As the lightning season almost upon us, now is the time to get your ducks in a row to ensure that you have proper Lightning protection.

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Typically South Africa’s lightning season starts in October and ends roundabout the end of March. South Africa is a lightning prone country, with the highest recorded lightning strike density in the Highveld and Eastern escarpment. These areas will annually receive as much as 10 to 15 lightning flashes per km2 per year.

The effect of a direct strike to property and or equipment cannot be accurately estimated, for lightning is truly unpredictable and where and what it hits is probably only known to Thor.

Lightning, like all acts of God causes Billions in losses annually. But unlike other natural occurrences, we can successfully and economically protect ourselves against the onslaught of nature.

Make sure that your lightning protection system is up to standard and working correctly to ensure that any direct lightning strike is effectively and safely put to ground.

Maintenance is key.

There is a common misconception that once one have installed a Lightning Protection System that all your problems are solved and no thought is given to it afterwards. This is not the case.

A typical lightning flash is about 300 million Volt, and about 30,000 Amps. The heat generated can reach just short of 30 000˚C five times hotter than the surface of the sun. This in turn can destroy any lightning protection system and cause damage to earthing systems.

It is imperative to do an annual inspection on all protection systems and regularly do ground resistivity test to ensure that the earthing material is not scorched and obsolete.

Allot has happened since the first scientific research in the 18th century by Benjamin Franklin’s famous Kite experiment. The lightning protection sector has had enormous technological developments in the last decades,

from the conventional air termination systems to advanced E.S.E (Early Streamer Emission) devices.

The main function of an Air termination, lightning protection system installed on an existing building is to capture a lightning strike and then conduct discharge current safety to the ground. In some conditions, however the active lightning system is the only possible method to protect from direct lightning strikes The lightning discharge is initiated by so called down conductor which creates an ionised air path (downwards or upwards) between the cloud and the ground for the necessary flow of any lightning currents.

The Operating Principle of an E.S.E lightning conductor is formed by two armatures. One of them is connected to ground, while the other remains at atmospheric potential. The great magnitude of the electric field during a thunderstorm produces that, although armatures are separated by a very short distance, the difference of potential between them during approaching lightning becomes considerable.

This difference of potential is the power supply of the lightning conductor internal device. The internal device is located in the body of the E.S.E and is called Variable Impedance Unit. Therefore, the device working is regulated by the atmospheric field. The advantages of these characteristics are, on one side, that in normal conditions the device is not working, avoiding then unnecessary stress to the components. On another side, during thunderstorms the device detects when a proper electric field exists, and when the downward leader is approaching, because it provokes a strong and rapid increase of the atmospheric electric field.

During normal atmospheric conditions, the charge is also neutral in every area (also at the air), and the internal device is not working.

The first difference with a simple lightning rod starts already when storm clouds appear. Inside the components of the internal device, equi-potential lines become very close together, causing the necessity of a strong concentration of charges at the armature surface. The device is designed in such a way that the transitory current does not get lost, but remains as electromagnetic fields in the components of the electrical device. The electric field value, able to ionise the air around the tip, is reached earlier than with a simple rod, because the internal device makes the voltage increase over ground level. Then, air charges become also a part of the internal current. Therefore, the ionised area is growing much faster than with a simple rod.

The previous phase to the formation of the upward leader is the formation of corona discharges (streamers) that propagate towards the downward leader. One of these streamers will become the upward leader, which will propagate continuously to the downward leader, forming then the lightning discharge path.

Inside the lightning conductor, the downward leader approaching and the strong increase of the electric field caused by it are the factors that activate the mean function of the internal device .When the voltage between the armatures exceeds a certain value which the circuit is designed for, then the internal trigger works, using the accumulated energy for pumping to designed for, then the internal trigger works, using the accumulated energy for pumping to inside the ionised area. The strong and sudden concentration of positive charges cause repellent forces in the ionised area, which break the existing border. The device has provoked then a streamer effect, avoiding the ‘’glow regime” that was lowering the effectiveness of a simple lightning rod.

The streamer emission under these conditions favours the upward leader formation, which will progress continuously till reaching the downward leader, forming then the discharge path. Then, as the E.S.E is the point where the upward leader was formed. It will be the receiver of the lightning strike and put it to ground.

Details of  E.S.E

1Air Terminal
2. Ion Generator
3. Accelerator and Atmospheric Electrodes
4. Grounding Connection Terminal

Example for E.S.E installation on Single-family-home; Protection Level 2

 

HJ Breytenbach                                                                   www.salightning.co.za

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