GB/T 155432008 PDF in English
GB/T 155432008 (GB/T155432008, GBT 155432008, GBT155432008)
Standard ID  Contents [version]  USD  STEP2  [PDF] delivered in  Name of Chinese Standard  Status 
GB/T 155432008  English  70 
Add to Cart

09 seconds. Autodelivery.

Power quality  Threephase voltage unbalance
 Valid 
GB/T 155431995  English  199 
Add to Cart

2 days

Quality of electric energy supply. Admissible threephase voltage unbalance factor
 Obsolete 
Standards related to (historical): GB/T 155432008
PDF Preview
GB/T 155432008: PDF in English (GBT 155432008) GB/T 155432008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.020
K 04
Replacing GB/T 155431995
Power Quality  Threephase Voltage Unbalance
ISSUED ON. JUNE 18, 2008
IMPLEMENTED ON. MAY 1, 2009
Jointly issued by. General Administration of Quality Supervision,
Inspection and Quarantine (GAQSIQ);
Standardization Administration (SAC) of the People's
Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative References ... 5
3 Terms and Definitions ... 5
4 Voltage Unbalance Factor Limit ... 7
5 Conversion of Permissible Values of Voltage Unbalance Factors
Caused by User ... 7
6 Measurement and Evaluating of Unbalance Factors ... 8
Appendix A (Informative) Calculation of Unbalance Factors ... 10
Bibliography ... 12
Foreword
This Standard replaces GB/T 155431995 "Quality of Electric Energy Supply 
Admissible Threephase Voltage Unbalance Factor".
Compared with GB/T 155431995, main contents revised in this Standard are as
follows.
— Application scope of this Standard is revised; clearly define that "Instant and
temporal unbalance factor problems are not applicable to this Standard".
— Relevant content on Zerosequence Unbalance Factor of Lowvoltage
Distribution System Lowvoltage Distribution System is added; all "unbalance
factors" of the previous standard are replaced by "negativesequence
unbalance factors".
— "Measurement and Evaluating of Unbalance Factors" in the appendix of
previous standard is upgraded to main text of this Standard; and adjustment is
made on measuring time and measuring method. For unbalance factors caused
by fluctuating load, the measuring time is 24h; measuring time interval of each
unbalance factor is 1min. For the common coupling point of the system, the
measuring time is adjusted to 1 week; measurement interval of each unbalance
factor is the integral multiple of 1 min.
— Because measuring method becomes part of the new standard content, the
name of this Standard is changed; "Admissible Threephase Voltage Unbalance
Factor" is changed to "Threephase Voltage Unbalance". At the same time,
adjustment is made to the English translation of "power quality", which
maintains consistency with the power quality used in other standards.
— content of "Normative References" is added; and terms are expanded.
— Clearly specify that threephase unbalance factor is the unbalance factor of the
fundamentalwave component.
— Adjust the content of "Unbalance Factor Calculation" in the appendix.
Appendix A is informative.
This Standard was proposed by and shall be under the jurisdiction of National
Technical Committee on Voltages, Current Ratings and Frequencies of
Standardization Administration of China.
Drafting organizations of this Standard. Wuhan Guoce Science and Technology Co.,
Ltd, China Electric Power Research Institute, China Productivity Center for Machinery,
Power Quality  Threephase Voltage Unbalance
1 Scope
This Standard specifies limits, calculation, measurement and evaluation methods of
threephase voltage unbalance.
This Standard is applicable to, AC power system of which the nominal frequency is
50Hz is operated in normal mode, voltage unbalance at common coupling point
caused by negativesequence fundamentalwave component; and voltage unbalance
at common coupling point caused by zerosequence fundamentalwave component of
the lowvoltage system.
Voltage permissible unbalance factor and permissible value of negativesequence
current of rated condition of electrical equipment shall still be specified by the various
standards, for example, rotating motors shall meet the requirements in GB 755.
Instantaneous and momentary unbalance problem are not applicable to this Standard.
2 Normative References
The following documents contain provisions which, through reference in this Standard,
constitute provisions of this Standard. For dated reference, subsequent amendments
(excluding corrigendum) or revisions of these publications do not apply. However,
parties who enter in agreement based on this Standard are encouraged to investigate
the possibility of applying the most recent editions of the standards indicated below.
For undated references, the latest edition of the normative document is applicable to
this Standard.
GB/T 1562007 Standard Voltage (IEC 60038.2002, MOD)
GB/T 12325 Power Quality  Deviation of Supply Voltage
3 Terms and Definitions
The following terms and definitions apply to this Standard.
3.1
Voltage unbalance
Threephase voltage is different in amplitude or (and) the phase difference is not 120°,
or both.
3.2
Unbalance factor
It refers to the unbalanced degree of threephase in the threephase power system. It
is represented by square mean root value percentage BETWEEN voltage, current
negativesequence fundamentalwave component or zerosequence
fundamentalwave component AND positivesequence fundamentalwave component.
Voltage, current negativesequence unbalance factor and zerosequence unbalance
factor are respectively represented by 2U , 0U , 12 and 10 .
3.3
Positivesequence component
It is the component of the positivesequence symmetric system, after the electric
quantity of the unbalanced threephase system is decomposed according to the
symmetrical component method.
3.4
Negativesequence component
It is the component of the negativesequence symmetric system, after the electric
quantity of the unbalanced threephase system is decomposed according to the
symmetrical component method.
3.5
Zerosequence component
It is the component of the zerosequence symmetric system, after the electric quantity
of the unbalanced threephase system is decomposed according to the symmetrical
component method.
3.6
Point of common coupling [Translator note. also abbreviated as. common coupling
point]
It refers to the connection point of more than one users in power system.
3.7
Factors Caused by User
Permissible values of voltage unbalance factors usually, in accordance with the
normal minimum short circuit capacity of the coupling points, can be converted into
the corresponding negativesequence current value, and be used as the basis of
analysis or measurement & calculation. For the neighboring users of large rotating
motors, the negativesequence impedance of the rotating motors shall be taken into
consideration in the conversion of negativesequence current value. Calculation of
relevant unbalance factors is shown in Appendix A.
6 Measurement and Evaluating of Unbalance Factors
6.1 Measurement conditions
Measurement shall be carried out when the electric power system is normally
operated in the minimum mode (or smaller mode), and the unbalanced load is under
normal condition and continuously operation. And ensure that the maximum work
cycle of the unbalanced load is included.
6.2 Measurement time
For common coupling point of the electric power system, duration time of
measurement is 1 week (168h); measurement interval of each unbalance factor can
be integral multiples of 1min. For fluctuating load, according to those specified in
Article 6.1, continuous measurement of a normal working day (24h) shall be used; the
measurement interval of each unbalance factor is 1 min.
6.3 Measurement evaluating
For common coupling point of the electric power system, the probability of 95% of 10
min squaremeanroot of the supply voltage negativesequence unbalance factor
measured value shall not be larger than 2%; and the maximum value of all measured
values shall be less than or equal to 4%. For unbalanced load of the daily fluctuation,
the maximum probability of 95% of 1 min squaremeanroot of the supply voltage
negativesequence unbalance factor measured value shall not be larger than 2%; and
the maximum value of all measured values shall be less than or equal to 4%.
Unbalanced load of daily fluctuation can be evaluated according to time. The time that
daily accumulative is more than 2% shall be less than or equal to 72min; and the time
that is more than 2% within each 30min shall be less than or equal to 5min.
Note 1. For the convenience of use, 95% probability value of measured values can be used to
list out the measured values in a descending order; 5% of the relative big values shall be
discarded; the maximum value of the remaining values shall be used.
A.3 Formula of approximate calculation of unbalance factors
A.3.1 Assume that the positivesequence impedance of the common coupling point
is equal to negativesequence impedance, then, the unbalance factor of
negativesequence voltage is.
)(＝ %1003 22
U S
UI ... (A.3)
Where,
I2 — the negativesequence current value, unit. (A);
Sk — the threephase short circuit capacity of common coupling point, unit. (VA);
UL — the line voltage, unit. (V).
A.3.2 Negativesequence voltage unbalance factor caused by the interphase
singlephase load may be approximated to.
%1002
U S
S ... (A.4)
Where,
SL — the singlephase load capacity, unit. (VA).
Bibliography
[1] GB/T 18039.42003 EMC environment factory level c...
...... Source: Above contents are excerpted from the PDF  translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
