- 2080 Chaitra · 4 marks
Conductor characteristics, aluminium vs copper
Short answer
An overhead line conductor should have high electrical conductivity, high tensile strength, low weight, low cost, low thermal expansion, corrosion resistance, and sufficient diameter for corona limitation. Aluminum (as ACSR) is lighter, cheaper, and its larger diameter reduces corona, but has lower tensile strength compensated by steel core; copper has higher conductivity and strength but is heavier and costlier.
Discuss the essential characteristics of a conductor for an overhead transmission line. Compare the performance of aluminum and copper conductors in this regard.
An overhead line conductor should have:
- High electrical conductivity (low resistivity), for low losses and voltage drop.
- High tensile strength, to support long spans and wind and ice loads.
- Low weight per unit length (low density), for less sag and lighter towers.
- Low cost and easy availability.
- Low coefficient of thermal expansion, so that sag changes little with temperature.
- Resistance to corrosion and weather.
- A large enough diameter to limit corona at high voltage.
- Easy jointing, and good resistance to fatigue and vibration.
Aluminium vs copper
| Property | Aluminium | Copper |
|---|---|---|
| Conductivity | About 61% of copper, so 1.6× the area is needed | Highest (reference) |
| Density | 2.7 g/cm³, about half the weight for equal resistance | 8.9 g/cm³, heavy |
| Tensile strength | Low; reinforced with steel (ACSR) | High |
| Diameter for equal resistance | About 1.26× larger, so less corona | Smaller |
| Thermal expansion | Higher, so more sag change | Lower |
| Cost | Cheaper and stable | Costly |
| Jointing | Needs special compression joints | Easy |
Aluminium (as ACSR or AAAC) is preferred for overhead transmission. It is lighter and cheaper, and its larger diameter reduces corona. The steel core of ACSR makes up for its low strength. Copper is used mainly where space is limited (cables, substations).
✓ Answer checked by Claude Opus 5.5 (high effort)
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