Should the spare core of the instrument cable be grounded?
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Regarding the grounding of the spare core wire in instrument cables: I would appreciate it if experts could share their opinions on whether this spare core wire should indeed be grounded or not Does grounding play a significant role? Does it have an impact? These are the requirements regarding the grounding of spare core wires as specified in GB50093-2013: These are the regulations on the grounding of spare core wires as outlined in the HG20513-2000 standards for the grounding design of instrument systems:
These are the requirements regarding the grounding of spare core wires as specified in GB50093-2013
I really don’t understand this; I need an expert to explain it.
It’s very simple: when strict requirements are placed on interference, the core and shielding layer of the spare cable (if it has one) are grounded at one end in accordance with the requirements for cable shielding； The HG standard means that when there is a shielding layer or metal conduit surrounding the cable, it is assumed that the cable already has good electromagnetic shielding, so there is no need to ground it. In my opinion, this has something to do with the personal preferences of the client’s boss; the contractor will surely try to slack off whenever possible, and it’s obviously better to have grounding than not.
There are usually quite a few spare core wires, and it’s quite troublesome to handle grounding in cabinet cable trays with limited space as well as on the grounding busbars. It’s also difficult to find spare core wires later on, so it seems that grounding isn’t done in most cases. So, are there any cases of interference caused by a lack of grounding? How strong is the interference generated, enough to affect the equipment inside the cabinet? I’ve never heard of any interference resulting from this. If it isn’t very effective, then what is the basis for this rule—does it come from ancient times? Those who write the guidelines haven’t actually done any research!
The specifications make it clear that when interference prevention is required, only one end of the spare core needs to be grounded. In the standard way of installing cables, they are placed in conduit channels; these conduits are usually galvanized steel tubes, while the cable trays are typically made of metal and also galvanized. Cables usually come with shielding. In my opinion, unless the area has high levels of electromagnetic interference, it’s sufficient to leave the spare core aside without grounding one of its ends
The specifications make it clear that when interference prevention is required, only one end of the spare core needs to be grounded. In the standard way of installing cables, they are placed in conduit channels; these conduits are usually galvanized steel tubes, while the cable trays are typically made of metal and also galvanized. Cables usually come with shielding. In my opinion, unless the area has high levels of electromagnetic interference, it’s sufficient to leave the spare core aside without grounding one of its ends
I am also a bit unsure regarding whether the spare core should be grounded; according to clause 11.4.2 of the \"SHT 3164-2012 Code for Design of Lightning Protection Systems in Petrochemical Instrumentation Systems\", the spare core of cables should not be grounded. It needs to be discussed further.