What material is often used to shield underground high voltage cables?

Metallic shielding is often used to protect underground high voltage cables for several reasons associated with both safety and functionality. High voltage cables generate electric and magnetic fields, and metallic shielding helps to contain these fields, preventing interference with nearby equipment and minimizing the risk of electrical hazards.

Moreover, metallic materials like copper or aluminum provide a robust barrier against environmental factors such as moisture, chemicals, and physical damage, which can degrade the performance of the cables over time. This shielding not only helps maintain the integrity of the electrical transmission but also ensures the safety of personnel who might be working near or above these cables.

In contrast, materials like copper tubing, wooden casing, and glass insulation do not provide the same level of protection or suitability for high voltage applications. Copper tubing, while conductive, isn't practically used as a shielding material; wooden casing lacks the necessary electrical and physical protective properties; and glass insulation is typically not used in underground settings where durability and resistance to environmental factors are critical. Thus, metallic shielding stands out as the most effective choice for safeguarding underground high voltage cables.