In actual work, some beginners will simply think that the zero line is the ground line, and the difference between the PE line and the PEN line often used in the power system is not well understood. In the low-voltage installation maintenance and overhaul, the various protection wirings of the household appliances are often confused, resulting in confusion and error in the protection wiring of the electrical appliances, causing unnecessary troubles, and even causing electric shock accidents. Therefore, Xiaobian will give a brief introduction to the meaning of various "lines" in the 380V/220V power system for reference.
Phase line
The phase line, commonly known as the fire line, is relative to the neutral line (zero line) and refers to any of the three phase lines L1, L2, and L3 in the three-phase AC circuit. Usually, household electricity uses only one of the three-phase power. The phase-to-ground (neutral) voltage is 220V, called the phase voltage. It forms a loop with the neutral line to make the current work through the household appliance. The voltage between the phase lines of different phases is 380V, called the line voltage. Normally, the three phase lines L1, L2, and L3 in the three-phase circuit are marked with three colors of yellow, green, and red, respectively.
Neutral line
In the three-phase four-wire or three-phase five-wire low-voltage power supply system, the neutral line is also called the neutral line, the neutral line, the working zero line, and the N line, and the line is marked with black. Usually the neutral line is a line drawn from the neutral point of the transformer. For the grounded grid, the neutral point of the transformer must be grounded, and the grounding resistance is generally not allowed to be greater than 4 Ω.
The role of the neutral line is to keep the phase voltages of the star-connected three-phase asymmetric load symmetrical. For a three-phase symmetrical load, since the neutral current is zero, the neutral line can be omitted. For a three-phase asymmetric load, due to the neutral current, there must be a neutral line balancing the voltage of the three-phase load. Otherwise, the phase voltages of the three-phase asymmetric load are no longer equal (balanced), and the impedance is small. Phase load voltage is low, and the phase with high impedance has a high load voltage, which may cause damage to household appliances. Therefore, in a low-voltage power supply system with asymmetric three-phase load, it is not allowed to install a fuse and a separately controlled switch device on the neutral line, and the neutral wire is usually made of steel-cored aluminum stranded wire to avoid neutral disconnection. have an accident. The difference between the phase line and the neutral line is that they have different voltages to ground, and the phase-to-ground voltage is 220V. Under normal conditions, the neutral-to-ground voltage is zero.
Protection line
The protection wire (also called PE wire, the English name is protecting earthing), is the wire that is connected to the earth through the deep buried electrode, that is, weNo.: 00111 material: Aluminum specification: 0-5m optional model: uqk-01l the principle of electronic liquid level switch is to detect the liquid level through the electronic probe, and then process the detected signal through the special liquid chip for level detection When the measured liquid reaches the action point, the chip outputs high-level or low-level signal, and then cooperates with the water level controller to control the liquid level No floating ball and reed, no external mechanical action, pollution resistance and durability, not afraid of the influence of floating objects It can be installed at any angle The vertical installation has certain anti - wave function and is suitable for immersion in water for a long time The working voltage is DC 5-24v, which is very safe This method is practical,
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