Now that household electricity is used, has the knife switch been eliminated? Is it necessary to use air switch instead of knife switch?

the knife and the air switch are both types of circuit breakers, which can make the circuit on and off. Both of them have their own advantages and disadvantages in the use of civil low-voltage lines. But overall, the use of knife is gradually decreasing. This is determined by their use characteristics.

the disadvantage of the knife switch is that it can only realize short-circuit protection by its own fuse, but cannot realize over-current protection.

that is to say, only when the circuit is directly short-circuited, a large short-circuit current is generated, and the fuse is blown, will the circuit be automatically cut off; However, if an overcurrent occurs (the current is large, but the fuse is not blown), the circuit will not be automatically cut off. However, over-current for a long time will accelerate the aging of household power lines due to fever, lead to lower insulation and easily cause accidents.

the air switch has both over-current protection and short-circuit protection. Therefore, the air switch is safer in use. However, because the disconnection point of the air switch is inside the switch, people cannot observe it. Therefore, electrician defines it as "no obvious disconnection point". At this time, if the air switch fails, "the external wrench is disconnected and the internal contacts are still connected (such as arc welding)" will not be found, resulting in the illusion that "the circuit has been disconnected". This is very dangerous when the circuit is overhauled.

the solution is to install a fuse in front of the open circuit. In this way, when the circuit needs to be definitely disconnected, the fuse is unscrewed to ensure that the circuit is disconnected.

so, when you have time, you don't need a knife, but you must have a fuse.