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Voltage level is a key parameter in the power system, which indicates the voltage value used in the transmission and distribution of electric energy at different stages. According to the functional requirements and safety requirements of the power system, the voltage level is divided into several different grades to meet the different requirements of each link of power generation, transmission, distribution and consumption. This division not only helps optimize the efficiency of power transmission, but also ensures the reliability and safety of the system.
1. Basic classification of voltage levels
In the power system, voltage levels are usually classified according to the voltage value, mainly including the following categories:
1. Low voltage (LV):
Low voltage generally refers to the voltage level below 1kV. Low voltage systems are widely used in residential areas, commercial areas and some small industrial facilities for power supply. Common low voltage values include 220V and 380V. The former is usually used for power supply of household and small commercial appliances, while the latter is often used for small industrial equipment and some high-power household appliances. Low voltage voltage level has relatively high safety due to its low voltage, but due to the limited transmission distance, it is suitable for short-distance power supply.
2. Medium Voltage (MV):
Medium voltage levels are generally between 1kV and 35kV, and are mainly used in distribution networks. Medium voltage power systems are common in urban distribution networks and internal power supply of medium and large industrial facilities. Typical medium voltage levels are 10kV, 20kV and 35kV. These voltage levels are usually stepped down by distribution transformers before being provided to end users. Medium voltage systems can effectively transmit power over long distances while maintaining a certain transmission efficiency and safety.
3. High Voltage (HV):
High voltage levels usually refer to voltages between 35kV and 220kV, which are mainly used for long-distance transmission and power transmission between substations. Common high voltage levels are 110kV and 220kV, which are widely used in inter-regional transmission networks. In high voltage transmission systems, due to the high voltage and relatively low current, this can effectively reduce the loss of power during transmission, while reducing the cross-sectional area of the transmission line, thereby reducing costs.
4. Extra High Voltage (EHV):
Extra high voltage refers to voltage levels between 220kV and 1000kV, mainly used for UHV transmission lines. The UHV power system is designed to transmit large amounts of electrical energy over longer distances, and is usually used to transmit electricity from distant power plants to load centers. Typical UHV levels include 330kV, 500kV, and 750kV. Within this voltage range, the power transmission efficiency is very high, but the requirements for power equipment are also more stringent, including higher insulation requirements and more complex system protection mechanisms.
5. Ultra High Voltage (UHV):
Ultra high voltage refers to voltage levels of 1000kV and above. The UHV power system is an important direction for the development of modern power system technology, mainly used for large-scale power transmission over ultra-long distances. The application of UHV can greatly reduce energy loss in long-distance transmission and improve the economy and stability of the system. China is one of the few countries in the world that has mastered UHV technology and applied it on a large scale. Typical UHV levels include 1000kV AC transmission and ±800kV DC transmission.
2. The significance of voltage level division
The division of voltage levels is of great significance in the power system:
1. Optimizing power transmission: Different voltage levels are suitable for different transmission distances and load requirements. Through reasonable voltage level selection, the power system can minimize power loss and improve economic benefits while meeting power supply needs.
2. Safety and reliability: The division of voltage levels can also improve the safety and reliability of the power system. By operating at different voltage levels, the power system can effectively isolate problems when faults occur and reduce the impact on the entire system.
3. Economy: Different voltage levels correspond to different equipment and material requirements. High-voltage equipment is usually more expensive, but its efficient transmission capacity can make up for this. Low-voltage equipment is less expensive and suitable for short-distance power supply. Therefore, the reasonable division of voltage levels helps to control the construction and operation costs of the power system.
The division of voltage levels is a basic and important principle in the design and operation of power systems. Through reasonable voltage level division, the power system can ensure the safety and reliability of the system while ensuring efficient transmission of electric energy, providing strong support for the society's power supply.
