Life is getting more and more progress, and everyone's pursuit is getting higher and higher. However, no matter how we pursue it, the first thing to ensure is our safety. Speaking of safety, electricity safety is also very important. Therefore, the leakage protector that came into being can be said to be in the limelight. Do you know the classification of leakage protectors?

Classification of leakage protectors

Leakage protectors can be classified according to their protection function, structural characteristics, installation mode, operation mode, number of poles, action sensitivity and so on. Here, it is mainly described according to its protection function and use, which can be generally 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 earth leakage protection relay consists of a zero sequence transformer, a release and an auxiliary contact for outputting signals. It can be used as the general protection of low-voltage power grid or as the monitoring protection of leakage, grounding or insulation of main road with high-current automatic switch.

When there is leakage current in the main circuit, because the auxiliary contact of the main circuit switch and the release are connected in series to form a circuit, the auxiliary contact connects the release and disconnects the air switch and AC contactor. , causing it to trip and cut off the main circuit. The auxiliary contact can also be connected with an acousto-optic signal device to send out a leakage alarm signal to reflect the insulation status of the line.

2. Leakage protection switch refers to a switching element that can turn on or off 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 turn on or off the main circuit according to the judgment result. It can be combined with fuse and thermal relay to form a fully functional low-voltage switching element.

At present, this form of leakage protection device is the most widely used, and the commonly used leakage protection switches in the market are divided into the following categories according to their functions:

(1) only has the function of leakage protection and power failure, and it must be used with protective elements such as fuses, thermal relays and overcurrent relays.

(2) At the same time, it has overload protection function.

(3) It has both overload and short-circuit protection functions.

(4) It also has short-circuit protection function.

(5) It has the functions of short circuit, overload, leakage, overvoltage and undervoltage.

3. 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 its leakage current is 6 ~ 30 mA, so it has high sensitivity, and is often used for the protection of hand-held power tools and mobile electrical equipment, as well as in civil places such as homes and schools.

Working principle of leakage protector

(1) When electric equipment leaks, there are two abnormal phenomena:

First, the three-phase current balance is destroyed and zero-sequence current appears;

Second, under normal circumstances, the uncharged metal shell appears voltage to the ground (under normal circumstances, the metal shell and the ground are at zero potential).

(2) The function of zero-sequence current transformer The leakage protector obtains abnormal signals through the detection of current transformer, which are converted and transmitted by the intermediate mechanism to make the actuator act and cut off the power supply through the switching device. The structure of current transformer is similar to that of transformer, which consists of two mutually insulated coils wound on the same iron core. When the primary coil has residual current, the secondary coil will induce current.

③ Working principle of leakage protector The leakage protector is installed in the line, the primary coil is connected with the line of the power grid, and the secondary coil is connected with the tripping device in the leakage protector. When the electrical equipment is in normal operation, the current in the line is in a balanced state, and the sum of the current vectors in the transformer is zero (the current is a direction vector, for example, the outflow direction is+,the reflux direction is-,and the back and forth currents in the transformer are equal in magnitude and opposite in direction, and the positive and negative cancel each other out). Because there is no residual current in the primary coil, the secondary coil will not induce, and the switching device of the leakage protector is in the closed state. When the equipment shell leaks electricity and someone touches it, a shunt is generated at the fault point, and this leakage current flows through the human body. Earth? Working grounding returns to the neutral point of the transformer (without passing through the current transformer), resulting in unbalanced current in and out of the transformer (the sum of current vectors is not zero), and residual current is generated by primary coil application. Therefore, the secondary coil will sense, and when this current value reaches the action current value defined by the leakage protector, the switch will automatically trip and cut off the power supply.

Do you know the classification of leakage protectors?