A common question for those starting out in solar energy is: where to install the DPS?
The answer is simple: at all necessary points, both on the direct current (DC) and alternating current (AC) side.
This is because electrical surges do not have a preferential side: they can come from either the solar generation side or the power grid side. For example, if lightning strikes near photovoltaic modules, a surge wave travels through the DC cables that connect the panels to the inverter.
Likewise, a surge from the utility company (due to a grid maneuver or even a lightning strike on the distribution line) will enter through the AC side and reach the inverter and even the modules. Without SPDs on both sides, the system has an “open door” for the surge to enter – and all it takes is a single gap for damage to occur.
Some inverters even have internal protectors (varistors, filters, etc.) on their DC input and AC output ports. However, you should not rely solely on the inverter's internal protection.
Manufacturers design inverters to withstand certain peak levels, but in the event of a nearby lightning strike, for example, the induced voltage exceeds the limits. The solution is to add dedicated external SPDs, sized correctly for each side of the circuit.
High incidence of lightning in Brazil drives adoption of DPS
In practice, this means installing a DC SPD in the string box or close to the solar modules, and an AC SPD in the AC distribution panel (usually close to the inverter or at the grid connection point).
It is worth remembering that each circuit requires a specific DPS – the same device cannot be used to simultaneously protect the DC and AC sides, as the electrical characteristics are different and the standards prohibit mixing both.
Therefore, type II SPDs are usually used for DC (typical working voltage of up to 1000 V or more, suitable for photovoltaics) and type II SPDs for AC (suitable for the 220V or 127/220V network, depending on the system). In areas highly subject to direct discharges, type I SPDs (which can withstand higher surge currents) must be included at the panel input, following the recommendations of NBR 5419.
The important thing is to ensure cascade protection. Each installed DPS acts as a barrier, reducing the level of residual overvoltage that reaches the equipment. For maximum effectiveness, the DPS must be as close as possible to the equipment they protect (generally, less than 10 meters from the inverter, to prevent even an induced surge between the DPS and the device from causing damage).
This way, the DC side (panels → inverter) and the AC side (inverter → grid) will be protected. This complete protection practice is advocated by experts and standardized by international standards.
Investing in two or more quality DPSs is certainly worth the cost of a new inverter or days of system downtime for maintenance. Remember: a safe photovoltaic system is one that is protected in all paths through which electricity flows.
UPE study proves the effectiveness of external DPS
To concretely illustrate the importance of DPS, the study “Analysis of the performance of solar inverters subjected to electrical surges caused by atmospheric discharges” by the University of Pernambuco, in partnership with CLAMPER.
The researchers subjected 3 kW solar inverters to lightning surge pulses, measuring how many pulses the inverters could withstand with and without an external SPD. The results were telling: Without additional SPD, the inverters failed after very few surges—on average, just five pulses on the AC side and one pulse on the DC side.
This shows that even when the electrical surges were within the withstand capacity of this protection, the inverters burned out. In contrast, when an external SPD was installed, both inverters withstood 100 surge pulses on both the DC and AC sides without failing. In other words, the useful life against surges increased dramatically with the SPD protections.
But the most impressive data was the measurement of the energy effectively diverted by the DPS: the analysis showed that the external DPS managed to divert at least 93,6% of the surge energy that would hit the inverter.
This means that less than 7% of that potentially destructive wave actually reached the equipment, a huge reduction in the electrical stress on the internal components. With much less stress, the inverter remains unharmed where before it would have certainly burned out.
The study categorically concluded that the use of external DPS in solar installations is an extremely effective and economically viable solution to avoid early inverter failures.
The researchers noted that the cost of the SPDs used was less than 8% of the cost of the lowest-priced inverter tested. Therefore, investing in external protectors is like paying a small insurance premium (about 5% to 8% of the cost) to ensure that an expensive piece of equipment lasts much longer.
This UPE study reinforces with objective data what practice already indicated: relying solely on internal inverter suppressors is risky, and quality external DPS are capable of absorbing the vast majority of the surge energy, saving the inverter and other components.
Integrators and engineers can use these results to educate customers and justify mandatory inclusion of SPDs in the budget – often, end users question the additional cost without realizing the enormous losses that a surge causes.
With evidence such as “deflecting 93% of lightning energy” and “increasing the system’s resistance to surges by 20x or more”, it is clear that external protectors are not superfluous accessories but rather crucial elements for the reliability of the solar plant.
Study link: https://clamper.com.br/dpsprodutos/artigos-estudos/universidade-de-pernambuco-upe/
Recommended solution: CLAMPER Solar SB, the certified protection for your photovoltaic system
Among the devices available on the market to protect photovoltaic systems, the CLAMPER Solar SB stands out as a complete and reliable surge protection solution. The CLAMPER Solar SB is essentially a pre-assembled string box (junction box) specially developed for solar systems.
It already comes equipped with a high-capacity DPS for direct current and an integrated disconnector switch (circuit breaker/disconnector), which allows you to disconnect the DC circuit of the panels when it is necessary to carry out any intervention or maintenance on the inverter.
In other words, this product brings together in a single robust box the vital protection and sectioning components on the DC side of your solar plant, making the integrator's life easier and increasing operational safety.
CLAMPER's credibility in the Brazilian market is a strong point – it is a specialized company with over 33 years in the surge protection market, with certified products widely used in electrical and photovoltaic installations.
In the case of the Solar SB model, the internal DPS is sized for the typical voltages of photovoltaic arrays (up to 1000 Vdc, for example) and has the appropriate terminals for connecting solar strings.
By protecting the direct current circuit, the CLAMPER string box prevents overvoltages from the panels or captured by the metal structures from reaching the inverter. As we have seen, this is one of the most critical points in the event of atmospheric discharges.
By diverting the surge energy to ground, the CLAMPER Solar SB protects the inverter from damage and, therefore, ensures the proper functioning of the photovoltaic plant, eliminating risks caused by electrical surges and reducing losses with maintenance and equipment replacement. In short, it is a certified, practical and efficient solution: installed between the modules and the inverter, it acts 24 hours a day as a “shield” for your solar generation.
Another important aspect is that using a product such as the CLAMPER Solar SB helps to meet the aforementioned regulatory requirements. Since it is a dedicated, high-quality external SPD, its presence already brings the installation into compliance with the need for protection against transient overvoltage on the DC side, as required by the standard (remember that NBR 5410 and RN 1000 require protection of circuits subject to lightning).
In addition, the string box makes it easier to organize the installation, avoiding improvisations when assembling separate DPS, and has an IP protection level suitable for outdoor environments, ensuring durability even in sun and rain. Integrators report that adopting ready-made solutions such as CLAMPER SB speeds up the installation and reduces human errors, as all internal components are already correctly specified and assembled at the factory.
In terms of investment, incorporating a quality DPS adds value to the system and is a differential that brings peace of mind to the customer, knowing that their panels and inverter (which cost tens of thousands of reais) are protected by a device developed by experts.
Take care of your investment, use quality DPS and choose qualified professionals
At the end of this discussion, the central message is clear: the importance of surge protection in photovoltaic systems should not be underestimated. Whether to preserve the safety of people, prevent material damage or comply with current regulations, installing suitable SPDs on the DC and AC sides is essential.
A solar system represents a significant, long-term investment – saving a few percent of the total cost by not installing protectors will cost you dearly in the future if a power surge occurs.
On the other hand, incorporating high-quality protection devices, such as the CLAMPER Solar SB and DPS for the AC side, ensures the continuity of generation even in the face of extreme events, protects equipment against burning and prevents unexpected interruptions.
For integrators and responsible engineers, the recommendation could not be clearer: always design your photovoltaic installations including SPDs in compliance with technical standards.
Educate the customer about the risks of surges and the benefits of protection – often, once homeowners understand that a lightning strike or power surge can damage the entire system, they begin to view SPD as an essential, not optional, item.
Also remember to use certified products from reliable sources that guarantee the expected performance at the critical moment. Low-quality or improvised equipment will fail just when it should work, leaving the system vulnerable.
The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of the author. Canal Solar.
