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Transmission and distribution of electrical power by underground system is superior to overhead system in respect of
Appearance and public safety
Maintenance cost
Failure and accidents
All of above
All of above
Underground transmission systems are considered superior to overhead lines in urban environments due to the complete elimination of exposure to weather, improved aesthetics, and higher public safety standards. While they involve significantly higher capital and maintenance costs, they offer better reliability in adverse weather and reduced risk of electrical accidents compared to overhead systems.
Underground transmission systems are considered superior to overhead lines in urban environments due to the complete elimination of exposure to weather, improved aesthetics, and higher public safety standards. While they involve significantly higher capital and maintenance costs, they offer better reliability in adverse weather and reduced risk of electrical accidents compared to overhead systems.
CcableтАЛ=ln(D/d)2╧А╧╡0тАЛ╧╡rтАЛтАЛ тАФ represents the capacitance of an underground cable, which is significantly higher than overhead lines, leading to charging currents.
The underground system utilizes insulated power cables buried in ducts or direct-buried trenches. Because the cables are shielded and insulated from the environment, they are immune to lightning strikes, wind, or tree contact, which are common failure points for overhead lines. However, the maintenance process is more complex because it requires specialized equipment and underground access to locate and repair faults.
Underground cables are protected from lightning, wind, and storm damage.
Elimination of overhead conductors provides a major aesthetic benefit for cities.
Accident risk is minimized as conductors are enclosed in earthed metallic sheaths.
The cost of insulation and burial typically makes underground systems 5 to 10 times more expensive than equivalent overhead lines.
Enhanced public safety due to insulation.
Immune to atmospheric hazards (lightning, storms).
Improved aesthetics (no clutter).
No interference with communication lines.
Extremely high initial capital cost.
Difficult and expensive fault location and repair.
High capacitive charging current leads to large dielectric losses.
Limited heat dissipation capability compared to air-cooled overhead lines.
High-density urban load centers.
Airport runways and vicinity.
Crossings of rivers, railway tracks, or busy roads.
Substations where space for overhead conductors is constrained.
| Feature | Underground | Overhead |
|---|---|---|
Initial Cost | Very High | Low |
Maintenance | Difficult | Easy |
Charging current is a critical technical parameter for underground systems because IcтАЛ=╧ЙCV.
The correct answer is D as underground systems offer better safety, reduced failure rates from external environment, and better appearance.
D is correct тАФ Underground systems provide superior aesthetic, safety, and reliability characteristics at the expense of higher capital costs.
In exams, remember that while underground systems are 'superior' in safety and aesthetics, they are economically inferior; always clarify the context of the question.