Guidelines for Lightning and Overvoltage Protection

Guidelines for Lightning and Overvoltage Protection

Definition: External and internal lightning protection We can make a differentiation between external and internal lightning protection for a building containing an electrical system:  External lightning protection: External lightning protection is the installation of air terminations that discharge the lightning current to the earth via a suitable earthing system.  Internal lightning protection, overvoltage protection: Internal lightning protection comprises measures taken against the effects of the lightning strike and its electrical and magnetic fields on metal installations and electrical systems. This means primarily the measures taken against equipotential bonding and overvoltage protection.

Guidelines for lightning protection The following guidelines should be observed for lightning and overvoltage protection:  The system should be divided into lightning protection zones with staggered protective measures, see table below.  All conductive parts that enter a zone should be connected to one another and with equipotential bonding strip at the edges of the individual zones.  The shielding for the zones should also be connected to these strips.  In addition, a connection to equipotential bonding strips to higher and lower priority protection zones.

NOTE: All lines going in and out of the system to be protected must be connected to the earthing system directly via spark gaps or protective devices (lightning arrestors). In the event of a lightning strike the potential of the system struck increases temporarily but no dangerous potential difference occurs within the system.

Lightning protection zones Dividing the system into lightning protection zones with staggered protective measures is done as follows:

Zone Definition

0 All objects are exposed to a direct lightning strike.

1 The objects are not exposed to direct lightning strikes, the magnetic field dampened depending on the shielding present. Measures

External lightning protection via surge arresters and down-leads to the earthing system

Building shield (steel reinforcement)

Zone Definition Measures

2 and additional zones(1) The objects are not exposed to direct lightning strikes, the magnetic field is better dampened, dissipated currents are reduced further. Room shield using steel mash mat Device shield (metal housing) Lightning conductor

1: If necessary, additional zones with further reduced currents and electromagnetic fields must be installed.

The following illustration shows an example of the division of a building into lightning protection zones