Because of the high height of wind turbine blades, the blades become the most vulnerable parts to direct lightning strikes. Blade is one of the most expensive parts of wind turbine. Most lightning accidents only damage the tip of the blade and a little damage the whole blade. There are two main aspects of blade damage caused by lightning: on the one hand, after lightning strikes the blade tip, a lot of energy is released, and the strong lightning current causes the internal temperature of the blade tip structure to rise sharply, and the water is heated to vaporize and expand, thus generating huge mechanical force, causing the blade tip structure to burst and damage, and even cracking the whole blade. On the other hand, the huge sound waves generated by lightning strike cause impact damage to the blade structure. It is also worth noting that lightning strike usually hits the upper wing surface of the blade.

According to the characteristics of lightning damage to equipment, the test proves that lightning damage can be avoided by reducing the internal impedance of the struck object structure and forming a path to the ground. According to this feature, carbon fiber with good conductivity and light specific gravity is added to the composite material of the airfoil on the blade, and lightning arrester is installed at the tip of the blade, which is connected with the flange of the blade through cable, and then the hub is connected with the grounding grid through the grounding wire in the tower to form a lightning channel. When lightning strikes the blade, the powerful lightning current flows into the earth through the lightning channel to achieve the lightning protection effect without damaging the blade and other equipment. In this way, in fact, the blade becomes a lightning rod, attracting the lightning around it and discharging it in advance. Therefore, special attention should be paid to the very small impedance of the lightning channel, the connecting wire should have enough conductive cross section and good conductivity, and the grounding grid must ensure the minimum impedance value.

On the other hand, the lightning energy is huge and the lightning strike mode is complicated. Taking reasonable and appropriate lightning protection measures can only reduce losses, and only the breakthrough and application of more new technologies can completely protect and utilize lightning.

References:

Lightning protection scheme for wind power generation system /html/ Yingyong/Li Dian/201410/0000004.html.