Electrical grounding and zero connection (pictures are not repeated)
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A protective method that reliably connects the metal shell of electrical equipment and the metal frame connected to the shell to the earth using a grounding device to ensure personal safety is called protective grounding, or grounding for short. The method of connecting the metal shell of electrical equipment and the metal frame connected to the shell to the neutral line of the power system with the neutral point grounded to protect personal safety is called protective zero connection (also called protective neutral connection), or zero connection for short. Protective grounding is generally used in power grids with ungrounded neutral points below 1,000 volts and power grids above 1,000 volts. Protective zero connection is generally used in three-phase four-wire power grids with a neutral point grounded below 1000 volts. Currently, protective zero connection measures are widely used in three-phase four-wire power grids with a neutral point grounded of 380/220 volts for lighting. In a system with an ungrounded neutral point, assume that the A-phase winding of the motor touches the metal shell due to insulation damage, and the shell is charged (see Figure 5-5). In the absence of protective grounding, when the human body touches the shell, the current passes through the human body and the ground insulation resistance Re and RC of the other two live wires (if the wire is very long, the capacitance between the wire and the earth must also be considered) to form a loop. If the other two live wires are not well insulated from the ground, the current flowing through the human body will exceed the safe limit and cause danger. In the case of protective grounding, when the human body touches the live shell, the current is divided into two paths at the point where phase A touches the shell. One path passes through the resistance Rd of the grounding device, and the other path passes through the human body resistance Rr. After these two paths merge, they pass through the ground insulation resistance Re and RC of the other two live wires to form a loop. Due to Re
well. . Why do I see grounded posts again? . I don’t know which era this theory was from. Looking at the straight hair:@ I asked the poster. . What are your backup measures against electrocution? (That is, leakage protection)? Nowadays, it is almost not recommended to use the zero connection method. Direct PE+N, and. Most of the neutral points of transformers also need to be grounded, commonly known as working grounding. Grounding the equipment end again should be called repeated grounding. This is the most commonly used power supply and protection mode, similar to TN-S (including TN-CS). . The above post actually said: The neutral point grounding system "should" adopt protective zero connection. . That waterfall is sweaty :L When did we return to TN-C in the era of Big Brother Soviet Union ;P
After doing electrical work for so many years, grounding and zero connection have always troubled everyone. The reason is that our country's standards are not in line with international standards. We electrical workers are still reluctant to abandon the outdated names that have been inherited. It is conceivable that it is even more difficult for non-electrical personnel to distinguish! Until now, people have been talking about the three-phase and several-wire system, putting aside the grounding form and just talking about grounding, zero connection, etc., so much so that some design drawings are marked like this. This may be our sorrow!
Today's leakage protectors can completely protect you when the grounding or zero connection effect is not good, and current equipment must be equipped with leakage protection devices, because you don't know whether the grounding is safe and reliable.
Supporting new norms and high technologies, and integrating with the world is the last word! GB 14050-2008 Types and safety technical requirements for system grounding
Our company uses TN-S and TN-CS wiring methods
Haha,,, learn again* ,,,good information
Don’t underestimate grounding, knowledge is huge. :victory:
good..................