Fretting Wear Behaviors of Aluminum Cable Steel Reinforced (ACSR) Conductors in High-Voltage Transmission Line

Evolution of Properties of High-Strength and High-Mg-Content CuMg Alloys After Being Subjected to Single Operation 50% Deformation in Hot and Cold Upsetting Tests

Since most hot and cold metal-forming processes originate from various casting processes, it is important to test their susceptibility to the deformation of new materials. Cast rods of CuMg alloys with a Mg content of 2, 2.4, 2.8, 3, 3.2, 3.6, and 4 wt.% were obtained in the continuous casting process with pure copper as a reference material in order to obtain information on the material's ability to withstand 50% deformation. The materials in the as-cast state were subjected to solutioning, cold drawing, and recrystallization. After each process, samples were taken and subjected to upsetting tests with 50% deformation applied in a single operation. Additionally, materials in the as-cast state were subjected to upsetting tests at 700 °C. The hardness and electrical conductivity of each sample were analyzed. Selected samples were subjected to microstructural analysis. The obtained results show an increase in hardness from 46 HB to 90-126 HB, and a further increase to 150-190 HB with a quasi-linear decrease of electrical conductivity, which proved the influence of solid-solution and strain hardening, respectively. The microstructural analysis proved that such deformation does not cause microcracks. Furthermore, in the case of CuMg up to 3 wt.% of Mg, the alloying additive completely dissolved after solutioning.

Characteristics of Heat Resistant Aluminum Alloy Composite Core Conductor Used in overhead Power Transmission Lines

The heat resistant aluminum alloy wire composite material core conductor (ACCC/HW) which was used in overhead transmission lines is developed and studied in this work. The composite material core is carbon fiber/glass cloth reinforced modified epoxy resin composite. Tensile stress tests and stress-strain tests of both composite core and conductor are taken at 25 °C and 160 °C. Sag test, creep test and current carrying capacity test of composite conductor are taken. The stress of composite conductor are 425.2 MPa and 366.9 MPa at 25 °C and 160 °C, respectively. The sag of conductor of 50 m length are 95 mm, 367 mm, and 371 mm at 25 °C, 110 °C, and 160 °C, respectively. The creep strain are 271 mm/km, 522 mm/km, and 867 mm/km after 10 years under the tension of 15% RTS (Rated Tensile Strength), 25% RTS and 35% RTS at 25 °C, and 628 mm/km under 25% RTS at 160 °C, according to the test result and calculation. The carrying capacity of composite conductor is basically equivalent to ACSR (Aluminum Conductor Steel Reinforced). ACCC/HW is suitable in overhead transmission lines, and it has been used in 50 kV power grid, according to the results.

Research on Failure Mechanisms of Broken Strands of Jumper Wires for EHV Transmission Lines in Strong-Wind Areas

The jumper wires of an extra-high voltage (EHV) transmission line in strong-wind areas in Northwest China frequently break down. We installed some acquisition devices to collect the data of the jumper wires and wind speed in the fault area of one 750-kV transmission line. We also developed a swing simulation machine based on the collected data. The machine could simulate the swing condition of the jumper wires under various wind speeds. We analyzed the broken aluminum wires obtained from the simulation experiment of jumper wires. Yield lines appeared on the surface of the broken aluminum wires in the simulation experiment. Proliferation of dislocation and grain deformation occurred in the broken aluminum wires using transmission electron microscopy observation. The results show that the aluminum wires in the experiment under a Level-6 wind and above were in a full yield state and demonstrated strain-fatigue failure condition. The fracture of the broken aluminum wires showed distinct strain-fatigue fracture characteristics using the scanning electron microscope fracture morphology analysis. From the combination of the abovementioned research, we conclude that the failure mechanism of the broken strands of the jumper wires of the EHV transmission line in the strong-wind area is mainly a strain-fatigue failure mechanism.