Surge is a kind of transient interference, which causes the instantaneous voltage on the power grid to exceed the rated normal voltage under certain conditions. Usually, the transient does not last too long, but the range may be quite high. It is possible to suddenly rise in just 1/1000000 seconds, such as thunder, or disconnect the inductor load, or turn on a large load will have a great impact on the power grid. In most cases, if the equipment or circuit connected to the power grid does not have surge protection measures, the device will easily be damaged, and the degree of damage will be related to the voltage withstand level of the device.

Photovoltaic systems are exposed to large areas of open space, usually in the wild or on top of buildings. Charged rain clouds that accumulate above such open sites tend to release charges in the form of lightning. In this case, a voltage surge is likely to occur. The wider the space, the greater the possibility of damage. Surges can easily damage electronic equipment to a catastrophic failure. If someone is present during the surge, it may also endanger their personal safety.

Poorly protected photovoltaic systems will suffer repeated serious damage, resulting in a large number of maintenance and replacement costs, system downtime and revenue loss. Properly installed surge protectors (SPD) will minimize the potential impact of lightning strikes.

In order to prevent high energy from passing through electronic equipment and causing high voltage damage to the photovoltaic system, voltage surge must have a grounding path. For this reason, all conductive surfaces should be grounded directly, and all wiring in and out of the system (such as Ethernet cables and AC power supplies) should be grounded through surge protectors. A surge protector is required for each set of array boxes, bus boxes, and DC isolators.