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I am currently managing the construction of a 21-story high-rise building. After reviewing the construction drawings, I found that the main incoming switch used by the designer in the power distribution box is mostly a 4P switch, while the dual power supplies below the main switch are 3P. Some people say that the main switch should not break the neutral line, otherwise poor contact will easily electrify the neutral line, causing the single phase to become 380V, which will burn the equipment in the branch circuit. I am very worried about this. Please give me some advice on this issue. Should I break the neutral line on the main circuit?
If leakage protection is provided. Others are rare
Dual power switching is 4P. Haven't seen much else
The main switch is the incoming line switch, and cutting off the neutral line is just to ensure safety.
The main switch should be 4P. According to what you said...there is no place to use the 4P switch? ;P From a design perspective, this should be fine. For a system, it is best to use a 4P switch from the main incoming line to ensure the independence of the entire system. As for the use of 3P switches for dual power supplies, it is worth discussing. . There are two situations: 1. If it is a double circuit (introduced by the same level substation), the problem is not big. 2. If it is a dual power supply (the upper level substation is two completely different power sources), the problem is more serious, and there are major safety hazards. . In the event of a fault, the 2-way incoming cable may become a tie line, and there is also the possibility of circulating current! ~!
I didn't pay much attention to this problem. I think it would be ok to use 4P with dual power supplies.
I think the dual power supply should use 4P. Assume that the other power supply of the dual power supply is taken from the generator. At this time, the problem is big. The electricity from the generator circuit will enter the other transformer through the N line, thus generating high voltage on the high-voltage side of the transformer. If someone happens to repair the transformer at this time, the problem will be big.
The dual power supply should use 4P.