高压XLPE电缆平滑铝复合护套的弯曲特性及结构设计

Bending Characteristics and Structure Design of Smooth Aluminum Composite Sheath in HV XLPE Cables

近年来,频发的波纹铝护套电缆缓冲层烧蚀故障引起了国内电力行业对平滑铝护套高压交联聚乙烯(XLPE)电缆的广泛关注,其弯曲性能是限制工程应用的技术难点。该文搭建平滑铝护套XLPE电缆的四点弯曲三维仿真模型,以内聚力模型模拟胶层的力学行为,研究有/无热熔胶粘接、缓冲层厚度、非金属外护套厚度及材料、电缆径向尺寸等对平滑铝护套复合结构弯曲性能的影响。结果表明,若铝护套不与外护套粘接,其抗弯曲变形能力差,易起皱并挤压内部绝缘;粘接后形成整体复合护套,其抗弯能力与总厚度有关,其中,铝护套厚度可根据短路容量要求确定,而由外护套补足抗弯强度所需总厚度,且外护套材料弹性模量不应低于800MPa;缓冲层厚度对铝护套弯曲性能影响较小,主要从吸收绝缘热膨胀角度进行设计。基于研究结论,试制了110kV平滑铝护套XLPE电缆并通过型式试验验证。

In recent years, the ablation failures of buffer layer frequently occurred in cables with corrugated aluminum sheaths have aroused the widespread attention of the domestic power industry to the smooth-aluminum-sheathed HV XLPE cables, whose bending performance is the key for engineering application. In this paper, a three-dimensional simulation model of four-point bending of a XLPE cable with smooth aluminum sheath was built, where the cohesive zone model was used to simulate the mechanical behavior of the adhesive layer. As for the bending performance of smooth aluminum composite sheath, the effects of the hot melt adhesive, the compressible thickness of buffer layer, the thickness and material of non-metallic outer-serving, and the inner diameter of aluminum sheath were studied. The results show that if the aluminum sheath is not bonded to the outer-serving, its resistance to bending deformation is so poor that it is prone to wrinkle and so as to squeeze the internal insulation. However, an integral composite sheath can be formed after being bonded, whose bending resistance is dependent on the total thickness. The aluminum sheath thickness is designed according to the short circuit capacity requirement, and the total thickness required for the bending resistance needs to be supplemented by the outer-serving, whose elastic modulus should be no less than 800 MPa. The buffer layer has little effect on the bending performance of aluminum sheath, so its thickness can be designed mainly from the absorption of the insulation thermal expansion. Finally, an 110 kV XLPE cable with smooth aluminum sheath was trial produced and type tested.