Protection of Buried Cable from Direct Lightning Strike

This paper presents studies of protection schemes for buried cables. A formula is introduced that gives the maximum peak lightning current for various ground resistivities. Maximum and minimum arcing distances beneath the surface are calculated using the internal breakdown gradient of the soil. The susceptible region for a buried cable is shown to be related to the maximum arcing distance, while the number of buried shield wires required for adequate protection is determined by the minimum arcing distance. The effectiveness of the proposed protective schemes is demonstrated by electrogeometrical theory. Finally, the qualifications of the new schemes are discussed.