开关柜工频磁场计算及壳体屏蔽效能分析

Power Frequency Magnetic Field Calculation of Switchgear and Shielding Efficiency Analysis of Enclosure

文中基于电磁场基本理论,建立了开关柜工频磁场数学模型,采用有限元法对开关柜的磁感应强度进行了计算,分析了壳体、壳体厚度和磁导率等对开关柜磁感应强度分布和屏蔽效能的影响,并研究了开关柜柜外母排长度对磁感应强度分布的影响,结果表明:开关柜外壳和隔板对工频磁场具有明显的屏蔽作用,增大壳体磁导率和厚度均可提高开关柜整体的屏蔽效能,但当壳体磁导率大于1 000和厚度超过3 mm时,屏蔽效能增长幅度较小;柜外母排长度对开关柜周围磁场分布影响较小,但对柜体顶部磁场分布的影响较大;研究可为开关柜磁场屏蔽措施的提出提供参考。

The power frequency magnetic field mathematical model of the switchgear is set up on the basis of theory of electromagnetic field in this paper. The magnetic induction intensity of the switchgear is calculated by using the finite element method(FEM). The influence of the enclosure,its thickness and magnetic permeability on the magnetic induction intensity distribution and shielding efficiency is analyzed,and the influence of the length of external busbar on the magnetic induction intensity distribution is studied. The results show that the enclosure and partition of the switchgear have obvious shielding effect on the magnetic field of power frequency. Increasing both permeability and thickness of the enclosure can improve the overall shielding efficiency of the switchgear. However,when the permeability is more than 1 000 and the thickness is more than 3 mm,the increase amplitude of shielding efficiency is small.The length of the busbar outside the switchgear has little influence on the magnetic field distribution around the switchgear,but has great influence on the magnetic field distribution at the top of the switchgear. The research can provide reference for the magnetic shielding measure of switchgear.