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The high-voltage power transmission is ABC three-phase, which is sent to the user end, and then the voltage is changed to the user target voltage through the transformer. The neutral point on the transformer is grounded and then leads out to the neutral line. What do you mean by the loop in the circuit?

The phase difference between any two of the three live wires is 120 °, so there is a potential difference between the two at any time, which can certainly form a loop.

380V between fire and fire. There is also a zero line, each of which is 220V between fire and zero. Generally, the main cable entering the distribution cabinet is a five wire three phase system, that is, three phase cables (three fire cables), one zero cable and one ground cable. When entering the house from the power distribution cabinet, one fire, one zero, and one ground are used. Fire and zero form a loop through the electrical appliance.

The three-phase electric phase angles differ by 120 degrees, and the electric ground electromotive force (voltage) and direction of each phase are different at the same time.

However, whenever the electromotive force of three phases is added to zero. When one line goes in, the other two lines go out, and the other two lines go in and out. Repeat the cycle 50 times per second.

Three of the three motors are live wires, and any two of them are loops. The waveforms of the three lines are staggered by 120 degrees, that is, the voltage peaks of the three lines are not at the same point, and the current flows back and forth between lines

The three live wires, that is, the phase line, are 120 degrees each, that is, they form a vector with directions. Normally, the three phases are balanced, equal in size, different in direction, and there is voltage between each phase, that is, line voltage. This is different from the phase to the zero line. When balancing, the neutral point is zero, because this is itself a balance body, For low-voltage users, the power supply is a loop composed of live line and neutral line, that is, three-phase four wire, three-phase and neutral line. The statement of self forming circuit you mentioned is not very clear. For AC power, normally, three-phase power exists at the same time, and there is a problem due to the lack of one on the contrary. Our common high-voltage transmission lines are three-phase transmission. From the power plant to the substation, or between the substations, users can not directly use the high-voltage power transmission. It is necessary to gradually reduce the voltage.

Answer the invitation of "Little Secretary Wukong"!

How can the three high-voltage power lines form their own loops?

The knowledge of electricity is profound, and those who understand it feel that it is too simple. For those old people who have not learned physics, they still do not understand after you say a lot of book knowledge. Today, I will throw aside foreign theories and say something simple that everyone knows.

I can wind inverters and various small transformers. I know a little about the working principle of transformers. Much the same, as long as it is AC power, if you want to use a transformer to reduce voltage, you need to use silicon steel sheet and enameled wire to wind the coil. The coil is wrapped on the silicon steel sheet insulation core, integrated and sealed. After the high-voltage input, a magnetic field is generated, and the secondary coil gets the induced current.
The transformer in our community inputs tens of thousands of volts of high voltage, but the number of output turns must be proportional to the number of input high-voltage turns when winding the transformer to get the voltage you need. For example, if I use 220V to wind a 12V small transformer, the 220V input is designed with 5 turns per volt, which is 1100 turns, and the output 12V low-voltage end is wound with 60 turns. If I want to wind it into three groups with output low voltage of 12v, you must wind it in three groups with 60 turns each. In this way, three electrical appliances can be used to supply power separately without interference. (If I want to balance the voltage of three groups of coils, connect one head of each group in parallel, which is the same principle as the transformer in the community!)

Although the transformer in the community is wound in three groups, there are six heads in total. They put one head of each group together and call it "neutral line". This neutral line should be connected to the transformer shell, and it should be buried underground before being led out. This neutral line and each of the three phases are 220V, and each of the three phases is 380V, All users can use electricity from the three-phase four wire distribution here. If the power consumption of which line is low, what will happen to the voltage used in this line?

I prepare three buckets of water. The bottom of the bucket and the bucket imitate the neutral line of the transformer. Use a thick pipe to connect the water in the bucket. What will happen if the bucket A discharges water? The water in bucket B and bucket C will naturally balance. This is the principle of transformer. The voltage of the three-phase line with the neutral line circuit will restrict and balance each other like the principle of three connected buckets.

How can this electricity be balanced? Because the total power of the input high-voltage primary coil is divided equally among three groups of low-voltage coils, and the other end of each phase coil of them is connected into a neutral line. The same turns and the same thick coil ensure that no matter which of the three phases is output through the zero line circuit, or the star or triangle connection of the three-phase motor, Will keep the three phases in balance.

Thank you for reading?!