Which statement best describes underground transmission cables in comparison to overhead lines?

• A. They have the same technical requirements as overhead lines.
• B. They are cheaper to install and require simpler construction.
• C. Cables that have different technical requirements than overhead lines and different environmental impacts.
• D. They require no environmental precautions.

Answer: (C)

Underground cables and overhead lines are built for very different environments, so their design and the effects they have on surroundings aren’t the same. Heat management is a key difference: buried cables can’t shed heat to the air as easily as lines in the open sky, so they often need larger conductors or special cooling/installation approaches to carry the same current without overheating. That leads to different insulation choices, ratings, and protection schemes, plus more complex joints and terminations that must withstand moisture and soil conditions.

Another big point is fault locating and repair. A fault in an underground cable is harder to find and fix, which means longer outage times and more involved maintenance planning. The installation process itself is also more involved: trenching, backfilling, conduit or duct systems, and surface restoration all add complexity and cost, as well as environmental considerations.

Because of these factors, underground cables have distinct technical requirements and environmental impacts compared with overhead lines. The surface-visible benefits of undergrounding don’t change the need for moisture control, soil and groundwater protection, and other environmental precautions, whereas overhead lines, while easier to access for repairs and generally cheaper to install, come with different exposure to weather and land-use impacts.