Aluminum core power cables are prone to increased contact resistance due to oxidation and corrosion in humid environments. The root cause lies in the chemical reactivity of aluminum, which rapidly forms an aluminum oxide film upon contact with oxygen and moisture in the air. Although aluminum oxide itself has protective properties, its high resistivity significantly hinders current conduction, especially at joints and terminals. The accumulation of the oxide film directly causes a surge in contact resistance, creating a risk of localized overheating and even electrical fires. Therefore, a systematic protection solution needs to be constructed from four aspects: material selection, structural design, installation process, and maintenance management.
At the material selection level, prioritizing the use of high-purity aluminum or aluminum alloys as conductor materials is crucial. Impurities such as iron and copper in insufficiently pure aluminum can damage the density of the oxide film, accelerating the electrochemical corrosion process. For example, aluminum with a copper content exceeding 0.1% corrodes more than ten times faster than pure aluminum in humid environments. Aluminum alloys, by adding elements such as magnesium, silicon, and zirconium, can not only improve mechanical strength but also optimize corrosion resistance. For example, after heat treatment, aluminum-magnesium-silicon alloys can form a stable oxide layer on their surface, effectively preventing moisture intrusion; aluminum-zirconium alloys, by increasing the recrystallization temperature, reduce the risk of oxide film rupture under high-temperature environments.
Structural design must focus on blocking humid environments. For outdoor aluminum core power cables, a double-sheath structure should be used. The inner layer should use water-resistant insulation materials such as cross-linked polyethylene, and the outer layer should be wrapped with a corrosion-resistant sheath such as low-smoke halogen-free polyolefin, forming a double barrier. At the joints, a waterproof sealing structure must be designed, such as using heat-shrink tubing and filling with waterproof adhesive, or using pre-applied waterproof joints to ensure complete isolation of moisture at the connection. For cables passing through humid soil or salt spray environments, a metal armor layer can be added to further resist mechanical damage and chemical corrosion.
Refined installation processes are the core of preventing oxidation and corrosion. Before laying the cable, the conductor surface must be thoroughly cleaned, the oxide layer removed with sandpaper or a wire brush, and conductive paste applied. The metal particles in the conductive paste can penetrate the microscopic irregularities of the contact surface, breaking down residual oxide films and forming a dense protective layer that isolates air and moisture. Direct contact between aluminum and copper should be avoided during connection, as the potential difference between them accelerates the electrochemical corrosion of aluminum. Copper-aluminum transition joints or tin plating should be used, with the tin layer acting as an intermediate medium to balance the potential. Furthermore, the torque must be controlled when tightening bolts to prevent excessive pressure from causing creep in the aluminum core and loosening of the connection.
Environmental control measures can significantly reduce the rate of oxidation and corrosion. In humid areas, such as basements and tunnels, cable trenches or cable wells should be installed, and the covers should be properly sealed to prevent rainwater infiltration. For existing cables, desiccant can be sprayed periodically, or desiccant packets can be added to the joints to absorb localized moisture. In coastal or high-salt-spray areas, outer sheath materials with salt-spray resistance should be used, and an anti-corrosion coating, such as epoxy resin or polyurethane, should be applied to the outer layer to form a physical isolation layer.
Regular maintenance and inspection are crucial for ensuring long-term stable operation. A periodic inspection system should be established, focusing on moisture-prone areas such as joints and bends. Infrared thermal imaging should be used to monitor for temperature anomalies and promptly detect signs of increased contact resistance. For joints showing signs of oxidation, they should be cleaned again and coated with conductive grease; seals should be replaced if necessary. Simultaneously, a resistance tester should be used to periodically check the line resistance. If the contact resistance exceeds 50% of the initial value, immediate action should be taken to prevent further damage.
Through comprehensive measures including material optimization, structural improvement, process control, environmental management, and maintenance upgrades, the oxidation and corrosion process of aluminum core power cables in humid environments can be effectively suppressed, ensuring that the contact resistance remains stable within a safe range and providing reliable protection for the safe operation of the power system.
