Ac power cables are divided into neutral lines with the letter "N". Firewire, marked with the letter "L". Electrical appliances are also connected to ground cables -- wires that connect to the earth.
Live wire, neutral wire, ground wire are connected to the three-hole socket wire, between the live wire and the neutral line to maintain a sinusoidal oscillating pressure difference. Because the ground and the zero line have the same potential, the fire line and the ground line also maintain a sinusoidal oscillatory pressure difference.
When THE human body CONTACTS 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, can produce electric shock accident, and the contact zero line will not be electric shock. The housing of electrical appliances that can conduct electricity is connected with the ground wire. In the case of leakage, the current will flow directly into the earth through the ground wire and not through the body, so as to avoid electric shock.
The null line is not well grounded. If it is well grounded, the current will flow into the ground and the pen will not be detected. If the electric pen detects that the neutral line is charged, the neutral line is either broken or not in good contact. But this is actually the result; not because the null line is charged.
The three-phase neutral wire is charged
1. Under normal circumstances, there should be no electricity on the zero line. So, once there is electricity, it is definitely a sign of failure; the simplest is electromagnetic induction, and at this time the null line is not well grounded, failed to form a loop;
2, electrical equipment leakage or phase line hit the shell, but the current is not large, so there is no trip. In the three-phase four-wire power supply system, if the neutral line grounding is not good or the ground end 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 to say, the neutral point is offset.
The specific zero line potential is related to the three phase load imbalance. The more unbalanced, the greater the neutral point offset, the higher the zero line potential. After zero line potential offset, the phase voltage of the three phases is generally not 220V. Some phases may exceed 220V, while others may fall below 220V.
When the offset of the neutral point is too large, the phase with the increase of the three-phase voltage may cause its electrical appliances to burn out, and the phase with the decrease of the three-phase voltage may cause its electrical appliances to not work. When the zero line reaches a certain value, touching the ground will cause the danger of electric shock accident.
3. The null line is broken, making the null line charged
4, in the connection to the power grid, some individuals, in order to protect electrical appliances and take grounding, make the neutral line live
5, take a long cable power supply, in the electrical equipment is not used when the induction charged, when the equipment is used, this phenomenon will disappear automatically.
6. The neutral line is directly grounded and not connected to the system neutral line.
7, zero wire and live wire lap
8, three-phase electrical load imbalance, zero potential drift, voltage.
The neutral line is live
1. Focus on checking the connection mode and connection effect of each connection of the zero line.
2. The neutral line should pass through all phase line currents. Generally, the area of the neutral line should be large enough, or multiple neutral lines should be arranged from the main switch box.
3. Check for wire breakage caused by various reasons, such as accidental injury caused by external forces such as wall drilling.
4, if the light caused by the zero line flash is broken, please check the lamp head is short circuit, light switch quality, if it is all parts of the zero line with points, please check the total switch box zero row; if the zero row is charged, the problem is the zero line before the zero row.
Case by case
1. There is leakage of electrical equipment on the line, and the protection device does not act, so that the neutral line is charged.
Solution: power outage maintenance, find out the leakage of equipment repair, and find the reason for the end of the protection device action.
2, there is a phase on the line, the total protection device in the power grid is not protected, so that the neutral line is charged.
Solution: After the power failure, first use the meter to measure the line to see if there is bad insulation of the line, and pay attention to the meter in the line to disconnect.
3. The neutral line is broken, and there is leakage or large single-phase load running in the electrical equipment behind the fracture, so that the neutral line is charged.
Solution: After the power failure, test whether the zero line is broken, and find and repair the broken line.
4, in the zero grid, there are individual electrical equipment to take protective grounding and leakage, so that the zero line live.
Solution: distinguish whether the system is a zero-connected system or a grounded system, or if the zero-connected system is repeatedly grounded. Then install the ground cable correctly.
5, in the zero power grid, there are single-phase electrical equipment using "one fire, one ground" that is, no working zero line, so that the zero line live.
Solution: Install N line, do not use PE line as N line.
6, in the grid some electrical equipment insulation resistance, has been damaged and leakage, so that the null line charged.
Solution: Check out if the insulation resistance does not meet the requirements of the equipment, repair.
7, in the transformer low voltage side of the working ground connection is poor contact, there is a large resistance, in the three-phase load imbalance current exceeds the allowable range, the zero line charged.
Solution: bad contact is not easy to find, to overhaul every year or according to the prescribed time, can not be lazy, to overhaul according to the rules.
8, high pressure into low pressure, so that the zero line electrified.
Solution: It's hard to find, and sometimes big problems. One of the toughest, most dangerous to humans. Be sure to follow the operating procedures.
9, high voltage to take two lines one ground operation mode, the grounding body and low voltage working grounding or repeated grounding body is too close to each other, the voltage drop on the high voltage working grounding, affect the low voltage side working grounding, so that the null line is charged.
Solution: find out the reason, according to the corresponding procedures for laying.
10. Magnetic field induction causes the null line to be charged.
Solution: Prevent magnetic field sensing.
11. Electrostatic induction causes the null line to be charged.
Solution: Prevent electrostatic induction.