What must individual conductors of an underground high voltage cable be provided with?

Individual conductors of an underground high voltage cable must be provided with metallic shielding around each power conductor. This is essential because metallic shielding serves multiple critical functions in high-voltage applications. It provides a barrier that helps contain electromagnetic fields generated by the high-voltage conductors, reducing the risk of interference with adjacent cables or equipment. Additionally, the shielding protects the insulation of the conductor from damage caused by external factors such as moisture, physical impact, or chemical exposure. Moreover, it plays a significant role in safety by ensuring that if there is a fault in the insulation, the fault current is safely directed to ground, thus preventing dangerous voltage levels from appearing on the cable surface. This effective protection and grounding capability is vital in maintaining the integrity and safety of the electrical system.

In contrast, while options like plastic insulation and rubber coating provide some degree of protection, they do not offer the same level of shielding against electromagnetic interference or fault scenarios. Air insulation is not practical for underground applications, as it would not provide the necessary protection against the environmental factors that high voltage cables are exposed to when buried.