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The methods used for laying of underground cables are
Direct laying
Draw in system
Solid system
All of above
All of above
The methods for laying underground cables are classified based on the environment, maintenance requirements, and cost-effectiveness. The three primary methods are Direct laying (trench burial), Draw-in system (conduit-based), and Solid system (trough-based).
The methods for laying underground cables are classified based on the environment, maintenance requirements, and cost-effectiveness. The three primary methods are Direct laying (trench burial), Draw-in system (conduit-based), and Solid system (trough-based).
RthтАЛ=2╧А╬╗1тАЛln(r1тАЛr2тАЛтАЛ) тАФ Thermal resistance of cable insulation
I=RthтАЛтЛЕRacтАЛ╬Ф╬╕тАЛтАЛ тАФ Current carrying capacity limitation
Direct laying involves placing armored cables directly in ground trenches filled with sand for thermal dissipation. The Draw-in system uses pipes or ducts to allow cable replacement without digging. The Solid system places cables in troughs filled with a bituminous compound to provide both mechanical protection and insulation against moisture.
Direct laying is the most economical method but offers the least protection.
Draw-in system is preferred in congested areas like cities for easy maintenance.
Solid system provides excellent mechanical protection against moisture and chemicals.
Cable rating depends on the thermal resistivity of the surrounding soil.
Direct laying: Low initial cost, simple process.
Draw-in system: Easy maintenance and replacement without road excavation.
Solid system: High mechanical integrity and longevity.
Direct laying: Difficult to locate faults and replace.
Draw-in system: High cost due to pipes/manholes.
Solid system: Very high labor cost and difficult to dissipate heat.
Direct laying: Open ground, rural areas.
Draw-in system: Busy urban streets, road crossings.
Solid system: Industrial plants, power stations.
| Feature | Direct Laying | Draw-in System |
|---|---|---|
Cost | Lowest | Highest |
Maintenance | Difficult | Very Easy |
Direct laying is standard for high-voltage cables laid in open terrain.
Solid system is rarely used for high-voltage transmission due to thermal limitations.
D is correct тАФ All listed options are recognized standard methods for the installation of underground cables in electrical power distribution.
When comparing cable installation, remember that as thermal resistivity of the soil increases, the permissible current carrying capacity (ampacity) of the cable decreases.