Question regarding instrument grounding.
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Regarding the issue of instrument grounding, during an inspection by the engineering department, it was found that all instruments in our factory were not properly grounded. Upon receiving this issue, we took immediate action to address it by grounding all instruments that were under voltage, including solenoid valves as well. The grounding method involved connecting the grounding points on the instrument enclosures to grounding wires, which were then led through conduit pipes. From there, these wires were connected to the protective grounding network of the low-voltage electrical equipment at the central junction box. Each conduit pipe and each junction box had its own grounding wire. As a result, multiple grounding wires from various instruments ended up at the protective grounding point of a single low-voltage electrical device; in some cases, there were as many as 10 or 20 such wires. During the current maintenance period, the supervising party pointed out that this grounding method is incorrect; it stipulated that there should not be more than 2 grounding wires per connection point (each individual grounding bolt). The recommended approach is to connect the wire ducts in series and then connect them to the ground point. However, after checking some standards, it was found that 10.2.4 of the standards specifies that series grounding is not allowed. However, it does not specify whether multiple ground wires can be connected to the same grounding point. I’d like to ask if anyone is familiar with or knows anything about grounding, including the requirements for electrical grounding. I would like to ask whether multiple wires can be connected to the same ground point simultaneously, and if there are any relevant standards. Thank you!
If the quantity is large, a dedicated grounding bar should be installed, which is then connected to a fixed grounding point. The actual diagram looks like the one on the right, but it is not in series configuration, as each point can be grounded independently; there is no issue where a break in an intermediate node would affect the subsequent nodes.
It is not appropriate to press multiple grounding wires under the grounding bolt, as this may result in a loose connection； When there are multiple grounding wires at one location on a street, a grounding busbar or grounding plate can be used ； The opinion given by the supervision unit is also inappropriate, because if one point is not properly connected during the wiring, all subsequent points will be disconnected as well.
Why is grounding necessary? First, it’s necessary to clarify this issue: if it’s protective grounding, no grounding is required at all.
First, it’s important to understand that grounding is necessary only when it’s required. Learn about the \"HGT20513-2014 Specifications for Grounding Design of Instrumentation Systems\". What the supervisor suggested is correct. The actual wiring on site ensured that each tube was grounded, but with so many wires connected at the same point, loose connections would inevitably occur over time. When there are multiple grounding wires at one location on a street, a grounding busbar or grounding plate can be used. At the site, the wiring method proposed by the supervision unit is indeed used: the grounding wires are connected in series without being disconnected, and they are pressed together sequentially so that no disconnections occur.