金属护套接地失效时电缆支架对电缆电气性能影响

Effect of Cable Bracket on Electrical Performance of Cable when Grounding of Metal Sheath Fails

通过建立用于对比的二维和三维电缆模型,用有限元静电场方法分析了两种模型下不同电缆支架对电缆各组成部分的电位和电场分布的影响。对比结果表明,二维电缆模型使电缆支架无限长的做法是错误的,同时也自证了三维模型的客观准确。金属护套接地失效时,其上感应电压相当大,支架材质影响甚微;复合材料电缆支架会造成电缆外护套压降超过其绝缘水平;不同支架材质,外护套中电场强度畸变严重的位置也不同;钢结构支架会造成外护套中电场强度异常增大,严重危及电缆的安全。复合材料电缆支架的综合性能优于钢结构电缆支架。

This paper establishes two-dimensional and three-dimensional cable models for comparison.The effects of different cable brackets on the potential and electric field distribution of each component of the cable were analyzed by the finite element electrostatic field method.The comparison results show it is wrong for the two-dimensional cable model to make the cable bracket infinitely long.It also proves the accurate objectivity of the 3D model.When the metal sheath has failed to ground,the induced voltage on it is quite large,and the material of the bracket has little influence.Composite cable bracket will cause the voltage drop across the cable sheath to exceed its insulation level.The material of the bracket is different,and the position where electric field strength is severely distorted is different,too. The steel structure bracket will cause an abnormal increase in the electric field strength in the outer sheath,which seriously jeopardizes the safety of the cable.The composite cable bracket has better overall performance than the steel cable bracket.