Aluminum is preferred for switchgear installation over copper due to

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Examoogle · Accepted Answer

Option D: All of above

Explanation & Concepts:
Aluminum is widely used in high-power switchgear and busbar systems because it provides the most economical balance between cost, weight, and conductivity. While copper has higher absolute conductivity, the lower cost and lighter weight of aluminum make it superior for bulk power applications.

Working Principle: The current carrying capacity of a conductor is determined by its conductivity ($\sigma$), cross-sectional area ($A$), and the allowable temperature rise. Since cost is proportional to volume, aluminum's lower density ($ho_{Al} \approx 2700 	ext{ kg/m}^3$) and lower price per unit mass mean that a larger aluminum conductor, which provides the same conductance as a smaller copper conductor, still costs significantly less.

Key Formulas: $R = ho \frac{l}{A}$ — Resistance of a conductor of length $l$ and area $A$; $I_{capacity} \propto \sqrt{\frac{\sigma}{ho_{material}}}$ — Relation between capacity, conductivity, and density

Key Points: Aluminum forms a stable, self-protecting oxide layer (Al₂O₃) that provides inherent corrosion resistance.; Copper has higher conductivity ($100\%$ IACS) compared to Aluminum ($approx 61\%$ IACS), but copper's high market price limits its use in large-scale busbar installations.; Aluminum's lower weight reduces the structural burden on insulators and mounting supports in switchgear cubicles.

Advantages: Lower initial investment costs; High strength-to-weight ratio; Good resistance to atmospheric corrosion due to passivation

Disadvantages: Higher thermal expansion coefficient than copper; Requires special jointing compounds to prevent oxidation at connection points; Lower conductivity requires larger cross-sections for the same current rating

Applications: High-voltage transmission busbars; Outdoor substations; Industrial distribution switchgear

Additional Info: Aluminum connections often require inhibitors to prevent galvanic corrosion when joined with other metals.. The 'All of above' option is valid as all listed attributes contribute to the industrial preference for Aluminum in bulk power handling.

Answer: D is correct — Aluminum is preferred in switchgear because it offers superior economic value, weight savings, and sufficient corrosion resistance for power distribution applications.

Exam Tip: Always remember that in switchgear sizing, current density limits are constrained by thermal equilibrium; aluminum's larger cross-section helps dissipate heat effectively despite lower conductivity.

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Option A: Higher conductivity

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Option B: Low cost for same current carrying capacity

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Option C: Excellent corrosion resistance

Feature	Aluminum	Copper
Conductivity	61% of IACS	100% of IACS
Density	2.7 g/cm³	8.9 g/cm³

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