Why should a leakage switch be installed in a residence? Abstract: there are several wrong ideas about whether to install a leakage switch in residential electricity. The leakage switch will malfunction and cause power failure, so it is not installed; As long as the grounding is reliable, leakage switch can not be installed. If leakage switch is installed, it doesn't matter whether the shell of electrical equipment is grounded or not; The leakage switch has been installed, and then the shell of the electrical equipment is connected with the water pipe. How authentic...
key words: precautions for residential leakage switch. There are several wrong views on whether to install a leakage switch for residential electricity. The leakage switch will malfunction, resulting in power failure, so the leakage switch is not installed; As long as the grounding is reliable, leakage switch can not be installed. If leakage switch is installed, it doesn't matter whether the shell of electrical equipment is grounded or not; The leakage switch has been installed, and then the shell of the electrical equipment is connected with the water pipe. How authentic it is; The leakage switch has been installed, and the electrical equipment is also grounded. There is no need to engage in local equipotential bonding in the bathroom with bathtub. The above errors are analyzed one by one below. 1. The tripping of leakage switch can be divided into normal tripping and abnormal tripping. Normal tripping indicates that if the leakage switch with a rated leakage action current of 30mA has a leakage current of more than 25mA in its load, the leakage switch will trip. Since it is safe for 25mA current to flow through human body, electric shock death will not occur; Similarly, there will be no danger to lines or electrical equipment, and the operation of electrical equipment will not produce abnormal phenomena. In this case, without analysis, it is extremely wrong to mistakenly think that there is a problem with the quality of the leakage switch, and arbitrarily remove the leakage switch. After removing the leakage switch, it is considered that the electrical equipment is working normally, which is a dangerous practice. Abnormal tripping is caused by the unqualified quality of the leakage switch itself, which is divided into two categories; Fail to close and sometimes trip without cause. When the leakage switch is connected to the power supply instead of the load, and we can also use the nature of recycled plastic. If it cannot be closed, it must be the quality problem of the leakage switch, and we must not repair it by ourselves, because it must be tested for technical performance after repair, and then it can be set into use. It is unsafe to use it without testing equipment. The second type is occasional tripping, especially in the middle of the night or when there is no one at home. This kind of tripping indicates that the anti-interference performance of the leakage switch is poor. The leakage switch with abnormal tripping should be removed and replaced with a good leakage switch. If the leakage current of normal tripping fluctuates up and down at 25mA, its phenomenon is similar to that of occasional tripping, which is often caused by the insulation aging of the conductor, that is, tripping when the environment is wet and not tripping when the environment is dry. Insulation materials refer to materials or material composite gates used for building enclosure or thermal equipment, and impedance heat flow transmission. The reliable way to distinguish this kind of normal tripping and occasional tripping is to measure the insulation resistance of lines and electrical equipment. According to the standard, the insulation resistance of each conductor shall not be lower than the 3-point zigzag test, 4-point zigzag test, sheet metal tensile test, thick plate tensile test, reinforced steel bar tensile test, chain tensile test, fixed part test, connecting rod test, change decadence test, bend twist composite decadence test, interactive zigzag decadence test, CT test, CCT test, gear decadence test under sinusoidal load 0.5m Ω material performance, and the insulation resistance of electrical equipment is usually greater than 0.5m Ω. If the total measured insulation resistance of the load connected to the leakage switch is less than 8.8k Ω (220v/25ma=8.8k Ω), normal tripping will occur. It is certainly wrong to regard the normal tripping as the malfunction of the leakage switch without installing the leakage switch. Because once the leakage expands, there will be a risk of electric shock when it is greater than 30mA. 2. Grounding of electrical equipment is the basic measure for power safety. However, even if the grounding resistance of the grounding electrode meets the requirements, the reliable grounding of electrical equipment cannot be guaranteed. The grounding wire of the electrical equipment in the house does not exceed 2.5mm2. There are many connection points from the grounding electrode, grounding trunk line, grounding branch line to the electrical equipment. As long as there is an unreliable or broken connection, especially the poor contact of the grounding pile head of the socket, the grounding of the electrical equipment will be unreliable. Therefore, it cannot be guaranteed that the grounding of the electrical equipment is absolutely reliable, or it can only be guaranteed that the grounding is reliable during measurement and inspection, not always reliable. Therefore, to take other measures to increase the safety of electricity, installing leakage switches is a very effective method. 3. The grounding of houses built in the past is not paid attention to. Although many families have three hole sockets, they only have two wires and lack grounding wires. Especially in old-fashioned public houses, adding grounding wires is very troublesome. In order to use electricity safely, each household installs leakage switches. After installing the leakage switch, once there is leakage, the switch will trip immediately to avoid the risk of electric shock. In this case, some people think that adding the grounding wire is too troublesome, and it is safe to install the leakage switch without adding the grounding wire. This view is wrong, because the leakage switch also has the possibility of failure, and with the grounding wire, the safety can be increased. 4. Up to now, many families still use the water pipe as the grounding wire, which is unreliable. First, the grounding resistance cannot be guaranteed, and second, the fault voltage is very easy to spread along the water pipe. Shanghai TV station once reported that in a Shikumen residence, the hemp electricity of various water pipe taps is an example; In the analysis of an electric shock accident reported in the electric world magazine, an old lady was shocked to death when she touched the faucet of the water pipe, and the electricity came from the water pipe. Grounding construction is an important concealed project, which must be constructed by a professional team and accepted by the supervisor. Grounding, like installing leakage switches, is not a once and for all thing. The grounding resistance of the grounding device should be retested once a year. Whether the connection of the grounding wire is reliable must also be checked frequently. 5. 6.5.2 of GB code for residential facilities stipulates that local equipotential bonding should be done in toilets. When people are completely wet, such as soaking in a bathtub, the resistance of the human body can be ignored. In this case, the voltage at which the risk of electric shock will occur is not regulated in China. IEC stipulates that it should not exceed 12V in its notes, while Japan stipulates that it should not exceed 2.5V. If equipotential bonding is not made, such a low dangerous voltage is very easy to exist. It is common for the voltage between the grounding wire and the neutral wire to exceed 10V. If the neutral wire of the lamp and the water pipe are short circuited, the lamp still works normally and people are sitting in the bath
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