Its application range is 50HZ AC rated voltage 380 volts and rated current 250 A. ..
Setting leakage protector in low-voltage distribution system is one of the effective measures to prevent personal electric shock accidents, and it is also a technical measure to prevent electrical fires and electrical equipment damage accidents caused by leakage. However, the installation of leakage protector does not mean absolute safety, and prevention should still be given priority in operation, and other technical measures should be taken to prevent electric shock and electrical equipment damage accidents.
1 Working principle of leakage protector
The leakage protector mainly includes detection elements (zero-sequence current transformers) and intermediate links (including amplifiers, comparators and trippers). ) and actuator (main switch).
And test elements.
Schematic diagram of working principle of leakage protector in three-phase four-wire power supply system. TA is the zero sequence current transformer, GF is the main switch, and TL is the parallel trip coil of the main switch.
Under the condition that the protected circuit works normally without leakage and electric shock, Uxie Hough's law shows that the phasor sum of current passing through the primary side of TA is equal to zero, that is, this TA.
The secondary side does not generate induced electromotive force, the leakage protector does not act, and the system maintains normal power supply.
When the protected circuit leaks electricity or someone gets an electric shock, due to the existence of leakage current, the phasor sum of each phase current flowing through the primary side of TA is no longer equal to zero, resulting in leakage current Ik.
Alternating magnetic flux appears in the iron core. Under the action of alternating magnetic flux, induced electromotive force is generated in the secondary coil of TL, and this leakage signal is processed and compared through the intermediate link.
When the preset value is reached, the shunt tripping coil TL of the main switch is energized, which drives the main switch GF to trip automatically, cutting off the fault circuit and realizing protection.
The working principle of leakage protector used in single-phase circuit and three-phase three-wire system is the same as this, so I won't repeat it here.
Question 2: What is the function of installing leakage protector at home? Your question is, can the leakage protector work only when the circuit is grounded? If that's what it means, then the answer is yes.
If you ask "household appliances must be equipped with leakage protectors to function", then the answer is "no".
Theoretically, according to the normal electricity consumption, the current flowing into the live wire is equal to the current flowing out of the neutral wire. When leakage occurs after the leakage protector, the current flowing through the live wire is equal to the current flowing from the zero line plus the leakage current. The principle of general leakage protector is to judge whether there is leakage by comparing the current difference between live wire and zero wire, which is somewhat similar to the principle of differential protection. When the live current is greater than the neutral current and exceeds the setting value of the protector, the protector trips.
After the general leakage protector is installed, if all the electrical appliances in the home have protective grounding and the electrical appliances have leakage, this situation will generally lead to frequent tripping of the leakage protector. I found that many families have such a situation, and finally there was no choice but to turn off the leakage switch.
Installing a leakage protector has the same function as grounding the electrical appliance shell, that is, it can protect personal safety when the electrical appliance leaks electricity, but their principles are different.
The principle of leakage protector has been mentioned before. The reason for grounding the electrical enclosure is to force the potential of the electrical enclosure to be the same as the ground potential. When there is leakage inside the electrical appliance, the leakage current is directly introduced into the earth through the grounding wire. In this case, even if someone touches the electrical enclosure, it is safe. But this must have a premise, that is, there must be a reliable grounding wire at home. Our household appliances generally have no grounding wire, and some people use tap water pipes as grounding wires. So many families have installed leakage protectors.
According to the working principle of leakage protector, if there is leakage behind the protector, the protector will trip. In fact, there are many slight electric leakage phenomena at home, such as washing machines, rice cookers and electric fans. Moreover, the damaged insulation layer of the wires installed in Tibet will also leak electricity. In this case, the leakage protector often trips or even cannot be turned off. Therefore, many families are often forced to quit after installing leakage protectors.
To sum up, in order to prevent electric leakage from hurting people at home, the best way is to introduce a reliable grounding wire to reliably ground the electrical enclosure that people can easily touch. The actual practice is that the socket installed at home should have three holes, and the grounding wire should be reliably connected to the above holes. However, it is necessary to increase the input of wires and introduce reliable grounding wires.
Question 3: What does the leakage protector do? What is the working principle? Leakage protector, commonly known as leakage switch, is used to prevent personal electric shock and electrical fire when the insulation of circuits or electrical appliances is damaged and short-circuited to ground. It is generally installed in the socket loop of each distribution box in the whole building and the power inlet of the main distribution box, which is specially used to prevent electrical fires. The working principle of leakage protector is:
A 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, such as the outflow direction is "+"and the backflow 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.
Question 4: What are the functions of air switch and leakage protector? The air switch plays the role of overload protection, using air as arc extinguishing medium and oil as arc extinguishing medium. The function is overload protection. For example, the instantaneous high current during short circuit can make the air switch open in less than one second without causing fire. Leakage protector is to protect people's safety. As long as the current in the line can leak to the earth through people or things to a certain value, it will trip, so that people will not get an electric shock, and opening the circuit will not protect people from getting an electric shock. The air switch should automatically turn off the switch, because the current in the circuit is too large (short circuit or excessive total power of electrical appliances may cause excessive current). The leakage protector that cuts off the circuit controls the switch by detecting the current difference between the ground wire and the live wire in the circuit. When there is leakage in the live wire (electric shock in the first line), the current flowing through the live wire is large, while the current flowing through the ground wire is small, which changes the magnetic flux around the core of the leakage protector and automatically turns off the switch. Leakage protection switch: there are two coil windings with the same size and number of turns in it, which are on the same iron core. The two coils are respectively connected in series in the live wire and the neutral wire of the circuit. When there is no magnetic leakage, the magnetic fields generated by the two windings cancel each other out, so no matter how much current flows (of course, it does not exceed the maximum rated current), the generated magnetic fields cancel each other out, so that the electromagnet will not attract the armature and the circuit will not open continuously. But when the circuit leaks, the current on the live wire is divided into two directions, one is the zero line and the other is the leakage point. At this time, the currents of the two coils on the electromagnet are different, resulting in a magnetic field, which attracts the armature to break the circuit and protect the safety of the electric shock or wires! ! At the same time, there is a test button on the main leakage protector. The principle is to actively generate a magnetic field to see if the circuit breaker can automatically turn off! ! After troubleshooting, turn on the switch and it will work normally! ! Air switch, also known as automatic switch and low-voltage circuit breaker. The principle is: short circuit, voltage loss, etc. when the working current exceeds the rated current. , the circuit is automatically cut off. At present, the common household master switches are porcelain plug-in safety knife switch (obsolete) or air switch (small circuit breaker with leakage protection).
Question 5: What is the difference between an open circuit and a leakage protector? Air switch and leakage protector
1, air switch is a familiar name, and its correct name is air switch. The air switch is generally low voltage, that is, the rated working voltage is 1Kv. Air switch is a switching device with multiple protection functions, which can cut off and connect the circuit under rated voltage and rated working current. The type and protection mode of its protection function are selected by users according to their needs. Such as short-circuit protection, over-current protection, shunt control and under-voltage protection. The first two protections are the basic configuration of the air switch, and the last two are optional functions. Therefore, the air switch can also cut off the circuit under fault conditions (load short circuit, load overcurrent, low voltage, etc.). ).
2. The leakage switch is properly called residual current protection device (RCD), which is an air switch with special protection function (leakage protection). It detects the residual current, that is, the algebraic sum of instantaneous values of phase line and neutral line current (including three-phase unbalanced current and neutral line harmonic current) in the protected circuit. Therefore, the setting value of RCD, that is, its action current I δ n, only needs to avoid the normal leakage current value, which is calculated in mA, so RCD can cut off the grounding fault of the protection circuit very sensitively, and can also be used as a backup protection to prevent direct contact and electric shock.
The earth leakage protector is a kind of protective electrical appliance that detects the earth leakage or electric shock current of the phase line in the protected power grid, sends out an action trip signal and completes the action trip task. Under normal circumstances, the leakage current from the phase line to the ground (unbalanced leakage current of the three-phase power grid) in the low-voltage power grid equipped with the leakage protector is very small, which cannot reach the action current value of the leakage protector, so the leakage protector does not act. When there is a fault such as leakage or electric shock in the protected power grid, when the component current detected by the leakage protector reaches its current value of leakage or electric shock, the leakage protector will issue an action trip command to trip the main circuit switch it controls and cut off the power supply, thus completing the task of leakage or electric shock protection. In addition to the basic function of the air switch, it can also quickly turn off the switch when there is leakage in the load circuit (when the leakage current reaches the set value), so as to avoid the injury to personnel and the adverse impact on electrical equipment when there is leakage in the load circuit.
3. Leakage switch cannot replace air switch. Although the leakage switch has one more protection function than the air switch, it often trips due to the possibility of leakage, which leads to frequent power failure of the load and affects the continuous normal operation of electrical equipment. Therefore, it is generally only used for temporary electricity consumption on the construction site or in the socket circuit of industrial and civil buildings.
Leakage switch can also be said to be a kind of air switch, and its mechanical action is similar to that of arc extinguishing. However, because the leakage switch mainly protects the human body, the general action value is mA.
In addition, the action detection mode is different: the residual current protection device is used for the leakage switch to detect the residual current, that is, the algebraic sum of instantaneous values of phase line and neutral line current (including three-phase unbalanced current and harmonic current in neutral line) in the protected loop. Therefore, its working current only needs to avoid the normal leakage current value (milliampere level), so it can cut off the grounding fault very sensitively and prevent direct contact and electric shock. The air switch is a pure overcurrent trip (ampere level).
Question 6: Is the leakage protector effective? First of all, it can automatically trip when the voltage of the wire is too high to prevent the line from burning out.
Personally, I think there are advantages and disadvantages. The leakage protector trips 5.6 times a day, which makes it annoying. If you encounter a problem like mine, Gong suggested checking the protector instead of imitating me. . . . .
Question 7: What is the difference between a leakage protector and a leakage circuit breaker? The leakage protector only has the function of leakage tripping, which is used to effectively protect the direct and indirect electric shock of low-voltage power grid, and can also be used as the open-phase protection of three-phase motors. It has single-phase and three-phase protection. The rated current of leakage protector is generally very small, which can directly protect an electrical appliance! In addition to leakage tripping, the leakage circuit breaker also has overcurrent tripping function; That is: including leakage, overload, short circuit, and some have overvoltage protection function; General leakage circuit breakers have large rated current and are suitable for full-line protection!
Question 8: What's the difference between a leakage circuit breaker and a leakage protector? What are the functions of leakage products such as leakage protectors and leakage accessories?
Used to protect human body from electric shock and equipment insulation from electric shock damage. What are the similarities and differences between leakage protectors and leakage accessories?
Both of them play the role of leakage protection. However, the leakage protector can be installed independently, and the leakage accessories must be used in conjunction with the small circuit breaker.
What are the similarities and differences between leakage circuit breakers, leakage protectors and leakage accessories?
The leakage circuit breaker integrates overload, short circuit and leakage protection, which is equivalent to adding a small circuit breaker to the leakage protector or a small circuit breaker to the leakage accessory.
Question 9: What kind of leakage protector is suitable for home use? I wonder how big your electric meter is. The rated current of the leakage protector cannot be greater than the maximum current of the electric meter.
Roughly estimate the total electrical power of your home: rice cooker1000 w; Electric kettle1000 w; Rice cooker 2000 w；; Air conditioning 2000 w；; Refrigerator150 w; Electric water heater 2000 w；; Computer 400W；; Television100 w; The total power is about 8650W, and the total current is about 39.3A The rated current of your leakage protector is 63A, which is acceptable.
But you need to install several sub-switches under the main switch, such as leakage protectors with rated current of 16A or 25A, and each leakage protector is connected to 1-3 electrical appliances. Separate control is convenient and safe.
Your rice cooker is short-circuited, and the current may not exceed 63A, so the leakage protector has not tripped.