Regarding the shield grounding of cables in the instrument junction box
Thread Content
https://bbs.hcbbs.com/forum.php?mod=image&aid=1851676&size=300x300&key=90c7d4f2ddce4fda&nocache=yes&type=fixnone As shown in the figure, these are the specifications for the shielded grounding of branch cables and main cables within the junction box. For the branch cables that go to the site and the main cables that go to the control cabinet, their shields are connected together inside the junction box. Is it still necessary to provide shield grounding on the other ends of these two types of cables? In actual on-site construction, is the shielding usually connected in accordance with these specifications? We generally provide shielding grounding on one side of the control cabinet.
Is this an intermediate junction box? Just connect it before and after shielding – isn’t it illustrated quite clearly in the diagram...?
There is no problem with this diagram; it isn’t grounded at the junction box, but rather the connections are combined together before being grounded in the cabinet room. The shield connection copper plate is insulated from the meter box.
Shield grounding: first, a shield can have only one ground connection； Secondly, the grounding should in principle be installed on the side of the control room. (The “one side” here does not necessarily mean it has to be in the control room.) In the wiring shown in the diagram, the busbar is not grounded; it is actually grounded in the control room through the main cable. The function of the busbar is to \"make a connection across the enclosure.\" If the busbars in the diagram are grounded, the shielding of the main cable should not be connected to the busbars, but rather grounded separately in the control room. This approach is rarely used in current designs or specifications