Photovoltaic fields consist of highly sensitive equipment that requires special protection. Since these fields generate direct current (DC) power, inverters—which convert this DC power to alternating current (AC)—are crucial components in their electricity generation process. Unfortunately, inverters are not only highly susceptible to lightning strikes but are also expensive. According to NFPA 780 12.4.2.3, if the system’s inverter is more than 30 meters away from the nearest combiner or re-combiner box, a surge protector is required at the DC input end of the inverter. If there are string protectors, such as fuses, DC breakers, or string diodes, install the surge protector between the fuse and the inverter.

Surge Protection for Correct and Incorrect Connection to Inverters Equipped with String Protectors

Surge Protection for Correct and Incorrect Connection to Inverters Equipped with String Protectors

 

To connect a surge protector to an inverter that has an integrated fuse box, ensure that you bypass the internal fuses and connect to external string fuses. Surge protectors should be installed outside the inverter, and if used outdoors, should be housed in a NEMA Type-3R or higher-rated enclosure. String inverters should be placed as close to the string as possible. The cable connecting the L+/L- network to the surge protector’s terminal block and the grounding bus bar should be less than 2.5 meters. The shorter the connecting cable, the more efficient and cost-effective the protection is. For inverters with only one MPP tracker, combine strings before the inverter and connect the surge protector at the interconnection point. For inverters with multiple MPP trackers, plan a surge protector combination for each input. Each input that integrates string diodes must use a surge protector.

Surge protector connected to an inverter equipped with an integral fuse box.

Surge protector connected to an inverter equipped with an integral fuse box

 

Conclusion

Operating photovoltaic equipment without proper surge protection is not just risky but reckless. To ensure that solar systems become part of a greener future, they must be safeguarded. While it’s impossible to prevent lightning, protection is essential. Given that photovoltaic systems are vulnerable to both direct and indirect lightning strikes, they should be built on the foundation of reliable and correctly installed surge protectors.