Lightning protection

Lightning protection is a system of devices and technical solutions whose task is to protect the building and its tenants against the direct and indirect effects of atmospheric discharges. Therefore, it is one of the basic installations to ensure the safety of the facility and people using it. The lightning protection system is also called the LPS installation or system (Lightning Protection System).

Thanks to the use of lightning protection, people (and animals) present in the building are less exposed to electric shock, the risk of damage to the electrical system and the occurrence of fire or explosion is negligible, and the force of the lightning strike will not weaken the roof or wall structure. In addition, the risk of permanent damage to equipment connected to the power supply is reduced, and surge energy, short-circuit and leakage currents are safely discharged to a place where they do not pose a threat.

IMPORTANT: General rules and basic recommendations regarding lightning protection of buildings with their technical equipment, as well as protection of people staying in these buildings are specified in the PN-EN 62305-1:2011 standard.

Basic elements of lightning protection

Lightning protection is – to put it simply - a network of metal wires mounted on the building, from the roof to the ground. Due to the fact that these elements touch the ground, the energy transmitted by lightning is safely discharged to it. Due to the enormous energy of atmospheric discharges, the lack of an efficient and effective installation may result in fire or electric shock.

A typical lightning protection system consists of the following elements:

1. vertical and horizontal feints – it is part of the lightning protection system mounted on the roof. These elements are usually made of galvanized steel, stainless steel, copper and aluminum alloy wire.

Horizontal air terminals are installed along the ridge (gable line) as well as on the roof edge to create a protective mesh. Wires are also placed on the chimney and antenna mast. If the roof is sloping, the cables are secured with brackets. The tasks of air terminals can also be fulfilled by some metal parts of the house, which should be connected to the building's earthing system (or provided with a separate earthing). Most often these are gutters, handrails, but also metal parts of the roof.

2. downpipes – are the elements that connect the air terminals and earth electrodes. They are made of the same materials that are used for air terminals (you can also use steel tape). They are mounted on the facade of the building (2 cm from the wall), along the gutters, and also under the facade in special lightning protection pipes.

The down-conductor should be connected to the ground using a test clamp. For safety reasons, security wires should not be installed closer than 2 m from the entrance to the building.

3. earth rods – are metal elements installed in the ground, whose task is to dissipate the lightning current. When making them, you can use the reinforcement of the building's foundation (the so-called natural earth electrode). It is also possible to perform an artificial earthing system by installing a closed ring system around the building. For this purpose, a galvanized steel tape is used, which should be buried at the appropriate depth, while maintaining a distance of 1 m from the building. Steel rods driven into the ground are also artificial earth electrodes.

Lightning protection inside the building

The internal part of the lightning protection system is primarily designed to prevent the occurrence of sparks in the protected facility caused by the operation of the external LPS system. Therefore, the basic element of internal lightning protection are reliable and reliable surge arresters. The internal LPS system can be implemented using equipotential bonding of the external system with the metal structural parts of the building and its installations, or by means of electrical insulation.

In installations coming from the outside to a building, limiters should be used to equalize potentials and protect against lightning current (this is the so-called first degree of protection). The next step is to use limiters (the so-called second degree of protection) protecting against all kinds of internal overvoltages (e.g. overvoltages caused by devices), atmospheric overvoltages induced in installations inside the building, overvoltages passed through the first degree of protection.

How a lightning protection installation works

Single-family buildings should have lightning protection:

• area over 500 m² and higher than 15 m,
• constructed of flammable materials - regardless of height,
• those for which the lightning hazard index calculated according to the rules in the standard exceeds the specified value.

A lightning protection system is therefore not always mandatory (the decisive voice in this matter should belong to the designer who performs a risk analysis in accordance with the relevant standards), but it is worth installing it to better protect the building, residents and devices connected to the network energy. When a lightning strikes a non-combustible material (e.g. concrete, brick), it can cause its rupture, while a hit to electrical wires can damage them, as well as damage devices connected to the power grid.

The lightning protection system works in such a way that its highest element (i.e. the air terminal) takes over the currents when the lightning strikes. The properties of properly designed and made air terminals mean that it is them, and not other elements of the roof, that lightning will strike.

The current then passes from the air terminals to the down conductors, and through them to the earth electrodes, which dissipate the energy from the lightning in the ground. This process makes the potential difference between the clouds and the ground equalized, and excess energy does not pose a risk of electric shock or fire.

What should be remembered in order for lightning protection to be effective

The installation will be effective when it is made on the basis of a reliable calculation of the lightning hazard indicator. The following building parameters will be important here:

• size and height,
• location,
• building materials used,
• construction and technology in which it was erected.

A very important element will also be the quality of the products used to create the installation. Therefore, it is recommended to use only tested, safety-certified and manufactured in accordance with applicable standards components.

Another important factor is the diligence of workmanship, in particular the connections of earth rods, horizontal air terminals, vertical air terminals, which must be welded or screwed together with screw clamps. The quality of the installation is also affected by the elimination of induction and overvoltages accompanying strong electromagnetic discharges caused by lightning strikes (this is achieved by making equipotential bonding and overvoltage protection).

The most common lightning protection errors

It is a common and dangerous mistake to believe that it is very easy to create a lightning protection installation. Meanwhile, even prosaic mistakes made in this process may result in a lack of adequate protection.

Among the most common negligence regarding the protective installation are:

• a conscious resignation from applicable standards and the use of solutions that are inconsistent with the regulations,
• lack of safe distances between the lightning protection system and electrical installations inside the building (this may result in sparkovers),
• lack of inspection of the condition of earth electrodes and the entire installation in the periods provided for by regulations,
• no maintenance of the lightning protection system,
• no safe separation distance between the air terminal and devices such as external fans,
• failure to carry out a risk analysis in accordance with the provisions of the standard.