Copper VS Aluminium
Copper cable has higher electrical conductivity, better mechanical flexibility and generally easier termination; aluminium cable is lighter and usually more economical for large cross-sections, but requires careful sizing, jointing and termination practices. For AGL, the choice matters most for series-circuit cables, feeder cables, transformer connections and underground distribution.
At a Glance
| Parameter | Copper (Cu) | Aluminium (Al) |
|---|---|---|
| Electrical conductivity | Higher | Lower |
| Cross-section for same resistance | Smaller | Larger |
| Weight | Higher | Much lower |
| Material cost | Higher | Lower |
| Flexibility | Better | Lower |
| Mechanical strength | Higher | Lower |
| Thermal expansion | Lower | Higher |
| Corrosion considerations | Generally easier | Requires careful treatment |
| Oxide layer | Not a major termination issue | Can increase contact resistance |
| Termination | Relatively straightforward | Requires compatible terminals/lugs |
| Jointing | Easier | More demanding |
| Long-distance feeders | Good | Very attractive |
| Small AGL connections | Usually preferred | Less convenient |
| Large power cables | Effective but heavy/costly | Often economical |
| Maintenance sensitivity | Lower | Higher at joints/terminations |
Why Cable Size Differs
Copper conducts electricity better than aluminium — approximately, copper conductivity is about 1.6× aluminium conductivity. To obtain roughly the same resistance, an aluminium conductor generally needs a larger cross-sectional area than an equivalent copper conductor.
Copper
Higher conductivity → smaller conductor → smaller cable size, for the same approximate resistance.
Aluminium
Lower conductivity → larger conductor → larger cable size, for the same approximate resistance.
Aluminium's lower density means the larger conductor can still end up substantially lighter than the equivalent copper cable.
Aluminium's Biggest Advantage
For comparable electrical performance, aluminium cable can be significantly lighter than copper cable. This matters particularly for long cable runs, large feeder cables, cable trays, transportation and installation handling.
For AGL, the weight advantage has to be considered alongside cable size, installation method, bending radius and termination space.
Material Cost vs Installed Cost
Copper is generally more expensive as a conductor material, which drives higher cable cost. Aluminium is generally cheaper, which can mean a lower project cost — but total installed cost is not simply conductor price.
You also need to consider:
- Larger aluminium cable size
- Larger glands
- Larger terminals
- Special lugs
- Jointing compounds
- Installation labour
- Termination procedures
Handling Around AGL Equipment
Copper is generally easier to bend and handle, which is particularly useful around AGL transformers, light bases, junction boxes, CCR connections and tight equipment enclosures. Aluminium conductors are generally less flexible for equivalent constructions.
For compact AGL equipment connections, copper is often more convenient.
The Biggest Practical Difference
Aluminium forms an oxide layer on its surface. Aluminium termination therefore requires appropriate aluminium-compatible lugs, terminals, jointing compounds where specified, surface preparation, torque control and installation procedures. Copper is generally less demanding in this respect.
Poor aluminium termination → higher contact resistance → local heating → joint deterioration → failure. Correct termination practice is essential.
Connection Stress Over Time
Aluminium expands and contracts more than copper with temperature changes, which matters at connections: temperature cycling causes conductor expansion/contraction, which creates connection stress and potential contact deterioration. Correct termination design and torque are particularly important for aluminium conductors.
Cable in the Constant-Current Circuit
AGL series circuits follow a special architecture: CCR → series cable → isolation transformer → fixture → isolation transformer → fixture → and so on. The cable is part of a constant-current series circuit, so selection should consider:
- Conductor resistance
- Voltage drop
- Cable insulation
- Current rating
- Environmental conditions
- Mechanical protection
- Installation method
- Circuit length
- Fault conditions
- Compatibility with connectors and transformers
You should not select AGL series-circuit cable solely based on ampacity.
Resistance and Circuit Length
Higher resistance produces greater voltage drop for a given conductor length and current. Copper's lower resistivity gives it an advantage: lower resistance → lower voltage drop. Aluminium's higher resistance means higher voltage drop for the same conditions.
For long AGL circuits, voltage drop and total circuit impedance therefore need to be checked during design.
What a Correct AGL Cable Selection Weighs
For a series circuit, cable selection should weigh current capacity, resistance, voltage drop, insulation, mechanical strength, installation method, termination and environmental conditions together.
The correct cable is the one that satisfies the complete design requirement, not simply the one with the lowest price.
Copper vs Aluminium in AGL Applications
| Application | Copper | Aluminium |
|---|---|---|
| Short fixture connection | Excellent | Less convenient |
| Isolation transformer connection | Excellent | Possible with suitable termination |
| CCR internal wiring | Excellent | Less common |
| Long feeder | Good | Very attractive |
| Large underground feeder | Good | Often economical |
| Flexible equipment connection | Preferred | Less suitable |
| Small cross-section | Preferred | Less advantageous |
| Large cross-section | Expensive/heavy | Cost/weight advantage |
Actual project specifications may mandate one conductor material.
Copper vs Aluminium Jointing Process
Copper jointing
Compatible connector → crimp/termination → joint. Generally straightforward.
Aluminium jointing
Surface preparation → compatible connector → jointing compound if specified → correct crimp/torque → joint. Requires more attention to installation quality.
Oxide Layers & Galvanic Risk
Copper and aluminium behave differently in corrosive environments. Aluminium can develop a protective oxide layer, but that oxide is electrically problematic at contact surfaces. Also, when copper and aluminium are directly connected, galvanic corrosion can become a concern under suitable environmental conditions.
Cu-to-Al transitions should use connectors specifically designed and approved for the combination. Don't simply connect a copper conductor to an aluminium conductor with an ordinary connector.
Maintenance Sensitivity
Copper
Usually more forgiving:
- Easier visual assessment
- Easier termination
- Less sensitivity to termination practices
Aluminium
Requires greater attention to:
- Terminal tightness
- Oxidation
- Joint condition
- Correct connector type
- Thermal cycling
This is particularly important in long-term underground installations.
Tests Apply Regardless of Conductor
Cable conductor material doesn't eliminate the normal electrical tests. Depending on project requirements, tests may include:
- Continuity
- Insulation resistance
- Conductor resistance
- High-voltage/dielectric testing where applicable
- Sheath testing where applicable
- Phase/polarity checks for applicable circuits
- Joint/termination inspection
Cable material is a design characteristic; electrical tests verify the installed cable system.
When to Choose Which
Choose copper when you prioritize
- Compact cable size
- Flexibility
- Easier termination
- Small equipment connections
- High mechanical robustness
- Simpler installation
Aluminium becomes attractive when you prioritize
- Low cable weight
- Large cable sizes
- Long cable runs
- Material cost reduction
- Large feeder applications
What You Should Not Assume
A complete comparison should include cable + connectors + glands + lugs + joints + installation labour + maintenance + voltage drop + service life. A cheaper conductor can become expensive if the termination system is poorly designed.
Easy Memory
Think: Copper
Conductive + compact + flexible + easy termination
Think: Aluminium
Light + economical + larger size + more termination care
Which Conductor Applies Where?
Copper is generally preferred where compact size, flexibility and easy termination are important; aluminium is attractive for larger and longer cable runs where weight and material cost are significant.
For an AGL series-circuit installation, the final selection should be based on current rating, circuit resistance/voltage drop, insulation, mechanical requirements, installation method, connector/termination compatibility and applicable project standards — not conductor cost alone.
Engineering & Expert Notes
Terminations Decide Aluminium's Reliability
TerminationUse connectors and compounds approved for aluminium and follow the manufacturer's tightening practice. Poor terminations cause most problems.
Compare on Installed Cost and Voltage Drop Together
SelectionLarger cross-section for the same duty changes duct size, bending and handling. Include these in the comparison.
Protect Joints From Moisture in Either Metal
EnvironmentCorrosion at joints damages both. Specify sealing and check it after installation.
Re-Check Connections After Thermal Cycling
MaintenanceSome connections loosen after heating and cooling. Plan a follow-up check.
Frequently Asked Questions
Not necessarily on a total installed basis. Aluminium's material cost is lower, but larger cable size, larger glands and terminals, special lugs and more demanding installation labour can offset the saving.
Not with an ordinary connector. Cu-to-Al transitions should use connectors specifically designed and approved for the combination, due to galvanic corrosion risk.
Aluminium forms an oxide layer that can increase contact resistance if not properly prepared, and it expands/contracts more with temperature, which stresses connections. Both call for aluminium-compatible lugs, correct surface prep and torque control.
Copper is generally preferred for compact equipment connections due to flexibility and easier termination; aluminium can be attractive for long feeder runs. The final selection should be based on the complete circuit design, not cable cost alone.
No. Continuity, insulation resistance, conductor resistance and other applicable tests apply to the installed cable system regardless of conductor material.
It's possible with suitable termination practice, but copper is generally the more straightforward and preferred choice for these compact, equipment-side connections.
Governing Documents
For an actual airport project, verify the current applicable editions of the relevant standards and the project's cable/conductor specification before using this comparison for project design.
FAA AC 150/5345-7 (L-824 Cable)
Specification for underground airport-lighting cable, including conductor, insulation and construction requirements.
Applicable IEC Cable & Connector Standards
Cover conductor construction, insulation, testing and Cu/Al-compatible connectors where specified for the project.
Project / Client Cable Specification
Many airport projects mandate a specific conductor material for series-circuit and feeder cables — always confirm before design.
Final Engineering Note
Conductor choice should follow current rating, voltage drop, insulation, mechanical and termination requirements together — not conductor price alone.
Copper favours compact, flexible, easy-to-terminate connections; aluminium favours large, long feeder runs where weight and cost dominate — but only with disciplined termination practice.
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