Research on Electromagnetic Pulse Welding Conditions of Aluminum Core Wire and Copper Connecting Tube of Power Cable
Lu Zhijian1, Chang Jiang2, Bai Xiaobin2, Lu Haohe1, Yang Lanjun1
1. State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong University Xi’an 710000 China; 2. State Grid Shaanxi Electric Power Co. Ltd Baoji Power Supply Company Baoji 721000 China
Abstract：The cable connector is generally used to make hydraulic clamp pressure. Limited by the shape of the mold, the cable joints are not crimped tightly. It will produce the spring between the connectors and cable cores, forming a gap. It can cause problems such as excessive contact resistance of the cable joints, partial discharge damage to insulation, and easy pull-off. Electromagnetic welding technology can replace the traditional hydraulic clamp technique and transition clamp, lifting the mechanical properties of the cable joints, electrical performance, and reliability. Therefore, this paper conducted simulation and experimental research on electromagnetic pulse welding of 70 mm2 aluminum stranded and copper connecting tubes. Firstly, the magnetic field distribution in the working area of the field shaper was measured by the magneto-optical effect method and compared with the simulation results. Secondly, the deformation process of the outer tube was analyzed by simulation, high-speed photography, and theoretical derivation. The electromagnetic welding conditions of the cable joints were obtained. Finally, the contact resistance, tensile force, and micro-interface were tested for the electromagnetic welding joints of the cable. The magnetic field measurement results show that the magnetic field on the central axis of the field shaper is roughly in a “bell-shaped” distribution, the magnetic field is the largest at the working area, and the magnetic field decreases rapidly at the position far from the working area. The distribution is relatively even at different radial positions of the field shaper working area. The distribution of the measured axial magnetic field is similar to the simulation, and the measured magnetic field in the center of the working area is about 3.9% smaller than the simulation. The deformation process of the outer tube is simulated, measured, and theoretically deduced. The acceleration stage velocity curves of the outer tube obtained from the theoretical deduction are similar to the simulation and the measured velocity waveforms. The theoretically calculated collision speed and the measured value are within 10%, which has an approximately linear relationship with the charging voltages. The resistance of the cable joints decreases with the increase of the charging voltages. When the charging voltage is 10 kV, the resistance of the joint is 35.12 μΩ, which has met the requirements of the national standard. When the charging voltage is higher than 12 kV, the resistance of the cable joints is 25.2 μΩ, which is only 60.8% of the required value. The strength of the cable joints increases with the increase of the charging voltages. When the charging voltage is 10 kV, the tensile strength of the cable joints meets the requirements of the national standard. When the charging voltage is higher than 12 kV, the aluminum stranded wire body breaks, indicating that the strength of the electromagnetic welding joints is higher than the strength of the base metal. However, when the charging voltage exceeds 16 kV, the aluminum-stranded wire is seriously damageddue to the high-speed collision between the copper outer tube and the aluminum stranded wire. Consequently, the mechanical properties of the cable joints are sharply reduced. The test results of the micro-interface of the cable joints show that when the charging voltage is 12 kV, a continuous wave-like interface is observed on the section of the welded joints. The wave peak is approximately 20 μm, and the wavelength is around 70 μm, which has achieved the welding effect. The outer tube’s measured and calculated collision speeds are 128.9 m/s and 134.7 m/s, and the deviations from the lower limit collision speed are 5.6% and 10.3%, respectively. Therefore, the discharge energy value required for two different materials to reach the welding conditions can be well predicted, providingan effective reference for future electromagnetic welding equipment design.
路志建, 常江, 白晓斌, 陆豪赫, 杨兰均. 电力电缆铝芯线与铜连接管的电磁焊接条件研究[J]. 电工技术学报, 2023, 38(20): 5620-5633.
Lu Zhijian, Chang Jiang, Bai Xiaobin, Lu Haohe, Yang Lanjun. Research on Electromagnetic Pulse Welding Conditions of Aluminum Core Wire and Copper Connecting Tube of Power Cable. Transactions of China Electrotechnical Society, 2023, 38(20): 5620-5633.
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2023, Vol. 38 
