Is the petrochemical unit a five-line system or a four-line system?
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The motors in our units are all grounded on site and then protected back to zero. Does anyone think this is okay? The main power distribution room to the workshop power distribution room is a four-wire system.
The motors all use four-core cables, and the power distribution uses five-core cables.
The motor uses a 3+1 cable, and now the shell is grounded repeatedly!
The incoming cables of motors generally use 4-core cables, and the incoming cables of maintenance sockets and lighting systems generally use 5-core cables.
The petrochemical industry must use a TN-S grounding system, sometimes four wires, sometimes five wires, depending on whether three-phase balanced electrical appliances are used. The balanced ones are four lines, and the unbalanced ones are five lines!
study* Just look at this standard to understand! GB14050-93 "Types and safety technical requirements for system grounding"
GB14050-2008 "Types and safety technical requirements for system grounding"
Most of the chemical industry uses the TN-S grounding system. The motor uses a four-wire cable, and the motor housing is set to be repeatedly grounded. I can’t remember where there is a regulation. Electrical appliances must be repeatedly grounded before they can be put into operation.
Where can I find GB14050-2008 "Types and Safety Technical Requirements for System Grounding"?
Are there any regulations that require motors to use 4 cores? Why do we use three cores here? .
Of course, the 5-wire safety system is used, which is TN-S, which can ensure that under normal circumstances, the PE line does not carry current, so the PE line has almost zero potential.