Electricity + Control October 2019

EARTHING + LIGHTNING PROTECTION

Surge protection recommendations apply for: - dc input on the inverter / per MPPT - ac output of the inverter / TN-S system - LV input / TT/TNS system - Data interface / two pairs of data cables. Structures with external lightning protection and insufficient separation distances For lightning protection systems where adequate separation distances cannot be maintained, the following measures should be put in place: - LPS in accordance with required lightning protection level - Surge protection by means of Class 1 lightning arresters and Class 2 and 3 surge arresters - Equipotential bonding by means of 16 mm² copper conductors or 50 mm² aluminium conductors. When the correct separation distances cannot be established the PV system is vulnerable to partial lightning currents. The inverters and data systems are therefore protected by means of Class 1 lightning arresters, not Class 2 surge arresters. In accordance with Supplement 5 of IEC 62305-3 all the PV lines entering the building from outside (that is, from the roof) must be protected by means of Class 1 lightning current arresters. In many cases, rooftop PV systems are installed on top of steel roofs. Here the separation distances cannot be maintained due to the type of structure. In all cases where the separation distance cannot be maintained, all the metal components of the PV system must be bonded directly to the external lightning protection system. An air termination system still needs to be installed to protect the PV system from direct lightning strikes and provide controlled interception and dissipation of lightning current.

Surge protection recommendations apply for: - dc input of the inverter / per MPPT - ac output of the inverter / TN-S system - LV input / TT/TNS system - Data interface / two pairs of cables.

Figure 12. Equipotential bonding.

Figure 13. Air termination finial.

Figure 14. Rolling sphere zone of protection.

Figure 15. Rolling sphere zone of protection.

Conclusion Solar power generation systems are an integral part of today’s electrical systems. They should be equipped with adequate structural lightning protection systems, lightning current arresters and surge arresters, to ensure faultless long-term operation as sources of electricity.

Figure 11. Where separation distances cannot be maintained, all the metal components of the solar PV installation must be bonded directly to the external lightning protection system.

30 Electricity + Control

OCTOBER 2019