Quality inspection of steel-cored aluminum stranded wire covers multiple dimensions, including structural dimensions, mechanical properties, electrical properties, and surface and plating quality, ensuring sufficient conductivity, tensile strength, and durability in transmission lines.
This type of inspection is conducted throughout the entire process of conductor production, grid connection acceptance, and in-service monitoring, and is a crucial link in ensuring the safe and stable operation of the power grid. The inspection is mainly based on national standards such as GB/T 1179-2017 "Round Wire Concentric Stranded Overhead Conductors" and GB/T 3428, combined with industry standards DL/T 371 series.
The main inspection items are as follows:
Structural Dimension Inspection
Measure the outer diameter of the stranded wire, the diameter of the aluminum single wire and the steel core, the pitch ratio, the number of strands, and their direction (usually the outermost layer is right-hand Z-direction).
Use micrometers, calipers, or multi-point diameter gauges to ensure compliance with design parameters.
Mechanical Performance Testing
Resolution Tensile Strength (RTS) Test: Conducted on a universal testing machine. The measured value must be no less than 95% of the nominal value, and slippage or end damage must not occur before fracture.
Stress-Strain Characteristics and Elastic Modulus: Deformation behavior during loading is recorded using an extensometer for sag calculation and tension design.
Stress Test at 1% Elongation: Evaluates the conductor's deformation capacity under long-term operating loads and is a key indicator of its mechanical stability.
Fatigue and Creep Performance: Simulates dynamic loads such as wind vibration and ice loads to verify the conductor's reliability during long-term service.
Electrical Performance Testing
DC Resistance Measurement: Measured using a four-terminal micro-ohmmeter under isothermal conditions. Used to calculate conductivity or resistivity and determine transmission efficiency.
High conductivity conductors also require AC resistance, current carrying capacity verification, and corona initiation voltage testing.
Coating and Corrosion Resistance Testing
Zinc Coating Adhesion (Wrapping Test): Tightly wrap the steel wire around a round bar for 8 turns, then unwind and rewind, checking for cracking or peeling.
Zinc Coating Weight Measurement: Use the copper sulfate etching method or weighing method to ensure compliance with corrosion resistance requirements.
Wires for special environments also require durability tests such as salt spray corrosion and stress corrosion sensitivity.
Surface Quality and Process Inspection
Visually inspect the surfaces of the aluminum wire and steel core for smoothness, cracks, burrs, oxidation, oil stains, or excessive grease.
Stretching should be uniform and tight, without loose strands or misalignment. Joint spacing should be greater than 15mm and neatly rounded.
Other Specialized Tests
Winding Test: Verify the toughness of the single wire under repeated bending to prevent breakage due to bending during construction.
Crimping quality inspection: The dimensions, gripping force, contact resistance, and internal defects (such as porosity and lack of compression) of the crimped parts of the connecting hardware are inspected.
