The leakage protector, also known as the leakage switch or leakage circuit breaker, is installed on the low-voltage circuit. When leakage and electric shock occur, the power supply will be automatically cut off within a limited time for protection when the working current value of the protector is reached.
The main uses of the leakage protection device are: first, to prevent electric shock accidents caused by leakage of electrical equipment and lines; second, to prevent single-phase electric shock accidents during power use; third, to promptly cut off the single-phase grounding fault in the operation of electrical equipment to prevent electrical fire leakage accidents; fourth, to prevent single-phase electric shock accidents during power use.
The leakage protector is mainly composed of three parts: detection element, intermediate amplification link and operation actuator. The detection element is composed of zero-sequence transformer, which detects leakage current and sends out signals; the amplification link amplifies weak leakage signals for different devices (the amplification part can use mechanical devices or electronic devices); after the actuator receives the signal, the main switch switches from the closed position to the open position, thereby cutting off the power supply, which is the tripping element between the protected circuit and the power grid
Knowledge point 1: leakage protector and air switch
The difference between leakage protector and air switch: the air switch will only trip when a short circuit accident or fault occurs, and the leakage protector will only trip when a person is electrocuted; the capacity of the air switch can be large or small, but the capacity of the leakage protection switch is not easy to increase, usually single-phase.
Principle difference: The leakage protector is only used to prevent people from electric shock and leakage. It does not play a protective role when the circuit is overloaded (short circuit); the air switch is used to prevent the circuit from being overloaded (some also have low voltage protection function, the principle can be imagined), it cannot protect against electric shock, but only acts as a fuse.
Therefore, the air switch and the leakage switch have different structures and principles, and the two are irreplaceable.
Knowledge point 2: Leakage protector and air switch, only install one?
In real life, there is no leakage protector, only air switch and knife switch are set, and there is actually a great safety hazard if the leakage protector is omitted.
Both the leakage protector and the air switch are protective switches. The former can monitor the leakage current of the protected line and disconnect the circuit when it reaches a certain value. The latter can monitor the large current in the circuit and will trip when the current exceeds a certain value, that is, it has the functions of short circuit and overload protection. The two have different functions respectively. If one is missing, the protection function is lost, and there are safety hazards.
Knowledge point 3: What should I do if the protector often trips?
The safest insurance method is to ask a professional electrician to help check the leakage of the household circuit. We may not know what method to use, but professionals must know that there are methods and tools. It is simple and easy, but it costs a certain amount of money.
Do not install a leakage protector only on the home bus. The wider the protection range of the leakage protector, the greater the probability and frequency of tripping. Therefore, in addition to setting up leakage protectors on the bus, places where leakage and electric shock are prone to occur are also set up. Even if there are places with leakage, there will not be a complete power outage. A simple air switch only has short circuit and overload protection functions; but there is another type that has short circuit and overload protection functions as well as leakage protection functions.
Knowledge point 4: Why is a leakage protector installed after protection zero connection (grounding)?
Protection zero connection is to connect the metal casing of the electrical equipment to the zero line of the power grid, and install a fuse on the power supply side. When the electrical equipment has a shell contact fault (a phase contacts the shell), a single-phase short circuit is formed on the relative zero line. The short-circuit current is large, and the fuse blows quickly, cutting off the power supply for protection. The working principle is to adjust the "shell collision fault" to "single-phase short-circuit fault" to obtain a large short-circuit current cut-off insurance.
However, electrical collision with the shell fault at the construction site is not very frequent, and leakage faults often occur, such as leakage caused by damp equipment, excessive load, too long lines, aging insulation, etc. These leakage current values are small and cannot be quickly cut off. In the case of long-term existence, the fault cannot be automatically eliminated. This leakage current poses a serious threat to personal safety, so it is necessary to install a highly sensitive leakage protector for supplementary protection.
Knowledge point 5: What should be paid attention to when installing a leakage protector?
The neutral line on the load side of the leakage protector shall not be shared with other circuits; when the leakage protector is marked with the load side and the power side, the wiring shall be installed according to the regulations and shall not be connected in reverse; when a leakage protector with short-circuit protection is installed, it must be ensured that there is enough arc distance in the direction of arc spray; the size of the arc distance depends on the leakage protector.
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