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Which of the following methods is used for laying of underground cables?
Direct laying
Solid system
Draw-in-system
All of the Above
All of the Above
Underground cables are laid using different methods depending on the environment, cost constraints, and maintenance requirements. The three primary methods are Direct Laying, Solid System, and Draw-in System, each offering distinct advantages in terms of heat dissipation, protection, and accessibility.
Underground cables are laid using different methods depending on the environment, cost constraints, and maintenance requirements. The three primary methods are Direct Laying, Solid System, and Draw-in System, each offering distinct advantages in terms of heat dissipation, protection, and accessibility.
RthтАЛ=P╬ФTтАЛ тАФ Represents the thermal resistance of the laying environment affecting cable current capacity
Direct laying involves placing the cable in a trench filled with sand, offering low cost but difficult maintenance. The Solid System uses troughs filled with bitumen or asphalt to protect the cable from moisture and mechanical damage. The Draw-in System utilizes conduits or pipes buried in the ground, allowing for cable replacement or addition without digging up the entire trench.
Direct laying is the most common and economical method for rural or open areas.
Solid systems are used in congested city areas where extra mechanical protection is needed.
Draw-in systems are preferred in high-traffic urban areas for easier maintenance without excavation.
Current carrying capacity (I) is significantly affected by the laying method due to heat dissipation characteristics.
Flexibility in installation based on urban planning.
Enhanced protection against external moisture and chemical corrosion.
Scalability in Draw-in systems.
High initial cost for conduits in Draw-in systems.
Difficult fault localization in buried systems.
Potential for thermal run-away if laying depth is insufficient.
Direct burial for transmission mains.
Solid system for road crossings.
Draw-in system for municipal utility ducts.
Solid system involves placing cables in troughs made of cast iron, stone, or earthenware.
Draw-in system uses circular pipes of stoneware, steel, or plastic (PVC/HDPE).
D is correct тАФ All listed options (Direct laying, Solid system, and Draw-in system) are standard engineering practices for laying underground power cables.
Always relate the cable laying method to the current rating; e.g., cables in air (Draw-in) require different derating factors compared to direct buried cables.