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GB/T 24276: Historical versions
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| GB/T 24276-2025 | English | 1014 |
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A method of temperature-rise verification of low-voltage switchgear and controlgear assemblies by calculation
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| GB/T 24276-2017 | English | 599 |
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A method of temperature-rise verification of low-voltage switchgear and controlgear assemblies by calculation
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| GB/T 24276-2009 | English | 999 |
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A method of temperature-rise assessment by extrapolation for partially type-tested assemblies (PTTA) of low-voltage switchgear and controlgear
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Basic data
| Standard ID | GB/T 24276-2025 (GB/T24276-2025) |
| Description (Translated English) | A method of temperature-rise verification of low-voltage switchgear and controlgear assemblies by calculation |
| Sector / Industry | National Standard (Recommended) |
| Classification of Chinese Standard | K31 |
| Classification of International Standard | 29.130.20 |
| Word Count Estimation | 50,581 |
| Date of Issue | 2025-12-31 |
| Date of Implementation | 2026-07-01 |
| Older Standard (superseded by this standard) | GB/T 24276-2017 |
| Issuing agency(ies) | State Administration for Market Regulation, Standardization Administration of China |
GB/T 24276-2025: A method of temperature-rise verification of low-voltage switchgear and controlgear assemblies by calculation
---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
ICS 29.130.20
CCSK31
National Standards of the People's Republic of China
Replaces GB/T 24276-2017
Calculations are performed on low-voltage switchgear and control systems.
A method for verifying equipment temperature rise
(IEC TR60890.2022, IDT)
Published on 2025-12-31
Implemented on July 1, 2026
State Administration for Market Regulation
The State Administration for Standardization issued a statement.
Table of contents
Preface III
Introduction V
1.Scope 1
2 Normative References 1
3.Terms and Definitions 1
4.Verification Conditions 1
5.Calculation Method 2
6.Further considerations 5
7 Design Evaluation 5
Appendix A (Informative) Example of Calculating Internal Air Temperature Rise 15
Appendix B (Informative) Guidelines on the Influence of Non-uniform Power Distribution 22
Appendix C (Informative) Guidelines on the Additional Temperature Rise Effects of Solar Radiation 24
Appendix D (Informative) Guidelines on the Influence of Different Shell Materials, Structures, and Surface Finishes 26
Appendix E (Informative) Guidelines on the Impact of Different Natural Ventilation Arrangements 28
Appendix F (Informative) Guidelines for Forced Ventilation Arrangements 29
Appendix G (Informative) Calculation of Power Loss Values 31
Appendix H (Informative) Guidelines on the Impact of Adjacent Walls on the Heat Dissipation Area of Complete Equipment 33
Appendix I (Informative) Operating Current and Power Loss of Copper Conductors 35
Appendix J (Informative) Guidelines for Magnetic and Eddy Current Power Dissipation 40
Appendix K (Informative) Forced Ventilation Airflow Calculation 41
References 43
Figure 1.Temperature rise characteristic curves of the casing with an area (Ae) exceeding 1.25 m².
Figure 2.Temperature rise characteristic curves of the casing with an area Ae not exceeding 1.25 m².
Figure 3.The casing constant k of a casing without vents and with an effective heat dissipation area Ae > 1.25 m².
Figure 4.Temperature distribution factor c of a casing without vents and with an effective heat dissipation area Ae > 1.25 m².
Figure 5.The shell constant k of a shell with ventilation openings and an effective heat dissipation area Ae > 1.25 m².
Figure 6.Temperature distribution factor c of a casing with vents and an effective heat dissipation area Ae > 1.25 m².
Figure 7.The shell constant k of a shell without ventilation openings and with an effective heat dissipation area Ae ≤ 1.25 m².
Figure 8.Temperature distribution factor c of a casing without vents and with an effective heat dissipation area Ae ≤ 1.25 m².
Figure 9 Calculation of air temperature rise inside the casing 14
Figure A.1 Example 1, Calculation of an outer shell without vents and internal horizontal partitions but with exposed sides 15
Figure A.2 Example 1, Calculation of a single shell 17
Figure A.3 Example 2, Calculation of wall-mounted enclosure with vents 18
Figure A.4 Example 2, Calculation of half of the shell 19
Figure A.5 Example 2, Calculation of wall-mounted enclosure with vents 20
Figure B.1 Example 22 of a complete set of equipment with horizontal partitions
Figure B.2 Temperature rise verification of higher power circuit 23
Figure C.1 Solar radiation phenomenon 24
Figure C.2 Interpolation curve 25
Figure D.1 Comparative test results 27
Figure E.1 Example 28 of cross-diagonal installation
Figure E.2 Effect of adding a filter 28
Figure F.1 Example 30 of a forced ventilation arrangement
Figure H.1 Wall-mounted complete set of equipment 33
Figure H.2 Floor-standing complete set of equipment 34
Figure J.1 Power consumption distribution of different pressure plates with the same rating 40
Table 1.Calculation methods, applications, formulas, and properties. 5
Table 2 Symbols, Units, and Names 6
Table 3 Surface Factor b6 Based on Installation Type
Table 4.Enclosure factor d for shells without vents and with an effective heat dissipation area Ae > 1.25 m².
Table 5.Enclosure factor d for enclosures with ventilation openings and an effective heat dissipation area Ae > 1.25 m².
Table 6 Equations from Figure 3 7
Table 7 Equations from Figure 4 8
Table 8 Equations from Figure 5 9
Table 9 Equation 10 of Figure 6
Table 10 Equation 11 of Figure 7
Table 11 Equation 12 of Figure 8
Table C.1 Approximate Solar Absorption Emissivity (Color-Related) 24
Table I.1 Operating current and power dissipation of single-core copper cables, permissible conductor temperature 70℃ (ambient temperature inside the casing. 55℃) 35
Table I.2 Degradation factor k1 of cables at an allowable conductor temperature of 70℃ (from GB/T 16895.6-2014, Table B.52.14) 37
Table I.3 DC and AC frequencies 16
3 Hz
50Hz to 60Hz, rectangular cross-section, horizontal operation and perpendicular to its maximum surface
Operating current and power loss of the exposed copper busbars (ambient temperature inside the enclosure. 55℃, conductor temperature. 70℃) 37
Table I.4 Different air temperature coefficients k4 39 inside the casing and/or conductors
Table K.1 Factor k for height above sea level 42
Foreword
This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1.Structure and Drafting Rules of Standardization Documents".
Drafting.
This document replaces GB/T 24276-2017 "A Method for Verifying Temperature Rise of Low-Voltage Switchgear and Controlgear Assemblies by Calculation".
Compared with GB/T 24276-2017, the main technical changes in the "Law" are as follows, apart from structural adjustments and editorial modifications.
---The file range has been changed (see Chapter 1, Chapter 1 of the.2017 edition);
---Added assumptions to the calculations (see 5.1);
---Increased the upper limit of the internal air temperature of the complete set of equipment (see 5.4);
---Added further considerations to the calculations (see Chapter 6);
--- Symbols, units, and names have been added (see Table 2);
---Increased the shell factor d when the number of partitions is 4 and 5 (see Tables 4 and 5);
---Add algebraic equations to the different curves included in this document (see Tables 6, 7, 8, 9, 10 and 11).
This document is equivalent to IEC TR60890.2022 "Verification of temperature rise of low-voltage switchgear and controlgear assemblies by calculation"
One method.
Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.
This document was proposed by the China Electrical Equipment Industry Association.
This document is under the jurisdiction of the Technical Committee on Standardization of Low Voltage Switchgear and Controlgear Assemblies (SAC/TC266).
This document was drafted by. Tianjin Electrical Science Research Institute Co., Ltd., Tianjin Tianchuan Electrical Control Equipment Testing Co., Ltd., and Beijing Herui Cell.
Electric Power Technology Co., Ltd., Andeli Group Co., Ltd., Jiangsu Hongqiang Electric Group Co., Ltd., Liruit Electric Co., Ltd., Hangzhou
Huachuang High-Tech Co., Ltd., Hongguang Electric Group Co., Ltd., Jiangsu Huaqiang Power Equipment Co., Ltd., Foshan Haoxiang Electric Co., Ltd.
Zhejiang Kere Electric Co., Ltd., Guangdong Bailin Electric Equipment Factory Co., Ltd., Zhongtian Electric Technology Co., Ltd., and Hunan Tianwei Electric Co., Ltd.
Zhejiang Yihui Electric Equipment Co., Ltd., Henan Fengyuan Electric Technology Co., Ltd., and Laiwu Luneng Kaiyuan Group Electric Co., Ltd.
The main drafters of this document are. Zhou Feng, Zhang Lei, Lu Lin, Chen Ping, Zheng Jiandong, Dai Hongbing, Zhang Huaxu, Zhang Yanhui, Yang Le, Chen Yingchao, and Zheng Yaochang.
Yang Guanming, Huang Songjie, Ji Hongzhi, Hu Ling, Fu Zhaohui, Sun Peiya, Liu Kun, Shan Hao, Qiao Chunlin, Cai Xianzheng, Ding Xiudong, Xu Jie, Zhao Chuan, Lin Yujing
Yang Bo, Xie Zhengxin, Xu Zhi, Xie Yancui, Lin Baiyang, Yu Dingyong, Ren Feng, Peng Sha, Chen Haoze, Liu Wenbin, Mao Lianghua, Huang Wenrong, Zheng Xiaoxiao, Han Ren
Wang Jingyuan, Hu Shaohui, Yao Jiuming, Chen Bing, Zhu Xihao, Yu Rongbo, Huang Dedao, Ni Junchang, Wang Jingru, Wang Siwei, Gao Dong, Zhang Kuan, Bao Kai, Ke Wei
Chen Shigang, Sun Ke, Gao Xiaofeng, Huang Liangfeng, Gong Ping, Ye Gaopei, Zeng Mingquan, Zhang Dongfang, Luo Jichang, Li Ming, Guo Dongmei, Zheng Baiyang, Luo Fan
Xu Zhengxiang, Tang Fangyin, Xu Feng, Zhang Bing, Chen Haiming, Ye Chunzhi, Ma Biao, Chen Kaixuan, Zhao Ming, Li Feng, Guo Xing, Liu Yang, Qian Chengjin, Yang Xian
Gai Zhongwei, Ni Tianxiang, Li Feng, Chen Liangliang, Han Weiping, Pan Zhengrui, Chen Hao, Wu Liangliang, Qian Sudan, Chen Jianchu, Feng Yuhua.
This document was first published in.2009, revised for the first time in.2017, and this is the second revision.
Introduction
The IEC 61439-1 standard specifies temperature rise verification for low-voltage switchgear and controlgear assemblies as part of a series of design verifications.
The test can be conducted, and other methods can be selected under specified conditions. The initial manufacturer is responsible for selecting the method for temperature rise verification. If applicable,
This document can also be used for temperature rise verification of similar products conforming to other standards (such as IEC 60204-1). For a given internal air temperature rise...
For enclosures conforming to IEC 62208, the calculation method can also be used to determine the heat dissipation capacity of the enclosure. The factors and coefficients set in this document are derived from...
Based on measurement data from a large number of complete sets of equipment, this method has also been verified by comparing it with experimental results.
Calculations are performed on low-voltage switchgear and control systems.
A method for verifying equipment temperature rise
1 Scope
This document specifies the calculation of internal air temperature rise within the enclosure of low-voltage switchgear and controlgear assemblies or similar products conforming to their respective standards.
One method.
This method is mainly applicable to enclosed complete sets of equipment or partitioned cabinet units of complete sets of equipment without forced ventilation. This document still applies to such cases.
Some technical guidelines are provided for adapting this method and applying it to forced ventilation. The results obtained using this method are subject to accurate power loss assessment.
The direct impact of temperature. This power loss is used as input for thermal calculation.
Note. The air temperature inside the enclosure is equal to the ambient air temperature outside the enclosure plus the air temperature rise caused by the power loss of the equipment installed inside the enclosure.
Using this method, the maximum daily average ambient air temperature outside the complete set of equipment at the installation location is specified to be between 10℃ and 50℃.
The daily temperature does not exceed the maximum daily average temperature by more than 5K.
Several appendices in this document provide information on how factors not considered in the calculation methods described herein affect the internal temperature rise of complete sets of equipment.
South. For example, the entire equipment is exposed to solar radiation. In this case, a different verification method than that used in this paper is employed to ensure the design's clear results.
Results and verification.
2 Normative references
The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.
For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies.
This document.
assemblies
Note. GB/T 7251 (all parts) Low-voltage switchgear and controlgear assemblies [IEC 61439 (all parts)]
3 Terms and Definitions
The terms and definitions defined in IEC 61439 (all parts) apply to this document.
4.Verification conditions
When this calculation method is applied to low-voltage switchgear and control equipment, the following conditions must be met.
---The complete set of equipment is designed for AC current not exceeding 1600A and frequency not exceeding 60Hz. For higher current ratings or frequencies...
Considering the eddy current effect on the internal temperature distribution of complete sets of equipment that meet relevant product standards, this method can be combined with additional verification.
Use them together.
Note 1.Considering the significant increase in power loss caused by magnetic effects (eddy currents, proximity effect, skin effect), IEC 61439-2 specifies a current limit of 1600A.
Additional requirements.
---The complete set of equipment is designed for DC current not exceeding 3200A. For higher rated currents, this equipment shall comply with the relevant product standards.
This method can be used in conjunction with additional validation.
---Conductors carrying AC currents exceeding.200A and the arrangement of adjacent structural components make eddy current and hysteresis losses negligible.
...
