Earthing, lightning and surge protection are today an exact science, and have progressed to the point where insurance companies insist on custom designed protection systems to safeguard installations from the harsh lightning conditions prevalent in many parts of South Africa.
Contrary to popular belief, direct lightning strikes account for a small percentage of damage to electrical and electronic systems. The majority of the damages are caused by inductive coupling and ground potential differences. It is therefore important to pay attention to both the earthing system and the fitting of lightning and surge protection devices.
It is vital to pay attention to the actual earthing of an installation, particularly if more than one building is involved or if different earthing spikes are used at various points in the installation. The use of more than one ground earthing point can be counterproductive, as during a lightning strike a potential difference will build up between various earthing points, and the nearest available electrical or communication cables will carry the equalising current and cause major damage. It is therefore important that all earthing points and the incoming mains earth are bonded together. When designing an installation, short cuts are often taken by installing earthing rods at various points where earthing is required, instead of bonding the entire earthing system using a solid low resistance earthing bonding cable or strip.
“The installation of an effective earthing system can be complex,” says Brian Mostert of Clearline Protection Systems. “I recommend that expert advice is sought. We have produced a software package that will assist with the design of an earthing system, and in addition we also offer technical assistance during the planning and installation.”
It is important to consider all aspects of an electrical and communications installation when designing lightning and surge protection. The first basic step is to fit lightning current arrestors at the main incoming mains distribution board. In international standards (IEC 61312-1) these arrestors are designated as class 1 devices and offer optimum protection. The Clearline DS100, 100KA range of class I arrestors complies with this standard. In addition, Clearline also manufactures a plug - a block system consisting of a high impact polycarbonate housing, which can house three Class 1 arrestors and one N/PE equalisation arrestor. A surge counter has been included to monitor of surge activity.
On sub-mains boards, class II type arrestors should be fitted. Clearline offers a range for both single and three phase installations. The SS range uses a high energy zinc oxide varistor for fast response and features fault indication, including a fault disconnect device.
The emergence of modular pluggable din mounted surge protection devices also makes maintenance so much easier and cost-effective. Defective devices are simply unplugged and a replacement unit is simply plugged in. There is no need to access the wiring connected to these surge protection systems.
The ever increasing application of electronic devices has increased the requirement for additional more sophisticated protection at the installation point of these systems. Clearline offers a vast range of devices from protected power strips, to surge plugs and custom designed lightning and surge protection devices for computers, telephone installations, security cameras and electronic gate systems. Visit www.clearline.co.za for a complete catalogue and advice on how to design an effective lightning and surge protection installation, or call 011 848 1100 for technical advice.
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