Roof mounted systems: Buildings with external lighting protection without sufficient separation distance

What does a lightning protection system for buildings with insufficient separation distance e.g. metal roofs look like?

Normative requirements and notes:

According to Supplement 5 of DIN EN 62305, a lightning protection system should be preferred which does not have a direct connection to the PV power supply system while maintaining the necessary separation distances.
If the separation distance calculated according to IEC 62305-2 cannot be maintained, it is recommended to establish lightning equipotential bonding and connect the PV frame directly to the lightning protection system.

Comprehensive protection for the d.c. side

Type 1 combined arresters are used for protecting the inverter on the d.c. side and the modules. The number of surge protective devices (SPDs) depends on the distance from the device to be protected. Another protective device is required every 10 m.

Comprehensive protection for the a.c. side

The a.c. side is protected by a combined arrester near the grid connection. If the distance between the grid connection and the inverter is more than 10 m, it is recommended to install another type 1 arrester on the a.c. side of the inverter.

 

Sample application:

Sample application for Buildings with external lighting protection without sufficient separation distance

A - DEHNventil®

Main distributions board: Combined arrester mounted directly at the entrance point to the building. Protects the electrical installation in the direct environment and, thanks to the patented RADAX Flow Technology, offers high follow current limitation and thus maximum system availablity.

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B - BLITZDUCTOR® XTU

Data interface: Combined arrester that protects balanced data interfaces (e.g. RS 485). Via the integrated actiVsense® Technology the arrester automatically detects the operating voltage of the useful signal and optimally adapts the voltage protection level to it.

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C - DEHNcombo YPV SCI

PV-installation: Combined arrester specially developed for use in PV installations. Protects the d.c. side of the inverter against partial lightning currents and surges. If the cable length between the PV system and the inverter is longer than 10 metres, an additional arrester is required in the roof area.

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D - DEHNshield® Basic FM

a.c. side inverter: Combined lightning current and surge arrester that fulfils the requirements LPS class III at the point of installation. Protects the inverter against any partial lightning currents and surges. If the cable length between the grid connection and the inverter is longer than 10 metres, an additional combined arrester is required at the inverter.

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E - UNI earthing clamps/saddle clamps

Equipotential bonding: Clamps suitable for integrating the mounting systems of PV installations in the functional equipotential bonding / the functional earthing or the lightning equipotential bonding.

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F - Air-termination and down conductor system

External lightning protection: Air termination rods and down conductors are required to protect the building and the PV installation and any additional components against the effects of direct lightning strikes.

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