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GB/T 12326-2008 English PDF (GBT12326-2008)

GB/T 12326-2008 English PDF (GBT12326-2008)

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GB/T 12326-2008: Power quality -- Voltage fluctuation and flicker

This Standard specifies the limits and test, calculation and evaluation methods of voltage fluctuation and flicker. This Standard is applicable to the rapid change of the voltage of the common connection point caused by the fluctuating load under the normal operation mode of the AC 50Hz power system and the occasion where people may obviously feel the light flicker.
GB/T 12326-2008
GB
NATIONAL STANDARD
OF THE PEOPLE REPUBLIC OF CHINA
ICS 27.100
F 020
Replacing GB 12326-2000
Power quality - Voltage fluctuation and flicker
ISSUED ON. JUNE 18, 2008
IMPLEMENTED ON. MAY 1, 2009
Issued by. General Administration of Quality Supervision, Inspection and Quarantine;
Standardization Administration Committee.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Limits of voltage fluctuation ... 7
5 Limits of flicker ... 7
6 Measurement and estimation of voltage fluctuation ... 9
7 Flicker measurement and calculation ... 11
8 Superposition and transfer of flicker ... 12
Annex A (Normative) Flicker measurement and calculation formulas ... 15 Annex B (Informative) Estimation method for total supply capacity StHV of high voltage (HV) ... 19
Annex C (Informative) Estimation method for flicker of electric arc ... 20 Annex D (Informative) Statistical method of flicker qualification rate ... 21 Bibliography ... 22
Foreword
This Standard replaces GB 12326-2000 Power quality--Voltage fluctuation and flicker.
Compared with GB 12326-2000, the main contents of this modification are as follows.
- adjusted the limits of flicker, used the long-term flicker value Plt as the limit for flicker, a certain degree of relaxation than the original flicker limit. For flicker caused by a single fluctuating load, according to the actual situation, it was still divided into three levels, but there was a certain simplification, and put forward a clear management requirements for excessive user;
- adjusted the criterion of the voltage fluctuation limit. For voltage
fluctuation of low voltage fluctuation frequency or regular periodic voltage fluctuation, the current limit was still used as the criterion; for irregular voltage fluctuations, it specified the maximum value of the voltage
fluctuation as criterion and adjusted the previous limit. This enhanced the voltage fluctuation measurement and judged whether the operability was
qualified;
- adjusted the flicker?€?s measurement duration, value method. The flicker of the common connection point of the power system used one week (168 h)
to measure. The flicker caused by a single fluctuating load used one day (24 h) to measure. They all took the maximum value as criterion for
qualification;
- simplified flicker estimation method; deleted the sine wave which was not commonly used, triangular wave voltage fluctuation Pst = 1 curve analysis method, the simulation method which was difficult to implement and flicker time analysis in the previous standard;
- simplified flicker analysis examples and evaluation methods involved in Annex C of the previous standard; used a more concise way to list various arc furnace flicker evaluation coefficients;
- expanded the application scope of voltage fluctuations and flicker limits to extra high voltage (EHV) system, regardless of the flicker transmission of EHV to the next voltage level; unified the flicker transfer coefficient to 0.8, the recommended value;
- added statistical method of flicker passing rate, so as to facilitate the assessment of flicker conditions.
Power quality - Voltage fluctuation and flicker
1 Scope
This Standard specifies the limits and test, calculation and evaluation methods of voltage fluctuation and flicker.
This Standard is applicable to the rapid change of the voltage of the common connection point caused by the fluctuating load under the normal operation mode of the AC 50Hz power system and the occasion where people may
obviously feel the light flicker.
2 Normative references
The following standards contain the provisions which, through reference in this Standard, constitute the provisions of this Standard. For dated references, subsequent amendments (excluding corrections) or revisions do not apply to this Standard. However, the parties who enter into agreement based on this Standard are encouraged to investigate whether the latest versions of these documents are applicable. For undated reference documents, the latest
versions apply to this Standard.
GB/T 156-2007 Standard voltage (IEC 60038.2002, MOD)
GB 17625.2 Electromagnetic compatibility (EMC) - Limits - Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment with rated current ??? 16 A (GB 17625.2-2007, IEC
61000-3-3.2005, IDT)
GB/Z 17625.3 Electromagnetic compatibility--Limits--Limitation of voltage fluctuations and flicker in low-voltage power supply systems for equipment with rated current greater than 16A (GB/Z 17625.3-2000, idt IEC 61000-3- 5.1994)
IEC 61000-4-15.1996 Electromagnetic compatibility (EMC) - Testing and
measurement techniques - Flicker meter - Functional and design
specifications
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. Each user, according to the ratio between its agreed capacity Si (Si = Pi /cos ??i) and the total capacity, shall determine the flicker limits of this user after considering the factors such as the effect of the last level on the next level flicker transfer (the transmission of next level to the last level is generally ignored). The flicker limits of single user can be calculated as follows.
First, calculate the total flicker limits G generated by all loads connected to PCC point.
where,
LP - Long term severity Plt limit of PCC corresponding voltage level;
LH - Long term severity Plt limit of last voltage level;
T - The flicker transfer coefficient of the last voltage level to the next voltage level, 0.8 as recommended. The flicker transfer of EHV system to the next level voltage system shall not be considered. The flicker limits of each voltage levels are shown in Table 2.
The flicker limit of single user Ei is.
where,
F - Simultaneous coefficient of fluctuating load of which the typical value F = 0.2 ~ 0.3 (but it must meets Si/F ??? St); the determination method for PCC?€?s total capacity StHV of HV system is shown in Annex B.
5.2.4 The third level regulation. For the single fluctuating load user which does not comply with the regulations of the second level, if it still exceeds its flicker limits after treatment, it shall relax the limit appropriately, based on PCC point actual flicker conditions and development forecast of grid. However, the flicker value of PCC point must comply with the provisions of 5.1.
6 Measurement and estimation of voltage fluctuation
The voltage fluctuation can be described by R.M.S. voltage shape U(t). The relative voltage change d and rate of occurrence of voltage changes r are indicators to measure the voltage fluctuation size and speed.
where,
??Si - Three-phase load changes.
For phase single-phase load.
where,
??Si - Phase single-phase load.
NOTE In absence of short-circuit capacity of normal smaller way, the system short-circuit capacity designed to take can be calculated by the maximum short circuit capacity of the system during production multiplied by 0.7, the coefficient.
7 Flicker measurement and calculation
Flicker is the cumulative effect of voltage fluctuations over a period of time. It reflects the light perception caused by the instability of the illumination. It is mainly measured by short term severity Pst and long term severity Plt. The calculation method of short term severity Pst is shown in Annex A. The long term severity Plt is obtained by the calculation of short term severity Pst contained in the measurement period.
where,
Pstj - The short term severity of No. j within 2 h.
The flickers caused by various types of voltage fluctuations can be directly measured by flicker meter which complies with IEC 61000-4-15.1996. This is the baseline method for determining the flicker value. For three-phase
equiprobable fluctuating load, it can select any phase to measure.
When the load is a periodic, interval and rectangular wave (or step wave), the flicker can be estimated by its relative voltage change d and rate of occurrence of voltage changes r. When the relative voltage change d and the rate of occurrence of voltage changes r are known, it can use Figure 1 (or Table 4). Use Pst = 1 curve, check out the relative voltage change dLim when Pst = 1 that corresponds to r and calculate its short term severity.
m - The value depends on the nature of the primary flicker source and the overlapping possibilities of its operating conditions;
m=1 - Used for a situation in which fluctuating load causes relative voltage change and a high overlap ratio;
m=2 - Used for a situation in which random fluctuating load causes relative voltage change simultaneously (for example, electric arc furnace of
overlapped melting period);
m=3 - Used for a situation in which fluctuating load rarely causes relative voltage change simultaneou...

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