Lightning is an electrical discharge that occurs within a cloud, between clouds, or between a cloud and the ground. Globally, there are about 40 to 50 flashes of lightning every second, which means that around 1.4_billion lightning bolts strike at somewhere every year.
Lightning is responsible for an annual cost of billions of dollars in damage to buildings, communication systems, power lines, and electrical equipment. Industries using metal towers for their operations are primary targets of lightning and lightning related damages. Telecommunication towers, radio-tv broadcast towers, tower cranes, wind turbines, weather observation towers are the first ones make sense.
How Does Lightning Strike?
First of all, let’s see how and where lightning forms. Lightning strikes from cumulative clouds and mostly from Cb(Cumulo Nimbus) types. These clouds are large enough to contain different charge groups in seperate layers and altitudes. All positive charges are collected at top of the cloud while bottom layer has all negative charges collected.
Normally, ground has positive and negative charges in balance. However, when a lightning cloud (Cb) approaches, negative charges at the bottom layer push all negative charges away from that area and leaves only positive charges on the ground just under cloud.
As the storm grows, negative charges start moving down in form of “packages” which are called the stepped leaders. The reason they are called “stepped” leaders is because they move and stop for a while, and move again and stop for a while and this happens step by step.
Then they completely stop at a height around 150 to 200 meters above the ground and start pulling the opposite (positive) charged “packages” to themselves. Those positive charges packages are emitted from any object on the ground and they are called “upward streamers”.
Finally, one of the upward streamers catch(or meet with) one of the stepped leaders and that forms a conductive channel between cloud and ground. This is called "Lightning" and it carries all high-voltage electricity from cloud to ground through the structure which emitted that special upward streamer.
All damage rise at the strike point and on the structure such as explosions, fires and failures of existing equipment.
And don’t let the process fool you, it takes only a few microseconds to have all these steps above to be completed. In fact, while you were reading up to this point, lightning has stroke somewhere on earth over 5000 times! Want to make the calculation?
Fortunately, there are protection methods against lightning related damages. They are simply classified in two groups: 1) Lightning arresters, 2) Lightning Preventers
1. Lightning Arresters
Lightning arresters are mostly used for buildings and such structures with concrete material where lightning arrester conductor cable is more conductive comparing to surrounding area. The purpose of these type of protection solutions is to attract lightning on themselves and transfer the lightning current to ground safely without letting the current jump into any equipment in protected structure.
Misuse of Lightning Arresters
Lightning arresters are reliable lightning protection products for most facilities excluding structures made of metal. The reason is simple; the metal structure is already highly lightning prone and an additional lightning arrester on top of it is increasing the risk of getting hit by lightning because it is lightning arrester’s duty to attract lightning.
For ordinary buildings, lightning arrester attracts lightning and transfers the current to conductor cable and let the current flow through conductor and reach to ground. However, when lightning arrester system is applied on a metal structure, it collects the lightning strikes on itself and transfers the current to conductor cable. But the metal structure is conductive enough for the current to prefer as path, so it jumps on the structure and damage all equipment on the structure and closeby.
So, lightning arresters are not to be used on metal structures such as telecom towers, radio-tv towers, tower cranes, wind turbines, etc..
2. Lightning Preventers
Lightning preventers are the appropriate solutions to avoid any lightning damage on metal structures. The purpose of these solutions is to dissipate the charges on metal structures and do not let a lightning channel form between cloud and the structure.
EvoDis® Lightning Prevention System
EvoDis® System is a unique lightning prevention solution for metal structures such as telecommunication towers, radio tv broadcast towers, tower cranes, wind turbines, weather station towers and security camera poles. During a storm, EvoDis® dissipates the charges on tower and makes the tower “invisible” to lightning. This keeps the site away from lightning strikes and keep all equipment on tower and inside shelter safe.
No lightning on site, no damage on equipment, no cost of maintenance and no loss of service for operators.
EvoDis® System has proven its 100% success by high voltage laboratory tests and field tests. Also hundreds of towers worldwide are protected against lightning strikes by EvoDis® and none of them have received any direct lightning-related problem.
EvoDis® Lightning Prevention System provides the real lightning protection for metal towers.
Contact us and let us know how we can support your business.