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Lightning protection, but how?

Lightning protection system

A complete lightning protection system consists of an external and an internal lightning protection

The function of the external lightning protection is to avoid a fire caused by a direct lightning strike. This usually is attained by "capturing" the lightning bolt and conduct its electrical energy to the earth ("grounding"). The aim is to avoid for human beings dangerous flashovers or touch voltages, as well as damages caused by thermal or electrical impacts.

To achieve this, metallic conductors (e.g. copper), the so called "air terminations", are installed on the roof. They consist of a conductor parallel to the roof ridge and air-termination rods, placed e.g. on chimneys, photovoltaic installation etc. Additionally they are connected to all metallic equipment on the roof and also to the rain gutter. The grounding is achieved via conductors running vertically down along the building into the soil.

The internal lightning protection on the other hand protects persons inside buildings, electrical installations, electrical devices and metal installations.

Surges inside buildings occur when a lightning strikes the building or a point in the near vicinity. Affected by this are power supplies and phone lines, gas pipes, plumbing etc. Here the protection is realized with the help of lightning conductors or surge arresters, which reduce the surge gradually so that even sensitive electronic devices are not damaged.

Lightning conductors are placed inside the electricity meter and protect the central power supply. They dissipate dangerous lightning energy into the soil and significantly reduce the overvoltages.

Surge arresters reduce the residual overvoltage of the power supply inside the building.

In addition sensitive electronic devices like computers can be individually protected against surges by providing surge arresters to their power supply. To obtain an optimal protection, all its components must be tuned, a task that requires the expertise of a specialist in lightning protection.

(Source: Committee for Lightning Protection and Lightning Research of the VDE: "How to protect oneself against lightning effects")

(Quelle: Ausschuss für Blitzschutz und Blitzforschung (ABB) des VDE "Wie kann man sich gegen Blitzeinwirkung schützen?")

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