1.in the lighting circuit in order to reduce the cost of the project, usually choose 1P circuit breaker, need to pay attention to the superior circuit breaker must have leakage trip function, must cut off the superior power supply;
2. Power maintenance in order to prevent the live line and the zero line is connected to the accident (when the live line and the zero line is connected to the 1P disconnect the zero line and did not disconnect the live line), can be used 1P+N short circuit device, that is often said DPN circuit breaker.
3. For the circuit breaker housing of the same size, there is a difference between 1P and 1P+N, the former has a higher breaking capacity than the latter under the state of short circuit accident. Therefore, it is recommended to use 2P circuit breaker for the more important circuit and frequent maintenance and operation circuit in the project, but the cost is higher.
In addition: 1P, 2P for single-phase, 3P, 4P for three-phase.
When it is zero protection, only 1P, 3P can be used; When it is a protective grounding, it is best to use 2P, 4P.
1P+N: the protector is only installed on the phase line, and the phase line is disconnected at the same time when the action is taken.