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.
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:
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.
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.
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.
Single-family buildings should have lightning protection:
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.
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:
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).
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: