Common Causes of Lightning Strikes
Outdoor network cables or power cables are routed overhead.
A switch(such as S6700-24-EI, S6720-30C-EI-24S-AC) is deployed outdoors but is not properly grounded.
Damages of Lightning Strikes
If power cables of a switch are routed overhead in an outdoor environment, lightning strikes may burn the power supplies.
If network cables of a switch are routed overhead in an outdoor environment, lightning strikes may burn interfaces of the switch.
When a switch undergoes lightning strikes, overvoltage is induced by lightning on network cables and transmitted to interior of the chassis. The surge protection measures, such as lightning rod and chassis grounding cannot prevent the damage. Therefore, surge protectors or surge protection circuits are recommended.

Surge Protector Use Precautions
Take the following precautions to protect a switch from lightning:

Ensure that the ground cable is connected to a ground bar or a ground point on the cabinet.
Avoid routing cables overhead in an outdoor environment. Bury cables underground or route them in steel tubes.
To protect network interfaces against lightning, use 8-line surge protectors (or Huawei certified 4-line surge protectors).
When installing a network interface surge protector, connect the IN end to terminals and the OUT end to network interfaces of the switch.
If a fixed switch is installed in a network box, as shown in Figure 1, follow these instructions:

Connect the ground cables of the switch and surge protectors to the ground bar in the network box.
The maximum length of a ground cable cannot exceed 40 cm, and a length of smaller than 15 cm is recommended.
If the network box is located outdoors and power cables are routed aerially over a long distance (more than 300 m) to the network box, it is recommended that you install a power supply surge protector in the network box. The decoupled power cable must be at least 3 m long.