Although most people think of lightning as the cause of most voltage transients, the most frequent source of this type of disruption is actually the local power grid.
Axis network cameras for outdoor installation are designed to withstand power surges and transients, and part of this design involves using a shielded twisted pair cable (STP) between the PSE (Power Sourcing Equipment)* and the camera, to ensure a path for the power surge to reach ground.
The combination of Axis cameras, STP network cabling and a properly grounded PSE has been tested to comply with industry immunity standards levels, for example for surge protection. Any other installation method will void the warranty and leave the unit at risk.
Always use an STP network cable between the camera and the PSE, and ensure that the PSE is properly grounded.