Join 60,000+ competitive exam aspirants
or with email
Your Cart
SubtotalтВ╣0
TotalтВ╣0
Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
Join 60,000+ competitive exam aspirants
Which type of cable is used for underground service connections?
Low tension 3.25 core cable
Low tension 3.5 core cable
Low tension 2.25 core cable
Low tension 2.5 core cable
Low tension 3.5 core cable
Low tension 3.5 core cable is the industry standard for underground 3-phase, 4-wire (3-phase + neutral) service connections. The 'half' core is designed for the neutral conductor, which is typically sized at half the cross-sectional area of the phase conductors to handle unbalanced currents in a distribution system.
Low tension 3.5 core cable is the industry standard for underground 3-phase, 4-wire (3-phase + neutral) service connections. The 'half' core is designed for the neutral conductor, which is typically sized at half the cross-sectional area of the phase conductors to handle unbalanced currents in a distribution system.
INтАЛ=IRтАЛ+IYтАЛ+IBтАЛ тАФ Neutral current in a 3-phase 4-wire system
AneutralтАЛтЙИ0.5├ЧAphaseтАЛ тАФ Standard sizing ratio for neutral core
In a 3-phase, 4-wire underground distribution system, the phase currents (IRтАЛ, IYтАЛ, IBтАЛ) flow through the three main cores. The neutral core is required to carry the return current (INтАЛ) resulting from an unbalanced load. Since the neutral wire does not need to carry the same continuous full-load capacity as the phases, using a reduced size cross-section (half-core) is cost-effective and technically sufficient for typical residential/commercial load distributions.
3.5 core cables are specifically used for 3-phase, 4-wire unbalanced systems.
The neutral conductor provides a path for return current in unbalanced star-connected loads.
Used extensively in underground LT (Low Tension) distribution service lines.
Reduces cable material costs by optimizing the neutral conductor size.
Cost-effective design due to reduced material usage for the neutral conductor.
Efficiently manages unbalanced current in low tension networks.
Limited for use in high-voltage transmission lines.
Not suitable for strictly balanced 3-phase loads where neutral current is zero.
Underground LT service mains for commercial and residential complexes.
Secondary distribution networks of power substations.
LT stands for Low Tension, generally referring to systems operating below 1kV.
Options like 3.25 or 2.25 core are non-standard designations and do not conform to standard IS (Indian Standard) cable specifications.
B is correct тАФ The 3.5 core cable is designed to provide three phase conductors and a reduced neutral conductor specifically for 3-phase, 4-wire underground distribution services.
Always remember that in distribution systems, the 'half' core refers to the neutral, which is sized to accommodate return currents from unbalanced loads, saving significant copper/aluminum costs.