This standard specifies the permissible values ​​of harmonics in public power grids and their test methods. This standard applies to public power grids with an AC rated frequency of 50Hz and a nominal voltage of 110kV and below. This standard does not apply to transient phenomena and short-time harmonics. GB/T 14549-1993 Power Quality Public Power Grid Harmonics GB/T14549-1993 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Electric energy qualityHarmonics in public supply network
Quality of electric energy supplyHarmonics in public supply networkApproved by the State Administration of Technical Supervision on July 31, 1993 and implemented on March 1, 1994
1 Subject and scope of application
This standard specifies the permissible values ​​of harmonics in public supply network and their test methods. GB/T 14549-93
This standard applies to public supply network with rated AC frequency of 50Hz and nominal voltage of 110kV and below. Public supply network with nominal voltage of 220kV can refer to 110kV for implementation. This standard does not apply to transient phenomena and short-time harmonics. 2 Reference standards
GB156Rated voltage
3 Terminology
3.1 Point of common couplingThe point where users connect to the public power grid.
3.2 Harmonic measurement points Harmonic measurement points The place where the harmonics of the power grid and users are measured. 3.3 Fundamental (component) fundamental (component) Perform Fourier series decomposition on the periodic alternating current and obtain the component with the same frequency as the power frequency. 3.4 Harmonic (component) harmonic (component) Perform Fourier series decomposition on the periodic alternating current and obtain the component with a frequency greater than 1 integer multiple of the fundamental frequency. 3.5 Harmonic order (h)
harmonic order (h)
Integer ratio of the harmonic frequency to the fundamental frequency. 3.6 Harmonic content (for voltage or current) harmonic content (for voltage or current) The quantity obtained by subtracting the fundamental component from the periodic alternating current. 3.7 Harmonic ratio (HR): The ratio of the root mean square value of the hth harmonic component contained in the periodic alternating current to the root mean square value of the fundamental component (expressed as a percentage). The hth harmonic voltage content is expressed as HRUn, and the hth harmonic current content is expressed as HRIh. 3.8 Total harmonic distortion (THD): The ratio of the root mean square value of the harmonic content in the periodic alternating current to the root mean square value of its fundamental component (expressed as a percentage). The total harmonic distortion of voltage is expressed as THDu and the total harmonic distortion of current is expressed as THD; 3.9 Harmonic source: Electrical equipment that injects harmonic current into the public power grid or generates harmonic voltage in the public power grid. 3.10 Short-duration harmonics: The harmonics contained in the current and the harmonic voltage caused by it when the impulse lasts no more than 2s and the interval between two impulses is not less than 30s.
Note: The mathematical expressions of harmonic terms are shown in Appendix A (Supplement). 4 Harmonic voltage limits
Public power grid harmonic voltage (phase voltage) limits are shown in Table 1. Table 1 Public power grid harmonic voltage (phase voltage) Grid nominal voltage
5 Permissible harmonic current values
Voltage total harmonic distortion rate
Each harmonic voltage content rate%
5.1 The harmonic current component (RMS value) injected into the common connection point by all users at the point shall not exceed the permissible value specified in Table 2 - When the minimum short-circuit capacity at the common connection point is different from the reference short-circuit capacity For the conversion of the permissible values ​​of harmonic currents in Table 2, see Appendix B (Supplementary). Table 2 Permissible values ​​of harmonic currents injected into the common connection point Standard Harmonic order and permissible values ​​of harmonic currents A Note 220kV reference short-circuit capacity is 2000MVA 5.2 The permissible value of harmonic currents injected into the power grid by each user at the same common connection point is allocated according to the ratio of the agreed capacity of this user at this point to the capacity of the power supply equipment at its common connection point. The calculation method for allocation is shown in Appendix C (Supplementary). 6 Measurement Methods for measuring harmonics, data processing and measuring instruments are shown in Appendix D (Supplementary). Appendix A Mathematical expressions of harmonic terms (Supplementary) A1 Hth harmonic voltage content HRUh: Where Uh - hth harmonic voltage (RMS value): Ui - fundamental voltage (RMS value).
A2hth harmonic current content HRIh
×100(0
wherein h
hth harmonic current (RMS value):
fundamental current (RMS value).
A3Harmonic voltage content UH:
A4Harmonic current content Ih:
A5Total harmonic distortion rate of voltage THDu:
×100(0
U×100(°）
A6Total harmonic distortion rate of current THD:
×100(
Appendix B
Conversion of allowable values ​​of harmonic current
(Supplement)| |tt||When the minimum short-circuit capacity of the grid common connection point is different from the reference short-circuit capacity in Table 2, the permissible harmonic current value in Table 2 shall be corrected according to the following formula
In the formula, Sk1—
the minimum short-circuit capacity of the common connection point, MVA: Sk2—reference short-circuit capacity, MVA:
the permissible value of the hth harmonic current in Table 2, A: the permissible value of the hth harmonic current when the short-circuit capacity is Sk1. Appendix C
Basic calculation formula for harmonics
(Supplement)
C1Relationship between the hth harmonic voltage content HRUi and the hth harmonic current component IJ3z.lh
Approximate engineering estimation according to formula (C2) Or calculate by formula (C3): 10UN
V3Uhln
where UN
-nominal voltage of the power grid, kV:
three-phase short-circuit capacity of the common connection point MVA: Ih——hth harmonic current, A:
Zh——hth harmonic impedance of the system, Q. (C1)
C2The same harmonic currents of two harmonic sources are superimposed on the same phase of a line. When the phase angle is known, calculate according to formula (C4):
=+2+60
where Ih—hth harmonic current of harmonic source 1, A: Ih2—hth harmonic current of harmonic source 2, A: Oh—hth harmonic impedance of harmonic source 1 and harmonic impedance of harmonic source 2 The phase angle between the h-th harmonic currents of source 2. When the phase angle is uncertain, it can be calculated according to formula (C5) (C4)
In the formula, the Kh coefficient is selected according to Table C1.
The value of the coefficient Kh in formula (C5)
When two or more harmonic currents of the same order are superimposed, the two harmonic currents are superimposed first and then superimposed with the third harmonic current, and so on.
The calculation formula for the superposition of harmonic voltages of the same order caused by two or more harmonic sources on the same node and the same phase is similar to formula (C4) or formula (C5)·
C3The allowable value of the h-th harmonic current (Ihi) of the i-th user at the common connection point is calculated according to formula (C6): Ihi = In(s,sa
Wherein, Ih is the allowable value of the hth harmonic current converted according to Appendix B. AS is the power consumption agreement capacity of the ith user in MVA: S
Capacity of the power supply equipment at the public connection point in MVA: Phase superposition coefficient, take the value according to Table C2.
Table C2 Phase superposition coefficient of harmonics
Appendix D
Methods for measuring harmonics Data processing and measuring instruments (supplements)
D1 The measurement of harmonic voltage (or current) should select the minimum operating mode that may occur when the power grid is normally powered and should be carried out during the period when the harmonic amount generated in the working cycle of the harmonic source is large (for example, an arc steelmaking furnace should be measured during the melting period) When a capacitor bank is installed near the measuring point, measurements should be carried out under various operating modes of the capacitor bank: D2 Measurement The harmonic order is generally from the 2nd to the 19th. According to the characteristics of the harmonic source or the test analysis results, the range of harmonic order measurement can be appropriately changed.
D3 For harmonic sources with fast load changes (such as rolling mill electric locomotives powered by thyristor converter equipment of steelmaking arc furnaces, etc.), the measurement interval is not more than 2 minutes, and the number of measurements should meet the requirements of mathematical statistics. Generally, it is not less than 30 times. For harmonic sources with slow load changes (such as chemical rectifiers, DC transmission converter stations, etc.), the measurement interval and duration are not specified.
D4 The data of harmonic measurement should be the largest phase value among the 95% probability values ​​of the actual measured values ​​of each phase during the measurement period, as the basis for judging whether the harmonic exceeds the allowable value.
However, for the harmonic source with slow load change, five close measured values ​​can be selected to take their arithmetic average. Note: For practical convenience, the 95% probability value of the measured value can be approximately selected by the following method. The measured values ​​are arranged in order from large to small, and the first 5% of the large values ​​are discarded to take the maximum value of the remaining measured values. D5 Harmonic measurement instrument.
D5.1 The function of the instrument should meet the measurement requirements of this standard: D5.2 In order to distinguish between transient phenomena and harmonics, the average value of the measured values ​​within 3s is recommended for each measurement result of the harmonic with fast load change: Vme
Wherein, Uhk——the root mean square value of the hth harmonic measured for the kth time within 3s: (DI)
The number of measurements taken at even intervals within 3s, m≥6. D5.3 Instrument accuracy
The allowable error of harmonic measuring instrument is shown in Table D1
Table D1 Allowable error of harmonic measuring instrument
Measured value
Uh1%UN
Uh≥1%UN
Ih3%IN
Ih3%IN
Uh3%UN
Uh≥3%UN
Ih10%IN
h=10%IN
Note: ①UN is the standard voltage, Uh is harmonic voltage: I is rated current, Ih is harmonic current allowable error
②A-level instrument frequency measurement range is 02500Hz, used for more accurate measurement instrument phase angle measurement error is not greater than soil 5″ or soil 1: B-level instrument is used for general measurement D5.4 instrument has a certain anti-electromagnetic interference ability, convenient for on-site use. The instrument should ensure that its power supply can work normally under the condition of nominal voltage soil 15%, frequency in the range of 49-51Hz, voltage total harmonic distortion rate not exceeding 8%, D6 for non-compliance with D5.2 Instruments can be used to measure harmonic sources with slow load changes. If used to measure harmonic sources with fast load changes, the measurement conditions and times should comply with the provisions of D1 and D3 respectively: D7 Within the frequency range of measurement, instrument transformers, capacitive voltage dividers and other harmonic sensing equipment should have good frequency characteristics, and the amplitude error introduced should not be greater than 5%: the phase angle error is not greater than 5. When there is no exact frequency response error characteristic: current transformers and low-voltage voltage transformers are used for harmonic measurement of frequencies of 2500Hz and below ＇6110k V electromagnetic voltage transformer can be used for frequency measurement of 1000Hz and below, and capacitive voltage transformer cannot be used for harmonic measurement. In harmonic voltage measurement, when there is a high demand for harmonic number or measurement accuracy, a resistor divider (UN1kV) or a capacitor divider (UN1kV) should be used.
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This standard is under the jurisdiction of the National Technical Committee on Voltage, Current and Frequency Standardization. This standard is drafted by the Ministry of Energy's Electric Power Department. Ministry of Energy Electric Power Research Institute Sichuan Electric Power Industry Bureau Huazhong University of Science and Technology
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