Ultra – high – voltage (UHV) transmission, with voltages of 1000 kV or higher, has become an important technology for long – distance and large – capacity power transmission. The principle behind UHV transmission is based on several key electrical concepts.
One of the main reasons for using UHV is to reduce power losses during transmission. According to Joule’s law, the power loss in a transmission line is given by P_{loss}=I^{2}R, where I is the current flowing through the line and R is the resistance of the line. When transmitting a large amount of power P = UI (where U is voltage and I is current), if the voltage U is increased, the current I can be decreased for the same amount of power. Since the power loss is proportional to the square of the current, reducing the current significantly reduces the power loss. For example, doubling the voltage while keeping the power constant reduces the current by half, and the power loss is reduced to one – fourth of the original value.
Another principle is related to the capacitance and inductance of the transmission line. In UHV systems, the long – distance transmission lines have significant capacitance and inductance. The capacitance can cause charging currents, and the inductance can lead to voltage drops. Special design techniques are used to manage these effects. For instance, shunt reactors are installed along the UHV lines to compensate for the capacitive charging current. This helps to maintain the voltage stability of the line.
UHV transmission also allows for more efficient use of land resources. Because UHV lines can transmit a large amount of power in a single circuit, fewer transmission lines are needed compared to lower – voltage systems for the same power transmission capacity. This reduces the land area required for right – of – way corridors, which is especially important in densely populated areas or areas with limited land availability.
In addition, the insulation requirements for UHV transmission are extremely high. Specialized insulators, such as long – rod composite insulators and large – diameter porcelain insulators, are used to prevent electrical breakdown. These insulators are designed to withstand the high electrical stresses associated with UHV.
In summary, the principle of UHV transmission involves reducing power losses through high – voltage, low – current operation, managing the electrical effects of capacitance and inductance, efficient land use, and ensuring proper insulation to enable the reliable long – distance and large – capacity transfer of electrical power.
