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Solid system of laying underground cables has the drawback of
Much higher cost
Reduced current carrying capacity of cable
More time in laying and repair
All of above
All of above
The solid system of laying underground cables involves placing the cables in open earthenware, asphalt, or concrete troughs, which are then filled with a bituminous compound. This method has significant drawbacks including high installation and material costs, reduced current carrying capacity due to the poor thermal conductivity of the compound, and extreme difficulty in maintenance or fault location.
The solid system of laying underground cables involves placing the cables in open earthenware, asphalt, or concrete troughs, which are then filled with a bituminous compound. This method has significant drawbacks including high installation and material costs, reduced current carrying capacity due to the poor thermal conductivity of the compound, and extreme difficulty in maintenance or fault location.
I=╬гRthтАЛTcтАЛтИТTaтАЛтАЛтАЛ тАФ relationship between current and total thermal resistance
In the solid system, cables are laid in troughs filled with a bituminous insulating compound. The compound acts as a thermal insulator, preventing heat dissipation from the cable conductors to the surrounding soil. This increases the thermal resistance, effectively lowering the permissible current rating (ampacity) of the cable compared to other laying methods like direct burial or duct systems.
Solid system is rarely used in modern distribution due to maintenance issues.
The filling compound has low thermal conductivity, trapping heat.
Trough materials like earthenware or concrete are susceptible to cracking over time.
Fault location requires excavation of the entire trench area, making repairs time-consuming.
Protects cable against mechanical injury.
Provides insulation against chemical corrosion.
High initial cost of troughs and compound.
Poor heat dissipation (lower current rating).
Difficult and slow process for repairs or extensions.
Historically used for street lighting cables.
Limited use in secondary distribution circuits.
Modern alternatives like XLPE insulated cables in HDPE ducts are preferred for better thermal performance.
Option A, B, and C are all verified technical limitations of the solid system.
D is correct тАФ The solid system suffers from high costs, thermal degradation of current capacity, and slow maintenance, making all the listed options valid.
Always remember that heat dissipation is the most critical constraint in cable design; any method that adds insulation layers (like the solid system) reduces the maximum current the cable can safely carry.