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The electricity used by the local government is 220V, and the industrial electricity is 380V. Why is the electricity coming out of the substation different from the user terminal? What is the difference between high pressure and low pressure?
Industrial electricity and residential electricity
Industrial power is actually the three-phase alternating current that we often refer to (the power system consisting of three AC circuits with the same frequency, equal potential amplitude and 120° phase difference), while the civil power uses a single-phase 220V pair. Residents supply electricity.
The three-phase alternating current can rotate the motor. When the three-phase alternating current flows into the three-phase stator winding, a rotating magnetic field is generated in the stator cavity. The rotor conductor that is stationary before the rotation is equivalent to the magnetic field line of the rotor conductor that relatively cuts the magnetic field under the action of the rotating magnetic field, thereby generating an induced current (electromagnetic induction principle) in the rotor conductor. These rotor conductors with induced currents move in the magnetic field, so industrial power is three-phase alternating current.
The voltage between the live and neutral lines of civil power is 220V, and the industrial power is 380V between the phases, and the voltage between the phases is 220V. Civil power is actually one of the three phases. The power plant to the residential substation is a 3-phase and 5-line. One of the functions of the substation is to divide the electricity into a number of 1-phase and 3-line lines for residents to use.
High pressure and low pressure boundary
According to the definition of 2.1 in GB/T 2900.50-2008, high [electrical] pressure generally refers to a voltage level higher than 1000V (not included), and low [electrical] pressure refers to a voltage of 1000V or less in an AC power system used for power distribution. Grade; internationally recognized high-voltage and low-voltage electrical appliances have a dividing line AC voltage of 1000V (DC is 1500V).
There is another saying in the industry that the voltage of 380V or above is called high-voltage electricity, so we are used to saying that 220V, 380V are low voltage, higher than this voltage is high voltage; before the electric industry regulations The prescribed boundary line is 250V. Although the new "Electricity Safety Work Regulations" has been introduced, many places have implemented the previous standards.
Popular classification of high voltage electrical appliances
1. There is no essential difference between the so-called high pressure, ultra high pressure and extra high pressure. (As the voltage increases, the insulation requirements and safety requirements will be different), but people's names are different. The dividing line is also customary and there is no clear regulation.
2. The power grid refers to the entire power supply and distribution system, including power plants, substations, lines, and power consumers.
3. For the purpose of protecting the normal operation of the equipment, the nominal voltage of the power grid is lower than the rated low voltage on the equipment, that is to say, the 12KV power equipment (or switch) is to be used for the 10KV power grid, and the 40.5KV power equipment. (or switch) to be used in the 35KV grid.
The voltage levels of substations that are common in China are generally divided into: national level generally 500KV, 750KV, provincial level 220KV, and prefecture level 110KV, 66KV, 35KV, 10KV, 400V. At the same time, in order to better improve the quality of high-quality power, the state requires that nationwide substations need to install power quality online monitoring devices to monitor each bus. ZLG Zhiyuan Electronics' E8000 series power quality online monitoring device has a measuring accuracy of 0.1%, meets national standards and requirements, and meets all domestic voltage level grid measurement. It has become an indispensable professional monitoring device in the industry.
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