What is generally true about the cost of underground transmission compared to overhead lines?

• A. Generally costs less and is easier to construct than overhead lines.
• B. Generally costs more and may be more complicated to construct than overhead lines.
• C. Costs about the same as overhead lines.
• D. Costs vary but not related to construction complexity.

Answer: (B)

Underground transmission requires more than burying cables. The installation process is typically more expensive and more complex than overhead lines because it involves extensive trenching or boring, installing conduits or duct banks, and building protective enclosures such as vaults or pull boxes. This adds material costs and a lot of labor for excavation, backfill, compaction, and restoring the surface. There’s also a need for moisture and heat management, waterproofing, and specialized splicing and termination practices that are unique to underground systems.

Access and repair are another big factor. When a fault occurs, locating and reaching underground cables can be slow and labor-intensive, requiring excavation or specialized equipment, which drives up maintenance and restoration costs. In contrast, overhead lines use simpler supports, are easier and faster to repair, and typically have lower upfront material and labor costs.

While underground systems can offer benefits like reduced right-of-way impacts and better aesthetics or weather resilience in some situations, the initial capital and ongoing maintenance costs are generally higher due to the added complexity and harsher conditions for installation and repair. That’s why, in general, underground transmission costs are higher and more complex to construct than overhead lines.