Lightning protection for solar farms: risk assessment and inspections

A solar farm can be affected by both a direct lightning strike and a surge caused by a nearby discharge. Damage can occur not only to panels and inverters, but also to communication lines, weather stations and control equipment. An individual air terminal or surge protective device therefore does not mean that the entire farm is adequately protected.

The protection solution must be based on a risk assessment that takes account of the site's location, structures, cable routes and connected equipment. The designer must assess the need for external lightning protection and its coordination with internal protection, observing the applicable requirements, including the EN IEC 62305 series of standards. It is important for the owner to retain both the design justification and the as-built documentation.

The earthing system, protective conductors and equipotential bonding connections must be assessed together. Connections to panel mounting structures, equipment enclosures and other conductive parts must comply with the design and manufacturers' requirements. Where external lightning protection is specified, it is essential to maintain the calculated separation distances or implement the bonding arrangements specified in the design.

Maintenance must include checks on the mechanical condition of connections, corrosion and any damage caused by excavation or grounds maintenance work. A qualified specialist must carry out electrical measurements appropriate to the design. A single earth resistance value does not, on its own, demonstrate compliance of the entire lightning protection system; the results must be assessed alongside connection continuity and the system configuration.

Surge protective devices, or SPDs, must be selected to suit the particular circuit and anticipated electrical stresses. The DC side of a solar farm requires devices designed for photovoltaic systems, with ratings suitable for the maximum system voltage, including under cold conditions. The required SPD type and placement are determined by the design, the external lightning protection configuration and the possible lightning current paths.

Protection must be coordinated across distribution boards, inverters and other sensitive equipment. The length and arrangement of connecting conductors, cable routing and minimisation of loop areas also matter. Communication and data lines must be provided with protection suitable for their interfaces where required by the risk assessment.

During maintenance, SPD status indicators and the operation of remote signalling, where installed, must be checked. Damaged modules or those that have reached the end of their service life must be replaced in accordance with the manufacturer's instructions, while also checking the associated protective devices. Work on electrical equipment must be carried out by qualified personnel following safe isolation procedures.

After a thunderstorm, the first step is to review monitoring alerts, inverter fault logs, communication outages and protective device operation. On-site inspections must only begin when conditions are safe. If burn marks, damaged insulation or other signs of danger are found, the affected part of the installation must be referred for specialist inspection rather than re-energised without assessing the cause.

Solar panel thermography under suitable operating and weather conditions can help identify thermal anomalies, while IV curve measurements can reveal deviations in the electrical characteristics of individual strings. Neither method alone proves that damage was caused by lightning, nor does either replace checks on earthing, insulation or protective devices.

When analysing changes in generation, irradiance, temperature, shading and soiling losses must also be taken into account. This helps avoid attributing deviations with other causes to the thunderstorm. Conclusions must be supported by event timings, photographic records and comparable measurements.

Inspection intervals must be determined in accordance with the design, applicable requirements, manufacturers' instructions and site risks. An additional assessment is required following suspected lightning effects, significant earthworks or system modifications. Expansion of the panel arrays, new communication lines or inverter replacement may require a review of the protection solution.

Maintenance documentation must include protection diagrams, an earthing plan, an SPD register, measurement reports and the rectification status of identified defects. Solar system maintenance in accordance with LVS EN IEC 62446-2:2020 helps structure operational activities, but does not replace specialist lightning protection design and inspections.

pvcare.eu can help with solar farm maintenance, monitoring and an O&M contract, as well as a thermal drone inspection with a report via dronepv.eu. These services help document deviations and plan the necessary specialist inspections.