Electricity + Control August 2015

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ELECTRICAL PROTECTION + SAFETY
PM
Periodic inspection of portable
earthing and short-circuiting devices
Reduced cable cross-sections of portable earthing and short-cir-
cuiting devices (EaS devices) resulting from copper corrosion and
breakage of conductor strands, or increased resistances in the con-
nections, may have fatal consequences when earthing and short-
circuiting devices are subjected to short-circuit currents.Therefore,
portable EaS devices must be tested prior to each use and at reg-
ular intervals.
So far, only a
visual inspec-
tion made eco-
nomic sense. A
newprocedure
is now availa-
ble which pro-
vides reliable
information on
the condition
of the portable
EaS device based on static and dynamic measurements of the
ohmic resistance. DEHN AFRICA offers this improved test for
portable EaS devices on the customers’ premises. An earthing and
short-circuiting device is tested in three steps and the resistance
values are compared with theoretically and experimentally deter-
mined limit values.The first step is the visual inspection for visible
signs of damage. A static test is performed in the second step, in
which the absolute resistance value is measured at the station-
ary earthing and short-circuiting device. Step three includes the
dynamic test, which notes the measurement of the relative change
in resistance at the moving earthing and short-circuiting device.
The measurement of the resistance change value ΔR between the
non-moving and the moving EaS device is a new approach which
allows for the detection of local damage, such as breakage of
conductor strands in the conductor cable.
Enquiries: Alexis Barwise.Tel. 011 704 1487
or email
Launch of lightning impulse
current laboratory
To prove the effectiveness of protection measures, it is often nec-
essary to perform lightning current tests on complete systems.
DEHN’s newly designed test laboratory generates extremely high
lightning currents with a peak value up to 400 kA in the standard-
ised 10/350 μs test wave form.
This powerful test laboratory allows for the testing of light-
ning protection systems for installations and systems requiring
maximum protection.The performance of the test laboratory has
been doubled so that lightning impulse currents twice as high as
that required for the maximum lightning protection level (LPL I:
200 kA (10/350 μs)) described in the latest IEC 62305-1 lightning
protection standard, can now be simulated.
The test centre consists of five different laboratories, extend-
ing over a floor space of 800 m2. It is equipped with the latest
devices and technologies essential for developing new products
and practical solutions.
Enquiries: Alexis Barwise. DEHN Africa.Tel. 011 704 1487
or email