The lead sheath of a cable is primarily for protecting the cable from what type of damage?

The lead sheath of a cable serves primarily to protect the cable from water damage. This is because lead is a dense, waterproof material that provides an effective barrier against moisture and water ingress. In environments where cables may be exposed to water, such as underground or in wet locations, the lead sheath ensures that the insulation and conductors within the cable remain dry and functional. This is critical for maintaining the integrity and operational reliability of the electrical system.

While the other options may address important concerns, they are not the primary function of the lead sheath. The mechanical protection could be offered by robust sheathing materials, but lead's primary role is moisture barrier. Electrical interference typically requires shielding materials rather than a lead sheath, and thermal damage is usually mitigated by specific insulation designed to withstand temperature changes. Thus, while the lead sheath may provide some incidental protection against those factors, its main purpose is to protect against water damage.