Best Practices for Aluminum Alloy Cable Installation in 35KV Systems

Aluminum alloy cables have become the standard choice for 35KV and below power transmission systems due to their excellent cost performance, lightweight design and corrosion resistance. However, many premature cable failures are caused not by material defects, but by improper installation practices.

Following standardized installation procedures is critical to achieving the full 25+ year service life of aluminum alloy cables. This guide covers industry-recognized best practices for handling, laying, termination and commissioning of medium-voltage aluminum alloy cable systems.

Pre-Installation Preparation and Handling

Storage and Transportation Guidelines

Proper handling before installation prevents hidden damage that may not appear until years after energizing.

• Always store cable drums on a flat, dry surface, standing on the flange edge — never lay drums flat on the ground
• Protect cable ends with sealed end caps at all times to prevent moisture ingress into the conductor
• Avoid dropping drums or exposing cables to impact, which can cause hidden insulation damage
• For outdoor storage, cover drums with waterproof sheeting and avoid prolonged direct sunlight exposure

Pre-Installation Inspection

Before pulling any cable, perform these basic checks:

• Verify cable specifications, voltage rating and conductor size match the project design
• Inspect the outer jacket for visible cuts, abrasions or damage from shipping
• Conduct an insulation resistance test with a megohmmeter to confirm no moisture penetration
• Confirm all installation tools, connectors and accessories are rated for aluminum alloy conductors

Cable Laying and Pulling Best Practices

Trench and Conduit Preparation

For direct burial 35KV installations:

• Maintain a minimum trench depth of 0.7 meters for general areas, 1.0 meters under roadways
• Remove all sharp rocks and debris from the trench bottom, and add a 50–100mm layer of fine sand or screened soil
• Use cable warning tape 200–300mm above the cable to alert future excavation crews
• For conduit installations, ensure all duct ends are deburred to prevent jacket damage during pulling

Pulling Force and Bend Radius

Aluminum alloy conductors are more flexible than pure aluminum, but still require careful pulling to avoid damage.

• Maximum pulling tension: Do not exceed 27 N per mm² of conductor cross-sectional area
• Minimum bend radius: Maintain at least 12x the cable outer diameter for static bends, 20x for dynamic pulling bends
• Use proper cable lubricant for long pulls to reduce friction and jacket wear
• Pull from the reel end, never push cable into conduit from both ends
• Use a tension meter for long pulls to avoid exceeding safe limits

Separation and Clearance

• Maintain minimum separation between power cables and low-voltage control cables to avoid electromagnetic interference
• Provide adequate spacing between parallel cables to ensure proper heat dissipation
• Follow local electrical codes for clearances from water lines, gas pipes and other underground utilities

Termination and Connection Quality

This is the single most common failure point for aluminum alloy cable systems. Poorly made connections cause overheating, oxidation and eventual system failure.

Use Rated Aluminum Connectors

Always use connectors specifically designed and tested for aluminum alloy conductors:

• Bi-metallic lugs are required for aluminum-to-copper transitions to prevent galvanic corrosion
• Connectors must match the exact conductor cross-section and alloy type
• Use only UL or TÜV listed compression connectors for medium-voltage applications

Proper Termination Procedure

1. Clean the exposed conductor surface with a stainless steel wire brush to remove oxidation
2. Apply a thin, even layer of antioxidant compound immediately after cleaning
3. Use a calibrated hydraulic crimping tool with the correct die size for the connector
4. Apply crimps in the correct sequence, starting from the conductor end
5. Insulate the completed connection with heat-shrink tubing and sealing mastic to prevent moisture ingress
6. Torque all bolted connections to manufacturer specifications — never under-tighten or over-tighten

Common Connection Mistakes to Avoid

• ❌ Using copper connectors on aluminum conductors
• ❌ Skipping antioxidant compound application
• ❌ Using the wrong crimp die size
• ❌ Reusing old or damaged connectors
• ❌ Improper torque on terminal connections

Post-Installation Testing and Commissioning

Before energizing a new 35KV aluminum alloy cable installation, complete these standard tests:

1. Insulation resistance test: Use a 5KV DC megohmmeter to measure phase-to-phase and phase-to-ground resistance
2. Continuity and resistance test: Verify conductor continuity and measure DC resistance to confirm no damage during installation
3. Partial discharge test: Recommended for critical installations to detect hidden insulation defects
4. Hi-pot withstand test: Apply AC test voltage per applicable standards for the specified duration
5. Sheath integrity test: Confirm the outer jacket has no punctures or ground faults

Document all test results for future maintenance reference and warranty validation.

Ongoing Maintenance for Long Service Life

Once installed, aluminum alloy cables require minimal but regular maintenance:

• Perform annual visual inspections of accessible terminations and junction boxes
• Conduct thermal imaging scans during peak load periods to detect loose connections early
• Re-torque bolted connections after the first 6 months of service, then every 3–5 years
• Keep accurate records of installation date, test results and any maintenance performed
• Inspect cable routes after major excavation work in the area to confirm no damage has occurred

Conclusion

Aluminum alloy cables deliver exceptional value and reliability for 35KV power distribution systems — when installed correctly. Following industry best practices for handling, pulling, termination and testing will ensure your cable system provides decades of trouble-free service. Most premature failures are entirely preventable with proper training and attention to detail during installation.

If you are planning an upcoming 35KV power project, our aluminum alloy cables are available with full technical support and installation guidance. Contact our engineering team for specification assistance and project pricing.