Sparks Electrical News January 2015

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sparks
ELECTRICAL NEWS january 2015
14 earthing, lightning and surge protection
EVERY year, lightning strikes result in
property damage and sometimes the
death of people and animals.
Severe lightning injuries and fatali-
ties are reported annually from all over
the world, especially on golf courses,
making shelters vital to protect golf-
ers from the effects of lightning. The
points below are not limited to shelters
on golf courses, but are equally ap-
plicable to hiking shelters, and other
exposed areas.
These shelters must not only protect
from storms and rain, but also from
the effects of a lightning strike. There
is no question that shelters must be
equipped with a lightning protection
system, as golf course operators have a
high duty of care towards their mem-
bers and golfers.
These shelters should not be located
in exposed locations; for example, on
hilltops, at the edge of woodland, or
under single trees. Shelters are only
lightning-proof if:
• They are equipped with adequate
lightning protection.
• Conductive systems, such as electri-
cal cables, are included in the equi-
potential bonding; and
• Suitable measures for preventing
touch voltages have been taken.
Lightning protection
Frequently, a lightning protection
system is simply a lightning rod. The
function of a lightning rod is to inter-
cept lightning and to safely conduct it
to the ground to prevent dangerous
sparking, thus protecting the structure
from fire andmechanical destruction.
Lightning safety for shelters
BLITZDUCTOR SP is a pluggable, multipole,
universal surge arrester for use as a terminal block
system inmeasuring and control circuits, bus,
alarm and telecommunication systems.
The surge arresters combine a permanently
high impulse current discharge capacity with an
extremely low voltage protection level for reliable
protection of terminal equipment against light-
ning effects and surges resulting from switching
operations.
To ensure safe operation, the arrester provides
protection against vibration effects and shock
loads up to a 30-fold acceleration of gravity. The
function optimised design of the arrester ensures
both quick and easy replacement of SPDmodules
which house all relevant protection elements. Up
to four lines can be connected on two levels mak-
ing the arresters especially suitable for terminal
block systems as lines of a pair belonging to each
Pluggable DIN rail mounted
surge arresters
Generally, the lightning protection
systemof a shelter consists of a rooftop
air-termination system (air-termination
conductor and/or rod), wall-mounted
down conductor (down-conductor
wire) and earth-termination system,
commonly called earth rods.
The formation of a high lightning
voltage in the ground, also referred
to as potential gradient area, also
presents a risk to persons in the shelter.
This voltage may be applied to the feet
of a person standing on the ground.
It is therefore also called step voltage.
Moreover, persons must maintain an
adequate safety distance to the light-
ning rod to prevent dangerous touch
voltages.
Effective lightning protectionmeas-
ures that protect golfers and hikers
from the effects of a lightning strike
can be implemented in shelters with a
relatively low effort. Apart from techni-
cal measures, it is equally important
to knowwhat to do during thunder-
storms. In the event of an impending
thunderstorm, seek shelter immedi-
ately and stay there until the thunder
or lightning has ended.
The additional considerations are
based on commonly used wood
shelters.
Prevention of touch voltages
To prevent dangerous high touch volt-
ages, an adequate safety distance must
be maintained between the lightning
rod and the persons in the shelter. In a
shelter of about 3 x 3 m, with an eaves
height also of 3 m, a safety distance of
at least 15 cm is required.
If the shelter has a minimumheight
of about 3 m, the safety distance to the
rooftop lightning rod (air-termination
conductor or rod) is already main-
tained. However, it is more difficult
to keep an adequate distance to the
outer walls. Therefore the wall/wall
construction where the lightning rod
(down-conductor wire) is conducted
to the groundmust have an adequate
wall thickness.
To connect the lightning rod with
the ground, earth rods (metal rods
of a defined lengthmade of material
appropriate to the local conditions)
are commonly used. On each down
conductor, the earth rods are vertically
buried in the ground at a depth of
about 6 to 9 m, depending on the type
of ground.
Log-structured shelters usually
have this wall thickness. However, the
situation is different when it comes to
sheds with thin wooden walls. In this
case, the down conductors must be
installed directly at the outer edges,
near the wall construction, to ensure
maximumwall thickness.
Another possibility tomaintain the
safety distance required to protect
shelters in case of a lightning strike is to
use highly insulating lightning rods. This
is essential for shelters that are smaller
than those described above.
Prevention of step voltages
Dangerous high step voltages, as a
result of strikes into the lightning rod
of a shelter or nearby lightning strikes,
must be prevented. To this end, there
are two options:
1. Prevention of dangerous step volt-
ages by insulating the ground. This
means that the floor must be made
of a 5 cm asphalt layer. As an alterna-
tive, a wooden floor can be used, if it
maintains a sufficient distance from
the ground to ensure adequate ven-
tilation and that the wooden floor
remains dry.
2. Prevention of step voltages by means
of potential control. Another method
of insulating the floor involves the
AS we begin a new year, I amoptimistic (for the
first time in a long time) about the future of the
electrical industry in this country. I believe that in
2015 the effective policing of electrical installa-
tions that was originally envisaged by the legisla-
tors – and which I actively upheld inmy previous
activities as an approved inspection authority
(AIA) – will be actively enforced and bring about a
cleaner, safer industry.
Over the past fewweeks, I have had some fruit-
ful discussions with the Department of Labour
and other industry role players and I am encour-
aged that my repeated calls for the contracting
industry, in particular, to work with policing agen-
cies will no longer be falling on deaf ears.
For a long time now, I have appealed to the
Department of Labour to send a clear message to
electrical contractors that there is, firstly, a mini-
mum safety standard to which existing electrical
installations must comply; and, secondly, that
there is an absolute standard for new, altered
or temporary installations. This is now of critical
importance as it has become increasingly appar-
ent that the electrical industry has continued to
fall into decline insofar as compliance with SANS
10142-1 is concerned. This decline has been exac-
erbated by the pressure exerted by uninformed
consumers who look for the best price – and
often find that the cheapest price comes from the
less than scrupulous contracting environment.
Fair play contractors
As long as we take effective policing out of play,
registered‘fair play contractors’will continue to
suffer the economic consequences of this indus-
try’s declining standards; and consumers (albeit
that many of them are the instigators here) will
continue to be on the receiving end of illegal and
often dangerous electrical installations.
I believe that the major contributing factor
to the decline in standards – especially where
Though old acquaintance be forgot …
Mark Palmer, Western Cape Electrical Inspection Authority (WCAEIA)
integration of a finely meshed metal
grid; for example a reinforced steel
mat, laid in concrete or a mesh earth
electrode, with a mesh size smaller
than1 x 1m, laiddirectly in theground
below the shelter floor. To ensure a
long service life of this metal grid, it
is advisable to use 10 mm round con-
ductors made of V4A stainless steel.
These round conductors should be
installed 0.1 mbelow the ground surface
at intervals of 1 x 1 m andmust be
connected with adequate clamps on all
cross points and down conductors.
Conclusion
In general, persons must stay in shelters
for about 30 minutes after they hear the
last rumble of thunder. Only then is the
thunder cell far enough away. Shelters
on golf courses or hiking trails require
both a lightning rod and adequate
measures to reduce the risk of impermis-
sibly high touch and step voltages. As
described above, these measures can be
implemented by simple means.
Enquiries: +27 11 704 1487
Certificates of Compliance are issued for existing
installations – is that the principle of“reasonably
safe”as referenced in the Electrical Installation
Regulations is not fully understood.
Many contractors do not grasp the fundamental
principle that the Electrical Installation Regula-
tions are subordinate to the Occupational Health
and Safety Act of 1993 (the Act) where this exact
terminology is not used. The principle of“rea-
sonableness”is more clearly defined in the Act
under the definition of that which is“reasonably
practicable”. This concept is – and always has been
– used in applying the“reasonable man”test when
matters are decided in court.
I will discuss the“reasonable man”test inmore
detail in future columns but, in the meantime, I
advise Registered Persons to apply their minds
to what would be determined as the actions of a
“reasonable man”when applying general safety
principles to electrical installations.
As I return to the‘fray’, I hope that my endeav-
ours in the AIA environment over the last 15 years
or so will bear some fruit – especially with regards
to Registered Persons. It has been very clear that,
due to a lack of ongoing relevant training, many
Registered Persons have lost touch with SANS
10142-1 and need to be re-acquainted with this
standard.
The Department of Labour has given its com-
mitment that in 2015 it will be more stringent with
enforcement when it comes to errant Registered
Persons and electrical contractors. I amhopeful
that, with support from the electrical contracting
environment, these persons may not need to face
these enforcement measures.
From the legitimate contractors’perspec-
tive, however, I am also hopeful that Registered
Persons will support the active regulating of this
industry. More importantly, I hope that Registered
Person will contact me to discuss re-alignment
training, which promotes a better understanding
of the law as well as the correct interpretation and
application of relevant standards.
Enquiries:
other are connected on top of one
another, over a width of 12 mm.
The protectionmodules feature
a fail-safe function. If an SPD is de-
stroyed by means of a lightning or
overvoltage incident exceeding the
device specification, this generally
causes a short circuit or an interrup-
tion of the signal line. In both cases
further over-voltages are inter-
rupted and short-circuited. Thus,
the overvoltage cannot damage the
systembeing protected. The signal on the line is
also interrupted and the system fails. By simply
removing the protectionmodule, the make-
before-break switch contact in the BXT base part
ensures no interruption of the signal transmission
and the BSP type base interrupts the signal when
it is removed. In both cases, after a new protec-
tionmodule has been plugged in, surge protection
is restored again.
A wide range of accessories, for example for la-
belling, earthing of unused lines or easy testing of
lines, completes the product range andmakes the
Blitzductor SP arrester particularly user-friendly.
Enquiries: +27 11 792 1303