The Advantages of AC Power
The advantages of AC power are mainly:
1. The generator of the AC system is relatively simple and the cost is relatively low.
2. The voltage conversion of the AC system is very convenient to use a transformer, and the efficiency is very high, which can reach more than 90%, and it is also very safe. This brings great convenience to the change of the transmission voltage and the use of household low-voltage appliances, such as mobile phone chargers, audio systems, DVDs, MP3s, emergency lights, notebook computers, and so on. If it is a DC system, it is necessary to step down the resistor. The power of the step-down resistor is sometimes very large, and the power consumed is also large. There are also security risks.
3. The motor of the AC system is more convenient to manufacture and use, especially the three-phase asynchronous motor used in three-phase power supply, which can automatically generate a rotating magnetic field to drive the rotor to rotate, and no starting circuit and brushes are needed at all. Simple structure and low cost. Can also be made into many types of brushless motors. Brushless motors have less interference with electrical systems and less noise. AC motors use a variable frequency speed control system to save power and be convenient, such as air conditioners and refrigerators. The sparks generated by the electric brush when the motor is rotating not only cause serious interference to the electrical system, but also generate ozone, pollute the air, and affect human health.
4. As for electromagnetic radiation, it is insignificant for low-frequency power frequency communication of only 50Hz. The impact on the human body is even smaller than that of mobile phones and computers.
In terms of long-distance transmission: The biggest disadvantage of AC high-voltage long-distance transmission is that as the transmission voltage continues to increase, the transmission loss and electromagnetic induction gradually increase. At this time, the power loss caused by electromagnetic radiation will be large. Because the two wires are equivalent to a capacitor, although the capacitance is small and the transmission frequency is relatively low, the leakage current generated at long distances and ultra-high voltages will be relatively large, resulting in relatively large transmission losses.
In addition, alternating current will generate electromagnetic induction, which will have a certain impact on conductive objects along the way. Plants under AC high voltage transmission lines are taller than elsewhere. The metal clothesline parallel to the AC high-voltage power transmission line will induce a higher voltage and cause an electric shock to the human body.
HVDC transmission has obvious advantages in UHV and long-distance transmission. Since direct current does not pass through capacitors, the leakage loss of the direct current transmission line is much smaller than the alternating current transmission of the same voltage. The electromagnetic induction of DC transmission is almost zero, and the effect on conductive objects along the way is also very small. Therefore, the loss of the electric DC transmission line is small, and the safety of the transmission is higher than the AC transmission of the same voltage.
Realization of DC UHV long-distance transmission: The power plant generates AC power, which is boosted to UHV when it is transmitted, and then becomes DC (the most critical technology) to form DC UHV (above 750KV), and then performs long-distance DC (Over thousands of kilometers).
We know that when the same electrical power is transmitted, the higher the voltage, the smaller the current in the wire, and the smaller the loss caused by the wire. At the end of the DC UHV transmission, the UHV DC must be changed to UHV AC (the most critical technology), and then the voltage is reduced by a transformer to become high-voltage AC power (about 220KV) and integrated into the existing regional power grid to implement AC power supply. In this way, DC UHV transmission is realized.
1. The generator of the AC system is relatively simple and the cost is relatively low.
2. The voltage conversion of the AC system is very convenient to use a transformer, and the efficiency is very high, which can reach more than 90%, and it is also very safe. This brings great convenience to the change of the transmission voltage and the use of household low-voltage appliances, such as mobile phone chargers, audio systems, DVDs, MP3s, emergency lights, notebook computers, and so on. If it is a DC system, it is necessary to step down the resistor. The power of the step-down resistor is sometimes very large, and the power consumed is also large. There are also security risks.
3. The motor of the AC system is more convenient to manufacture and use, especially the three-phase asynchronous motor used in three-phase power supply, which can automatically generate a rotating magnetic field to drive the rotor to rotate, and no starting circuit and brushes are needed at all. Simple structure and low cost. Can also be made into many types of brushless motors. Brushless motors have less interference with electrical systems and less noise. AC motors use a variable frequency speed control system to save power and be convenient, such as air conditioners and refrigerators. The sparks generated by the electric brush when the motor is rotating not only cause serious interference to the electrical system, but also generate ozone, pollute the air, and affect human health.
4. As for electromagnetic radiation, it is insignificant for low-frequency power frequency communication of only 50Hz. The impact on the human body is even smaller than that of mobile phones and computers.
In terms of long-distance transmission: The biggest disadvantage of AC high-voltage long-distance transmission is that as the transmission voltage continues to increase, the transmission loss and electromagnetic induction gradually increase. At this time, the power loss caused by electromagnetic radiation will be large. Because the two wires are equivalent to a capacitor, although the capacitance is small and the transmission frequency is relatively low, the leakage current generated at long distances and ultra-high voltages will be relatively large, resulting in relatively large transmission losses.
In addition, alternating current will generate electromagnetic induction, which will have a certain impact on conductive objects along the way. Plants under AC high voltage transmission lines are taller than elsewhere. The metal clothesline parallel to the AC high-voltage power transmission line will induce a higher voltage and cause an electric shock to the human body.
HVDC transmission has obvious advantages in UHV and long-distance transmission. Since direct current does not pass through capacitors, the leakage loss of the direct current transmission line is much smaller than the alternating current transmission of the same voltage. The electromagnetic induction of DC transmission is almost zero, and the effect on conductive objects along the way is also very small. Therefore, the loss of the electric DC transmission line is small, and the safety of the transmission is higher than the AC transmission of the same voltage.
Realization of DC UHV long-distance transmission: The power plant generates AC power, which is boosted to UHV when it is transmitted, and then becomes DC (the most critical technology) to form DC UHV (above 750KV), and then performs long-distance DC (Over thousands of kilometers).
We know that when the same electrical power is transmitted, the higher the voltage, the smaller the current in the wire, and the smaller the loss caused by the wire. At the end of the DC UHV transmission, the UHV DC must be changed to UHV AC (the most critical technology), and then the voltage is reduced by a transformer to become high-voltage AC power (about 220KV) and integrated into the existing regional power grid to implement AC power supply. In this way, DC UHV transmission is realized.