2.2.2. Experimental Method

In order to simulate the lightning stroke of PV modules under thunderstorm clouds, an experimental platform was set up in the high voltage laboratory. The long gap discharge of PV module by SJTU-3000 impulse voltage generator (IVG) was used to simulate the spatial potential and electric field distribution of PV modules during the scene of lightning downward leader descending process.

The schematic diagram of the experimental platform is shown in Figure 7a. Place Sample A and Sample B horizontally on the ground. Keep the metal frame well grounded. The rod electrode connected with SJTU-3000 IVG was located directly above the center of PV modules, with a vertical distance of 2 m. The layout of the experimental platform is shown in Figure 7b. As more than 90% of lightning in nature is negative, SJTU-3000 IVG was used to apply negative lightning impulse voltage with 1.2/50 μs waveform for 20 times. In order to prevent the subsequent experiment from being affected by the breakdown of the solar cells, the solar cells surface of the experimental sample was covered with 5 mm thick glass. Moreover, the insulation blanket was used to cover the sharp corners to prevent lightning striking at these corners because these sharp corners do not exit when BIPV is installed on the building roof. Therefore, the influence of glass and insulating blanket on this test can be ignored. After each discharge, the location of lightning striking attachment point was recorded to calculate the lightning striking attachment probability of the samples, with the lightning protection effect of different PV modules evaluated.

**Figure 7.** Lightning attachment experiment (**a**) Schematic diagram of experimental platform; (**b**) Layout of experimental setup.
