Are Overhead transmission lines less economical than underground transmission cable?

• A. No they are more economical, bc they make use of air for insulation
• B. Yes they are less economical
• C. Only in urban areas
• D. They are equally economical

Answer: (A)

Overhead transmission lines are typically more economical because air serves as the insulating medium. When the conductor runs through the air between tall structures, there’s no need for the heavy, expensive dielectric insulation and protective ducting that underground cables require. The hardware for overhead lines—towers, insulators, and conductors—is generally simpler and faster to install, which lowers both material and labor costs. In contrast, underground routes demand costly cable designs, buried ducts or conduits, moisture protection, trenching or boring, backfill, and numerous access points, plus more complex fault locating and repair. These factors push underground installations to be significantly more expensive upfront and in ongoing maintenance. Of course, in urban areas or where reliability, space, or environmental concerns outweigh cost, underground may be chosen despite the higher expense.