Lightning Protection for Solar Panels — Technical Guide
Photovoltaic installations have specific characteristics that make them particularly vulnerable to lightning strikes. Their large metallic surfaces, extensive cabling, and often elevated or open-field locations make them susceptible to both direct lightning strikes and induced overvoltages. Therefore, comprehensive and appropriate protection is essential to ensure continuous power production and the safety of personnel.
Why are solar installations exposed to lightning?
Contrary to popular belief, solar panels do not attract lightning more than any other surface of the same height. However, their particular configuration creates specific vulnerabilities.
- Large conductor metallic surface exposed to electromagnetic fields
- Long DC cables between panels and inverter — antennas prone to induced surges
- Inverters and monitoring systems — transient-sensitive electronics
- Rooftop or open field installation — direct exposure
- Metal chassis structures — risk of lightning current if poorly grounded
Therefore, effective protection requires two complementary levels: external protection (lightning rod) against direct impacts, and internal protection (surge arresters) against induced overvoltages.
Dual Protection Required: Lightning Rod + Surge Protector (SPD)
The IEC 62305 standard clearly distinguishes between the two levels of protection. Furthermore, the IEC 61643 standard complements this by specifically covering surge arresters for low-voltage installations.
- External protection (IEC 62305-3): lightning rod capturing the direct impact, down conductor, earth connection
- Internal protection (IEC 62305-4 and IEC 61643): DC surge arresters on the panel side, AC surge arresters on the inverter side
- Equipotential Spark Gap between metallic structures and the earthing system
- Separation distance between the LPS and the electrical wiring is respected
Thus, the two protections are complementary and not interchangeable. A surge protector alone does not protect against a direct strike; a lightning rod alone does not protect against overvoltages induced by a distant lightning strike.
DC Surge Arrester — Solar Panel Side Protection
The DC side of a photovoltaic installation is particularly vulnerable. Indeed, the DC cables connecting the panels to the inverter over lengths that can reach several tens of meters, acting as veritable antennas for induced overvoltages.
- Type 1 (T1) DC : required if the lightning rod is installed on the roof — protects against partial lightning strikes
- Type 2 (T2) DC : protection against induced overvoltages — to be installed in a junction box or before the inverter
- Residual protection voltage Up lower than the inverter's withstand voltage (generally ≤ 1.5 kV DC)
- Nominal discharge current In adapted to the installation configuration
Furthermore, DC surge arresters must be sized according to the maximum voltage of the solar string (Uoc × number of modules).
AC Surge Protector — UPS and Grid Side Protection
The inverter is the electronic heart of the photovoltaic system. Therefore, its protection against AC overvoltages is equally critical.
- Type 1+2 (T1+T2) AC : at the head of the main low-voltage distribution board (TGBT) if the building is equipped with a lightning rod
- Type 2 (T2) AC : in a sub-distribution board or directly upstream of the inverter
- Type 3 (T3) AC : fine protection at the inverter output, near monitoring equipment
- Coordination T1+T2+T3 according to IEC 62305-4 and NF C 17-100
Types of Surge Arresters according to IEC 61643-11
The IEC 61643-11 standard defines the categories of surge arresters for low-voltage installations. Therefore, choosing the correct type is crucial for effective protection.
- Type 1 (T1) — tested with 10/350 µs current waveform (Iimp) — first level of protection
- Type 2 (T2) — tested with 8/20 µs current waveform (Imax) — secondary protection
- Type 3 (T3) — thin protection at the equipment output — combined wave
- Key criterion: lowest possible residual protection voltage Up
Grounding of Metal Structures
Grounding the frames supporting solar panels is both a safety and regulatory requirement. Furthermore, it determines the effectiveness of the entire protection system.
- All metallic components of the panel supports are connected to earth by suitable down conductors.
- Target earth resistance ≤ 10 Ω (measured and documented)
- Earthing rods made of copper-plated or stainless steel, depending on the soil type
- Equipotential Spark Gap between chassis, lightning rod and electrical panel
When is a lightning rod necessary for a solar installation?
IEC 62305-2 provides the method for determining whether a lightning rod is necessary. Specifically, this depends on the local lightning density (Ng), the surface area of the installation, and the acceptable level of risk.
- Isolated open-field installations — high risk, lightning rod often required
- Rooftop installations on a building already equipped with an LPS — integrating the panels into the existing protected area
- Urban installations on flat roofs — case-by-case assessment
- If roof-mounted lightning rod: franklin simple rod compliant with IEC 62305 recommended
Applicable Standards
- IEC 62305 — Protection against lightning (4 parts: generalities, risk management, physical damage, electrical systems)
- IEC 61643-11 — Low voltage surge protectors
- IEC 61643-32 — Application guide for DC surge arresters for PV installations
- NF C 15-100 — Low voltage electrical installations (French requirements for surge arresters)
- NF C 17-100 — Protection against the indirect effects of lightning
Manage the Installation with LPS Manager
After the installation of lightning protection, document management and periodic inspections are essential. LPS Manager allows for the centralization of the entire photovoltaic installation file: diagrams, surge protector references, earth measurements, inspection reports, and maintenance alerts.
- Complete installation guide with photos and product references
- Automatic reminders for annual inspections
- IEC 62305 compliant PDF reports generated in one click
- Integration with Strike Radar for post-impact alerts
Frequently Asked Questions
Do solar panels attract lightning?
No, solar panels do not attract lightning more than any other surface of the same height. However, their large metallic surface area and long cables make them particularly vulnerable to power surges induced by nearby lightning strikes, even without a direct impact on the installation.
Which surge protector should I choose for a solar installation?
For a photovoltaic installation, DC surge protectors must be installed in the junction box or upstream of the inverter (Type 2 minimum, Type 1+2 if a lightning rod is present), and AC surge protectors must be installed upstream of the inverter on the grid side (Type 2 minimum). The residual protection voltage Up must be lower than the inverter's withstand voltage.
How to protect a solar installation from lightning?
Complete protection of a solar installation requires: (1) a lightning risk assessment according to IEC 62305-2, (2) if necessary, an IEC 62305 lightning rod with down conductor and earthing ≤ 10 Ω, (3) DC and AC surge arresters according to IEC 61643, and (4) equipotential earthing of all metallic frames.
Is a surge protector sufficient to protect a solar installation?
A surge protector alone protects against induced overvoltages but does not protect against a direct lightning strike. If the IEC 62305-2 risk assessment indicates that a lightning rod is required, the two protections must be combined. Conversely, if the risk of a direct strike is low, the surge protector alone may suffice for electronic protection.
What earth resistance is required for a solar installation?
The earth resistance must be as low as possible, with a target value ≤ 10 Ω in accordance with IEC 62305-3. In resistive soils (dry clay, rock), multiple interconnected earthing rods or buried horizontal earth conductors can achieve this value.
Do rooftop solar installations require a lightning rod?
Not necessarily. The IEC 62305-2 risk assessment will determine this. If the building is already equipped with a Local Protection System (LPS), the panels must be integrated into the existing protected area. If the building is not equipped with one, the risk assessment will determine whether an LPS is required, taking into account the addition of the panels.
How to report a lightning strike on a solar installation?
In the event of a suspected lightning strike, it is recommended to call in a qualified technician to inspect the entire installation. Strike Radar can verify whether a strike has actually occurred near the site and document the event for insurance purposes.
