Electricity + Control October 2019

EARTHING + LIGHTNING PROTECTION

Figure 5. Using the angle of protection method to protect a rooftop PV installation.

Figure 7. The solar PV system must be installed within the protected volume formed by the external lightning protection system.

Figure 6. Using the rolling sphere protection method to protect a rooftop PV installation.

Structures with external lightning protection and adequate separation distances Where adequate separation distances can be maintained between the LPS and the PV system, the PV system should be protected as follows: - LPS in accordance with the required lightning protection level (as assessed) - 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 to earth bar only – there should be no bonding to air terminals. In order to protect the PV system from direct lightning strikes, the system must be installed within the protected volume formed by the external lightning protection system. The protected volume is created by the installation of air termination rods and the rolling sphere or angle of protection methods are used to calculate the height and placement of the air terminals. Establishing the correct separation distances prevents partial lightning currents from entering the building and electronic equipment via the PV system’s cabling. Inverters and data systems are protected by means of Class 2 surge arresters, not Class 1 lightning arresters. The overall cost of the lightning protection system is therefore reduced and the installation is in line with the preferred method of protection.

Figure 8. Equipotential bonding.

Figure 9. Air termination system.

Figure 10. Earth termination system.

Electricity + Control

OCTOBER 2019

29