This standard specifies the permissible value of three-phase voltage unbalance and its calculation, measurement and value-taking methods. This standard applies to the voltage unbalance at the common connection point caused by negative sequence components in the normal operation of the power system with an AC rated frequency of 50Hz. GB/T 15543-1995 Power quality three-phase voltage permissible unbalance GB/T15543-1995 Standard download decompression password: www.bzxz.net

UDC621.31.015
National Standard of the People's Republic of China
GB/T 15543—1995
Admissible three-phase voltage unbalance factor
Quality of electric energy supplyAdmissible three-phase voltage unbalance factor1995-04-06Promulgated
State Bureau of Technical Supervision
Implementation on 1996-01-01
National Standard of the People's Republic of China
Electric energy quality
Admissible three-phase voltage unbalance factor
Quality of electric energy supplyAdmissible three-phase voltage unbalance factor1Subject content and scope of application
This standard specifies the allowable values ​​of three-phase voltage unbalance and its calculation, measurement and value-taking methods. GB/T15543-1995
This standard applies to the voltage unbalance at the common connection point caused by the negative sequence component in the normal operation of the power system with an AC rated frequency of 50Hz.
2 Terms and symbols
2..1 Unbalance factor
Refers to the degree of three-phase imbalance in a three-phase power system, expressed as the percentage of the root mean square value of the negative sequence component of the voltage or current to the positive sequence component. The voltage or current unbalance is represented by u or sr respectively. 2.2 Positive-sequence component The component in the positive-sequence symmetrical system after the electric quantity of the unbalanced three-phase system is decomposed according to the symmetrical component method: 2.3 Negative-sequence component The component in the negative-sequence symmetrical system after the electric quantity of the unbalanced three-phase system is decomposed according to the symmetrical component method. 2.4 Point of common coupling The connection point of more than one user in the power system. 3 Allowable value of voltage unbalance
3.1 The allowable value of normal voltage unbalance at the common connection point of the power system is 2%, and shall not exceed 4% for a short time (see Appendix A for the value). The allowable voltage unbalance and negative sequence current allowable value of rated working conditions of electrical equipment are still specified by their respective standards. For example, rotating motors are specified in GB755 "Basic Technical Requirements for Rotating Motors". 3.2 For each user connected to the common connection point, the allowable value of normal voltage unbalance caused by the point is generally 1.3%. It can be appropriately changed according to the load conditions of the connection point, the requirements of adjacent generators, relay protection and automatic equipment and safe operation, but it must meet the provisions of Article 3.1. 4 Conversion of allowable value of voltage unbalance caused by users The allowable value of voltage unbalance can generally be converted into the corresponding negative sequence current value based on the normal minimum short-circuit capacity of the connection point as a basis for analysis or measurement; for users adjacent to large rotating motors, the negative sequence impedance of the rotating motor should be considered when converting their negative sequence current values. For the calculation of unbalance, see Appendix B.
5 Measurement of unbalance (see Appendix A)
Approved by the State Administration of Technical Supervision on April 6, 1995 and implemented on January 1, 1996
GB/T15543-1995
Appendix A
Measurement and value of unbalance
(Supplement)
A1 The ε value in this standard refers to the measured value in the production (operation) cycle when the voltage unbalance caused by the load is the largest under the minimum mode of normal operation of the power system. For example, the steelmaking arc furnace should be measured during the melting period; for daily fluctuating loads, the typical day 24h measurement can be taken. A2 The normal ε allowable value specified in this standard should be compared with the arithmetic mean of the five measured close values ​​for occasions with small fluctuations, and compared with the 95% probability value of the measured value for occasions with large fluctuations to determine whether it is qualified. Its short-term allowable value refers to the limit value that cannot be exceeded at any time. bZxz.net
For practical convenience, the 95% probability value of the measured value can be arranged in descending order by arranging the measured values ​​(no less than 30), discarding the first 5% of the large values, and taking the maximum value of the remaining measured values; for daily fluctuating loads, it can also be judged according to the cumulative exceeding time not exceeding 72 minutes, and the exceeding time in every 30 minutes not exceeding 5 minutes. A3 The unbalance measuring instrument shall meet the measurement requirements of this standard. For each measurement, the value is generally taken according to the 3s root mean square. For discrete sampling measuring instruments, it is recommended to calculate according to the following formula:
(A1)
Where: - the first measured unbalance within 3s; - the number of uniformly spaced values ​​within 3s (m≥6). For special circumstances, it shall be agreed upon by the power supply and user. The absolute error of the voltage unbalance measurement of the instrument shall not exceed 0.2%; the absolute error of the current unbalance measurement shall not exceed 1%. Appendix B
Calculation of unbalance
(Supplement)
B1 Expression of unbalance
X100 (%)
Where: U,--Root mean square value of the positive sequence component of the three-phase voltage, V; U.
--Root mean square value of the negative sequence component of the three-phase voltage, V. If U, U, in formula (B1) are replaced by II, I2, the corresponding expression of current unbalance e is obtained. (B1)
B2 Accurate calculation formula of unbalance
B2.1 In a three-phase system with a zero-sequence component, the symmetrical component method is used to calculate the positive sequence component and the negative sequence component respectively, and the unbalance is calculated by formula (B1).
B2.2 In a three-phase system without zero-sequence component, when the three-phase quantities a, b, and c are known, the unbalance degree is calculated using the following formula: 1-3-6
1+Y3-61
×100 (%)
·（B2）
Where: L=(a*+b+c)/(a++c)2
B3 Approximate calculation formula for unbalance degree
GB/T15543-1995
B3.1 Assume that the positive-sequence impedance and negative-sequence impedance of the common connection point are equal, then Y31·Ur
Where: I2——negative-sequence value of current, A; Sk three-phase short-circuit capacity of the common connection point, MV·A; Ur—line voltage, kV.
B3.2 Expression of voltage unbalance caused by phase-to-phase single-phase load Eu
Where: S.
- single-phase load capacity, MV·A.
Additional remarks:
This standard is proposed by the Ministry of Electric Power Industry of the People's Republic of China. × 100
(%)
(%)
This standard is under the jurisdiction of the National Technical Committee for Standardization of Voltage, Current and Frequency. (B3)
(B4)
This standard was drafted by the Electric Power Research Institute, the Mechanical Standardization Research Institute, the North China Electric Power College, the Ministry of Railways Scientific Research Institute, the Shanghai Electric Power Research Institute, the Beijing Power Supply Bureau, the Water Resources and Electric Power Information Research Institute and other units. The main drafters of this standard are Lin Haixue, Yu Xinmin, Shi Chuanli, Yin Qinfang, Guo Zhongpan, Dai Fazhou and Xiang Haiping. National Standard of the People's Republic of China Permissible Unbalance of Three-Phase Voltage GB/T15543—1995 Published by China Standards Press No. 16, Sanlihebei Street, Fuxingmenwai, Beijing Postal Code: 100045 Tel: 8522112 Printed by China Standards Press Qinhuangdao Printing Factory Xinhua Bookstore North Distributed by Beijing Publishing House Sold by Xinhua Bookstores in all regions. Exclusive copyright. No reproduction allowed.
Format: 880×12301/16 Printing sheet 1/2
: Number of words: 6,000
First printing in January 1996
First edition in January 1996
Print run: 1-2000
Book number: 155066·1-12131
Heading: 279-45
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.