to every specimen. After
Moreover, it can be connected in cross and parallel arrangement which being loaded with lightning current, the specimens must not show signs
also has to be tested. This means that there are eight possible test com- of damage.
binations for the MV clamp used (Figures 3 and 4). In addition to the electrical tests where the specimen is subjected to elec-
trodynamic forces in case of a lightning current load, a static-mechanical
In accordance with EN 62561 each of these test combinations has to load was integrated in the EN 62561-1 standard. This static-mechanical
be tested on three suitable specimens / test set-ups. This means that test is particularly required for parallel connectors, longitudinal connec-
24 specimens of this single MV clamp have to be tested to cover the tors, etc. and is carried out with different conductor materials and clamp-
complete range. Every single specimen is mounted with the adequate ing ranges. The connection components are prepared with a defined
tightening torque in compliance with normative requirements and is tightening torque and then loaded with a mechanical tensile force of 900
subjected to artificial ageing by means of salt mist and humid sulphur- N (± 20 N) for one minute. During this test period, the conductors must
ous atmosphere treatment as described above. For the subsequent not move more than one millimetre and the connection components
must not show signs of damage. This additional
static-mechanical test is another test criterion
Steel Aluminium Copper StSt Titanium Tin for connection components and also has to be
Steel (St/tZn) yes yes no yes yes yes documented in the manufacturer’s test report in
Aluminium yes yes no yes yes yes addition to the electrical values.
The contact resistance (measured above the
Copper no no yes yes no yes clamp) for a stainless steel clamp must not
StSt yes yes yes yes yes yes exceed 3 mΩ or 1 mΩ in case of other mate-
Titanium yes yes no yes yes yes rials. The required loosening torque has to be
ensured. A manufacturer’s test report is pre-
Tin yes yes yes yes yes yes
pared for every test combination. A detailed
Table 1: Possible material combinations for air-termination systems and down conductors and for test report is available from the manufacturer
connection with structural parts. upon request or a less detailed report can be
downloaded from the internet (www.dehn-in-
ternational.com => Product data).

Consequently, installers of light-
ning protection systems have to
select the connection components
for the duty (H or N) to be expected
on site. A clamp for duty H (100 kA), for
example, has to be used for an air-termination
▲ new components rod (full lightning current) and a clamp for duty N
▼ aged components (50 kA) has to be used in a mesh or at an earth
entry (lightning current already distributed).

Conductors
EN 62561-2 also places special demands on
conductors such as air-termination and down
conductors or earth electrodes e.g. ring earth
electrodes, for example:
Figure 3: New and aged components.
• Mechanical properties (minimum tensile
strength, minimum elongation),
• Electrical properties (max. resistivity) and
• Corrosion resistance properties
(artificial ageing as described above).

Figure 4: Test combinations for MV clamps Figure 5: Specimen fixed on insulating plate
(parallel and cross arrangement). (MV clamp) for a test in the
impulse current laboratory.
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