Lightning, a natural phenomenon that has fascinated and terrified mankind since time immemorial, represents a force of nature that can cause considerable damage and threaten the lives of living beings. Curiosity and the need for protection have led to the invention and development of lightning protection systems. One of the first and most important inventions in this field was the lightning rod, discovered by chance by Benjamin Franklin about 270 years ago.
The Discovery of the Lightning Rod by Benjamin Franklin
Benjamin Franklin, an American politician and inventor, was the first to discover the principle of the lightning rod by chance. 270 years ago, while flying a kite during a thunderstorm, a lightning bolt struck the kite, generating a spark. This event led him to wonder if he could replicate this effect on a large scale to protect buildings and structures from the fury of lightning. In 1752, Franklin built his first version of a lightning rod that attracted lightning energy to a safe point to prevent damage, marking a milestone in thunderstorm protection and reducing mankind’s fear of lightning.
The Nature of Lightning and its Hazard
Lightning is a natural electrical discharge that occurs during thunderstorms. They are generated largely in the lower part of clouds, creating a negatively charged electric field in the clouds and a positive charge on the ground near the storm. When the electrostatic field reaches a certain level, an electric arc, known as lightning, can be produced. Lightning can reach lengths of up to 100 km and carry extremely strong currents, which can exceed 30,000 amperes, with temperatures that can reach 30,000 °C, five times the surface temperature of the Sun. These natural phenomena can cause fatalities and significant property damage.
Types of Lightning Protection Systems
To mitigate the risks associated with lightning, two main types of external protection systems have been developed: passive lightning rods, also known as single-pole systems, and active or ionizing lightning rods.
Passive Lightning Rods or Single Pole Systems
Passive lightning rods, also called single-pole systems, do not perform any special action during the process of a thunderstorm. These systems rely on the arrangement and morphology of the rods to protect structures. The positive charge generated in the ground during a thunderstorm rises through the grounding connection to the lightning rod tip, which, being located in a high position, becomes a prone point for the lightning strike, preventing the discharge from occurring in another part of the installation. The lightning rods can reinforce the protection of a grounding grid, a grounded metallic net that covers the entire building and distributes the lightning discharge, thus reducing the damage to the facility.
Active Lightning Rods or PDC (Priming Device) Lightning Rod Systems
Active lightning rods, also known as PDC (priming device) lightning rod systems, are intended to anticipate the lightning strike in order to keep a larger area protected. These systems operate on the same principle as single spike, but incorporate an additional ionization system that extends the protection radius. The additional ionization creates an upward tracer that attracts the lightning to the lightning rod. Once the lightning is attracted to the location of the lightning rod, the protection system safely conducts it to the ground, thus keeping the entire installation protected. This type of ionization does not lose capacity over time, allowing active protection with a wider protection radius, covering not only the structure, but also its surroundings and open areas.
Differences between Active and Passive Protection
The main difference between active and passive protection systems lies in the activity they perform during a thunderstorm and the radius of protection they can achieve.
- Protection radius: Active protection systems have a much wider protection radius than passive lightning rods, being able to reach double or more the protection radius than the latter, depending on the specific model.
- Cost: In some cases, installing an active protection system can be more economical than installing a large number of franklin tips to cover a wide area. This is because active systems can cover a larger area of protection with fewer elements, reducing the overall cost.
- Visual Impact: Because they require fewer elements to cover an area, active systems can have a smaller visual impact on the aesthetics of the protected structure or area.
- Scope of protection: Active protection not only protects the main structure, but also protects its surroundings and open areas, providing more complete protection compared to passive lightning rods.
- Sustainability: Active lightning rods, by having a larger protection radius, contribute to reduce the use of material in large installations, which can result in environmental and economic benefits by reducing production, transportation and maintenance costs.
Grounding System for Effective Protection
One of the crucial aspects of any lightning protection system is the grounding system. The purpose of grounding is to limit the voltage that the metallic masses can present at a given moment and to allow the passage to ground of fault or discharge currents of atmospheric origin, thus dissipating the energy associated with lightning.
Grounding System for PDC Active Lightning Rods
The grounding system efficiency for a PDC active lightning rod system is of vital importance. The design and arrangement of the grounding electrodes will depend on the resistivity of the soil in which the system is installed. Grounding in this type of system is classified into two main types: A and B.
- Type A:
- A1: Goose Foot Configuration.
- A2: Union of multiple vertical pickets in line or triangle, separated a distance equal or greater than their length.
- Type B: Conductive ring outside the structure, in contact with the ground for at least 80% of its length, installed at a depth of 0.5 meters and at a distance of 1 meter from the structure. It is recommended for rocky soils and structures with electronic systems or high fire risk.
Grounding System for Franklin Rod System or Faraday Cage
For passive lightning rod systems, grounding is also critical to ensure effective protection. The arrangement of the grounding electrodes varies according to the type of system.
- Type A: Horizontal or vertical electrodes installed outside and connected to each down conductor. The number of electrodes should not be less than 2 and should be evenly distributed.
- Type B: Conductor ring outside the structure, in contact with the ground for at least 80% of its length, installed at a depth of 0.5 meters and 1 meter away from the structure. Recommended for rocky ground and structures with electronic systems or high fire risk.
The proper choice of the type of grounding, considering soil resistivity and other factors, is essential to ensure the effectiveness of the lightning protection system.
Conclusions: Protecting Lives and Property against Sky's Fury
Benjamin Franklin’s discovery of the lightning rod was a milestone in thunderstorm protection and eased mankind’s fear of lightning. Over the years, the understanding of the nature of lightning and the evolution of technology have led to the development of increasingly effective protection systems.
Both passive and active lightning rods play a crucial role in protecting lives and property from the fury of the sky. The choice between one system or the other will depend on several factors, including the size of the area to be protected, cost, visual impact and sustainability.
In addition, proper implementation of a grounding system is essential to ensure the effectiveness of any lightning protection system. Proper grounding dissipates the energy generated by a lightning strike safely into the ground, thereby protecting the structures and the people within them.
In conclusion, lightning protection is essential in a world where thunderstorms are a common phenomenon. The constant evolution of technology and the deep understanding of the nature of lightning allow us to continue advancing in the improvement of these protection systems, thus safeguarding lives and property from the fury of the sky. In this context, Alher Sem stands out as a reference in security solutions in the industry, with more than 16 years of experience in providing specialized systems and services to protect people and assets from the risks associated with lightning storms. Its constant commitment to innovation and excellence in security has contributed significantly to the protection of critical infrastructures and the welfare of society in general.
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