Lightning can cause photovoltaic (PV) system failures as lightning that strikes the system from a great distance away, or even between clouds, can generate high-voltage surges. Considering this, in the fourth edition of the LPI Group technical blog we will explore how failures of renewable energy solar power systems can be avoided during a lightning event by installing a professionally designed code-compliant lightning protection system.
First, what do we mean by the term ‘lightning protection’?
Lightning protection can be described by considering the three aims of lightning protection:
- To reduce the probable risk of damage due to a direct lightning strike.
- To control the magnitude of galvanic coupling and induced surges.
- To deliver an effective discharge path into the ground.
Upon considering these aims, earthing systems, surge protection devices and air termination networks play a crucial role in providing lightning protection for solar power systems in line with the industry standards IEC 62305, IEC TR 63227 and IEC 61643-32, to protect against the negative impacts caused from lightning.
Earthing is a fundamental and important component within a lightning protection system, especially to safeguard a solar panel farm. Generally, we cannot avoid surge propagation into the solar panel power circuits, but we can control the magnitude of the surge and effectively give it a direct path into the ground. An electrical path to the ground will discharge static energy that builds up in an aboveground structure on a regular basis.
With the professional design and installation of an earthing system, lightning arrestors and surge protectors can function appropriately. Figure 1 shows an appropriate earthing system in a mesh configuration operating in a free field solar panel farm.
Surge Protective Devices (SPD)
The lightning current of a lightning discharge can be injected into PV power supply systems in different ways and in some circumstances generate a voltage magnitude of some hundred kilovolts at the effective conventional earth impedance. These voltages can damage the components of the solar system power circuit. To mitigate the negative effects, appropriate SPDs must be used in the power supply system of the solar panels. Therefore, the SPDs work as overvoltage protectors and mitigators.
As per figure 2, in all configurations of a lightning protection system, we must employ appropriate surge protective devices in the power supply circuit of solar power systems.
Furthermore, figure 3 clearly demonstrates an example of the distribution of a lightning current into the solar panel power supply circuit system when SPDs are employed.
Air Termination Network
Suitable measures of external lightning protection are supposed to catch direct lightning and feed it into an earthing system such that no galvanically coupled currents can have an effect on metal building installations and the PV power supply system. The purpose of these measures is to prevent damage to the building (mechanical damages up and including fire and its effects), as well as damage to the PV power supply system (supply networks, controls and electrical protective equipment).
Figure 4 depicts an adequate air termination network used to protect solar panels on a rooftop. As demonstrated, the most appropriate technique known as the rolling sphere method is used to define the arrangement of the air termination network.
Conclusion – Your Integrated Protection Solution
In conclusion, to bring the risk of loss of economic value under control and to mitigate the side effects of the lightning current propagation that could be discharged through the solar panel supply system, an appropriate protection system must be installed to discharge the lightning current into the ground, which will mitigate the magnitude of the overvoltage. Subsequently, this will prevent damage to the equipment and the interconnection ports comprised within the power supply circuits of solar panels.
Figure 5 shows an appropriate integrated lightning protection system for a sample solar power system located on a building at roof level, while figure 6 depicts a free field solar panel farm equipped with a lightning protection system. Both examples include the discussed air termination network, SPDs and earthing system.
If you are planning your upcoming renewable energy project, the specialist team at LPI Group are available to carry out a detailed lighting protection design and to install our lightning protection solution in accordance with the code of compliance standards, ensuring “Cloud to Ground Protection for Your Industry”. Contact a local specialist by email at firstname.lastname@example.org or call a local technical consultant here.
By Hadi Beik Daraei, Senior Design Manager at LPI Group