Hey

In some forums and discussions about photovoltaic systems, I have seen installers and users advising people to manually open the PV DC breaker (disconnect the solar panels from the inverter) when a thunderstorm approaches. The reasoning usually given is that the long DC cables between the PV array and the inverter can act like an antenna and may pick up electromagnetic pulses or induced surges from nearby lightning activity. According to this argument, disconnecting the array could reduce the possibility of a surge entering the inverter.

However, I am personally skeptical about this idea. Lightning is capable of traveling through kilometers of air, so it is difficult for me to believe that a small air gap of a few centimeters inside an open DC breaker would meaningfully stop or block such energy if a strong surge actually occurs. From a physical standpoint, it seems unlikely that opening the breaker alone would provide real protection.

At the same time, I have seen at least two installers who strongly recommend this practice during storms, claiming that it can help protect the inverter in some cases. Because of this conflicting advice, I am trying to understand whether there is any real technical basis for this recommendation or whether it is simply a precaution that people repeat without clear evidence.

So I would really appreciate hearing the opinions and field experience of engineers, installers, and long-term PV system operators:

Your proposed approach aligns closely with recognised best practices for lightning and surge protection in photovoltaic systems in South Africa, particularly in regions prone to frequent thunderstorms.

We as equipment suppliers strongly recommend the installation of Type 1 or combined Type 1+2 surge protection devices (SPDs) such as those from reputable brands like DEHN HAGAR CHINT on both the DC and AC sides of the system.

These devices are specifically rated to handle high energy impulses from direct or nearby lightning strikes, offering superior protection compared to Type 2 SPDs alone, which are more suited to induced surges.Earthing remains fundamental.

Install a dedicated earth electrode 1.5 m copper clad rod or multiple bonded rods at the PV array, connected via heavy-gauge cable typically 16–35 mm² copper to the panel frames, racking, and SPDs.

Aim for a ground resistance of less than 10 ohms, as commonly required for compliance and effective surge diversion. A common equipotential bonding conductor 6–16 mm² should then interconnect this to the inverter, main distribution board, and building earth system.

This creates a single, low-impedance path to ground, minimising dangerous potential differences during a strike and ensuring surge currents follow the path of least resistance away from sensitive equipment.

For enhanced protection, incorporate multiple SPD installation points one set at the array or combiner box particularly with longer cable runs and another immediately before the inverter on the DC side, complemented by AC side protection.

This staged or cascaded arrangement progressively diverts energy, significantly improving system resilience in high lightning areas.

In locations with elevated risk such as exposed rural sites or high keraunic level zones consider external lightning protection measures, including air terminals (lightning rods) with down conductors, in accordance with a risk assessment per SANS 10313 or IEC 62305.

This is typically reserved for more extreme conditions and may not be necessary for standard residential installations.

Regarding insurance and compliance

A valid Certificate of Compliance (CoC) issued by a registered electrician is essential for grid-tied or hybrid systems, and insurers frequently require it for lightning related claims.

The CoC should document key elements, including measured ground resistance (ideally smaller than 10 ohms), SPD installations, equipotential bonding, and adherence to SANS 10142-1 (and related standards such as NRS 097 for grid interconnection).

Without properly certified documentation, claims are often declined.

In summary, this layered strategy combining high capacity SPDs, robust equipotential earthing, multi stage diversion, and full certification provides the most reliable defence against lightning induced damage.

It far outperforms reliance on manual disconnection of the DC breaker alone and positions the installation well for long term reliability, safety, and insurance acceptance.

I am sure there are a lot of installers and engineers on the forum that can add their opinions however some of these topics are hotly contested and debated however we prefer to follow best practice advice bound to the SANS Regulations to our clients.

Good information in the reply above. I would like to point out that the distance between positive and negative wires can act like an antenna for nearby strikes. The biggest risk area would be under your PV panels. If your positive and negative cables aren't running together in this area, ask how big your antenna is.