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The earth wire should not be of size smaller than
10 SWG copper
8 SWG copper
6 SWG copper
4 SWG copper
10 SWG copper
According to the Indian Electricity Rules and BIS standards (IS 3043), the cross-sectional area of a copper earth continuity conductor must not be less than 10 SWG (Standard Wire Gauge). This minimum size ensures that the earth path has sufficient thermal capacity to carry fault currents without melting, allowing protective devices to operate effectively.
According to the Indian Electricity Rules and BIS standards (IS 3043), the cross-sectional area of a copper earth continuity conductor must not be less than 10 SWG (Standard Wire Gauge). This minimum size ensures that the earth path has sufficient thermal capacity to carry fault currents without melting, allowing protective devices to operate effectively.
R=╧БALтАЛ тАФ Resistance of the earth conductor
Q=I2Rt тАФ Heat generated in the conductor during fault
When a phase-to-earth fault occurs, the earth wire provides a low-impedance return path for the fault current IfтАЛ. The resistance of this path is given by ReтАЛ=╧БAlтАЛ. By maintaining a minimum diameter (10 SWG), the cross-sectional area A is kept large enough to ensure ReтАЛ remains low and the wire can withstand the I2Rt heat generated during the disconnection time of the fuse or circuit breaker.
10 SWG copper wire corresponds to approximately 2.5 mm┬▓ to 3.0 mm┬▓ area.
The earth wire must be mechanically robust to prevent breakage.
Under fault conditions, the earth wire carries the full short-circuit current.
Standardization (IS 3043) ensures uniformity in earthing system design across India.
Ensures low impedance return path
Prevents structural metal parts from reaching dangerous potentials
Facilitates rapid operation of circuit protective devices
High initial material cost for thick copper conductors
Susceptible to theft in outdoor environments
Domestic wiring earthing
Industrial machinery equipment grounding
Distribution board earthing
SWG (Standard Wire Gauge) is a British standard for wire diameter; lower SWG numbers indicate larger diameters.
Using a wire smaller than 10 SWG is prohibited because the high fault current could vaporize the conductor before the breaker trips, leading to a fire hazard.
A is correct тАФ The minimum size for a copper earth continuity conductor is specified as 10 SWG to ensure safe thermal and electrical performance during fault conditions.
Always remember that lower SWG values correspond to thicker wires, while higher values mean thinner wiresтАФthis is a frequent trap in technical competitive exams.