Lightning rods are instruments, whose origin dates back to 1753 thanks to Benjamin Franklin, whose aim is to prevent an ionized lightning strike from the air from causing damage to people or buildings by drawing the discharge towards the ground, thus preventing it from directly impacting against them.
Lightning is a strong natural discharge of static electricity produced during a thunderstorm that generates an electromagnetic pulse. The precipitated electric discharge of the lightning is accompanied by the emission of light (known as lightning) caused by the passage of electric current, which ionizes the air molecules; and by the sound of thunder, caused by the shock wave. Electricity passing through the atmosphere rapidly heats and expands the air, producing the characteristic noise of thunder.
Lightning can cause different effects: thermal, physiological, electrodynamic or electrochemical, among others. Thermal and physiological are the most important. The thermal effects are due to the high temperature reached by the channel through which the lightning current flows, leaving temperatures of up to 20,000 degrees. On the other hand, the physiological effects affect living beings and are due to the stresses after the lightning discharge on earth.
who invented the lightning rod
Benjamin Franklin began his experiments on electricity in 1949, defending the idea that storms are electrical phenomena. In 1752 he published an article in which he proposed placing steel rods on roofs to protect against lightning strikes, which began to be tested in England and France.
In 1953 he presented the so-called single fluid theory to explain the two types of atmospheric electricity: positive and negative. From then on, lightning rods were born, which were designed to excite and attract the discharge and then lead it towards the ground, contrary to what its name indicates.
In 1753, the Russian Georg Wilhelm Richmann attempted to continue Franklin’s research related to the shielding effect, but was soon killed by lightning. Two centuries later, in 1919, Nikola Tesla correctly defined the operating principle of the lightning rod and refuted Benjamin Franklin’s theories. Since then, the lightning rod industry has evolved and different types are now manufactured, although all with the same physical principle.
What is a lightning rod for?
A lightning rod is an air terminal that performs the external protection of a building or structure from the possible direct impacts of lightning. It must always be installed above the highest part of the structure to be protected and it will be responsible for safely capturing and channeling the lightning discharge.
Lightning rods have a metallic body and a tip connected by a conductive network to a grounding system where the lightning discharge is dissipated. A lightning rod installation is made up of three elements: a capture electrode, which is the lightning rod, an electrical ground connection and a cable to conduct the lightning current.
The lightning rod focuses on ionizing the air from a natural electric field generated on the ground by the storm to capture the lightning that could fall in the area to be protected.
The elements of a lightning rod. Photo: Wikipedia
There are currently four protection systems endorsed by the regulations: the Franklin lightning rod, the Faraday cage, the lightning rod with a priming device and the guard cables. The lightning rod with PDC priming device is the most widely used, since it provides a greater protection radius and its installation is simpler and cheaper.
A lightning rod with a triggering device is an instrument that incorporates a triggering device (PDC), which may or may not be electronic, which guarantees that the lightning strike will be at a greater height, increasing the coverage area and facilitating the protection of large areas.
Regulations for lightning rods in Spain
Lightning rod installations are regulated in each country by recommendation guides or standards. It is a mandatory regulatory framework in Spain in which the basic quality requirements that buildings must meet in relation to safety and habitability are regulated.
The regulations have a section called , which indicates the obligation to install devices for external protection against lightning, depending on the risk index of the installation to be protected.
“The installation of a lightning protection system will be necessary, in the terms established in section 2, when the expected frequency of impacts Ne is greater than the admissible risk Na”, indicates the regulation.
“Buildings in which toxic, radioactive, highly flammable or explosive substances are handled and buildings whose height is greater than 43 meters will always have lightning protection systems with efficiency E greater than or equal to 0.98”, he adds.
The table indicates the protection level corresponding to the required efficiency. Photo: SUA
On the other hand, ‘Protection of structures and buildings and open areas by means of lightning rods with priming devices’ indicates the measures to be adopted to design an effective protection system against lightning in structures by means of lightning rods with priming devices and sets the guidelines for carrying out of the protection system.
According to this regulation, “among the structures in which the installation of a lightning protection system will be necessary, the following can be mentioned: buildings or open areas with public attendance, high-rise buildings and, in general, elevated constructions, constructions and warehouses in which dangerous materials are handled and/or contained, buildings that contain especially vulnerable or valuable equipment or documents.
surge protection
Overvoltages are voltage rises that can appear on electrical distribution lines that can cause, among other things, damage to equipment connected to the network. Overvoltages are produced by direct and indirect atmospheric discharges, disconnection of inductive loads, network commutations and faults in them.
Overvoltages are large voltage spikes with a steep slope and short duration, even so, their effects on electronic equipment are remarkable. For proper protection of the equipment, a low ohmic value grounding system must be made and connected to the external protection system.
Installing external lightning protection and surge protectors considerably reduces the risk of lightning damage to structures, equipment and people.
Climate change increases the electrical activity of the atmosphere
Climate change is one of the factors causing the increase in storms and lightning density. The growth of solar activity increases the electrical activity of the atmosphere and generates electromagnetic and thermodynamic storms. This electrical activity is, among other meteorological phenomena, another trigger for the increase in cloud-to-ground or ground-to-cloud lightning activity.
Although you can never be safe, there are dates when the chances of lightning striking a person are much greater, coinciding with the seasons when thunderstorms are more frequent. The largest number of people affected by lightning occurs in summer, especially in July and late in the afternoon.
Experts have concluded that the odds of being struck by lightning is 1 in 3,000,000. However, it is estimated that approximately 24,000 people die from lightning each year worldwide. It is pertinent to clarify that this figure includes incidents such as fires; deaths from direct hits are much lower.
As a curious fact, men are 5 percent more likely than women to be struck by lightning. In fact, most of the people affected by these meteorological phenomena are men between the ages of 15 and 35. It makes sense if you take into account that a large part of the people who suffer a lightning strike are dedicated to construction or work in agriculture, jobs dominated mostly by men.
Although we often think that most people who are struck by lightning die, this is not really the case. Only 10% die, largely from a heart attack. Most injuries are burns, trauma, neurological problems, and muscle, skin, or eye injuries.
What to do if you are surprised by a storm in the open field? The first thing to do is seek shelter. If there is nothing around, avoid seeking shelter under a tree. The best posture to protect yourself from lightning is to sit with your feet together with your head against your chest or placed between your knees. Never lie down on the ground, as you will be bigger than lightning. Cover your ears and close your eyes to protect yourself from lightning and wait for the storm to pass.
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