Standards related to:

GB/T 12326-2008**GB/T 12326-2008: PDF in English (GBT 12326-2008) **

GB/T 12326-2008

GB

NATIONAL STANDARD

OF THE PEOPLE’S 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 φi)

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,

ΔSi - Three-phase load changes.

For phase single-phase load.

where,

ΔSi - 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...

......

Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.