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Which of the following transmission line have more initial cost?
Overhead Transmission
Underground transmission
Both have almost the same initial cost
none of these
Underground transmission
Underground transmission systems have significantly higher initial costs compared to overhead lines due to the complex requirements of insulation, civil works, and specialized installation equipment. While overhead lines use air as a natural, free insulator, underground cables require expensive solid or oil-impregnated dielectric materials and pressurized conduits.
Underground transmission systems have significantly higher initial costs compared to overhead lines due to the complex requirements of insulation, civil works, and specialized installation equipment. While overhead lines use air as a natural, free insulator, underground cables require expensive solid or oil-impregnated dielectric materials and pressurized conduits.
CtotalтАЛ=CinsulationтАЛ+CcivilтАЛ+CinstallationтАЛ тАФ Representation of total capital expenditure for underground transmission lines.
I2RlossтАЛтИЭA1тАЛ тАФ Relation showing cross-sectional area requirements for cables.
The high cost is primarily driven by three factors: the necessity for high-grade insulation capable of operating under high electrical stress, the expensive excavation and ducting process required for laying cables, and the complex jointing/terminating techniques needed to prevent insulation failure and localized heating.
Underground cables require extensive use of dielectric insulation materials like XLPE or oil-filled paper.
Overhead lines use air as an insulator, which has zero cost and self-restoring properties.
The cost of underground transmission is generally 5 to 10 times higher than an equivalent overhead line.
Maintenance cost is also higher for underground cables due to difficulty in locating and repairing faults.
Immune to lightning and weather-related outages
Less prone to theft or vandalism
No electromagnetic interference with nearby communication lines
Very high initial installation and material costs
Difficult to locate and repair faults
Limited current carrying capacity due to poor heat dissipation
Highly populated urban areas
Near airports (safety requirements)
Submarine power transmission
| Feature | Overhead | Underground |
|---|---|---|
Initial Cost | Lower | Higher |
Underground cables have high charging current due to high capacitance, limiting the distance for AC transmission.
Overhead lines are preferred for long-distance bulk power transmission due to lower impedance and better heat dissipation.
B is correct тАФ Underground transmission involves massive expenses related to expensive insulating materials and civil construction, making its initial cost much higher than overhead lines.
Always remember that while underground lines have higher CAPEX (Capital Expenditure), they are often used in dense urban planning where space constraints and aesthetic/safety regulations outweigh the financial burden.