power transmission system power

In order to make full use of power resources, reduce fuel transportation, and reduce power generation costs, it is necessary to build hydropower
stations where there are water resources and thermal power plants where there are fuel resources. However, these places with power resources are often far away from power centers, so high-
voltage transmission lines must be used for long-distance power transmission, as shown in Figure 15-1.
    A power generation, transmission, transformation, distribution and consumption entity that connects some power plants, substations and power users through power lines of various voltage levels
  is called a power system. The power lines of various voltage levels in the power system and their associated substations are called
  power circuits or power networks ;. But it is customary to distinguish electric power supplies by voltage and other strong components, such as lOkV power grid or lOkV
    1:
  system.
    The electricity or system referred to here actually refers to the entire interconnected power line of a certain voltage level.
    The power grid can be divided into regional power grid and local power grid according to the voltage level and power supply range. The scope of the regional power grid is limited, and the voltage is generally 220kV
  and above. The scope of the local power grid is small, and the maximum voltage generally does not exceed 110kV. The factory power supply system is a type of local power grid.
    The power system plus the power part of the main power plant and its thermal energy system and thermal energy users are called the power system. .
    Nowadays, the power systems established by various countries are getting larger and larger, and even transnational power systems or combined power grids are established. The establishment of a large power system or a
  combined power grid can make more economical and reasonable use of power resources (first of all, make full use of water resources), reduce fuel transportation costs, reduce power consumption
  , reduce power generation costs, and ensure the quality of power supply (that is, the voltage and frequency are within specifications) requirements), and greatly improve the reliability of power supply, which is conducive to the sustainable development of the entire
  national economy .
    The process of high-voltage transmission is shown in Figure 15-1. The high-voltage power lines that step up the voltage from the power plant or substation and transmit the power to the step-down substation are called
  transmission lines, and the voltage is generally above 35kV.
    The power line that sends power from the step-down substation to the distribution transformer is called a high-voltage distribution line, and the voltage is generally 3, 6, or 10 kV.
    The line that delivers power from the distribution transformer to the point of consumption is called a low-voltage distribution line, and the voltage is generally 380V or 220V.
    As far as distribution lines are concerned, those with voltages generally between 1 and 10 kV are called high-voltage distribution lines, and those with voltages below 1 kV are called low-voltage distribution lines.
    At present, the voltage levels of my country's power lines are: 6kV, 8kV, 10kV, 35kV, 110kV, 220kV, and 330kV.