BS IEC 60826:2017
$215.11
Overhead transmission lines. Design criteria
| Published By | Publication Date | Number of Pages |
| BSI | 2017 | 84 |
NEW! IEC 60826:2017 is available as /2 which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition. IEC 60826:2017: specifies the loading and strength requirements of overhead lines derived from reliability-based design principles. These requirements apply to lines 45 kV and above, but can also be applied to lines with a lower nominal voltage. This document also provides a framework for the preparation of national standards dealing with overhead transmission lines, using reliability concepts and employing probabilistic or semi-probabilistic methods. These national standards will need to establish the local climatic data for the use and application of this standard, in addition to other data that are country- specific. Although the design criteria in this standard apply to new lines, many concepts can be used to address the design and reliability requirements for refurbishment, upgrading and uprating of existing lines. This document does not cover the detailed design of line components such as supports, foundations, conductors or insulators strings. This fourth edition cancels and replaces the third edition published in 2003. It constitutes a technical revision. The main technical changes with regard to the previous edition are as follows: This standard has been further simplified by removing many informative annexes and theoretical details that can now be found in CIGRE Technical Brochure 178 and referred to as needed in the text of the standard. Many revisions have also been made that reflect the users experience in the application of this standard, together with information about amplification of wind speed due to escarpments. The annexes dealing with icing data have also been updated using new work by CIGRE. Key words: Overhead lines, Overhead transmission lines, reliability, energy
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 4 | CONTENTS |
| 9 | FOREWORD |
| 11 | 1 Scope 2 Normative references 3 Terms, definitions, symbols and abbreviations 3.1 Terms and definitions |
| 14 | 3.2 Symbols and abbreviations |
| 17 | 4 General 4.1 Objective 4.2 System design |
| 18 | 4.3 System reliability 5 General design criteria 5.1 Methodology 5.1.1 General Figures Figure 1 – Diagram of a transmission line |
| 19 | 5.1.2 Reliability requirements Figure 2 – Transmission line design methodology |
| 20 | Tables Table 1 – Reliability levels for transmission lines |
| 21 | 5.1.3 Security requirements 5.1.4 Safety requirements 5.2 Load-strength requirements 5.2.1 Climatic loads |
| 22 | 5.2.2 Design requirements for the system Table 2 – Default γT factors for adjustment of climatic loads in relation to return period T versus 50 years |
| 23 | 5.2.3 Design formula for each component Table 3 – Design requirements for the system |
| 24 | 6 Loadings 6.1 Description 6.2 Climatic loads, wind and associated temperatures 6.2.1 General 6.2.2 Field of application |
| 25 | 6.2.3 Terrain roughness 6.2.4 Reference wind speed VR Table 4 – Classification of terrain categories |
| 26 | 6.2.5 Assessment of meteorological measurements Table 5 – Factors describing wind action depending on terrain category |
| 27 | 6.2.6 Determination from gradient wind velocities 6.2.7 Combination of wind speed and temperatures Figure 3 – Relationship between meteorological wind velocities at a height of 10 m depending on terrain category and on averaging period |
| 28 | 6.2.8 Number of supports subjected in wind action, effect of length of line 6.2.9 Unit action of the wind speed on any line component or element |
| 29 | 6.2.10 Evaluation of wind loads on line components and elements Table 6 – Correction factor τ of dynamic reference wind pressure q0 due to altitude and temperatures |
| 30 | Figure 4 – Combined wind factor Gc for conductors for various terrain categories and heights above ground Figure 5 – Span factor GL |
| 32 | Figure 6 – Combined wind factor Gt applicable to supports and insulator strings |
| 33 | Figure 7 – Definition of the angle of incidence of wind |
| 34 | Figure 8 – Drag coefficient Cxt for lattice supports made of flat sided members Figure 9 – Drag coefficient Cxt for lattice supports made of rounded members |
| 35 | Figure 10 – Drag coefficient Cxtc of cylindrical elements having a large diameter |
| 36 | 6.3 Climatic loads, ice without wind 6.3.1 Description 6.3.2 Ice data Table 7 – Drag coefficient of polygonal pole sections Table 8 – Drag coefficient of structures having a triangular section |
| 37 | 6.3.3 Evaluation of yearly maximum ice load by means of meteorological data analysis |
| 38 | 6.3.4 Reference limit ice load Figure 11 – Factor Kd related to the conductor diameter Table 9 – Statistical parameters of ice loads |
| 39 | 6.3.5 Temperature during icing 6.3.6 Loads on support Figure 12 – Factor Kh related to the conductor height |
| 40 | Figure 13 – Typical support types |
| 41 | 6.4 Climatic loads, combined wind and ice loadings 6.4.1 General 6.4.2 Combined probabilities – Principle proposed Table 10 – Non-uniform ice loading conditions |
| 42 | 6.4.3 Determination of ice load 6.4.4 Determination of coincident temperature 6.4.5 Determination of wind speed associated with icing conditions Table 11 – Return period of combined ice and wind load |
| 43 | 6.4.6 Drag coefficients of ice-covered conductors Table 12 – Drag coefficients of ice-covered conductors |
| 44 | 6.4.7 Determination of loads on supports Figure 14 – Equivalent cylindrical shape of ice deposit |
| 45 | 6.5 Loads for construction and maintenance (safety loads) 6.5.1 General 6.5.2 Erection of supports |
| 46 | 6.5.3 Construction stringing and sagging 6.5.4 Maintenance loads |
| 47 | 6.6 Loads for failure containment (security requirements) 6.6.1 General 6.6.2 Security requirements 6.6.3 Security related loads – Torsional, longitudinal and additional security measures |
| 48 | Figure 15 – Simulated longitudinal conductor load (case of a single circuit support) |
| 49 | 7 Strength of components and limit states 7.1 General 7.2 General formulas for the strength of components 7.2.1 General Figure 16 – Diagram of limit states of line components Table 13 – Additional security measures |
| 50 | 7.2.2 Values of strength factor ΦN Table 14 – Number of supports subjected to maximum load intensity during any single occurrence of a climatic event |
| 51 | 7.2.3 General basis for strength coordination Table 15 – Strength factor ΦN related to the number N of components or elements subjected to the critical load intensity |
| 52 | 7.2.4 Strength factor ΦS related to the coordination of strength 7.2.5 Methods for calculating strength coordination factors ΦS Table 16 – Values of ΦS2 Table 17 – Typical strength coordination of line components |
| 53 | 7.3 Data related to the calculation of components 7.3.1 Limit states for line components |
| 54 | Table 18 – Damage and failure limits of supports |
| 55 | Table 19 – Damage and failure limits of foundations Table 20 – Damage and failure limits of conductors and ground wires |
| 56 | 7.3.2 Strength data of line components Table 21 – Damage and failure limit of interface components |
| 57 | 7.3.3 Support design strength Table 22 – Default values for strength coefficients of variation (COV) Table 23 – u factors for log-normal distribution function for e = 10 % |
| 58 | 7.3.4 Foundation design strength 7.3.5 Conductor and ground wire design criteria 7.3.6 Insulator string design criteria Table 24 – Value of quality factor ΦQ for lattice towers |
| 60 | Annexes Annex A (informative) Technical information – Strength of line components A.1 Calculation of characteristic strength |
| 61 | Table A.1 – Values of ue associated to exclusion limits |
| 62 | Annex B (informative) Formulas of curves and figures B.1 General B.2 Formula for Gc – Figure 4 B.3 Formula for GL – Figure 5 B.4 Formula for Gt – Figure 6 B.5 Formula for Cxt – Figure 8 (flat-sided members) |
| 63 | B.6 Formula for Cxt – Figure 9 (round-sided members) B.7 Formulas for Cxtc – Figure 10 |
| 64 | Annex C (informative) Atmospheric icing C.1 General C.2 Precipitation icing C.2.1 Freezing rain C.2.2 Wet snow |
| 65 | C.3 Dry ice C.4 In-cloud icing |
| 66 | C.5 Physical properties of ice C.6 Meteorological parameters controlling ice accretion Figure C.1 – Type of accreted in-cloud icing as a function of wind speed and temperature Table C.1 – Physical properties of ice Table C.2 – Meteorological parameters controlling ice accretion |
| 67 | C.7 Terrain influences C.7.1 In-cloud icing C.7.2 Precipitation icing C.8 Guidelines for the implementation of an ice observation program |
| 68 | Figure C.2 – Strategy flow chart for utilizing meteorological data, icing models and field measurements of ice loads |
| 69 | C.9 Ice data C.9.1 Influence of height and conductor diameter C.9.2 The effect of icing on structures C.10 Combined wind and ice loadings C.10.1 Combined probabilities Table C.3 – Approximate values of ice weights on lattice structures |
| 70 | C.10.2 Drag coefficients of ice-covered conductors Table C.4 – Combined wind and ice loading conditions Table C.5 – Drag coefficients and density of ice-covered conductors |
| 71 | Annex D (informative) Application of statistical distribution functions to load and strength of overhead lines Table D.1 – Parameters C1 and C2 of Gumbel distribution |
| 72 | Table D.2 – Ratios of x / for a Gumbel distribution function, T return period in years of loading event, n number of years with observations, vx coefficient of variation |
| 73 | Annex E (informative) Effect of span variation on load-strength relationship – Calculation of span use factor E.1 General |
| 74 | E.2 Effect of use factor on load reduction and its calculation Table E.1 – Use factor coefficient γu |
| 75 | Annex F (normative) Conductor tension limits F.1 General |
| 76 | F.2 Limits for lines with short spans F.3 Recommended conductor limit tensions F.3.1 Initial tension limit Table F.1 – Variation of conductor sag with catenary parameter C |
| 77 | F.3.2 Maximum final tension limit F.4 Benefits from reducing conductor tensions Table F.2 – Conductor tensioning – recommended catenary parameter limits |
| 78 | Annex G (informative) Methods of calculation for wind speed up effects due to local topography G.1 Application |
| 79 | G.2 Notes on application Figure G.1 – Diagram of typical topographical cross-section Table G. 1 – Values of μ and γ |
| 81 | Bibliography |
