Lightning protection zone concept
The lightning protection zone concept allows to plan, implement and monitor protection measures. All relevant devices, installations and systems must be reliably protected to an economically reasonable extent. To this end, a building is divided in zones with different risk potentials. Based on these zones, the required protection measures can be determined, in particular the lightning and surge protection devices and components.
An EMC-based (EMC = electromagnetic compatibility) lightning protection zone concept includes external lighting protection (air-termination system, down conductor, earthing), equipotential bonding, spatial shielding and surge protection for the power supply and information technology system. The lightning protection zones are defined below.
Lightning protection zones and comprehensive protection measures
Surge protective devices are classified into lightning current arresters, surge arresters and combined arresters according to the requirements on their place of installation. Lightning current and combined arresters which are installed at the transition from LPZ 0A to 1 / LPZ 0A to 2 fulfil the most stringent requirements in terms of discharge capacity. These arresters must be capable of discharging partial lightning currents of 10/350 µs wave form several times without destruction, thus preventing injection of destructive partial lightning currents into the electrical installation of a building.
Surge arresters are installed at the transition from LPZ 0B to 1 and downstream of the lightning current arrester at the transition from LPZ 1 to 2 and higher. Their function is to mitigate the residual of the upstream protection stages and to limit the surges induced in the installation or generated in the installation.
The described lightning and surge protection measures at the boundaries of the lightning protection zones must be taken both for power supply and information technology systems. The consistent implementation of the described measures ensures permanent availability of a modern infrastructure.
Definition of lightning protection zones
LEMP protection of structures with electrical and electronic systems in accordance with IEC 62305-4
- LPZ 0A Zone where the threat is due to the direct lightning flash and the full lightning electromagnetic field. The internal systems may be subjected to full lightning surge current.
- LPZ 0B Zone protected against direct lightning flashes but where the threat is the full lightning electromagnetic field. The internal systems may be subjected to partial lightning surge currents.
- LPZ 1 Zone where the surge current is limited by current sharing and by SPDs at the boundary. Spatial shielding may attenuate the lightning electromagnetic field.
- LPZ 2 Zone where the surge current may be further limited by current sharing and by additional SPDs at the boundary. Additional spatial shielding may be used to further attenuate the lightning electromagnetic field.