1. Hidden dangers behind the booming photovoltaic industry

In recent years, the global photovoltaic market has been growing at an astonishing rate, much like a rocket. I still remember when I attended the solar energy exhibition in Germany five years ago, the mainstream module power was around 300W. Now, it's not uncommon to see 600W+ bifacial modules. However, amid this installation boom, a crucial issue is often overlooked - system protection.

Last year, our company handled a case from Turkey: a 5MW ground-mounted power station. Three months after being connected to the grid, four inverters were burned out in succession. During the on-site investigation, it was found that the owner had saved costs by omitting the surge protection devices on the DC side. The final loss was as high as over 200,000 US dollars, which was enough to purchase hundreds of high-end SPDs. Such lessons are not uncommon in the industry.

2. "Voltage assassins" faced by photovoltaic systems

2.1 Lightning strike: the most dangerous threat

I have come across a fishery-radiation power complementing project in Hainan. The local area has more than 90 days of thunderstorm days each year. Their operation supervisor informed me that before installing SPD, they were always on edge during the thunderstorm season every year. The most serious incident was that an induced lightning strike caused all the string-type inverters in the entire array to "go on strike" collectively.

Interestingly, many people think that only direct lightning strikes are dangerous. In fact, our detection data shows that lightning strikes within a 3-kilometer radius can generate an induced surge strong enough to damage equipment. There was once a Brazilian project where the lightning strike point was on the neighboring farm, yet it caused all the monitoring modules of the photovoltaic system to fail.

2.2 Grid Fluctuation: The Invisible Killer

When we were involved in the commissioning of a rooftop project in Vietnam last year, we recorded astonishing data: The voltage fluctuation of the local power grid during peak electricity consumption periods often exceeded 15%. This continuous voltage distortion is more detrimental to equipment lifespan than instantaneous surges.

The more troublesome issue is the surge current generated by the photovoltaic system itself. Remember, once when testing a certain brand of inverter, the voltage spike it produced during shutdown was actually four times the rated voltage! This kind of "self-generated and self-consumed" surge current is something that many property owners simply fail to notice.

3. How does SPD protect the photovoltaic system?

3.1 Multi-layer protection: Put on a "bulletproof vest" for the system

A good protection system should be like an onion with multiple layers of defense. We usually recommend that customers adopt a three-level protection strategy:

Array level: Install Type 2 SPD at the combiner box to protect against most induced lightning.

Inverter level: Use dedicated photovoltaic SPD on the DC input side. Pay special attention to the selection of Uc voltage.

Grid connection point: Install SPD that is adapted to the local grid characteristics on the AC side.

3.2 Selection Misunderstanding: The higher the parameter, the better

It is often observed that customers blindly pursue high Imax values. In fact, for most distributed projects, a 20kA discharge capacity is sufficient. The key lies in:

- Voltage matching capability (Uc ≥ 1.2 × Maximum system voltage)

- Residual voltage level (This is crucial as it determines whether the equipment can truly be protected)

- Degradation indication function (This is extremely important as it can prevent "zombie SPD")

An Australian customer insisted on installing a SPD with a rating of 40kA. However, due to the selection of a too low Uc voltage, the SPD prematurely aged when the system was under light load.

3.3 Don’t let protection shortcomings drag down investment returns

I have witnessed too many meticulous homeowners who are willing to spend a lot of money on top-notch components but are overly cautious about system protection. In fact, a well-designed SPD (Surge Protective Device) solution usually accounts for only 0.3% to 0.5% of the total project cost, yet it can prevent over 80% of electrical failures.

It is suggested that everyone should take into account the following during the design phase:

- Local data on thunderstorm days (which can be easily obtained from the meteorological bureau)

- Grid quality reports

- Surge tolerance standards set by equipment manufacturers

Conclusion

For a photovoltaic system to operate stably for 25 years, it needs reliable surge protection. It's like working at heights without wearing a safety belt – maybe you manage to stay safe for the first 99 times, but the 100th time could cost you dearly.