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Attention should be paid to leakage protector when used

2018/10/24 8:07:25 Viewers:
Speaking of leakage protector should be familiar to everyone, but asked about the principle of leakage protector is not very clear, in fact, the principle of leakage protector is not complicated, is the use of overload or short-circuit power at home when the protection device, remind everyone to check the current power consumption and stop unsafe behavior of the relay Continue. Now there will be leakage protectors in the home, because more and more household appliances are used, and the use of electricity is a certain danger, we need to leakage protectors to protect us to a certain extent, then what is the principle of leakage protectors, in the use of what should be noted.

1. What is leakage protector?

Leakage protector, referred to as leakage switch, also known as leakage circuit breaker, is mainly used in equipment leakage fault and fatal personal contact protection, overload and short circuit protection functions, can be used to protect the line or motor overload and short circuit, but also under normal circumstances as a line of infrequent switching. Switch to boot.

Two. Principle of leakage protector:
The leakage protector mainly consists of three parts: the detection element, the intermediate amplification link and the operation execution mechanism. Its working principle is:

The leakage protector is installed in the line, and the primary coil is connected with the line of the grid, and the secondary coil is connected with the tripper of the leakage protector.

When the electrical equipment is in normal operation, the current in the circuit is in balance state, and the sum of the current vectors in the transformer is zero (the current is a directional vector, such as "+" in the direction of outflow and "-", and the current in the transformer is equal in magnitude, opposite in direction, and the positive and negative are offset each other). Since there is no residual current in the primary coil, the secondary coil will not be induced, and the switching device of the leakage protector is in a closed state.

When a leakage occurs in the shell of the equipment and someone touches it in time, a shunt will occur at the fault point. The leakage current will return to the neutral point of the transformer (not through the current transformer) through the human body-earth-work grounding, resulting in the imbalance of the current (the sum of the current vectors is not zero), and a coil will be left. Residual current. Therefore, the secondary coil will be induced, when this current value reaches the limit of the leakage protector action current value, automatic switch tripping, cut off the power supply.

Three. Points for attention in leakage protector:

1. Leakage protector is suitable for low-voltage distribution system where neutral point of power supply is directly grounded or grounded by resistance or reactance. For power source neutral grounding system, leakage protector is not suitable. Because the latter can not constitute a leakage electrical circuit, even if a grounding fault occurs, resulting in greater than or equal to the rated action current of the leakage protector, the protector can not act in time to cut off the power supply circuit; or rely on the human body to connect the fault point to constitute a leakage electrical circuit, to promote the leakage protector action, cut off the power supply back. The road. But this is not safe for the human body. Obviously, it is necessary to have the condition of grounding device. When the leakage current of electrical equipment occurs, and when the leakage current reaches the action current, it can immediately trip within 0.1 seconds, cutting off the main circuit of power supply.

2. The neutral line N of the leakage protector to protect the line must pass through the zero sequence current transformer. Otherwise, when it is connected, there will be an unbalanced current which makes the leakage protector malfunction.

3, zero protection line (PE) is not allowed to pass zero sequence current transformer. When the protection line (PE) passes through the zero-sequence current transformer, the leakage current passes through the PE protection line and then passes back through the zero-sequence current transformer, resulting in the current cancellation, and the leakage current value can not be detected on the transformer. When a fault occurs, the leakage protector will not act and will not protect.

4. The working neutral line of the control loop can not be repeatedly grounded. On the one hand, when grounded repeatedly, part of the working current will return to the neutral point of the power supply through repeated grounding under normal working conditions, and unbalanced current will appear in the current transformer. When the unbalanced current reaches a certain value, the leakage protector will produce misoperation; on the other hand, the leakage current on the protection line may pass through the individual line of the current transformer and return to the neutral point of the power supply, which cancels the leakage current of the transformer and makes the protector refuse to operate.

5. The neutral line N and the protective line (PE) behind the leakage protector can not be integrated into one. If the two are combined together, when leakage fault or electric shock occurs, the leakage current flows back through the current transformer, and the result is similar to case 3, causing the leakage protector to refuse to operate.

6, the lines between the protected electrical equipment and the leakage protector can not touch each other. If there is a line collision or zero-line intersection, it will immediately destroy the zero-sequence balanced current value, resulting in leakage protector maloperation; in addition, the protected electrical equipment can only be installed in parallel after the leakage protector, the connection is guaranteed to be correct, and the electrical equipment is not allowed to connect to the connection of the test button.

What is the principle of leakage protector, I believe that we all know now, leakage protector can be in the event of leakage fault automatically tripped off power, our safety has a great protective effect, so we must not be less in the home decoration leakage protector installation and use.