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Main drawback of underground system over overhead system is
Exposure to lightning
High initial cost
Exposure to atmosphere hazards
Inductive interference between power and communication line
High initial cost
The main drawback of underground (UG) cable systems compared to overhead (OH) lines is the significantly high initial capital investment required for excavation, cable construction, insulation, and protective shielding. While UG systems offer better aesthetics and immunity to atmospheric hazards, the cost of installation and repairs is often several times higher than that of overhead lines.
The main drawback of underground (UG) cable systems compared to overhead (OH) lines is the significantly high initial capital investment required for excavation, cable construction, insulation, and protective shielding. While UG systems offer better aesthetics and immunity to atmospheric hazards, the cost of installation and repairs is often several times higher than that of overhead lines.
CUGтАЛтЙИ(5тИТ10)├ЧCOHтАЛ тАФ Represents the approximate ratio of initial capital cost between Underground and Overhead systems
The high cost is attributed to the complex manufacturing of multi-layer insulated cables (conductor, dielectric, metallic sheath, bedding, armouring, and serving), the expensive labor-intensive process of trenching and laying pipes, and the difficulty of locating and repairing faults. In contrast, overhead systems use air as the primary insulation and require minimal supporting structures, leading to a much lower initial cost.
Underground cables require extensive insulation (paper, oil, or XLPE) to prevent dielectric breakdown.
Overhead lines use ambient air as the primary insulator, which is cost-effective.
Fault localization is easier and faster in overhead lines compared to underground cables.
Underground systems are immune to lightning strikes and wind damage, providing superior reliability in high-density areas.
Aesthetically superior
Less prone to environmental hazards (lightning/wind)
Reduced risk of accidents and public interference
High initial cost
Difficult fault location and repair
Limited current carrying capacity due to poor heat dissipation
High-density urban areas
Areas with severe weather conditions
Under river/sea crossings
| Feature | Underground | Overhead |
|---|---|---|
Initial Cost | Very High | Low |
Repair Ease | Difficult/Slow | Easy/Fast |
Option A is incorrect because underground systems are shielded from lightning.
Option C is incorrect because underground lines are protected from atmospheric hazards like dust, ice, and storms.
Option D is an issue, but is mitigated by proper shielding and cable design, whereas cost is the primary barrier to universal adoption.
B is correct тАФ High initial cost is the primary disadvantage due to complex insulation and excavation requirements.
Always remember that in electrical design, there is a trade-off between reliability (UG) and economic viability (OH).