When the protected electrical equipment and the line are leaking or someone is getting electric shock, there is a ground fault current, so that the current vector flowing through the detecting transformer is not zero, the magnetic flux is induced in the transformer core, and the secondary winding has induction. The current is generated and output after being amplified, so that the operation of the leakage release device pushes the automatic switch to trip to achieve the purpose of leakage protection. The short circuit protection and overload protection function of the leakage switch is the same as the air switch principle, which will not be discussed here. The principle of leakage protection is shown in Figure 1.
The following causes and solutions for leakage faults of leakage switches:
Type 1: The rated current of the leakage switch is less than the actual operating current of the line, and an overload protection trip occurs.
Fault phenomenon: When the power load is large, the leakage switch trips.
The cause of the fault: The wiring of the analyzed line is correct. 1. The error of the load calculation leads to the wrong selection of the leakage switch. The rated current of the switch is less than the actual working current of the line, causing the leakage switch to trip. The load is calculated correctly. The leakage switch is used correctly. The use of high-power electrical equipment causes the leakage switch overload protection to trip.
Solution: 1. Replace the leakage switch with the maximum allowable working current; 2. Inform the electric appliance user to prohibit the use of high-power electrical equipment.
Type 2: The electrical equipment itself is damaged by insulation and leakage (ie, the N line in the equipment is shorted to the PE line).
Fault phenomenon: When the socket circuit is powered, the socket circuit leakage switch trips.
Fault reason: After the analysis of the wiring is correct, the load calculation is matched with the leakage switch, so it is judged that the electrical equipment itself is damaged by insulation and leakage (ie, the N line in the equipment is shorted to the PE line).
Solution: Replace or repair the electrical equipment to ensure that the electrical equipment has good insulation.
Type 3: The line is wet, causing the insulation strength to decrease or the line short circuit to cause the leakage switch to trip.
Fault phenomenon: When the power is off, the socket circuit leakage switch trips.
Fault reason: After analysis, 1, the wet insulation strength of the line is reduced, causing the leakage current to exceed the allowable leakage current value of the leakage switch. 2. Due to short circuit.
Solution: 1. Dry the line and increase the insulation strength. 2. If the inspection line is short-circuited, eliminate the short-circuit fault.
Type 4: Someone gets an electric shock and the outlet loop leakage switch trips.
Symptom: The socket circuit leakage switch suddenly trips.
Cause of the malfunction: Someone has an electric shock.
Solution: Publicize and educate users on safe use of electricity to avoid electric shock accidents. If someone is found to have an electric shock, they should promptly rescue the injured.
Type 5: The employee wiring is incorrect, and the N line is connected to the PE line in the Lighting circuit.
Fault phenomenon: The socket circuit can be used normally. When the lighting circuit is powered, the total leakage switch in AL1 trips.
Fault reason: After analysis, the wiring of the line is incorrect, and the N line in the lighting circuit is mistakenly connected to the PE line.
Solution: Change the line and change the PE line in the lighting loop to the N line.
Type 6: The employee wiring is incorrect, and the N and PE wires in the socket box are incorrectly connected.
Fault phenomenon: The lighting circuit can be used normally. When the socket circuit is powered, the socket leakage switch in ALY trips, and sometimes the total leakage switch in AL1 also trips.
The cause of the fault: After analysis, the wiring of the line is incorrect, and the N line and the PE line in the socket box are connected incorrectly.
Solution: Reroute the line and reverse the N line in the socket box to the PE line.
Type 7: The employee wiring is incorrect. The N line and the PE line are mixed in the AL1 box.
Symptom: When the socket circuit or lighting circuit is powered, the total leakage switch in AL1 trips.
Fault reason: After analysis, the wiring of the line is not correct, and the N line and the PE line in the AL1 box are mixed.
Solution: Reverse the N line and the PE line at the total leakage switch load end of the AL1 box.
Conclusion In summary, the leakage switch can not only be used to protect the line from overload and short circuit, but also can be used as a leakage protection device. It plays an important role in our office power and protects the safety of our consumers. Through the introduction of the leakage switch principle and the analysis of the fault trip, this paper hopes to guide the electrical operators to correctly use the leakage switch. After the switch fault trips, it can quickly and accurately find the cause, and timely handle the fault recovery and power transmission.
Use a multimeter to quickly check the leakage point
1. Disconnect the main disconnector of the user's power supply line and turn off all the user's power load, such as unplugging the refrigerator and disconnecting the water pump switch.
2. Place the gear of the digital multimeter on the 200M block of the ohm file, one pen on one of the two outlets on the load side, and the other pen touches the wall, preferably touch the ground wire or temporarily Ground wire. After the number displayed on the multimeter is stabilized, the insulation resistance value of the main line is read. If the insulation resistance value is less than 0.5 megohm, then the main line has a problem. If the insulation resistance is above 0.5 megohm, then it can be excluded. There is a problem with the main line. Use the same method to measure another wire and check the value to see if there is a problem with the main line.
3. Check the insulation resistance values ​​of the shunt and each electrical appliance, and use the same method to detect one by one until the fault point is found.
Operational precautions
1. When using the 200M block of the multimeter ohm block, be careful not to touch the metal part of the test pen by hand during the measurement, which will make the reading inaccurate.
2. When measuring each electrical equipment, be sure to discharge it first to prevent the capacitive current in the electrical equipment from injuring people.
This method is a safer way to find fault points in the absence of electricity. This method is also suitable for the search of power users and plant leakage, but in the search, not only to disconnect the power supply, but also to disconnect the neutral line to avoid electric shock.
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