Is the current in the cable shielding layer of the DCS cabinet normal?
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Is it normal to find current in the cable shielding layer of a DCS cabinet? I believe the shielding layer is connected to the working ground; charges are induced on the shielding layer and flow to the working ground, from where they eventually reach the earth. It is normal for there to be current in the working ground. Has anyone measured it on-site?
1: Is there current? What is the current strength? 2: The specifications require that \"the shielding layer is generally single-ended grounded, usually at the control room.\" Since it is single-ended grounded, no circuit will be formed; how can a circuit current exist without a circuit?
Is current detected? What is the current level? Could it be that the multimeter is giving incorrect readings? Try using another meter to take a measurement; theoretically, as mentioned above, there should be no current flow. If that really exists, then there would be multiple grounding points that are blocked, along with an induced electromotive force, and it is only in this way that a current can be generated.
Does this cable come from the electrical system or from the field instruments? If it’s powered by electricity, disconnect the grounding of that electrical supply; grounding is sufficient only in the control room. The same treatment should be applied on-site. Generally, when electricity is used, there is induced voltage, which can be very painful, so deal with it promptly
This post was last edited by yuchenchf on 2016-9-1 at 16:37. Generally, it is required that the shielding layer be grounded at a single point so that no current flows. . The presence of current may be due to two points being grounded, creating a circuit. Instead, it will interfere with the signals inside the shielding layer.
I personally think it’s normal. It’s unusual to spend so much money on installing a shielding layer only for it to serve no purpose at all. If it is necessary to make the ground wire thicker.
With single-ended grounding, no current should flow
It’s probably still a problem with the single-point grounding; check to see if there is multi-point grounding, which is not allowed
Carefully check whether the grounding is reliable. Release the current
You have a slight misunderstanding. Grounding indeed transfers the induced electricity to the earth. But this is not a continuous and stable process. So it cannot be measured using a regular meter. If it is detected, it only indicates a leakage. The insulation cover is damaged.