With the arrival of another thunderstorm season in the Northern Hemisphere, the issue of disconnecting a solar photovoltaic system during lightning strikes has resurfaced on installation and maintenance checklists. Most industry standards, installation recommendations and best practices regarding both residential and commercial PV systems indicate that the answer is usually "no," provided the system has adequate surge and lightning prevention features.
Understanding the Risks
Thunderstorms can give rise to two critical hazards for solar photovoltaic (PV) systems. The first of those hazards is a natural lightning exposure-the direct lightning strike can destruct a solar panel and associated support systems. The second hazard is the induced surge of electricity by electromagnetic force that leads to transient overvoltages across the electronic systems including the inverter.
Integrated Lightning Protection Measures
Modern PV systems are designed with multilayered protection strategies to mitigate these risks.
First, systems usually have air-termination devices placed to intercept direct strikes. The rolling sphere method is commonly used, but protection of the PV array is calculated without shadowing each individual module.
Second, surge protection devices, or SPDs, can be installed at several prominent locations-at the DC input lines close to the junction box, and at the AC output lines-to provide surge current diversion in the event of an indirect strike. For example, an SPD at the inverter output lines, generally referred to as the AC side, will mitigate the risk of overvoltages damaging sensitive devices connected to the grid.
Third, grounding and bonding are essential. To ensure lightning currents are dissipated safely, a low-resistance grounding system must be used. Metallic supports are installed at intervals of 10 m and connected to the main grounding network to eliminate voltage differences and reduce the occurrence of side-flash phenomena.
Resilience to Hail and Wind
In addition to electrical hazards, PV modules are carefully reviewed for mechanical strength. Quality manufacturers test their panels to determine hail impact resistance-for example, 25-mm ice balls at 23 m/s, or 30.7 m/s for conditions with a more severe maximum wind speed. Modules approved under the requirements of IEC 61215 have respectable impact and hail damage tolerance. Similarly, resistance to wind load is addressed through rigorous mounting systems and structural design that incorporates local wind load data.
Do You Need to Disconnect? A Condition-by-Condition Answer
Considering the protections described above, disconnecting the system is usually not necessary. A well-designed PV system following proper lightning mitigation practices can operate safely during storm conditions. However, there are limited instances when disconnection may be appropriate.
Scenario | Should the system be disconnected? | Reason or basis
System has compliant SPDs and low-resistance grounding/bonding | No | The protection design is intended to divert surge current before it reaches sensitive equipment. Disconnection adds no safety benefit and loses generation.
An SPD has operated, for example the circuit breaker has tripped | Wait until the storm passes, then reset | The SPD has performed its protective function. Resetting after the storm restores protection; permanent disconnection is not required.
System lacks proper grounding protection or SPDs | Disconnect the DC side and arrange professional inspection | Without adequate protection layers, direct-strike and induced-surge risk cannot be controlled. Disconnection reduces exposure until corrective work is completed.
Users should regularly maintain the system and schedule professional inspections to identify possible upgrades that improve ongoing protection.
Frequently Asked Questions
Q: Do solar panels need to be disconnected during a thunderstorm?
In most cases, no. If the PV system has compliant surge protection devices, low-resistance grounding and proper bonding, it can remain connected and operate safely during a thunderstorm. Disconnection is normally only needed when an SPD has tripped or when protection is missing.
Q: What should I do if the SPD trips during a storm?
Wait until the storm has passed, then reset the system. An SPD trip indicates that the device has operated to divert a surge. After the storm, the system can be reset and protection restored.
Q: Does IEC 61215 cover hail resistance for PV modules?
Yes. Modules approved under IEC 61215 are tested for mechanical strength, including hail impact. Typical test conditions include 25-mm ice balls at 23 m/s, with higher speeds such as 30.7 m/s used for more severe maximum wind conditions.
Q: Why is grounding and bonding important for rooftop PV?
A low-resistance grounding system safely dissipates lightning currents. Bonding metallic supports at intervals of 10 m and connecting them to the main grounding network eliminate
