The Overhead system for power transmission started in early 1912. Although underground power systems are widely replacing low, and medium voltage transmission networks within cities, the use of overhead lines for high voltage networks outside cities can never be negated. Given below are 10 differences between overhead and underground transmission lines.
- Initial cost: The initial cost of underground transmission lines is more due to the high cost of trenching, cable laying, manholes, and specialized underground systems. The underground transmission system can be three to ten times more expensive than overhead transmission system.
- Safety factor: The underground lines are invisible for the general public, birds, and other wildlife, whereas overhead conductors and pylons are visible and are dangerous when safety is considered.
- Fault: In an underground system there is very little chance of fault occurrence, whereas in overhead system faults are expected to occur very often.
- Visual Appearance: Underground transmission lines are invisible and don’t impact the look of the area. While the overhead transmission is visible and impacts the overall look of areas.
- Fault location: In the underground system the chances of faulty occurrences are very rare. However, if that happens it is difficult to locate fault as compared to overhead lines.
- Repair: Repair and maintenance operations on overhead lines are comparatively easier than underground systems.
- Current carrying capacity: Current carrying capacity of overhead lines is better than underground transmission lines.
- Useful life: Underground transmission lines have a useful life of around 40 years, while overhead transmission lines have a useful life of around 80 years.
- Interference: Underground transmission lines have no interference with surrounding telecom/radio circuits, while overhead lines can face such interferences
- Power restoration: Once some damage happens to the underground system the power restoration in underground systems takes a lot more time than as compared to overhead systems.