Leakage protector, also known as leakage switch or leakage circuit breaker, is mainly used to protect people in fatal danger from electric shock when leakage fault occurs in equipment. It has overload and short circuit protection functions, which can be used to protect line or motor overload and short circuit, and can also be used as infrequent switching and starting of lines under normal circumstances.
Classification
Leakage protector can be classified according to its protection function, structural characteristics, installation method, operation mode, number of poles and wires, action sensitivity, etc. Here it is mainly described according to its protection function and purpose. It can generally be divided into three types: leakage protection relay, leakage protection switch and leakage protection socket.
1. Leakage protection relay refers to a leakage protection device that has the function of detecting and judging leakage current, but does not have the function of cutting off and connecting the main circuit. The leakage protection relay consists of a zero-sequence transformer, a releaser and auxiliary contacts for outputting signals. It can be used in conjunction with a large current automatic switch as the total protection of the low-voltage power grid or the leakage protection of the main road, grounding or insulation monitoring protection.
When there is leakage current in the main circuit, since the auxiliary contact and the main circuit
circuit switch release are connected in series to form a loop, the auxiliary contact connects the release, disconnects the air switch, AC contactor, etc., causing it to trip and cut off the main circuit. The auxiliary contact can also be connected to the sound and light signal device to send out a leakage alarm signal to reflect the insulation status of the line.
2. The leakage protection switch refers to a switch element that can connect or disconnect the main circuit like other circuit breakers, and has the function of detecting and judging leakage current. When the main circuit has leakage or insulation damage, the leakage protection switch can open or close the main circuit according to the judgment result. It can form a fully functional low-voltage switch element with the cooperation of fuses and thermal relays.
At present, this form of leakage protection device is the most widely used. The leakage protection switches on the market are commonly used according to their functions. The following categories:
1) It only has leakage protection and power-off functions, and must be used with fuses, thermal relays, overcurrent relays and other protection elements.
2) It also has overload protection function.
3) It also has overload and short circuit protection functions.
4) It also has short circuit protection functions.
5) It also has short circuit, overload, leakage, overvoltage and undervoltage functions.
3. A leakage protection socket refers to a power socket that can detect and judge leakage current and cut off the circuit. Its rated current is generally less than 20A, and the leakage current is 6 ~ 30 mA. It has high sensitivity and is often used for the protection of handheld power tools and mobile electrical equipment and in civilian places such as homes and schools.