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By which of the following method electric power may be transmitted from one location to another location?
UnderGround System
Overhead system
UnderGround System & Overhead system
None of the above
UnderGround System & Overhead system
Electric power transmission is achieved primarily through either overhead lines (conductors supported by structures) or underground cables (insulated conductors buried in the ground). Both systems serve the purpose of transporting bulk electrical energy from generating stations to substations or load centers.
Electric power transmission is achieved primarily through either overhead lines (conductors supported by structures) or underground cables (insulated conductors buried in the ground). Both systems serve the purpose of transporting bulk electrical energy from generating stations to substations or load centers.
L=2╧А╬╝0тАЛтАЛln(rDтАЛ) тАФ Inductance per unit length for overhead lines
C=ln(R/r)2╧А╧╡тАЛ тАФ Capacitance per unit length for underground cables
Overhead systems utilize air as an insulator and are suspended by towers or poles, making them cost-effective for long-distance, high-voltage transmission. Underground systems utilize specialized insulation materials like cross-linked polyethylene (XLPE) or oil-impregnated paper to contain the electric field within the cable, allowing power transport in dense urban areas where overhead lines are impractical.
Overhead lines are preferred for long-distance, high-voltage transmission due to lower cost and easier fault detection.
Underground cables are chosen in congested urban areas for aesthetic, safety, and reliability reasons.
Underground cables have significantly higher capacitance than overhead lines due to the close proximity of the core and sheath.
The choice between the two depends on voltage level, environmental constraints, population density, and installation costs.
Overhead: Lower initial cost, simpler repairs, better heat dissipation.
Underground: Immune to weather/lightning, aesthetic appeal, lower right-of-way requirements.
Overhead: Exposed to environmental hazards, aesthetic concerns, right-of-way issues.
Underground: Higher installation/maintenance cost, difficult to locate faults, thermal limits.
High Voltage Direct Current (HVDC) and Extra High Voltage (EHV) long-distance grids.
Dense city power distribution networks and substation interconnects.
| Feature | Overhead | Underground |
|---|---|---|
Insulation | Air | Solid/Oil/Gas |
Cost | Low | High |
The surge impedance of overhead lines is typically 400-500 ╬й, while underground cables are much lower, around 30-50 ╬й.
Option C is the correct choice because modern grid architecture integrates both technologies based on the specific terrain and load requirement.
C is correct тАФ Electric power can be reliably transmitted using both overhead systems for long-distance transport and underground cables for urban or specialized environments.
Always remember that underground cables have much higher shunt capacitance than overhead lines, which significantly impacts long-distance underground transmission due to Ferranti effect and charging current issues.