The importance of earth wire

Earth wire, also known as lightning conductor, is used to lead the current into the earth wire; electrical leakage, the current into the earth through the earth wire. The symbol for earth wire is E (Earth) ; can be divided into power supply earth wire, circuit earth wire two. According to the current standard of our country, the third circuit in GB2681, which is marked by the color of the conductor, should generally be the phase line-a phase yellow, B phase green, C phase red. Zero line-light blue, the right is the fire line. To put it simply: grounding wire is a way of electrical protection. Its function is that when your electrical equipment leakage or induction is charged can quickly through the grounding wire to lead the current into the Earth so that the device shell is no longer charged, so as to ensure the safety of equipment after personnel. For example: household electrical equipment due to poor insulation or the use of humid environment, will lead to its shell with a certain amount of static electricity, serious electric shock accidents will occur. To avoid accidents, connect a wire to the metal casing of the appliance and connect the other end of the wire to the ground. The grounding wire will bring static electricity to the ground and release it if the appliance leaks. In addition to electrical maintenance personnel in the use of electric soldering iron welding circuit, sometimes because of electric soldering iron electrification and breakdown of damaged electrical integrated circuits, which is more important. Use computer friends will sometimes ignore the mainframe case grounding, in fact, the mainframe to the computer grounding earth wire, to a certain extent, can prevent the appearance of the crash phenomenon. Grounding in power systems: an important tool for securing staff in the event of unexpected voltages on equipment and lines that have been shut off. According to regulations, the grounding wire must be more than 25mm2 bare copper wire made. In electrical appliances: grounding is connected to the electrical equipment shell and other parts of the timely will be due to a variety of causes of unsafe charge or leakage current derived from the line. Common Point: Earthing can prevent the electrostatic or leakage of the surface of electrical equipment to cause electric shock injury, high-power electrical appliances in particular need of attention. What does the earth wire do?

If it is not grounded, once the leakage phenomenon of equipment occurs, people touch the electrified body, it is possible to have an electric shock accident. Household electrical grounding wire is to protect personal safety, to prevent household electrical leakage after personal shock. Not Lightning proof. There are two types of grounding, system grounding and protective grounding. The task of system earthing is to establish zero potential reference point, and the task of protecting earthing is to protect personal safety. For protective grounding, its mission is: 

A) to provide a low-impedance connection between the device and the grounding body, thereby also reducing the risk of personal electrical injury; B) to provide a low-impedance path back to the power supply for the grounding fault current to enable the fuses or circuit breakers to operate. Note 1: in the TN system, the single-phase-to-ground fault current is magnified to a short-circuit current relative to N, so the overcurrent protector can perform the protective operation; Note 2: Let's look at the lower left-hand corner of the above image. In the left image, we see that when a single-phase-to-ground fault occurs, the current flowing through the body is greatly reduced because the resistance of the earth wire is much smaller than the contact resistance of the human body; in the right image, the system is not grounded, so when a single-phase-to-ground fault occurs, the human body is exposed to the phase voltage, so the possibility of electric shock injury is great. 

C) provide a low-impedance ground-to-ground discharge path for the Lightning induced current. What are the possible consequences of ungrounded? A: there may be personal injury accidents. If the electric cooker's metal shell is grounded, when a single-phase grounding fault occurs, RCD and the main switch will trip protection, of course, the main switch protection current will be greater. If the metal shell of electric cooker is not grounded, when the single-phase grounding fault occurs, RCD and the main switch will not trip protection, so personal injury accidents may occur. The insulation of electrical equipment is damaged, the shell is electrified, when people touch the equipment shell, the current will flow into the human body, endangering human life and safety. If a earth wire is attached to the device housing, the leakage current flows through the earth wire into the earth, and there is no danger of human contact with the housing. Only the earth wire and the earth connection is to do the Earth Pole, and the requirements of Earth Wire and earth resistance should not be greater than 4 ω. If the grounding resistance is greater than 4 ω, the human body contact with leakage equipment is still dangerous. It is not so easy for the family to do the earth, so many people use the galvanized angle iron about 1.5 meters to hit the ground in the damp place, and then lead the wire to the indoor. Others connect grounding wires to metal pipes that reliably touch the earth, such as water mains, which are not standard, but are better than no protection. Some people hit a nail in the wall wiring, which can only release the device on the accumulation of static electricity, can not play a protective role. Such as instruments, meters, computers and other precision equipment when static electricity will affect the normal work of the equipment, you can release static electricity earth wire, the earth wire as long as the house wall or floor contact on it.