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Application Scheme of Photovoltaic Solar DC Surge Protector


The lightning protection system combines basic components such as air terminals, appropriate down conductors, equipotential bonding of all current carrying components, and appropriate grounding principles to provide a roof that prevents direct impact. If your photovoltaic site has any lightning risk, I strongly recommend hiring a professional electrical engineer with professional knowledge in the field to provide risk assessment research and protection system design if necessary.

It is important to understand the difference between lightning protection systems and SPDs. The purpose of lightning protection systems is to guide direct lightning strikes to the ground through a large number of current carrying conductors, thereby preventing structures and equipment from being in the discharge path or being directly hit. SPD is applied to electrical systems to provide a grounded discharge path to protect the components of these systems from high-voltage transients caused directly or indirectly by lightning or power system anomalies. Even with an external lightning protection system, without SPD, the impact of lightning can still cause significant damage to components.

For the purpose of this article, I assume that some form of lightning protection is already in place and have examined the types, functions, and benefits of additional use of appropriate SPDs. Combined with appropriately designed lightning protection systems, the use of SPD at critical system locations can protect major components such as inverters, modules, equipment in combiner boxes, and measurement, control, and communication systems.

In addition to the consequences of direct lightning strikes on the array, interconnecting power supply wiring is highly susceptible to electromagnetic induced transients. Transients caused directly or indirectly by lightning, as well as transients caused by utility switch functions, expose electrical and electronic equipment to extremely high overvoltages of extremely short duration (tens to hundreds of microseconds). Exposure to these transient voltages may lead to catastrophic component failures, which may be evident due to mechanical damage and carbon tracking, or may not be apparent but still result in equipment or system failures.

Long term exposure to low amplitude transients can cause the dielectric and insulation materials in photovoltaic system equipment to deteriorate until they eventually break down. In addition, voltage transients may occur in measurement, control, and communication circuits. These transients may appear to be incorrect signals or information, leading to equipment failure or shutdown. The strategic placement of SPD alleviates these issues as they serve as short-circuit or clamping devices.