In our life, we will use a lot of large electrical appliances, so if we don't pay attention to it, there may be a hidden danger of electric shock, in order to protect our safety, the leakage circuit breaker was invented.
Leakage circuit breaker is a kind of anti-leakage safety protection device, leakage circuit breaker work is based on the circuit, generally speaking, when the line is working normally, the sum of our three-phase current phasor through the main circuit of the zero sequence current transformer is equal to zero, and the leakage protector works in a closed state. When a leakage or electric shock accident occurs, the sum of the three-phase currents is no longer equal to zero, but equal to a certain current value Is. IS will form a loop through the human body, the earth and the neutral point of the transformer, so that the secondary side of the zero sequence current transformer will generate the induced electromotive force corresponding to Is, which will be added to the tripper, and when IS reaches a certain value, the tripper will act, push the lock of the main switch, and break the main circuit, so that it can play a role in power-off and ensure our personal safety.
Let's take a look at the installation diagram, installation precautions, trip causes, common faults, and how to choose the leakage circuit breaker.
Illustration of the installation of a leakage circuit breaker
1. The protected circuit power line, including phase wire and neutral wire, should be threaded into the zero sequence current transformer.
2. A section of power cord penetrating into the zero sequence transformer should be wrapped tightly with insulating tape, bundled into a bundle, and then penetrated through the center of the zero sequence current transformer hole, the purpose of which is to eliminate the unbalanced magnetic flux generated in the iron core due to the asymmetry of the wire position.
3. The zero line drawn from the zero sequence transformer cannot be repeatedly grounded, otherwise the unbalanced current will be generated when the three-phase load is unbalanced, and all of it will not return from the zero line, and only a part will return from the bottom. Therefore, the vector sum of the current through the zero-sequence current transformer cannot be zero, and when the secondary coil has an output, it may cause an incorrect operation.
4. The zero line of each protection loop should be dedicated, and the zero line cannot be overlapped nearby, nor can the zero line be connected to each other, otherwise the three-phase unbalanced current or the current of the single-phase electric shock protector phase line will be shunted to the zero line of the different protection circuits connected by the line, resulting in an unbalanced magnetodynamic potential of the zero sequence current transformer core of the second circuit.
5. After the leakage circuit breaker is installed, it can be energized, and press the test button to test to check whether the leakage circuit breaker is operating normally.
Precautions for installation of leakage circuit breakers
1. Before installation, check whether the data on the nameplate of the leakage circuit breaker is consistent with the use requirements.
2. Do not be too close to the high-current bus and AC contactor during installation.
3. When the operating current of the leakage circuit breaker is greater than 15mA, the equipment shell protected by it should be reliably grounded.
4. The power supply mode, voltage and grounding form of the system should be fully considered for the power supply line.
5. Install a leakage circuit breaker with short-circuit protection, and it is necessary to ensure that there is enough arcing distance.
6. The control loop connected externally of the combined leakage circuit breaker shall use copper wires, and the cross-sectional area shall not be less than 1.5m㎡.
7. After the installation of the leakage circuit breaker, the original low-voltage line or the original grounding protection measures of the equipment cannot be removed, and the neutral wire on the load side of the circuit breaker shall not be shared with other circuits to avoid misoperation.
8. When installing, it is necessary to strictly distinguish between the neutral wire and the protective grounding wire. The neutral wire of the three-pole four-wire and four-pole leakage circuit breaker should be connected to the circuit breaker, and the neutral wire passing through the circuit breaker can no longer be used as a protective grounding wire, nor can it be repeatedly grounded or connected to the electrical equipment shell. The protective ground wire shall not be connected to the leakage circuit breaker.
9. The protection range of the leakage circuit breaker should be an independent circuit, and it should not be electrically connected with other circuits. Residual current circuit breakers cannot be used in parallel to protect the same line or electrical equipment.
10. After the installation, the test button should be operated to check whether the leakage circuit breaker can operate reliably. In general, it should be tested more than three times, and it can be operated normally.
Leakage circuit breaker trip cause
First, the circuit breaker selection is too small
This happens, mainly due to the fact that the user changed the circuit during the renovation and did not replace the circuit breaker. For example, it was originally a five-pin socket, but it was changed to an air conditioning socket by the user. Some developers may use a C16 circuit breaker for a five-prong socket circuit breaker in order to save costs. If this kind of circuit breaker drives the air conditioner, it will inevitably cause the circuit breaker to be overloaded, which will cause tripping.
Solution: Replace the trip circuit breaker, and the air conditioning socket circuit breaker should be C20, C25, C32. If it is confirmed that the tripping is caused by the change of the five-pin socket to the air conditioning socket, you don't have to worry about the wire square problem, because the wire behind the air conditioner socket is generally 4 square.
Second, the circuit breaker installation failure
Loose wires at the lower mouth of the circuit breaker will cause poor wire contact, which can easily be identified as leakage by the leakage protector.
Solution: After the power is off, fix the wire at the lower end of the circuit breaker with a change cone. If the binding post of the circuit breaker is slippery, the circuit breaker should be replaced in time.
Third, the power consumption of the line is too large
The number of sockets pre-installed by the developer often does not meet the actual needs of users, so users need to add the number of sockets themselves when renovating. Especially in places with dense electrical appliances such as kitchens, multiple sockets often lead from under the same circuit breaker. The circuit breaker is installed on the trunk road, if the sockets of each branch are used at the same time, it will cause the overload of the trunk circuit current, trigger the overload protection function of the circuit breaker, and cause tripping.
Solution: The best thing to do is not to use multiple outlets (outlets of the same circuit) at the same time. If this is not possible, the circuit breaker needs to be replaced, but at the same time as the circuit breaker is replaced, the wire side of the trunk wire needs to be replaced.
Fourth, electrical equipment leakage
This problem most often occurs in air-conditioning circuits. If the grounding device inside the air conditioner fails, it is easy to generate leakage current in the line, which will cause tripping. To identify whether it is due to the leakage of electrical equipment that causes tripping, you can unplug the electrical appliance (not to turn it off, but to pull out the plug), and then close it to see if it is still tripping.
Solution: Contact the manufacturer's after-sales service for maintenance.
Fifth, the line leakage
Inferior wires, after a few years of use, may occur insulation skin damage, resulting in line leakage. If the insulating skin is damaged and tripped, it must be due to the damage of the live wire or neutral wire, and if the ground wire is damaged, it will not cause tripping. When judging whether the live wire or the neutral wire is damaged, you can unplug all the sockets of the circuit and observe whether the circuit is still tripped, if so, it is the live wire is damaged; if it does not trip, and plug in any electrical appliance is tripped, it is the zero wire is damaged.
Solution: Replace the damaged line, the project is huge. Experienced masters will choose to use ground wire (if the ground wire is not damaged) instead of broken wires, but in this way, the socket has no ground wire, and only low-power electrical appliances can be used, which is easier to operate. The user should not do this for the purpose of not happening otherwise.
6. Wrong wiring
When connecting to the socket, if the neutral wire and the ground wire of a socket are reversed (commonly found in places where the wire color is not used in accordance with the regulations), it will cause tripping when the circuit socket is used for the first time during the decoration acceptance or the first use. (Of course, there are times when it won't trip, but there is no power in the outlet.) It mainly depends on what appliance is plugged into the outlet. ）
Solution: Disassemble the socket and re-wire.
7. Mixed circuits
This is a mistake that is taken for granted, and the average user or an electrician who is not skilled in the field is prone to making such mistakes when his brain heats up when changing the circuit. If you want to add a lamp or socket, use the nearest lead. However, the zero wire and the live wire are two circuit breakers. Lamps are more susceptible to this kind of failure than sockets, because there are two junction boxes at the neutral and live wires of the lamps.
Solution: Remove the newly installed lights or sockets.
8. Short circuit of electrical equipment or lines
Short-circuiting is rare in households, and if it does, it is likely to be due to the heat inside the socket melting, causing metal to stick. If this happens during the decoration acceptance, it is necessary to consider that the live wire and the neutral wire are shorted during the wiring. Short circuits in electrical equipment, commonly found in electrical appliances with internal motors, may melt the metal and cause adhesion after burning.
Solution: Replace a burned-out outlet or appliance.
9. The voltage is too low
It usually happens in the main switch, which is the so-called "tripping as soon as the power goes out", and if this happens, your neighbor should also trip, unless the user replaces the distribution box or circuit breaker during the renovation. This is due to the addition of an undervoltage trip inside the main switch, which is to prevent damage to the appliance due to sudden calls.
Many appliances nowadays also have under-voltage protection devices inside, the most obvious being air conditioners: they stop running after a power outage, and they don't automatically start running when a call comes in.
Solution: No need to solve it, it is a protection device for the circuit. If it is too troublesome, the trip switch can be replaced.
10. The voltage is too high
Too much of a voltage is obviously more harmful than too low a voltage. It can range from burning electrical appliances to starting fires. It often occurs in places where the voltage is unstable, such as new buildings or remote areas. This is due to the voltage in the line being too high, causing the current in the line to be too large, which triggers the overload protection of the circuit breaker, resulting in tripping.
Solution: Call the power supply bureau and ask it to repair it (to put it bluntly, there is no way). If it is a new building, the developer will hand over the house when the circuit is not successfully commissioned, and at this time, calling the power supply bureau to complain will often have a miraculous effect. Call 95598 to complain about the local power supply bureau (office), not to complain about the developer.
Common faults of leakage circuit breakers
First, put into tripping
1. The three-phase power line, including the neutral line, does not pass through the zero sequence current transformer in the same direction, and the wiring can be corrected.
2. The circuit with the installation of the leakage circuit breaker and the line without the installation of the leakage circuit breaker is electrically connected, and the two circuits can be separated.
3. There is a fire and a ground load in the line, and such a load can be eliminated.
4. There is a repeated grounding phenomenon on the working zero line of the zero sequence current transformer, and the repeated grounding should be eliminated.
5. The leakage circuit breaker itself is faulty and should be replaced.
2. Malfunction
1. Caused by overvoltage. If the circuit breaker can be operated when the operating overvoltage occurs in the line, the leakage circuit breaker with delay or impulse voltage can be selected, and the resistor-capacitance absorption circuit can also be installed between the contacts to suppress the overvoltage, and the overvoltage absorption device can also be thrown into the line.
2. Electromagnetic interference. If there are magnetic equipment or high-power electrical equipment nearby, the installation position of the residual current circuit breaker should be adjusted to stay away from such electrical components.
3. Circulation influence. If two transformers run in parallel, they have their own grounding, because the impedance of the two transformers cannot be completely equal, which will produce a circulation current in the grounding wire, causing the circuit breaker to move, and a grounding wire can be removed. In addition, the same transformer supplies power to the same load through two parallel circuits, and the currents in the two circuits cannot be exactly the same, and circulation currents may occur, so the two circuits should be operated separately.
4. The insulation resistance of the working neutral line is reduced. When the insulation resistance of the working neutral line is reduced, if the three-phase load is unbalanced, there will be a relatively large working current on the neutral line, and it will flow to other branches through people, so that the leakage current can occur on each leakage circuit breaker, so that the circuit breaker malfunctions.
5. Improper grounding. If the neutral line is repeatedly grounded, it will cause the malfunction of the leakage circuit breaker.
6. The impact of overload or short circuit. If the leakage circuit breaker has short-circuit protection and over-current protection at the same time, malfunction will occur when the setting current of the over-current protection tripper is not suitable, and the setting current value can be adjusted at this time.
How to choose a leakage circuit breaker
1. Due to the serious consequences of direct electric shock and the greater harm, it is recommended to choose a product with better flexibility in the selection of leakage circuit breaker. This kind of leakage circuit breaker should be installed on the circuit of the circuit, it is best to choose a product with a current of 30mA, and the working time should be kept at 0.1s.
2. If there is a problem of inter-contact electricity in different places, the damage to the human body is not the same, so it is necessary to select the corresponding leakage circuit breaker products according to the actual situation of the place. Compared with dry space, wet space is more prone to electric shock problems, so it is necessary to choose a leakage circuit breaker with an installation current of 15-30mA and a working time of 0.1s.
3. If it is an electrical product used in water, the current value between 6-10mA and the working time of the leakage protector should be selected for the product within the US, and the other personnel should stand on the metal electrical appliance. Once the current exceeds 24V, a leakage circuit breaker with a current of less than 15mA and a holding time within US should be selected.
The above is to share with you the installation diagram, installation precautions, trip reasons, common faults, how to choose?
There are many kinds of leakage circuit breakers, and we need to choose them according to the purpose of use and operating conditions.
According to the purpose of use, in order to prevent people from being electrocuted, we can choose a high-sensitivity and fast leakage circuit breaker. However, if it is a branch line that is used to ground the equipment for the purpose of preventing electric shock, you can choose a medium-sensitivity, fast leakage circuit breaker. If it is a trunk line for the purpose of preventing fire caused by leakage and protecting lines and equipment, a medium-sensitivity, time-delay leakage circuit breaker should be selected.
According to the power supply mode, when we are protecting a single-phase line, we can choose a single-pole two-wire or two-pole leakage circuit breaker, and when we are protecting a three-phase line, we can choose a three-pole product. When there are both three-phase and single-phase on the line, three-pole, four-wire or four-pole products are selected.