冲击电场作用下屏蔽体屏蔽效能实验研究

Experimental Research of Shielding Effectiveness Against Impulse Electric Field for Shielding Enclosure

电磁屏蔽体对电力系统二次设备的冲击电场防护作用明显,其屏蔽效能的实验研究对保护小室、机箱等屏蔽体设计有指导意义。为此,搭建了一套基于光电电场传感器的冲击电场作用下屏蔽体屏蔽效能实验研究系统;比较了不同材料屏蔽体的屏蔽效能,研究了网格尺寸对金属网格屏蔽体屏蔽效能的影响;对比了不同频率下金属网格屏蔽体的屏蔽效能差异,研究了接地电阻对金属网屏蔽体屏蔽效能的影响。研究表明:金属材料屏蔽体的屏蔽效能较好;金属网格尺寸<10 cm的屏蔽体可获得>20 dB的屏蔽性能;操作波和雷电波作用下的屏蔽效能基本相同,前者略大于后者;减小接地电阻可有效提高金属屏蔽体的屏蔽效能。

Electromagnetic shielding enclosure provides significant protection for secondary devices in power system against impulse electric fields. The experimental research of the enclosure＇s shielding effectiveness （SE） can guild the shield designs of protective chambers and equipment cases. Hence, we set up an experimental system using integrated optical electric field sensors. The SE of shielding enclosure with different materials was compared; the impacts of mesh- ing size and grounding resistance on the SE of metal grid shielding enclosure were studied; the SE of metal grid shielding enclosure was compared under electric field impulses of various frequencies; influence of grounding resistance on the SE was also investigated. The results show that, compared with other materials, the shielding enclosure made of metal has much higher SE. When a metal grid shielding enclosure has meshing size smaller than 10 cm, its SE is larger than 20 dB. The SE of the metal grid shielding enclosure against lightning impulse is slightly higher than that against switching impulse, but generally the two are close. Reducing grounding resistance improves a shielding enclosure＇s SE significantly.