The insulation of an underground conductor is its first and most important line of defense. Unlike overhead lines, which are suspended in open air and rely on air as an insulator, underground cables are in direct contact with the ground and moisture. The insulation's primary function is to contain the electrical current, preventing leakage and ensuring a safe, efficient flow of power. Without proper insulation, the electrical current could escape, causing short circuits, system failure, and severe safety hazards. It also protects the conductor from environmental factors like moisture, soil chemicals, and physical stress, which could otherwise lead to premature failure.