A recent electrician friend talked about the problem of zero-line charging in the home circuit, small In response to everyone's discussion, I compiled some reasons for the zero-line electrification and solutions for your reference.
Firewire, neutral, and ground are all wires connected to the three-hole socket, and the sinusoidal oscillation is maintained between the live and neutral wires. Pressure difference. Since the earth and the zero line potential are the same, the live line and the ground line also maintain a sinusoidal oscillation pressure difference. When the human body touches the fire line, the person is standing on the ground. The current of the fire line flows into the earth or the zero line through the human body, and an electric shock accident occurs, and the contact zero line is not subjected to electric shock. The outer casing of the electrical device that can conduct electricity is connected to the ground wire. In the case of leakage, current flows directly into the earth through the ground wire without passing through the body, thereby avoiding an electric shock accident.
The neutral line is not reflected in good grounding. If it is well grounded, the current will flow in. Underground, it will not be detected with an electric pen. If the electric pen is used to detect the neutral line, either the neutral line is broken or the contact is not good. However, this is actually the result, not the reason for the neutral line.
Under normal circumstances, there should be no electricity on the zero line. Therefore, once there is electricity, it is definitely a manifestation of failure;The simplest is electromagnetic induction, and at this time the zero line is not well grounded and fails to form a loop;
Secondly, the electrical equipment Leakage or phase line hits the shell, but the current is not too large, so there is no trip. In the three-phase four-wire power supply system, if the neutral line is not well grounded or the grounding terminal is broken, the consequence is that the potential of the neutral line is not equal to 0 when the three-phase load is unbalanced, that is, the neutral point is biased. shift.
The specific zero line potential is related to the three-phase load imbalance. The more unbalanced, the larger the neutral point offset, the more the neutral line potential high. The phase voltage of the three phases after the zero line potential shift is generally not 220V. Some phases may exceed 220V, and some may be lower than 220V.
The neutral point offset is too large, and the phase of the three-phase phase voltage increases, which may cause it to be burned by electrical appliances, and the phase voltage of the three phases is reduced. The phase may make it impossible for the electrical appliance to work. After the potential of the zero line rises,Touching the ground wire when a certain value is reached will cause a risk of electric shock.
Common causes and solutions for common neutrals
1, there are electrical equipment on the line Leakage, and the end of the protection device, the zero line is charged.
Remedy: Power outage for repair, find the equipment that leaks for repair, and find out the reason for the end of the protection device.
2. There is a phase connection on the line. The total protection device in the power grid is protected at the end to make the neutral line live.
Remedy: After power failure, first measure the line with a shaker to see if the line has poor insulation. Pay attention to the meter in the line when measuring. To disconnect.
3, zero line break,In the electrical equipment behind the break, there is leakage or a large single-phase load operation, which causes the neutral line to be charged.
Remedy: After the power failure, test whether the zero line breaks, the fault is found and repaired.
4. In the zero-connected power grid, some electrical equipment adopts protective grounding and leakage, which causes the neutral line to be charged.
Remedy: Declare whether the system is connected to the ground system or the grounding system, or the grounding system is repeatedly grounded. Then proceed to the correct installation ground.
5. In the zero-connected power grid, there is a single-phase electrical equipment that uses "one fire, one ground", that is, no working zero line, so that the zero line is charged.
Remedy: Install N line, can not use PE line as N line.
6, electrical insulation in the power grid resistance, has been damaged and leakage, so that the zero line is charged.
Remedy: Check the equipment whose insulation resistance does not meet the specified requirements and repair it.
7. In the transformer low-voltage side working ground connection, poor contact, large resistance, unbalanced current in three-phase load When the allowable range is exceeded, the neutral line is charged.
Remedy: Bad contact is not easy to find, it should be repaired every year or according to the prescribed time, can not be lazy, should be repaired according to the regulations.
8, high voltage into the low voltage, so that the zero line is charged.
Remedy: not easy to find,Sometimes there are big problems. The most difficult type to deal with is dangerous to people. Be sure to follow the operating procedures.
9. The high voltage adopts the two-line one-ground operation mode. When the grounding body is too close to the low-voltage working ground or the repeated grounding body, the voltage drop on the high-voltage working ground , affect the low-voltage side working ground, so that the zero line is charged.
Remedy: Find out the cause and lay it according to the corresponding regulations.
10. Magnetic field induction causes the neutral line to be charged.
Remedy: Prevent magnetic field induction.
11, static inductance should cause the neutral line to be charged.
Remedy: Prevent static electricity from occurring.