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In India high voltage transmission is mostly done by
Overhead system
Underground system
Either (a) or (b)
None of above
Overhead system
In India, high voltage transmission is predominantly achieved through overhead transmission lines due to economic feasibility and ease of insulation. Overhead lines utilize the surrounding air as a natural dielectric medium, significantly reducing the capital expenditure compared to insulated underground cables.
In India, high voltage transmission is predominantly achieved through overhead transmission lines due to economic feasibility and ease of insulation. Overhead lines utilize the surrounding air as a natural dielectric medium, significantly reducing the capital expenditure compared to insulated underground cables.
C=ln(rDтАЛ)2╧А╧╡0тАЛтАЛ тАФ Capacitance of overhead lines
CugтАЛ=ln(rRтАЛ)2╧А╧╡╧╡0тАЛтАЛ тАФ Capacitance of underground cable
Overhead systems rely on bare conductors supported by towers and insulators. The high voltage is insulated by the clearance provided by the air gap, which allows for efficient cooling and easier fault detection. Underground cables, conversely, require expensive pressurized oil, gas, or solid XLPE insulation layers to handle high electrical stress, making them prohibitively expensive for long-distance high-voltage power transmission.
Air is the primary insulating medium for overhead lines.
Overhead systems have lower installation and maintenance costs compared to underground.
High Voltage Direct Current (HVDC) is increasingly used for long-distance overhead transmission.
Corona discharge is a major limiting factor in overhead line design.
Significantly lower initial installation cost.
Faults can be visually located and repaired quickly.
Better heat dissipation due to ambient air exposure.
Susceptibility to environmental hazards like lightning and wind.
Aesthetic impact (visual pollution) in urban environments.
Requirement for large Right-of-Way (ROW) clearances.
Long-distance bulk power transmission (e.g., 400kV, 765kV).
Rural and sub-transmission networks.
Inter-state power grids.
| Feature | Overhead | Underground |
|---|---|---|
Insulation | Air | Solid/Oil/Gas |
Cost | Low | Very High |
Underground cables are primarily used in densely populated urban areas where overhead lines are physically restricted or unsafe.
Option B (Underground) is technically feasible but economically unviable for long-distance HV transmission.
A is correct тАФ The overhead system is the most cost-effective and practical method for long-distance high-voltage transmission in India.
Always remember that while underground transmission is safer in cities, the charging current in cables is significantly higher due to higher capacitance, limiting their use in long-distance AC transmission.