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GB/T 1094.7-2024: Power transformers - Part 7: Loading guide for mineral-oil-immersed power transformers
Status: Valid GB/T 1094.7: Evolution and historical versions
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Power transformers - Part 7: Loading guide for mineral-oil-immersed power transformers
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GB/T 1094.7-2024
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| GB/T 1094.7-2008 | English | 1019 |
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Power transformers -- Part 7: Loading guide for oil-immersed power transformers
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PDF similar to GB/T 1094.7-2024
Basic data | Standard ID | GB/T 1094.7-2024 (GB/T1094.7-2024) | | Description (Translated English) | Power transformers - Part 7: Loading guide for mineral-oil-immersed power transformers | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | K41 | | Classification of International Standard | 29.180 | | Word Count Estimation | 78,796 | | Date of Issue | 2024-11-28 | | Date of Implementation | 2025-06-01 | | Older Standard (superseded by this standard) | GB/T 1094.7-2008 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | GB/T 1094.7-2024: Power transformers - Part 7: Loading guide for mineral-oil-immersed power transformers
---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 29.180
CCSK41
National Standard of the People's Republic of China
Replaces GB/T 1094.7-2008
Power transformers Part 7.
Loading Guidelines for Oil-Immersed Power Transformers
(IEC 60076-7.2018,MOD)
Released on 2024-11-28
2025-06-01 Implementation
State Administration for Market Regulation
The National Standardization Administration issued
Table of Contents
Preface III
Introduction VI
1 Scope 1
2 Normative references 1
3 Terms and Definitions 1
4 Symbols and abbreviations 3
5 Effect of Loading Beyond Nameplate Rating 5
6 Relative aging rate and transformer insulation life 7
7 Limit 12
8 Determination of temperature 15
9 Impact of Tap Changer 26
Appendix A (Informative) Expected insulation life and relative aging rate considering the effects of oxygen and moisture 28
Appendix B (Informative) Core Temperature 32
Appendix C (Informative) Explanation of capacity exceeding nameplate rating 33
Appendix D (Informative) Description of Q, S and H factors 35
Appendix E (Informative) Example 37 of the solution of the exponential equation method
Appendix F (Informative) Thermal Model Parameters 42
Appendix G (Informative) Calculation of winding and oil time constants 45
Appendix H (Informative) Oil Index and Winding Index 47
Appendix I (Informative) Application of Difference Equation Solutions 52
Appendix J (Informative) Flowchart of the example in Appendix E 58
Appendix K (informative) Examples of calculation and presentation of overload data 59
Appendix L (Informative) Geomagnetic Induction Current 63
Appendix M (Informative) Alternative Oils 64
References 65
Figure 1 Cellulose structure 7
Figure 2 Correlation between tensile strength and DP value 8
Figure 3 Accelerated aging in mineral oil at 140°C, oxygen content < 6000μL/L, and water content 0.5% 9
Figure 4 Life expectancy of non-thermally modified paper and its dependence on moisture content, oxygen content and temperature10
Figure 5 Expected life of thermally modified paper and its relationship with moisture content, oxygen content and temperature11
Figure 6 Heat distribution diagram 16
Figure 7 400MVA, ONAF-cooled three-phase transformer zigzag-cooled high-voltage winding phase at 1.0pu load current (negative) tapping
The temperature rise of the top oil temperature (in the oil tank) is 65.8℃.
Figure 8 Coil edge (the sensor should be placed at the edge where the calculated temperature rise is higher) 18
Figure 9 Temperature rise relative to the top oil temperature at the end of the 8h hot no-load test at 110% rated voltage
Figure 10 Zigzag cooling winding with equal distance between segments (oil baffles are placed in the oil passages between segments)
Figure 11 Top view of a rectangular winding with a “shrinking cooling oil channel arrangement” under the iron yoke 20
Figure 12 Block diagram showing differential equation 21
Figure 13 Temperature response to a step change in load current 22
Figure 14 Curve of the function Δθh(t)/Δθhr obtained from the values in Table 4
Figure 15 Principle of loss as a function of tap position 27
Figure A.1 Arrhenius curve of the aging process 28
Figure E.1 Response of hot spot temperature to a step change in load current 40
Figure E.2 Response of top oil temperature to a step change in load current 41
Figure F.1 Overall model of hot spots and top oil 44
Figure H.1 Extended temperature rise test 50
Figure H.2 Transformer index estimation Figure 51
Figure I.1 Input data in the example 54
Figure I.2 Output data in example 57
Figure K.1 Allowable load of large power transformers with OF cooling at normal life loss 62
Figure L.1 GIC flows into power transformer 63
Table 1 Relative aging rate caused by hot spot temperature12
Table 2 Maximum permissible temperature limits for loads exceeding nameplate ratings 13
Table 3 Recommended current limits for loads exceeding nameplate ratings13
Table 4 Recommended values of thermal characteristic parameters for exponential equations 23
Table 5 Correction of ambient temperature rise caused by surrounding volume 26
Table A.1 Activation energy (EA) and environmental factor (A) of oxidation and hydrolysis 29
Table A.2 Expected life of paper under different conditions 29
Table A.3 Effects of hot spot temperature, oxygen and moisture content on relative aging rate of non-thermally modified paper 30
Table A.4 Effects of hot spot temperature, oxygen and moisture content on relative aging rate of thermally modified paper 31
Table E.1 Load stages for 250MVA transformers 37
Table E.2 Temperature at the end of each load stage 41
Table I.1 Input data in the example 52
Table I.2 Output data in example 55
Table K.1 Examples of parameters related to transformer load capacity 59
Table K.2 contains the permissible loads during the load cycle and the corresponding loss of life in days (in "normal" days) and
Example of maximum hot spot temperature rise Table 60
Foreword
This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for standardization work Part 1.Structure and drafting rules for standardization documents"
Drafting.
This document is Part 7 of GB/T 1094 "Power Transformers". GB/T 1094 has published the following parts.
--- Part 1.General;
--- Part 2.Temperature rise of liquid immersed transformers;
--- Part 3.Insulation levels, insulation tests and external insulation air gaps;
--- Part 4.Guidelines for lightning impulse and switching impulse tests on power transformers and reactors;
--- Part 5.Ability to withstand short circuit;
--- Part 6.Reactors;
--- Part 7.Guidelines for loading of oil-immersed power transformers;
--- Part 10.Determination of sound levels;
--- Part 101.Application Guidelines for Sound Level Determination;
--- Part 11.Dry-type transformers;
--- Part 12.Guidelines for loading of dry-type power transformers;
--- Part 14.Liquid immersed power transformers using high temperature insulating materials;
--- Part 15.Gas-filled power transformers;
--- Part 16.Transformers for wind power generation;
--- Part 18.Frequency response measurement;
--- Part 23.DC bias suppression device.
This document replaces GB/T 1094.7-2008 "Power transformers Part 7.Loading guidelines for oil-immersed power transformers" and
Compared with GB/T 1094.7-2008, in addition to structural adjustments and editorial changes, the main technical changes are as follows.
--- Added some new research results on insulation life (see Chapter 6);
--- Added the recommended maximum core temperature (see Chapter 7);
--- Increased the number of fiber optic sensors recommended for use in temperature rise tests (see Chapter 8);
--- The thermal model has been modified and rewritten in a generally applicable mathematical form (see Chapter 8, Chapter 8 of the.2008 edition).
This document is modified to adopt IEC 60076-7.2018 "Power transformers Part 7.Guidelines for loading of oil-immersed power transformers".
This document has made the following structural adjustments compared to IEC 60076-7.2018.
Adjust Annex H, Annex E and Annex G of IEC 60076-7.2018 to Annex E, Annex G and Annex H respectively.
The technical differences between this document and IEC 60076-7.2018 and their reasons are as follows.
--- The normative references GB/T 1094.2 and GB/T 1094.14 replace IEC 60076-2 and IEC 60076-14 respectively, to apply
According to the technical conditions of our country;
--- Added normative references to GB/T 2900.95 (see Chapter 3);
--- Deleted the last paragraph of 5.5."For sealed transformers without pressure relief devices, the problem of excessive pressure should be considered to avoid
The fuel tank is not allowed to deform permanently when the load exceeds the nameplate rating, in order to meet the actual situation in my country.
The following editorial changes were made to this document.
---The content of Chapter 1 has been adjusted;
--- Adjust "Note 1" in 3.4, 3.5, 3.11, 3.13, 3.14, 3.15 and 3.16 to "Note";
--- In Chapter 4, an introductory phrase is added, and "WOP" is changed to "WCO", "ppm" is changed to "mg/L", and the arrangement of symbols and abbreviations is adjusted.
The column order was adjusted;
--- Change IEC 60076-1.2011 in Note 5.2 to GB/T 1094.1-2013;
---Change "ppm" in paragraph 5 of 6.2 to "uL/L", "200%" in paragraph 6 to "200", and "ppm" in the title of Figure 3
Change to "uL/L";
--- Correct the paragraph in Table 1 of 6.3 to a note;
--- Correct "150mWb/phase or less" in c) of 8.1.3 to "≤150mWb/phase";
--- Correct Table 5 in the note of 8.2.1 to Table 4;
---Change EA (kJ/mol) in the third row of Table A.1 to EA (J/mol), 128 to 128000, 89 to 89000, 86 to
86000, 82 changed to 82000; Deleted the fifth paragraph of A.2 "The same method can also be used to improve the IEEE on aging
The content of "Equation for the speed coefficient FAA and the equivalent aging coefficient FEQA"; Correct the paragraphs in Table A.3 and Table A.4 to Notes; Change Table A.4
Correct 10.07 to 10.1; Correct “E” in formula (A.3) to “EA”;
--- The text structure of Appendix C and Appendix E (Appendix G in this document) has been adjusted;
--- Correct 8.2.3 in paragraph 1 of F.1 to 8.2.2;
--- In Appendix G (Appendix H in this document), the "x-axis --- loss, in kW" and "y-axis --- loss, in kW" in the symbol description of Figure G.1 are replaced by
The time in hours is corrected to "x-axis --- time in hours (h)" and "y-axis --- loss in kilowatts"
(kW)”; Correct the first sentence of 3) in G.4.“After recording the thermal resistance measurement value at rated current” to “70% of rated current”
After the thermal resistance measurement value of the flow is recorded";
--- Correct "time (y axis)" in the symbol description of Figures I.1 and I.2 to "abscissa axis --- time";
---Correct "θo(t=1)=76.5℃" and "θh(t=1)=111℃" in Appendix K to "θo(t=31)=76.5℃" respectively.
and "θh(t=31)=111℃", "Δθhi1=4.95K" was corrected to "Δθhi2=4.95K", and Table K.1 and Table K.2 were adjusted.
structure;
---The references were adjusted.
Please note that some of the contents of this document may involve patents. The issuing organization of this document does not assume the responsibility for identifying patents.
This document was proposed by the China Electrical Equipment Industry Association.
This document is under the jurisdiction of the National Technical Committee on Transformer Standardization (SAC/TC44).
This document was drafted by. Shenyang Transformer Research Institute Co., Ltd., Xi'an Xidian Transformer Co., Ltd., TBEA Hengyang Transformer
Co., Ltd., Shandong Electric Power Equipment Co., Ltd., China Electric Power Research Institute Co., Ltd., Chint Electric Co., Ltd., Changzhou Xidian
Transformer Co., Ltd., TBEA Shenyang Transformer Group Co., Ltd., Guangzhou Siemens Energy Transformer Co., Ltd., China Southern
Guiyang Branch of Ultra-high Voltage Transmission Company of Power Grid Co., Ltd., Mingzhu Electric Co., Ltd., Jiangsu Huapeng Transformer Co., Ltd., Chint High
Pressure Electric Equipment (Wuhan) Co., Ltd., Chengdu Xidian Zhongte Electric Co., Ltd., Baoding Tianwei Baobian Electric Co., Ltd., Jiangsu
Huachen Transformer Co., Ltd., Guangxi Nanbaote Electric Manufacturing Co., Ltd., Baoding Tianwei Group Special Transformer Co., Ltd., Wujiang Transformer
Co., Ltd., Shanghai Zhixin Electric Amorphous Co., Ltd., Guangdong Pengxin Electric Technology Co., Ltd., Hunan Huaxia Special Transformer Co., Ltd., Ning
Boox Intelligent Technology Co., Ltd., Zhejiang Jiangshan Transformer Co., Ltd., TBEA Ultra-High Voltage Electric Co., Ltd., Zhejiang
Baiyun Zhebian Electric Equipment Co., Ltd., Shenda Electric Group Co., Ltd., Haihong Electric Co., Ltd., Yangzhou Huading Electric Co., Ltd., Yunnan
People's Electric Power Co., Ltd., Wolong Electric Yinchuan Transformer Co., Ltd., Hefei Yuanzhen Electric Power Technology Co., Ltd., State Grid Jilin Province
Electric Power Research Institute of China Electric Power Co., Ltd., Shuifa Chixiang Electric (Shandong) Co., Ltd., Electric Power Research Institute of Guangdong Power Grid Co., Ltd.
Institute, China Southern Power Grid Co., Ltd. Ultra-high Voltage Transmission Company Power Research Institute, Chenglai Electric Technology Co., Ltd., Tianjin TBEA
Transformer Co., Ltd., Guizhou Power Grid Co., Ltd. Electric Power Science Research Institute.
The main drafters of this document are. Gao Minhua, Zhao Yongjin, Fu Huanqiu, Dong Honglin, Zhang Jin, Li Jinbiao, Qu Jianfeng, Zhou Fan, Chi Zhusheng, Lü Gang,
Cai Dingguo, Zhuang Jie, Zhang Chengfei, Liu Kun, Zhang Dong, Jiang Shuowen, Li Bin, Zhang Yajie, An Zhen, Shi Wenbo, Zhong Hanliang, Zhang Ximing, Guo Weiqiang, Jiang Zhenjun,
Duan Wei, Li Zhi, Zheng Jun, Liang Qingning, Kaohsiung Ying, Zhang Peng, Lu Wei, Xiong Shifeng, Zhao Chunming, Ma Liming, Zhou Dan, Deng Jun, Zheng Guopei, Zhao Wenzhong,
Liu Jun.
The previous versions of this document and the documents it replaces are as follows.
---First published in.1994 as GB/T 15164-1994 and first revised in.2008 as GB/T 1094.7-2008;
---This is the second revision.
Introduction
The purpose of formulating the power transformer standard is to establish a set of optimal evaluation criteria for power transformers, and to provide a reference for the selection of raw materials for power transformers.
GB/T 1094 series of standards aims to provide guidance on the matters needing attention in selection, design, production, inspection, selection, operation and maintenance.
The 16-part series of regulations will be used to formulate principles and rules for the design, manufacture, testing, operation and maintenance of power transformers.
constitute.
--- Part 1.General. The purpose is to establish the principles that need to be followed for the design, manufacture and production testing of various types of power transformers.
General principles and relevant rules.
--- Part 2.Temperature rise of liquid immersed transformers. The purpose is to establish the temperature rise of various types of liquid immersed power transformers
technical requirements and test methods.
--- Part 3.Insulation level, insulation test and external insulation air gap. The purpose is to establish the requirements for various types of liquid immersed power transformers.
Technical requirements and insulation test methods for insulation levels, insulation tests and external insulation air gaps of devices.
--- Part 4.Guidelines for lightning impulse and switching impulse tests on power transformers and reactors. The purpose is to establish
Technical requirements and test methods for lightning impulse tests and switching impulse tests on power transformers and reactors.
--- Part 5.Short-circuit withstand capability. The purpose is to establish the short-circuit withstand capability applicable to various types of power transformers.
Technical requirements and test methods.
--- Part 6.Reactors. The purpose is to establish technical requirements and test requirements applicable to various types of reactors.
--- Part 7.Loading guidelines for oil-immersed power transformers. The purpose is to evaluate the performance of various mineral oil-immersed power transformers from the perspective of operating temperature and thermal aging.
Provide guidance on the loading conditions of immersion-type power transformers.
--- Part 10.Sound level measurement. The purpose is to establish technical specifications for sound level measurement for various types of power transformers and reactors.
Technical requirements and test methods.
--- Part 101.Guidelines for the application of sound level measurement. The purpose is to provide guidance on the application of sound level measurement for various types of power transformers and reactors.
Provide guidance on this.
--- Part 11.Dry-type transformers. The purpose is to establish technical requirements and test requirements applicable to various types of dry-type power transformers.
--- Part 12.Guidelines for loads on dry-type power transformers. The purpose is to provide guidance on the load operation of various types of dry-type power transformers.
For guidance.
--- Part 14.Liquid immersed power transformers using high temperature insulation materials. The purpose is to establish the applicable
Technical requirements and test requirements for liquid immersed power transformers of materials.
--- Part 15.Gas-filled power transformers. The purpose is to establish technical requirements and test methods applicable to various types of gas-filled power transformers.
Test requirements.
--- Part 16.Transformers for wind power generation. The purpose is to establish technical requirements and test methods applicable to various types of wind power transformers.
Test requirements.
--- Part 18.Frequency response measurement. The purpose is to establish technical requirements for frequency response of various types of power transformers.
Summation test method.
--- Part 23.DC bias suppression devices. The purpose is to establish technical requirements and test methods applicable to various types of DC bias suppression devices.
Test requirements.
GB/T 1094 defines the technical contents of various types of power transformers and reactors through 16 parts, and gives specific technical specifications.
Technical requirements, test items, test procedures, test methods and operation instructions, etc. By establishing clear scope, terminology, technical requirements for various products
and test requirements, so that personnel engaged in related product design, production, testing, use, operation and maintenance can more clearly and accurately
To lay a foundation for the design and manufacture of high-quality products, better promote trade, exchanges and technical cooperation, and provide a solid foundation for my country's power grid
To ensure the normal operation of the system.
This document provides guidelines for the specification and loading of power transformers from the perspective of operating temperature and thermal aging.
The system provides guidance for designers in selecting appropriate ratings and loading conditions for new equipment.
Power transformers Part 7.
Guidelines for loading of oil immersed power transformers
1 Scope
This document describes the effects of operating a transformer at different ambient temperatures and load conditions on its lifetime.
This document applies to mineral oil immersed power transformers.
Note. The user should consult the manufacturer for the special load capacity of the electric furnace transformer.
2 Normative references
The contents of the following documents constitute essential clauses of this document through normative references in this document.
For referenced documents without a date, only the version corresponding to that date applies to this document; for referenced documents without a date, the latest version (including all amendments) applies to
This document.
GB/T 1094.2 Power transformers Part 2.Temperature rise of liquid immersed transformers (GB/T 1094.2-2013, IEC 60076-2.
2011,MOD)
GB/T 1094.14 Power transformers Part 14.Liquid-immersed power transformers using high temperature insulating materials (GB/T
1094.14-2022,IEC 60076-14.2013,MOD)
GB/T 2900.95 Electrical terminology transformers, voltage regulators and reactors (GB/T 2900.95-2015, IEC 60050-421.
1990,NEQ)
3 Terms and definitions
The terms and definitions defined in GB/T 2900.95 and the following apply to this document.
3.1
Small power transformersmalpowertransformer
Power transformers, regardless of rating, without attached (removable) radiators, coolers or radiator pipes (including corrugated oil tanks).
3.2
Power transformers with a maximum three-phase rated capacity of 100MVA and a maximum single-phase rated capacity of 33.3MVA.
3.3
Power transformers with a three-phase maximum rated capacity greater than 100MVA and a single-phase maximum rated capacity greater than 33.3MVA.
3.4
Cyclic loading
A load that varies periodically (the duration of the cycle is usually 24 hours) is considered based on the accumulated aging within one cycle.
Note. Cyclic loads can be either normal loads or long-term emergency loads.
3.5
Normal cyclic loading
During part of a load cycle, the ambient temperature is high or a load greater than the rated load current is applied, but from the relative thermal
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