The LPZ concept according to IEC 62305-4:2010 makes it easier to plan, implement and monitor comprehensive protection measures.
In this approach, the building is subdivided into zones with different risk potentials. Based on these zones, the necessary arrester types are determined.
Outer zones:
LPZ 0 = Zone where the threat is due to the unattenuated lightning electro- magnetic field and where the internal systems may be subjected to full or partial lightning surge current.
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 thre- at is the full lightning electromagnetic field. The internal systems may be subjected to partial lightning surge currents.
Inner zones:
LPZ 1 = Zone where the surge current is limited by current sharing and isolating interfaces and/or by SPDs at the boundary. Spatial shielding may attenuate the lightning electromagnetic field.
LPZ 2 ... n = Zone where the surge current may be further limited by current sharing and isolating interfaces and/or by additional SPDs at the boundary. Additional spatial shielding may be used to further attenuate the lightning electromagnetic field.
Surge protective devices are categorised as lightning current arresters, surge arresters and combined arresters.
The highest requirements are placed on the discharge capacity of lightning current arresters and combined arresters used at the transition from lightning protection zone 0A to 1 or 0A to 2. These arresters must be capable of conducting partial lightning currents of 10/350 μs wave form without being destroyed in order to prevent the ingress of destructive partial lightning currents into the electrical installation of a building.
At the transition point from LPZ 0B to 1 or downstream of the lightning current arrester at the transition point from LPZ 1 to 2 and higher, surge arresters are used to protect against surges. Their task is both to reduce the residual energy of the upstream protection stages even further and to limit the surges induced or generated in the installation itself.
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