In fact, there are no mandatory surge requirements or standards in solar systems. Surge specs and performance are mainly decided by the vendors based on inverter’s deployment scenarios and lifetime quality guarantees. However, there are some technical codes that can be used as references. For example, surge requirement and lighting protection design can refer to China local standard DL/T 1364:2014 (Technical code for protection of photovoltaic power station against lighting), which are widely adopted in the industry

Table 5-3 shows nominal discharge current (8/20us) of DC SPD which is translated from DL/T 1364:2014. It requires ≥ 10KA surge current capability for terminals in front of inverter, which means PV strings. Note that inverter here can include string inverter, residential inverter and hybrid inverter, and so on, which have PV strings in front of the inverter. Note that the surge requirements are more reasonable to base on system level, but not device level.