Nominal voltage of the system, the upper limit of the output voltage of the system power supply. The nominal voltage usually refers to the open circuit output voltage, that is, the voltage value at which no load is connected and there is no current output. It is consistent with the rated voltage of the protected system; in the information technology system, this parameter indicates the type of protector that should be selected, and it marks the effective value of the AC voltage. (System) The nominal voltage is for the system. It is usually established by a standard and has a voltage that determines the value of the voltage level.
The introduction of the nominal voltage of the system is consistent with the rated voltage of the protected system; in the information technology system, this parameter indicates the type of protector that should be selected, and it marks the effective value of the AC voltage.
The nominal voltage usually refers to the open circuit output voltage 1, that is, the voltage value at which no load is connected and there is no current output. Therefore, it can also be considered that this is the upper limit of the output voltage of the power supply.
Nominal voltage of a system: A given value used to mark or identify the system voltage. (GB/T 2900.50-1998, 2.1 No. 601-01-21).
Rated voltage: The voltage specified by the manufacturer for an electrical device under specified working conditions. (GB/T 2900.1-2008, 3.5.86).
Among them, these two voltages are both effective value or root-mean-square value.
The difference between these two voltages is:
(System) The nominal voltage is for the system. It is usually established by a standard and has a voltage that determines the value of the voltage level. For example, the GB/T 156-2007 standard voltage gives some nominal voltage values: 220V, 380V, 3kV, 10kV, 110kV, 220kV, etc.
The rated voltage (of the equipment) is specific to the equipment. Established by the manufacturer, it usually refers to the maximum voltage that the equipment can work normally for a long time. In this case, the rated voltage of the equipment is higher than the nominal voltage of the system. That is, the rated voltage of the circuit breaker is 12kV), it can be seen that 12kV is higher than the nominal voltage of the system 10kV. Usually the voltage on the nameplate that we can see is the rated voltage.
As for the bus example, we usually say 10kV bus, 110kV bus, etc. The voltage level here is the nominal voltage of the corresponding system. The actual busbar rated voltages are 1kV, 3.15kV, 6.3kV, 10.5kV, 35kV, etc. (GB/T 8349-2000).
Related introduction Rated voltage refers to the optimal voltage when electrical equipment works normally for a long time2, and the rated voltage is also called the nominal voltage. When the working voltage of the electrical equipment is higher than the rated voltage, it is easy to damage the equipment, and when the voltage is lower than the rated voltage, it will not work normally (such as the abnormal light of the bulb and the abnormal operation of the motor).
Rated voltage is the standard voltage for long-term stable operation of electrical equipment (including electricity and power supply equipment)
Power system composition
The rated voltage can be understood from both the electrical equipment and the power supply equipment. The rated voltage of the electrical equipment represents the optimal input voltage designed when the equipment leaves the factory, and is usually the power supply voltage that is relatively easy to obtain. The rated voltage of the power supply equipment represents the optimal output voltage of the power supply system, which needs to be matched with the rated voltage of the electrical equipment, including the rated voltage of the grid, the rated voltage of the generator, and the rated voltage of the power transformer.
Under the rated voltage, electrical equipment, generators and transformers have the greatest economic benefits during normal operation. At this time, all the components in the equipment are working in the best condition, the performance is relatively stable, and the service life is relatively long. Specifying the rated voltage of electrical equipment is conducive to the production standardization and serialization of the electrical manufacturing industry, the standardization and selection of design, the interconnection and replacement of electrical appliances, and the production and maintenance of spare parts. In addition, in order to avoid the unlimited expansion of the number of voltage levels, leading to difficulties in interconnection, the rated voltage of the power grid must be standardized. In order to achieve the best technical and economic performance, power equipment needs to be optimally designed, manufactured and used under the rated voltage.
The grid voltage is graded, and the rated voltages of the power equipment in the grids at all levels are quite different. The rated voltage level of the power grid is formulated and promulgated by the state after comprehensive analysis and demonstration in accordance with the needs of national economic development, the rationality of technology and economy, and the manufacturing level of electrical equipment.
The rated voltage of the electrical equipment,
Rated voltage of electrical equipment = rated power x resistance.
The calculation method of the rated voltage of electrical appliances is the same as that of ordinary voltage calculation, but it is usually a fixed value to facilitate matching with the power supply system. The rated voltage of the electrical equipment is consistent with the rated voltage of the grid. In fact, due to the voltage loss in the power grid, the actual voltage at each point deviates from the rated value. In order to ensure the good operation of electrical equipment, the state has strict regulations on the deviation of the grid voltage at all levels. Obviously, electrical equipment should have a wider range of normal operating voltage than the allowable deviation of the grid voltage.
The National Standard of the People's Republic of China "Standard Voltage (GB/T 156-2007)" is published by China Standard Press.