National standards related to power quality
The nominal frequency of my country's power system is 50Hz. GB/T15945-2008 "Power Quality Power System Frequency Deviation" stipulates that the frequency deviation limit is ±0.2Hz under normal operation conditions of the power system. When the system capacity is small, the deviation limit is It can be relaxed to ±0.5Hz, and there is no limit on the size of the system capacity in the standard. In the "National Power Supply Regulations", it is stipulated that "the allowable deviation of the power supply frequency of the power supply bureau: ±0.2HZ for grid capacity of 3 million kilowatts and above; ±0.5HZ for grid capacity below 3 million kilowatts. Actual operation , From the operation of all major power systems across the country, it is maintained within the range of no more than ±0.1HZ.
GB/T12325-2008 "Power Quality Supply Voltage Deviation" stipulates that the absolute value of the positive and negative deviations of the power supply voltage of 35kV and above shall not exceed 10% of the nominal voltage; the deviation of the three-phase power supply voltage of 20kV and below is the nominal voltage The deviation of 220V single-phase power supply voltage is +7%, -10% of the nominal voltage.
Three-phase voltage unbalance
GB/T15543-2008 "Power Quality Three-phase Voltage Unbalance" stipulates that the voltage unbalance limit of the public connection point of the power system is: when the power grid is operating normally, the negative sequence voltage unbalance shall not exceed 2%, and shall not exceed 4%; The zero sequence voltage limit of the low-voltage system is temporarily not specified, but the voltage of each phase must meet the requirements of GB/T12325. The allowable value of the negative sequence voltage imbalance caused by each user connected to the common connection point is generally 1.3%, and does not exceed 2.6% in a short time.
Utility grid harmonics
GB/T14549-93 "Power Quality Public Grid Harmonics" stipulates that the total harmonic distortion rate of public grid voltage (phase voltage) at all levels of 6～220kV is 0.38kV to 5.0%, 6～10kV is 4.0%, and 35～ 66kV is 3.0%, 110kV is 2.0%; the allowable value of harmonic current injected into the grid by the user should ensure that the harmonic voltage of the grid at all levels is within the limit, so the national standard specifies the total harmonic distortion rate of the voltage generated by the harmonic source of the grid at all levels Yes: 0.38kV is 2.6%, 6～10kV is 2.2%, 35～66kV is 1.9%, and 110kV is 1.5%. For 220kV grid and its power users, refer to this standard 110kV.
Interharmonics in public grid
GB/T24337-2009 "Power Quality Public Grid Interharmonics" stipulates: Interharmonic voltage content rate is 1000V and below <100Hz is 0.2%, 100~800Hz is 0.5%, above 1000V <100Hz is 0.16%, 100~ 800Hz is 0.4%, and 800Hz above is under study. The inter-harmonic content rate of a single user is 0.16% for 1000V and below <100Hz, 0.4% for 100~800Hz, 0.13% for 1000V above <100Hz, and 0.32% for 100~800Hz.
Fluctuation and flicker
GB/T12326-2008 "Power Quality, Voltage Fluctuation and Flicker" stipulates: the public connection point of the power system, in the small mode of system operation, with one week (168h) as the measurement period, all long-term flicker values Plt meet: ≤ 110kV, Plt=1; >110kV, Plt=0.8. And the relevant regulations for individual users.
Voltage dips and short interruptions
The definition of GB/T30137-2013 "Power Quality Voltage Sag and Short-term Interruption": Voltage sag refers to the sudden decrease of the root-mean-square value of the power frequency voltage at a certain point in the power system to 0.1pu~0.9pu, and after a short duration of 10ms~1min The phenomenon of returning to normal; short-term interruption refers to the phenomenon that the root-mean-square value of the power frequency voltage at a certain point in the power system suddenly drops below 0.1pu, and returns to normal after a short duration of 10ms~1min.