Lightning arrestors more specifically Surge Protection Devices (SPD) should only be used as the last step in your full defense against lightning, as these only protect against the surge effect of lightning notably the Galvanic (direct Electrical Contact), Electrostatic coupling, Electromagnetic Induction and some also protected against Radio Frequency interference (RFI). A well-designed lightning protection system, which if designed well can mitigate 20,000°C temperatures and currents of 250,000 amperes or more that can result from a direct lightning strike. Also, even if you avoid a direct lightning strike remember indirect lightning strikes from under 1KM radius can result in the increase in the ground voltage which in turn could damage your gear again. Having said that I have witnessed firsthand in one project where the location was assessed to be in a 'lightning belt' (extremely prone to lightning) where a ground conductivity assessment, addition of grounding enhancers, copper earthing conductors linked to air terminals (lightning rods) have successfully protected sensitive a Port and container logistics equipment against direct lightning. When designing it is best method is to conduct an assessment of grounding properties of the site, first obtain the Isoceraunic maps and check the frequency and strength of lightning in your client’s location. Next is to get a specialized company to test of the soil substrates to ascertain grounding conductivity as this identifies that conductivity of the soil or whether additives are required as some soil types are poor conductors. Next, I would strongly consider the use of air terminals is the region is lightning prone, ascetics aside. Finally, any lightning protection system implemented requires maintenance so all of the above recommendations comes down to risk management and the total cost of your ICT investment against the cost of implementing a lightning protection system. However, I believe starting with Isoceraunic maps will aid you better make those decisions. Hope this helps.
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