Leakage Circuit Breaker / The working principle of the leakage circuit breaker is
When functioning normally, there is no leakage current passing through the leakage protector except for the working current in the circuit. At this time, the current flowing through the zero-sequence current transformer (detection transformer) is equal in magnitude and opposite in direction, resulting in a total of zero. The induced magnetic flux in the transformer core is also zero, and the secondary winding has no output, keeping the automatic switch in the closed state, with the leakage protector operating normally. When the protected appliance or line experiences leakage or someone gets an electric shock, a grounding fault current occurs, causing the vector sum of the current flowing through the detection transformer to be non-zero. This induces magnetic flux in the transformer core, generating induced current in the secondary winding, which is amplified and outputted, causing the leakage trip mechanism to act and the automatic switch to trip, achieving leakage protection. The short circuit and overload protection functions of the leakage circuit breaker are similar to those of an air switch, which will not be discussed here. The principle of leakage protection is shown in Figure 1.
The following are several types of leakage circuit breaker tripping faults and their
causes and solutions
1st Type: The rated current of the leakage circuit breaker is less than the actual working current of the line, resulting in overload protection tripping.
Fault Phenomenon: The leakage circuit breaker trips when the load is high.
Fault Cause: Analysis shows the wiring is correct. 1. Incorrect load calculation leads to selecting the wrong leakage circuit breaker; the rated current of the switch is less than the actual working current of the line, causing overload tripping. 2. If the load calculation is correct and the leakage circuit breaker is used properly, using high-power electrical appliances can still cause the leakage circuit breaker to trip.
Solution: 1. Replace with a leakage circuit breaker that has a higher maximum allowable working current; 2. Inform users to avoid using high-power electrical appliances.
2nd Type: The electrical device itself has insulation damage causing leakage (i.e., the N line in the device is short-circuited with the PE line).
Fault Phenomenon: The leakage circuit breaker trips when using the socket circuit.
Fault Cause: Analysis shows the wiring is correct and the load calculation matches the leakage circuit breaker, leading to the conclusion that the electrical device itself has insulation damage causing leakage.
Solution: Replace or repair the electrical device to ensure it has good insulation.
3rd Type: Moisture in the line reduces insulation strength or short circuits cause leakage circuit breaker faults.
Fault Phenomenon: The leakage circuit breaker trips when not in use.
Fault Cause: Analysis shows that 1. Moisture in the line reduces insulation strength, causing leakage current to exceed the allowable leakage current value of the leakage circuit breaker. 2. Caused by a short circuit.
Solution: 1. Dry the line to improve insulation strength. 2. Check the line for short circuits and eliminate the fault.
4th Type: Someone gets an electric shock, and the leakage circuit breaker trips.
Fault Phenomenon: The leakage circuit breaker suddenly trips.
Fault Cause: Someone gets an electric shock.
Solution: Educate users on safe electricity use to prevent electric shock accidents. If someone is shocked, provide timely rescue.
5th Type: Incorrect wiring by staff, connecting the N line to the PE line in the lighting circuit.
Fault Phenomenon: The socket circuit can be used normally, but when using the lighting circuit, the total leakage circuit breaker in AL1 trips.
Fault Cause: Analysis shows incorrect wiring, with the N line in the lighting circuit mistakenly connected to the PE line.
Solution: Rewire to connect the PE line in the lighting circuit to the N line.
6th Type: Incorrect wiring by staff, incorrectly connecting the N line and PE line in the socket box.
Fault Phenomenon: The lighting circuit can be used normally, but when using the socket circuit, the leakage circuit breaker in ALY trips, and sometimes the total leakage circuit breaker in AL1 also trips.
Fault Cause: Analysis shows incorrect wiring, with the N line and PE line in the socket box connected incorrectly.
Solution: Rewire to swap the N line and PE line in the socket box.
7th Type: Incorrect wiring by staff, mixing the N line and PE line in the AL1 box.
Fault Phenomenon: The total leakage circuit breaker in AL1 trips when using either the socket or lighting circuit.
Fault Cause: Analysis shows incorrect wiring, mixing the N line and PE line in the AL1 box.
Solution: In the AL1 box, swap the N line and PE line at the load side of the total leakage circuit breaker.
In conclusion, the leakage circuit breaker can not only protect against overload and short circuits but also serve as a leakage protection device, playing an important role in our office power use and protecting the safety of users. This article introduces the principle of leakage circuit breakers and analyzes tripping faults, hoping to guide electrical workers to use leakage circuit breakers correctly, quickly and accurately identify the cause after a switch trips, and promptly handle faults to restore power supply.
Quickly Finding Leakage Points with a Multimeter
1. First, disconnect the main isolation switch of the user’s power supply and turn off all electrical loads, such as unplugging the refrigerator or disconnecting the water pump switch.
2. Set the digital multimeter to the ohm range at 200M. Place one probe on one of the two outgoing wires on the load side, and the other probe against the wall, preferably touching the ground wire or a temporary ground wire. Wait for the number on the multimeter to stabilize, and read the insulation resistance value of the main circuit. If the insulation resistance value is less than 0.5 megaohms, there is a problem with the main circuit. If the insulation resistance is above 0.5 megaohms, the main circuit can be ruled out as the problem. Use the same method to measure the other wire and check the value to see if there is an issue with the main circuit.
3. Check the insulation resistance values of the branch circuits and each electrical appliance using the same method, testing one by one until the fault point is found.
Operational Precautions
1. When using the multimeter in the ohm range of 200M, be careful not to touch the metal parts of the probes during measurement, as this can lead to inaccurate readings.
2. When measuring various electrical devices, be sure to discharge them first to prevent any capacitive current from injuring someone.
This method is a relatively safe way to locate fault points without power. This method is also applicable for finding leakage in power users and factories, but during the search, not only should the power supply be disconnected, but the neutral line should also be disconnected to avoid electric shock accidents.
Source: This article is reprinted from the internet, and copyright belongs to the original author. If there are any copyright issues, please contact us for deletion. Thank you!
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