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EARTHING + LIGHTNING PROTECTION
arise as soon as the lightning current flows through them. In order
to test the worst case, not only the different conductor combinations
but also the material combinations must be tested.
Possible material combinations for air-termination systems, down
conductors and for connection to structural parts.
Steel Aluminium Copper StSt Titanium Tin
Steel (St/tZn)
Yes
Yes
No Yes Yes Yes
Aluminium Yes
Yes
No Yes Yes Yes
Copper
No
No
Yes Yes
No Yes
StSt
Yes
Yes
Yes Yes Yes Yes
Titanium Yes
Yes
No Yes Yes Yes
Tin
Yes
Yes
Yes Yes Yes Yes
The testing of the clamps must comprise all of the possible conduc-
tor combinations and the aged as well as the new components. The
clamp connections are then subjected to lightning current impulses
of 10/350 μs wave shape with 50 kA and 100 kA being applied to
each specimen. The clamps must show no signs of damage and the
transition resistance must not exceed 2,5 m
Ω
. The result of the tests
showed that two types of clamps are applicable:
• Heavy Duty (H) = 100 kA (lightning protection level I and II)
• Normal Duty (N) = 50 kA (lightning protection level III and IV)
The selection of the right type of clamp should be done by the whether
there is any current division before the clamp location. This test pro-
cedure must be performed for all types of connection components.
Detailed test reports should be made available for each lightning
protection designer and should be based upon various factors like
lightning protection level or lightning protection component.
Test procedure for electrodes
The SANS / IEC 62561-2 standard places special requirements on
conductors such as air termination conductors, down conductors
and earthing conductors. These requirements are:
• Mechanical properties (minimum tensile strength, minimum
elongation)
• Electrical properties (max. Resistivity)
• Corrosion resistant properties (via artificial ageing)
The mechanical properties of all lightning protection conductors
must be tested and observed. Additional tests like the bending test
and the current carrying ability must also be applied and observed.
Data sheets for all conductors should be available on request by all
lightning protection manufacturers and installers.
In order to be able to create long earth electrodes (3 m to 30 m
long), the earth electrodes are extendable via rod couplings. Both
the earth electrodes and the rod couplings are subject to testing in
terms of the standards.
SANS / IEC 62561-2 [2] specifies the requirements for earth
electrodes such as material, geometry, minimum dimensions as
well as mechanical and electrical properties. The coupling joints
linking individual rods are weak points, for this reason, additional
mechanical and electrical tests have to be performed to test the
quality of the coupling joints. Generally earth electrodes are made
of the following materials:
• Hot dipped galvanised steel rods
• Stainless steel rods
• Solid copper rods
• High tensile, low carbon copper clad rods
By far the majority of rods that are installed are the copper clad
rods. In order to comply with the requirements of the standards, the
minimum copper cladding shall be as follows:
99,9% Pure electrolytic copper clad to a minimum thickness
of 250 microns (0,250 mm) = Grade ‘A’
Lightning protection components are
subject to natural weathering and
exposure to corrosion.
Self supporting
air-termination rod.
Test in salt mist chamber.
Electricity+Control
October ‘15
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