Which type of insulation material is often used in underground electrical cables?

• A. Wood
• B. Polyvinyl chloride (PVC)
• C. Cotton
• D. Paper

Answer: (B)

Polyvinyl chloride (PVC) is widely used as insulation material in underground electrical cables due to its favorable properties that suit the harsh conditions of underground environments.

One of the main reasons for this is PVC’s excellent resistance to moisture, chemicals, and soil acidity, which are common factors that can degrade insulation materials over time when buried underground. Additionally, PVC is durable, flexible, and has a good electrical insulation property, making it a reliable choice for protecting conductors from physical damage and environmental conditions.

The use of materials like wood and cotton is typically not viable for underground applications. Wood is susceptible to rot, moisture absorption, and pests, leading to deterioration. Cotton can absorb moisture as well and lacks the necessary resistance to chemicals and humidity, making it unsuitable for underground environments. Paper, while historically used, does not provide the same level of durability and moisture resistance as PVC, as it can deteriorate quickly when exposed to moisture, reducing its effectiveness as insulation.

Overall, the selection of PVC for underground electrical cables is based on its resilience, longevity, and excellent insulating properties, ensuring safe and efficient electrical transmission in subterranean installations.