The news of a lightning strike that caused severe damages in a small village reveals a lack of knowledge in society about the protection against the effects of the discharges.
At the end of June we got via Internet news assuring that a lightning strike had "broken household appliances and paralyzed services" in a town with around 1000 inhabitants, even affecting villages in a radius of 10 kilometres. According to the same source, "the powerful strike on the City Hall's lightning air terminal was felt throughout the village and blocked offices and industries". Concern with this case, we found out that actually there is no air terminal but a very high antenna, unprotected. Besides, power supply lines and other services are overhead all over the town.
Despite being very common, lightning is little known outside specialized forums. However, for personal safety and to safeguard the equipment, everybody should be aware of at least some key points:
- Lightning air terminals should be at least two meters above any other object to be protected. Taller objects are not protected.
- An air terminal protects some meters around if it is a Franklin rod and some tens of meters in case or Early Streamer Emission Air Terminals (maximum 120m for the less exigent protection level and only if the air terminal is 60 meters! above the object to be protected)
- Air terminals protect against direct lightning strikes to the structures but not against the overvoltages caused by these discharges nor against distant strikes to lines. Therefore, for the protection of electrical and electronic equipment, the installation of surge protective devices is essential.
- Such need is even greater if power lines are not buried nor shielded, since then they can get a direct strike and, anyway, they are more sensitive to the huge electromagnetic fields caused by lightning.
- Anyway, during thunderstorms you should always take cover inside a structure (preferably protected), disconnect services and keep far away of metallic elements.