High Voltage Cable Protection

I had heard of something, called lightning arresters, being utilised against lightning strike. Employ them.

Please check number 5th in this search

High Voltage Transmission Line Protection

Put an earthed lightning rod up in the air not far away.

Lightning arrestors (LA) are generally installed at each end of the underground cable distribution system to protect long (say > 100m) underground cables. The LA installed at the far end of the underground cable provides adequate protection to the transformer as well.

Metal oxide varistors (MOV) of proper voltage rating can easily protect the termination and the cable insulation, but introduce a travelling wave in the cable which traverses the cable at a very high velocity and gets reflected back, if the far end of the cable presents a high impedance such as a transformer or an open isolating switch. If LA is not provided at the far end, the positive reflection produces nearly double voltage that can damage the cable and the connected transformer.