Is it good or bad to have repeated grounding for the distribution box and welding machine?
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Today I encountered a construction team whose electricians grounded the distribution box, but the welding machine was not grounded. When I asked about this, they said that grounding more than once is not allowed. So, what are the safety regulations in this regard? ? ? Is repeated grounding really good or bad?
This is related to the wiring of the power supply; in a five-wire power supply circuit, repeated grounding is not allowed. The so-called prohibition on repeated grounding means that after passing through the user’s leakage circuit breaker, it is not allowed for the neutral wire N to be connected again to the PE wire; in other words, this rule applies when neutral grounding protection and earth grounding protection cannot be used. In some four-wire power supply systems, to achieve the functionality of a five-wire system, the PE wire is separated before it enters the building; once inside the building, it is not allowed to connect the N wire and the PE wire together.
The three-phase power supply, distribution box, and welding machine are each grounded separately
The question posed by the original poster isn’t very clear. For a welding machine’s grounding, is it the secondary coil that should be grounded, the enclosure, or the workpiece? Furthermore, the temporary electrical system used in construction projects adopts the TN-S system; I wonder why the construction site in question uses grounding protection instead of neutral grounding protection