Rooftop systems: Buildings with external lightning protection system and sufficient separation distance

How does a lightning protection system for buildings with sufficient separation distance look like?

Normative requirements and notes:

According to Supplement 5 to DIN EN 62305-3, 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. The modules must be located in the protected volume of the isolated air-termination system.

Comprehensive protection for the d.c. side

If the separation distance calculated according to IEC 62305-3 is maintained, type 2 surge arresters are used to protect the inverter on the d.c. side and for the modules. The number of surge protective devices (SPDs) depends on the distance from the device to be protected. An additional 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 2 arrester on the a.c. side of the inverter.

 

Sample application:

Sample application for Buildings with external lightning protection system and 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 - DEHNguard® M YPV

PV-installation: Type 2 arrester specially designed for application in PV systems. Protects the DC side of the inverter against surges from inductive couplings. If there is more than 10 metres of cable between the PV system and the inverter, a further arrester is necessary in the roof area.

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C - DEHNcube YPV SCI 1000

Alternatively: Type 2 arrester that provides comprehensive protection for a PV system in an enclosure. It is mounted directly upstream of the inverter and is available in two versions, 1 MPPT and 2 MPPT. If there is more than 10 metres of cable between the PV system and the inverter, a further arrester is necessary in the roof area.

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D - DEHNguard® M

a.c. side inverter: Surge arrester that protects against overvoltages from inductive couplings by distant lightning strikes and from switching overvoltages. If there is more than 10 metres of cable between the service entrance box and the inverter, a further type 2 surge 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 - HVI®Conductor

External lightning protection: With the high-voltage-resistant insulated down conductors it is possible to make optimum use of the roof surface whilst still maintaining the separation distance from conductive parts.

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