Urgently need help with issues regarding the shielding layer of instrument cables
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I would like to ask the experts: When leading the instrument cable to the DCS cabinet, is it better to directly braid its shielding layer and connect it to the working ground bus?； Should we connect the shielding layer of each cable to a terminal, and then cross-connect these terminals to the working ground busbar (in which case each cable’s shielding layer would require its own terminal), or should we do something else? Which of the two approaches is better? Or which one is more standardized?
According to the standards, the first method is the correct one; it’s also more convenient. Connecting the terminals to the ground requires no additional steps, and the result is the same. However, this approach is troublesome and not aesthetically pleasing
Which specification does the expert upstairs refer to? In the \"Code for Grounding of Chemical Process Instruments\" HG/T 20513-2000, it is specified that in the field wiring box, the shielding layer should first be connected to the terminals and then bonded together, with no working ground busbar provided within the field wiring box. See page 263 of this specification: Figure 5.1.5.
The main shielding is connected directly by braiding to the grounding bar; the secondary shielding is connected to the grounding terminal only when grounding is required, after which the terminal leads are connected to the grounding bar.
With the first method, the shielding layers of multi-core cables are simply braided together; several cables can be grouped together and connected directly to the bus bar.
“With the first method, the shielding layers of multi-core cables are simply braided together; several cables can be grouped together and connected directly to the busbar. Isn’t this approach not very standard? Because when there are many cables, each with its own shielding layer, it’s difficult to braid all those shielding layers together. And if all the shielding layers are connected to the terminals, and those terminals are then bridged to the ground busbar, it will be very neat. I would appreciate further guidance from those who are more experienced.
It is a standard practice to connect the shielding layer of each cable to terminal blocks, and then to cross-connect these terminals to the working ground busbar.
DCS cabinets typically have two busbars: one for shielding grounding and one for instrument operation grounding. The procedure involves connecting the shielding layer of each cable to terminal blocks, then bridging these terminals to the busbars inside the cabinet. Finally, the grounding wires of each cabinet are connected from the busbars to the operation grounding assembly board
That approach is more standardized; please advise!
What I saw in the cabinets was that bunched grounding wires led off from the main cable, but I also noticed that some cabinets had separate grounding terminals. It seems there is no uniform approach to this; different situations require different solutions. Could someone explain this?
I would appreciate it if someone could give me some guidance by analyzing the advantages and disadvantages of these two approaches. Thank you.
I would appreciate it if someone could give me some guidance by analyzing the advantages and disadvantages of these two approaches. Thank you.
Take a look at the post at http://bbs.hcbbs.com/thread-394060-1-1.html; it will be helpful to you.
Which of the two approaches is better? Or which one is more standardized?
What my friend on the 8th floor said makes sense; generally it is like that
It’s not necessary to use the braiding method; if there are too many cables, they can end up looking messy and unattractive. Instead, we usually leave a small section of the cable’s shielding layer, solder it together with a 4-square-millimeter wire, and then connect it to the ground wire, which results in an orderly and neat arrangement. Because there is an additional step from the cabinet terminals to the terminal block, which is also troublesome.