DCS system grounding resistance
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The DCS system is shielded and grounded; using a multimeter to check that the shield grounding inside the DCS cabinet is connected to the chassis grounding – is this correct? Should there be resistance between the working area and the protection area? Ultimately, it flows into a grounding electrode.
The working area and the protected area are separated and connected to separate grounding electrodes.
It is normal for them to be the same; generally, the instrument grounding and protective grounding are connected together on a single grounding bus within the cabinet, which is then connected to the electrical grounding electrode.
The entire plant is designed with equipotential grounding, and the casing ground and the shielding ground are connected to each other. Shield grounding relies on the working ground grid, while chassis grounding relies on the protective ground grid. The entire plant is designed with equipotential grounding, and these two networks are connected to each other. It is only necessary to keep the connection points of the two grounding grids as close to the ground as possible (so that the working ground is affected less). You can check HG 20513 or SH 3081 online
Similarly, all of them will eventually converge at the plant’s main grounding grid
It is recommended to review several grounding standards for the petrochemical industry.
The concept of grounding for instruments can be somewhat ambiguous. In fact, instrument cabinets typically have an instrument ground and a system ground; the instrument ground is connected to a separate grounding bus, while the system ground is connected to another grounding bus. These two buses are then connected to a ground electrode. As a result, when measuring, there is continuity, with the resistance generally being less than 4 ohms. However, in areas where the groundwater level is high, it is quite important to check whether the grounding is proper, as the resistance value can sometimes exceed 4 ohms.