The most exciting concept to come out of the Lightning Protection sector for centuries is the idea of 'Lightning Strike Prevention'.
Now, preventing lightning itself is outside the scope of any working installation today. And maybe something for the scientific communities to think over. However, preventing an STRIKE-attachment to a structure IS something that is here and now!
Lightning Strike Prevention
Let's be clear about one thing. Do not confuse Lightning Strike Prevention technology with the ESE (early streamer emitter). In fact, Lightning Strike Prevention is the polar opposite conceptually. So, digging a little deeper with the help from LEC President, Matt Napier, let's find out why ...
Lightning is nature’s attempt to equalize the voltage between storm clouds and the earth. In order for lightning to strike, it must connect. Lightning is an electric discharge that attempts to equalize voltage between storm clouds and the earth.
The difference in polarity between the bottom of the cloud and the ground is the charge differential. When this charge differential is high. The cloud begins to form downward leaders and objects on the ground begin to form upward streamers.
A leader then connects with a streamer, giving lightning the path it needs to exchange charge between the earth and the cloud, reducing the charge differential to upward streamers, which reach up from earth-bound objects when the electrical field is strong enough.
DAS (Dissipation Array System - a charge transfer system) interrupts the formation of these upward streamers through point discharge (c.1930), a phenomenon where a well-grounded point exchanges ions between the air and the ground. Point discharge becomes more efficient when multiple points are connected to a low-impedance grounding system, and more ions can be transferred with a greater number of points. DAS® technology takes advantage of these principles with an optimal point configuration able to interrupt / neutralise the formation of upward streamers, thereby preventing direct strike attachments.
What is Your Lightning Risk?
The chance that your facility will be hit varies on a number of factors such as location, structure height, temperature, and humidity. If all the factors are just right, even areas with infrequent thunderstorms can experience rare, but high intensity, lightning strikes.
Lightning can have devastating effects on any operation, whether taking a direct strike or being subjected to the secondary effects from nearby strikes. A single lightning strike to a mission-critical facility poses unacceptable risks which can cripple operations. These risks include fire, loss of product, damage to infrastructure, communications downtime, and loss of life.
It is often said; "Prevention is better than cure". It follows that preventing a strike-attachment from occurring is intellectually a better choice than allowing the attachment to take place. Then deal with the resulting after-effects and remaining risks. However, if it were that simple, Lightning Strike Prevention would be the only choice, but it isn't. The reality is that Protection of any kind is an engineering decision based on many factors. Not least the risk/cost/benefit analysis of the nature of the structure being protected. However, being able to virtually take Lightning Strike attachments off the table as a risk for the mission-critical should mean that preventative solutions like the DAS should be a must to throw into anyone's mix.
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This post is written by Ian Griffiths, Principal Engineer at GreyMatters, an Earthing & Lightning Consultant of 27 years, one of the top 1% accredited CDEGS consultants and professional advisor to international utility companies, data centre and infrastructure developers.