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Instrument transformers - Part 100: Guidance for application of current transformers in power system protection
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Basic data | Standard ID | GB/Z 20840.100-2023 (GB/Z20840.100-2023) | | Description (Translated English) | Instrument transformers - Part 100: Guidance for application of current transformers in power system protection | | Sector / Industry | National Standard | | Classification of Chinese Standard | K41 | | Classification of International Standard | 29.180 | | Word Count Estimation | 106,127 | | Date of Issue | 2023-12-28 | | Date of Implementation | 2024-07-01 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | GBZ20840.100-2023: Instrument transformers - Part 100: Guidance for application of current transformers in power system protection
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GB /Z 20840:100-2023: Transformers Part 100: Application Guidelines for Current Transformers for Power System Protection
ICS 29:180
CCSK41
National Standardization Guiding Technical Documents of the People's Republic of China
Transformers Part 100: For power system protection
Current Transformer Application Guidelines
(IEC TR61869-100:2017, MOD)
Published on 2023-12-28
2024-07-01 Implementation
State Administration for Market Regulation
Released by the National Standardization Administration Committee
Table of contents
Preface V
Introduction VII
1 Scope 1
2 Normative references 1
3 Terms, definitions and symbols 1
4 Responsibilities during current transformer design process 5
4:1 History 5
4:2 Breakdown of current transformer design process 5
5 Basic theoretical equations of transient design 6
5:1 Circuit 6
5:2 Transient phenomena 10
6 working cycle 14
6:1 CO working cycle 14
6:2 COCO working cycle 38
6:3 Transient design summary 42
7 Numerical calculation method of transient area coefficient Ktd 43
7:1 Overview 43
7:2 Basic circuit 44
7:3 Algorithm 45
7:4 Calculation method 45
7:5 Reference Example 46
8 Core saturation and residual magnetism 49
8:1 General definition of saturation 49
8:2 Gap core and non-gap core 52
8:3 Possible causes of residual magnetism 54
9 Practical suggestions 57
9:1 Risks of specifying different PR accuracy levels for the same winding57
9:2 Limitations of the TPY stage transient area coefficient Ktd on the phase difference Δφ and the secondary loop time constant Ts 57
10 Relationship between different accuracy levels57
10:1 Overview 57
10:2 Calculation of electromotive force under extreme conditions 58
10:3 Calculation of excitation (or magnetizing) current under extreme conditions 58
10:4 Application examples 59
10:5 Minimum requirements for accuracy level specifications59
10:6 Replacing the gapless core with a gapped core 60
11 Protection functions and their amendments to CT specifications 61
11:1 Overview 61
11:2 General application recommendations 61
11:3 Overcurrent protection: ANSI code: 50/51/50N/51N/67/67N; IEC symbol: I > 64
11:4 Distance protection: ANSI code: 21/21N; IEC symbol: Z< 66
11:5 Differential protection 73
Appendix A (informative) This document corrects IEC TR61869-100:2017 82
Appendix B (informative) CO duty cycle software code 84
Appendix C (informative) Software code for calculating transient area coefficient Ktd 87
Reference 94
Figure 1 Definition of fault initial angle γ 2
Figure 2 Main components of the protection circuit 6
Figure 3 Complete electrical circuit 7
Figure 4 Primary short circuit current 8
Figure 5 Nonlinear magnetic flux of LCT 9
Figure 6 Linearized magnetizing inductance of current transformer 9
Figure 7 Single-phase short circuit characteristics simulated with nonlinear model11
Figure 8 Three-phase short circuit characteristics12
Figure 9 Composition of magnetic flux 13
Figure 10 Short-circuit current at two different fault initial angles15
Figure 11 Curve 15 of the highest magnetic flux value Ψmax
Figure 12 Primary current curves in four cases at 50Hz and φ=70°16
Figure 13 Four typical situations of short-circuit current affecting magnetic saturation of current transformer17
Figure 14 Relevant time range for transient coefficient calculation19
Figure 15 The relationship between the time of the first magnetic flux peak and Tp at 50Hz20
Figure 16 Functional relationship between the most unfavorable fault initial angle θtf, Ψmax and Tp and t'al21
Figure 17 Functional relationship between the most unfavorable fault initial angle γtf, Ψmax and Tp and t'al 21
Figure 18 Ktf,Ψmax calculated using the most unfavorable fault initial angle θtf,Ψmax 22
Figure 19 Polar coordinate plots of Ktf,Ψmax and γtf,Ψmax22
Figure 20 Determination of Ktf in time frame 123
Figure 21 Primary current curve (50Hz, Tp=1ms, γΨmax=166°, t'al=2ms) 28
Figure 22 The most unfavorable fault initial angle (50Hz, Tp=50ms,,Ts=61ms) 29
Figure 23 Transient coefficients in different time ranges29
Figure 24 Ktf 30 in all time ranges at different t'al at 50Hz, Ts=61ms
Figure 25 Partial enlargement of Figure 24 31
Figure 26 Primary current under smaller primary time constant 31
Figure 27 Ktf value 32 under a certain smaller primary time constant
Figure 28 Short-circuit current under different fault initial angles 33
Figure 29 Transient coefficient 33 for different fault initial angles
Figure 30 The most unfavorable fault initial angle at each time step (50Hz) 34
Figure 31 Primary current at two different fault initial angles (16:67Hz) 34
Figure 32 Transient coefficients at different fault initial angles (16:67Hz) 35
Figure 33 The most unfavorable fault initial angle (16:67Hz) at each time step 35
Figure 34 Fault occurrence situation given in reference [5] 36
Figure 35 Statistical distribution of failures over several years37
Figure 36 Transient coefficient Ktf calculated with different fault initial angle γ 38
Figure 37 Magnetic flux of the gapless iron core in the COCO working cycle 39
Figure 38 Typical flux curve of core with air gap in COCO working cycle (the flux is higher during the second energization) 40
Figure 39 Typical flux curve of air-gap core in COCO operating cycle (higher flux during first energization) 40
Figure 40 Magnetic flux curve 41 when saturation is allowed in COCO cycle
Figure 41 Core saturation is used to reduce the magnetic flux peak42
Figure 42 Curve summary of transient design 43
Figure 43 Basic circuit diagram for calculating Ktd using numerical method 44
Figure 44 Ktd calculation in CO duty cycle 46
Figure 45 Ktd calculation when there is no magnetic saturation in the first cycle of COCO working cycle 47
Figure 46 Ktd calculation when there is magnetic saturation in the first cycle of COCO working cycle 47
Figure 47 Calculation of Ktd in COCO working cycle after asymmetry is reduced 48
Figure 48 Calculation of Ktd in COCO working cycle when t'al and t″al are small 48
Figure 49 Ktd calculation of COCO working cycle of core without air gap 49
Figure 50 Comparison of saturation flux definitions between GB 1208 and GB/T 20840:2 50
Figure 51 Residual magnetization coefficient Kr 50 defined in GB 1208
Figure 52 Applying the DC method to determine the saturation magnetic flux and residual magnetic flux of the air-gap core51
Figure 53 Applying the DC method to determine the saturation magnetic flux and residual magnetic flux of the gapless iron core 51
Figure 54 Electric arc furnace transformer CT secondary current fault wave recording 54
Figure 55 Four-wire connection 55
Figure 56 CT secondary current fault recording during the second fault during automatic reclosing56
Figure 57 Application of instant/delay overcurrent protection (ANSI code 50/51) with definite time characteristics 64
Figure 58 Delayed overcurrent protection time characteristics 65
Figure 59 CT configuration example (delayed overcurrent protection) 65
Figure 60 Distance protection principle (time-distance diagram) 66
Figure 61 Distance protection principle (R/X diagram) 67
Figure 62 Distance protection CT design example 68
Figure 63 Primary current 70 in COCO working cycle
Figure 64 Transient coefficient Ktf and its envelope Ktfp 71
Figure 65 Transient coefficient Ktf of TPY class CT (saturation occurs during the first fault) 71
Figure 66 Transient coefficient Ktf of TPZ level CT (saturation occurs during the first fault) 72
Figure 67 Transient coefficient Ktf 72 of TPX level CT
Figure 68 Differential protection principle 73
Figure 69 Transformer differential protection (fault) 74
Figure 70 Transformer differential protection 75
Figure 71 Bus differential protection (outside fault) 77
Figure 72 Current simulation of CT for bus differential protection 79
Figure 73 CT design of simple double-ended line 80
Table 1 Four typical situations of initial angle of short-circuit current16
Table 2 Summary of formulas for transient design 43
Table 3 Comparison of saturation point definitions 52
Table 4 Measured residual magnetization coefficient 53
Table 5 Regulations for different PR levels of the same winding57
Table 6 Definition of electromotive force 58
Table 7 Conversion of electromotive force value 58
Table 8 Conversion between calculation coefficients 58
Table 9 Definition of limit current 59
Table 10 Minimum requirements for accuracy level specifications59
Table 11 Characteristics of air-gap and non-air-gap cores 60
Table 12 Application recommendations 61
Table 13 Calculation results of TPY core expansion area coefficient 76
Table 14 Calculation results of PX grade core expansion area coefficient 77
Table 15 Line differential protection calculation scheme 81
Table A:1 This document corrects IEC TR61869-100:2017 82
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 is Part 100 of GB/T (Z) 20840 "Transformers": GB/T (Z)20840 has released the following parts:
---Part 1: General technical requirements;
---Part 2: Supplementary technical requirements for current transformers;
---Part 3: Supplementary technical requirements for electromagnetic voltage transformers;
---Part 4: Supplementary technical requirements for combined transformers;
---Part 5: Supplementary technical requirements for capacitive voltage transformers;
---Part 6: Supplementary general technical requirements for low power transformers;
---Part 7: Electronic voltage transformer;
---Part 8: Electronic current transformers;
---Part 9: Digital interface of transformer;
---Part 14: Supplementary technical requirements for DC current transformers;
---Part 15: Supplementary technical requirements for DC voltage transformers;
---Part 100: Application Guidelines for Current Transformers for Power System Protection;
---Part 102: Ferromagnetic resonance in substations with electromagnetic voltage transformers;
---Part 103: Application of transformers in power quality measurement:
This document is modified to adopt IEC TR61869-100:2017 "Transformers Part 100: Application of current transformers for power system protection"
Guidelines": The document type was adjusted from IEC 's technical report to my country's national standardization guidance technical document:
Compared with IEC TR61869-100:2017, this document has made the following structural adjustments:
---Added Appendix A;
---Appendix B and Appendix C of this document correspond to Appendix A and Appendix B of IEC TR61869-100:2017:
The technical differences between this document and IEC TR61869-100:2017 and their reasons are as follows:
---Deleted the term "3:1:7 time" in IEC TR61869-100:2017 because the term is the same as its concept and duplicates the abbreviation;
---Adjust the content of "Note" to the main text (see 6:1:3:6) to improve the standard technical content;
---Deleted the last paragraph of 8:2 of IEC TR61869-100:2017, the first sentence of paragraph 2 in 11:2:1, and the last one of Table 12
The content on high impedance protection in the first row and the third row from the bottom is in line with the actual situation in our country;
---In "Torque is no longer required, a rated current of 1A is sufficient, even a value of 0:1A is now being discussed and already used in special fields
"However, for the transient protection current transformer with large primary current (such as generator outlet with more than 10000A)", "
For the inductor, a larger value can be selected for the secondary current, such as 5A (this is considered from the perspective of CT manufacturing), and the corresponding resistive load should also be in accordance with
"convert with the square of the current" (see 11:2:2) to conform to the actual situation in my country;
---Change "ALF or Kssc greater than or equal to 20" to "ALF or Kssc greater than or equal to 10" (see 11:3:2) to comply with my country's
The actual situation;
---Deleted the content about "high impedance differential protection" in 11:5:6 of IEC TR61869-100:2017 to conform to my country's actual situation
Condition:
The following editorial changes have been made to this document:
---The figure of the full text has been redrawn, and the curve description in the figure is directly marked in the figure: Change the inductor symbols in Figure 3, Figure 43 and Figure 59
Adjusted to commonly used domestic symbols;
---Adjust the three-phase terminal marks of IEC TR61869-100:2017 from "L1, L2, L3" to "A, B, C";
---Numbered the unnumbered formulas in IEC TR61869-100:2017 and adjusted the numbers of other formulas in the full text;
---Change "Note 1" in 3:1:3 to "Note";
---In Figure 14, vertical lines at the ordinate and ttfp,max are added;
---Adjust "δ=3°" in the text above Figure 24 to "Δφ=3°";
---The "unit value" has been deleted from the ordinate in Figure 31;
--- Figure 38 adds t″al and its description, Figure 39 adds the description of t″al;
---The symbol "^Ψsc" representing the AC magnetic flux component of the short-circuit current is added to the previous sentence of equation (30);
---The duplicate im has been deleted from the symbol description in Figure 43;
---Change "TPY20×5:5" in the first paragraph of 10:4 to "TPY level, Kssc=20, Ktd=5:5";
---In Table 10, the quotation "Standard Specification:" is added to the requirements for TPX, TPY and TPZ, and "Note" is adjusted to "Note 1", adding
Added "Note 2: For the transient accuracy level, GB/T 20840:2 stipulates that the two specification methods cannot be mixed, otherwise the
The requirements for current transformers may be excessive", and the footnotes and notes are interchanged;
---Added introductory words to 11:4:3:1:2, 11:5:2 and 11:5:3:2, and changed the content of "note" in 11:4:3:1:2;
---Added note 11:4:3:1:3;
---Changed the current flow direction in Figure 68;
---The format of Table 2 and Table 3 has been adjusted, and the expression form of some contents of Table 2 has been adjusted: Table 4, Table 5, Table 7, Table 8,
Table 11, Table 13, Table 14 and Table 15 complete the header and part of the content, Table 6 and Table 9 add a header, and the footnote form of Table 13
Adjustments have been made, and the superscript "Ktd=0:5(1)" in the first column has been deleted in Table 15;
---Corrected the error in IEC TR61869-100:2017, see Appendix A;
---Replaced IEC 61869-2 with the informative reference GB/T 20840:2 (see 4:1, 5:1:1, 5:1:2, 6:1:3:6, 6:3, 7:1,
8:1:2, 8:1:4, 10:1);
---Replaced IEC 60044-6 with the informative reference GB 16847 (see 4:1, 4:2, 5:1:1, 5:2:3, 6:1:3:2, 6:3, 8:1:2,
11:1);
---Replaced IEC 60044-1 with the informative reference GB 1208 (see 8:1:2, 8:2, 11:1);
---Deleted the informative reference to IEC 60617-3:1996 in IEC TR61869-100:2017 (see 11:1):
Please note that some content in this document may be subject to patents: The publisher of this document assumes no responsibility for identifying patents:
This document is proposed by the China Electrical Equipment Industry Association:
This document is under the jurisdiction of the National Instrument Transformer Standardization Technical Committee (SAC/TC222):
This document was drafted by: State Grid Jiangxi Electric Power Co:, Ltd: Electric Power Research Institute, Shenyang Transformer Research Institute Co:, Ltd:, Nanjing South
Ruijibao Electric Co:, Ltd:, China Electric Power Research Institute Co:, Ltd:, Dalian No: 1 Transformer Co:, Ltd:, Zhejiang Tianji Transformer
Co:, Ltd:, Jiangsu Kexing Electric Co:, Ltd:, Yunnan Power Grid Co:, Ltd: Electric Power Research Institute, Dalian Northern Transformer Group
Co:, Ltd:, Xi'an High Voltage Electrical Apparatus Research Institute Co:, Ltd:, and Electric Power Research Institute of State Grid Shaanxi Electric Power Company:
The main drafters of this document: Yan Nianping, Liu Yufeng, Wan Hua, Zhang Yu, Xu Lei, Liu Yong, Sha Yuzhou, Zhao Xicai, Tang Fuxin, Yang Feng, Wang Benjin,
Liu Hongwen, Xu Bichuan, Chen Lianyou, Zeng Leilei, Liu Bin, Lu Hang, Feng Jianhua, Deng Xiaopin, Yang Xiaoxi:
Introduction
The establishment of transformer standards is to establish a set of best evaluation criteria for transformers, from raw material selection, design, production to
Provide guidance on the precautions required in production, inspection, selection, operation and maintenance: GB/T (Z) 20840 is intended to stipulate that it is applicable to transformers
The principles and relevant rules for design, manufacturing, testing, operation and maintenance are planned to be composed of 14 parts:
---Part 1: General technical requirements: The purpose is to stipulate the requirements for the design, manufacture and production testing of various types of transformers:
General technical requirements for compliance:
---Part 2: Supplementary technical requirements for current transformers: The purpose is to specify complementary technologies suitable for various types of current transformers
Require:
---Part 3: Supplementary technical requirements for electromagnetic voltage transformers: The purpose is to stipulate that it is applicable to various types of electromagnetic voltage transformers
Supplementary technical requirements:
---Part 4: Supplementary technical requirements for combined transformers: The purpose is to specify complementary technologies applicable to various types of combined transformers
Require:
---Part 5: Supplementary technical requirements for capacitive voltage transformers: The purpose is to stipulate that it is applicable to various types of capacitive voltage transformers
Supplementary technical requirements:
---Part 6: Supplementary general technical requirements for low power transformers: The purpose is to provide for the compensation of various types of low power transformers:
Fulfill technical requirements:
---Part 7: Electronic voltage transformer: The purpose is to specify supplementary technical requirements applicable to various types of electronic voltage transformers:
---Part 8: Electronic current transformer: The purpose is to specify supplementary technical requirements applicable to various types of electronic current transformers:
---Part 9: Digital interface of transformer: The purpose is to specify the technical requirements for digital interfaces applicable to various types of electronic transformers:
---Part 10: Supplementary technical requirements for low-power passive current transformers: The purpose is to establish suitable for various types of low-power passive power
Supplementary technical requirements for current transformers:
---Part 11: Supplementary technical requirements for low power passive voltage transformers: The purpose is to establish suitable for various types of low-power passive power
Supplementary technical requirements for pressure transformers:
---Part 14: Supplementary technical requirements for DC current transformers: The purpose is to specify the compensation requirements applicable to various types of DC current transformers:
Fulfill technical requirements:
---Part 15: Supplementary technical requirements for DC voltage transformers: The purpose is to specify the specifications applicable to various types of DC voltage and current transformers:
Supplementary technical requirements:
---Part 100: Application Guidelines for Current Transformers for Power System Protection: The purpose is to use various current transformers in power systems
Provides guidance on the application of protection:
---Part 102: Ferromagnetic resonance in substations with electromagnetic voltage transformers: The purpose is to control various types of electromagnetic
Provide guidance on the generation mechanism and suppression of ferromagnetic resonance in voltage transformer substations:
---Part 103: Application of transformers in power quality measurement: The purpose is to analyze the application of various types of transformers in power quality measurement:
Provide guidance on usage:
GB/T (Z) 20840 clarifies the technical specifications of various types of transformer products through 14 parts, and provides specific technical requirements, tests
Projects, test procedures, test methods and operation guidance, etc: By establishing clear scope, terminology, technical requirements and test requirements for various products
etc:, so that personnel engaged in related product design, production, testing and use can operate more clearly and accurately, thus providing a basis for design,
It lays the foundation for manufacturing high-quality products, better promotes trade, exchanges and technical cooperation, and provides guarantee for the normal operation of my country's power grid:
Since the promulgation of GB 16847-1997 "Technical Requirements for Transient Characteristics of Current Transformers for Protection", the application of current transformers for transient protection has
The scope of use continues to expand: Therefore, the theoretical background for designing according to power system requirements becomes increasingly complex: This document is for
Supplement to the technical content of GB/T 20840:2, and at the same time, background information on transient protection characteristics and its historical version of GB/T 20840:2
The technical content in this book is compared and explained, which is helpful for users to further understand the technical content of GB/T 20840:2:
Transformers Part 100: For power system protection
Current Transformer Application Guidelines
1 Scope
This document provides advanced information for understanding the definition and requirements of electromagnetic current transformers (CT) for the general user or expert:
information to help protective relay manufacturers, current transformer manufacturers and project engineers understand how current transformers respond to simplified or standard
Standardized short circuit current signal: Where necessary, some abstract concepts are also covered, and responsibilities in the current transformer design process are discussed:
aspects of the problem:
This document applies to electromagnetic current transformers for protection that comply with the requirements of GB/T 20840:2:
2 Normative reference documents
The contents of the following documents constitute essential provisions of this document through normative references in the text: Among them, the dated quotations
For undated referenced documents, only the version corresponding to that date applies to this document; for undated referenced documents, the latest version (including all amendments) applies to
this document:
GB/T 15544:1-2023 Calculation of short-circuit current in three-phase AC systems Part 1: Current calculation (IEC 60909-0:2016,
MOD)
Note: There is no technical difference between the quoted content of GB/T 15544:1-2023 and the quoted content of IEC 60909-0:2001:
GB/T 20840:1-2010 Transformers Part 1: General technical requirements (IEC 61869-1:2007, MOD)
Note: There is no technical difference between the quoted content of GB/T 20840:1-2010 and the quoted content of IEC 61869-1:2007:
GB/T 20840:2-2014 Transformers Part 2: Supplementary technical requirements for current transformers (IEC 61869-2:2012,
MOD)
Note: There is no technical difference between the quoted content of GB/T 20840:2-2014 and the quoted content of IEC 61869-2:2012:
3 Terms, definitions and symbols
3:1 Terms and definitions
The terms and definitions defined in GB/T 20840:1-2010 and GB/T 20840:2-2014 and the following apply to this document:
3:1:1
Rated primary short-circuit current ratedprimaryshort-circuitcurrent
Ipsc
The root mean square value of the AC component of the transient primary short-circuit current is the benchmark for the accuracy performance of the current transformer:
[Source: GB/T 20840:2-2014,3:3:206]
3:1:2
rated short-time thermal current ratedshort-timethermalcurrent
Ith
When the secondary winding is short-circuited, the maximum primary current root mean square value that the current transformer can withstand for a specified short time without damage:
[Source: GB/T 20840:2-2014,3:3:203]
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