| 控制电缆金属屏蔽为什么要接地 |
| 添加时间：2017/8/28 17:55:54 浏览次数： |
| 金属屏蔽层最在电缆屏蔽接地是为防止电气设备因受电磁干扰造成误动和危害，为避免电磁干扰，控制电缆的屏蔽层均应接地。 The metal shielding layer in the cable shield grounding is to prevent electrical equipment due to electromagnetic interference caused by misoperation and harm, to avoid electromagnetic interference, shielding control cable shall be grounded. 屏蔽电缆的屏蔽层两端接地使电磁感应在屏蔽层上产生一个感应纵向电流，该电流产生一个与主干扰相反的二次场，抵消主干绕场的作用，显著降低磁场耦合感应电压，可将感应电压降到不接地时感应电压的1%以下。当然屏蔽电缆的屏蔽层两端接地也存在以下两个情况： The shield cable shield grounded at both ends of the electromagnetic induction to generate an induction current in the longitudinal shielding layer, the current one opposite the main interference in the two field, the main offset around the field effect, significantly reduce the magnetic field induced voltage, the induced voltage drop to ground when the induction voltage of 1% the following. Of course, the grounding of shielding layer at the ends of shielding cable also has the following two situations: ①、当接地网上出现短路电流或雷击电流时，由于电缆屏蔽层两点的电位不同，使屏蔽层内流过电流，会引起额外的冲击或干扰电压。 When the short-circuit current or lightning current occurs on the grounding network, because of the potential difference between the two points of the cable shielding layer, the current flowing through the shield will cause additional impact or interference voltage. ②、当屏蔽层内流过电流时，对每个芯线将产生干扰信号。但对应用于继电保护和自动装置回路的屏蔽电缆，由于其输入和输出均有一端在电网的高压或超高压环境中，电磁干扰是主要因数，为防止暂态过电压，故电气继电保护和自动装置的电缆屏蔽层宜在两端接地。 When the current flows through the shield, interference signals will be generated for each core. But the shielded cable applied to relay protection and automatic device circuit, as its input and output are at one end of the power grid high voltage or extra high pressure environment, electromagnetic interference is the main factor to prevent transient overvoltage, the cable shielding layer of the electric relay protection and automatic device should be grounded at both ends. |
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