The reason for using high voltage for long-distance power transmission is as follows: The reason for using this method of power transmission is that under the same transmission power, according to the formula P=UI, the transmission current I must be reduced, while the transmission power P remains unchanged (large enough ), it is necessary to increase the transmission voltage U. The higher the voltage, the smaller the current, so that high-voltage power transmission can reduce the current during power transmission, thereby reducing the heat loss caused by the current and reducing the material cost of long-distance power transmission. According to Joule's law Q=I^2Rt, there are three ways to reduce the heat generation Q: one is to reduce the transmission time t, the other is to reduce the resistance R of the transmission line, and the third is to reduce the transmission current I. It can be seen that the third method is very effective: the current is reduced by half, and the lost electric energy is reduced to a quarter of the original. To reduce the loss of electric energy, the transmission current must be reduced. On the other hand, power transmission is to transmit electric energy, and the transmitted power must be large enough to be practical.Obviously, high pressure delivery is economical. After the high voltage is used to transmit electric energy to the power consumption area, the voltage needs to be lowered successively to return to the normal voltage. The electric energy sent from the power station is generally sent to various places where electricity is used through transmission lines. Different high voltages are used according to the distance of the power transmission distance. From the perspective of my country's power situation, when the power transmission distance is 200-300 kilometers, 220 kV is used for power transmission; when it is about 100 kilometers, it is 110 kV; 10 kV, 12 kV are used for ~20 kilometers, and some use 6300 volts. Lines with transmission voltages of 110 kV and 220 kV are called high-voltage transmission lines, lines with transmission voltages of 330, 550, and 750 kV are ultra-high voltage transmission lines, and lines with transmission voltages of 1000 kV are called It is called UHV transmission line.