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Hunter Allen
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Learn How to Apply IEC 60826:2017 for Overhead Line Design in Different Regions and Scenarios



- What are the main objectives and scope of this standard? - How to download the PDF version of this standard? H2: Loading and strength requirements of overhead lines - What are the reliability-based design principles used in this standard? - What are the main loading and strength parameters considered in this standard? - How are these parameters calculated and applied to different line components? H3: Framework for national standards based on IEC 60826 - What are the benefits of using reliability concepts and probabilistic or semi-probabilistic methods for overhead line design? - What are the main steps and considerations for preparing national standards based on IEC 60826? - How to establish the local climatic data and other country-specific data for the application of this standard? H4: Design and reliability aspects for refurbishment, upgrading and uprating of existing lines - How can the design criteria in this standard be used to address the needs and challenges of existing lines? - What are the main factors affecting the performance and reliability of existing lines? - How to assess and improve the reliability of existing lines using this standard? H2: Detailed design of line components - What are the main components of overhead transmission lines and how are they designed? - How does this standard provide guidance and references for the detailed design of supports, foundations, conductors and insulator strings? - What are some examples of line component design using this standard? H3: Supports - What are the types and functions of supports for overhead lines? - How to determine the loading and strength requirements for supports using this standard? - How to select and design suitable supports for different line configurations and environmental conditions? H4: Foundations - What are the types and functions of foundations for overhead line supports? - How to determine the loading and strength requirements for foundations using this standard? - How to select and design suitable foundations for different soil types and site conditions? H4: Conductors - What are the types and functions of conductors for overhead lines? - How to determine the loading and strength requirements for conductors using this standard? - How to select and design suitable conductors for different line voltages, currents, spans and environmental conditions? H4: Insulator strings - What are the types and functions of insulator strings for overhead lines? - How to determine the loading and strength requirements for insulator strings using this standard? - How to select and design suitable insulator strings for different line voltages, clearances, pollution levels and environmental conditions? H2: Technical changes in the fourth edition of IEC 60826 - What are the main technical changes in the fourth edition of IEC 60826 compared to the previous edition? - Why were these changes made and what are their implications for overhead line design? - How to use the new features and information provided in this edition? H3: Simplification of informative annexes and theoretical details - What are the informative annexes and theoretical details that were removed from this edition and where can they be found now? - How does this simplification make this standard more user-friendly and practical? - How to use the CIGRE Technical Brochure 178 as a complementary source of information for this standard? H3: Revisions based on user experience and feedback - What are the main revisions that were made based on user experience and feedback in applying this standard? - How do these revisions improve the accuracy, consistency and clarity of this standard? - How to apply these revisions to existing and new overhead line design projects? H4: Amplification of wind speed due to escarpments - What is the phenomenon of wind speed amplification due to escarpments and how does it affect overhead line design? - How does this edition provide new information and guidance on this phenomenon? - How to calculate and apply the amplification factor for wind speed due to escarpments using this standard? H4: Icing data and models - What are the effects of icing on overhead line design and performance? - How does this edition provide updated and improved icing data and models based on new work by CIGRE? - How to use the new icing data and models for different regions and scenarios using this standard? H2: Conclusion - What are the main benefits and challenges of using IEC 60826 for overhead line design? - What are the key takeaways and recommendations from this article? - How to access more information and resources on this topic? H3: FAQs - What is the difference between IEC 60826 and other standards for overhead line design? - How can I get a PDF version of IEC 60826? - How often is IEC 60826 updated and revised? - How can I provide feedback or suggestions for IEC 60826? - How can I learn more about overhead line design using IEC 60826? # Article with HTML formatting Introduction




Overhead transmission lines are essential components of the power system, connecting generation plants with load centers and enabling the exchange of electricity across regions and countries. The design of overhead transmission lines involves many technical, economic, environmental and social aspects, such as loading, strength, reliability, safety, cost, aesthetics, land use, public acceptance and regulatory compliance. Therefore, it is important to have a comprehensive and consistent set of design criteria that can guide the engineers and planners in developing optimal and robust solutions for overhead line projects.




iec 60826 design criteria of overhead transmission lines pdf download



One of the most widely used and recognized standards for overhead line design is IEC 60826, which specifies the loading and strength requirements of overhead lines derived from reliability-based design principles. This standard applies to lines 45 kV and above, but can also be applied to lines with a lower nominal voltage. It 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.


IEC 60826 was first published in 1987 and has been revised several times since then. The latest edition, which is the fourth edition, was published in 2017. It incorporates many technical changes and improvements based on user experience, feedback and new research. It also simplifies some informative annexes and theoretical details that can now be found in CIGRE Technical Brochure 178, which is a complementary document that provides more information on the background, theory and application of IEC 60826.


If you are interested in learning more about IEC 60826 and how to use it for overhead line design, you have come to the right place. In this article, we will cover the following topics:


  • The loading and strength requirements of overhead lines based on reliability-based design principles.



  • The framework for national standards based on IEC 60826.



  • The design and reliability aspects for refurbishment, upgrading and uprating of existing lines.



  • The detailed design of line components such as supports, foundations, conductors and insulator strings.



  • The technical changes in the fourth edition of IEC 60826.



  • The conclusion and FAQs.



By the end of this article, you will have a better understanding of IEC 60826 and how to apply it to your overhead line design projects. You will also know how to download the PDF version of this standard from the official website of IEC or other authorized sources.


Loading and strength requirements of overhead lines




The main objective of IEC 60826 is to specify the loading and strength requirements of overhead lines derived from reliability-based design principles. These principles aim to ensure that the probability of failure or damage of any component or element of an overhead line due to external or internal loads does not exceed a certain acceptable level. The acceptable level of reliability depends on various factors such as the consequences of failure, the cost of maintenance, the availability of spare parts, the redundancy of the system, the public perception and the regulatory requirements.


The main loading and strength parameters considered in IEC 60826 are:


  • Wind load: The force exerted by the wind on the line components, such as supports, conductors and insulator strings. The wind load depends on the wind speed, direction, turbulence, terrain and exposure of the line.



  • Ice load: The weight of ice accumulated on the line components, such as conductors and insulator strings. The ice load depends on the ice thickness, density, shape and temperature.



  • Snow load: The weight of snow accumulated on the line components, such as supports and cross-arms. The snow load depends on the snow depth, density and shape.



  • Temperature: The variation of temperature along the line and its effects on the thermal expansion and contraction of the line components, such as conductors and insulator strings. The temperature also affects the electrical resistance and sag of the conductors.



  • Short-circuit current: The high current that flows through the line in case of a fault or abnormal condition. The short-circuit current causes electromagnetic forces and thermal effects on the line components, such as conductors and insulator strings.



  • Broken wire: The condition when one or more wires of a conductor or an insulator string break due to fatigue, corrosion, vandalism or other causes. The broken wire causes an imbalance of forces and moments on the line components, such as supports and cross-arms.



These parameters are calculated and applied to different line components using various methods and models provided in IEC 60826. These methods and models take into account the statistical distribution, correlation and combination of the parameters, as well as the uncertainties and variations in the data and assumptions. The methods and models also consider the effects of dynamic and nonlinear behavior of the line components under different loading scenarios.


The loading and strength requirements for each line component are expressed in terms of limit states, which are defined as follows:


  • Ultimate limit state (ULS): The state when a line component reaches its ultimate strength or capacity and fails or collapses. The ULS is associated with a very low probability of occurrence and a very high consequence of failure.



  • Serviceability limit state (SLS): The state when a line component exceeds its serviceability criteria and causes unacceptable performance or damage. The SLS is associated with a higher probability of occurrence and a lower consequence of failure than the ULS.



The limit states are checked by comparing the design actions (the loading effects) with the design resistances (the strength capacities) of each line component. The design actions and resistances are calculated using partial safety factors that account for the uncertainties and variations in the data and assumptions. The partial safety factors are derived from reliability analysis using target reliability levels for each limit state. The target reliability levels depend on various factors such as the consequences of failure, the cost of maintenance, the availability of spare parts, the redundancy of the system, the public perception and the regulatory requirements.


Framework for national standards based on IEC 60826




IEC 60826 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 methods allow for a more rational and consistent approach to overhead line design than traditional deterministic methods that use fixed safety factors or margins. These methods also enable a more flexible and adaptable design that can account for different climatic conditions, site characteristics, operational requirements and risk preferences.


The main steps and considerations for preparing national standards based on IEC 60826 are:


  • Establish the local climatic data for the use and application of IEC 60826. The local climatic data include the wind speed, direction, turbulence, terrain and exposure of the line, as well as the ice thickness, density, shape and temperature, and the snow depth, density and shape. The local climatic data can be obtained from historical records, measurements, surveys, maps or models. The local climatic data should be representative of the design life of the line and should cover the extreme and frequent events that may affect the line performance and reliability.



  • Establish other country-specific data for the use and application of IEC 60826. These data include the electrical parameters of the line, such as the nominal voltage, current, frequency and short-circuit level, as well as the mechanical parameters of the line components, such as the material properties, dimensions, weights and configurations. These data also include the operational and maintenance aspects of the line, such as the loading history, inspection frequency, repair methods and spare parts availability. These data should be consistent with the design standards and practices of the country and should reflect the actual conditions and requirements of the line.



  • Select the reliability-based design methods and models for applying IEC 60826. These methods and models include the probabilistic or semi-probabilistic methods for calculating and combining the loading and strength parameters of each line component, as well as the reliability analysis methods for deriving the partial safety factors and checking the limit states. These methods and models should be compatible with IEC 60826 and should be validated by experimental or analytical studies. These methods and models should also be calibrated by comparing their results with existing or new lines designed using traditional or other methods.



  • Select the target reliability levels for each limit state of each line component. The target reliability levels are expressed in terms of probabilities or frequencies of failure or damage over a given period of time. The target reliability levels depend on various factors such as the consequences of failure, the cost of maintenance, the availability of spare parts, the redundancy of the system, the public perception and the regulatory requirements. The target reliability levels should be consistent with IEC 60826 and should be justified by cost-benefit analysis or risk assessment.



  • Prepare and document the national standard based on IEC 60826. The national standard should include all the necessary information and guidance for applying IEC 60826 to overhead line design in a clear and concise manner. The national standard should also include any deviations or modifications from IEC 60826 that are specific to the country or region. The national standard should be reviewed and approved by relevant authorities and stakeholders before publication and implementation.



Design and reliability aspects for refurbishment, upgrading and uprating of existing lines




Although the design criteria in IEC 60826 apply to new lines, many concepts can be used to address the design and reliability requirements for refurbishment, upgrading and uprating of existing lines. Refurbishment refers to restoring or improving an existing line to its original or better condition. Upgrading refers to increasing or enhancing an existing line to meet new or higher standards or requirements. Uprating refers to increasing or enhancing an existing line to carry more power or operate at higher voltage or current.


The main factors affecting the performance and reliability of existing lines are:


  • Aging: The deterioration or degradation of the line components due to wear and tear, corrosion, fatigue, creep, erosion or other causes. Aging reduces the strength and serviceability of the line components and increases the risk of failure or damage.



  • Obsolescence: The outdatedness or inadequacy of the line components due to changes in technology, standards, regulations or requirements. Obsolescence reduces the efficiency and compatibility of the line components and increases the cost of operation and maintenance.



  • Overloading: The excess or surplus of load on the line components due to increased demand, generation or interconnection. Overloading increases the stress and strain on the line components and reduces their safety margin and lifespan.



The main methods for assessing and improving the reliability of existing lines using IEC 60826 are:


  • Inspection: The examination or observation of the line components to detect any defects, damages or anomalies that may affect their performance or reliability. Inspection can be done by visual, mechanical, electrical, acoustic or other means. Inspection can help identify the current condition and remaining life of the line components and provide information for maintenance or replacement decisions.



  • Maintenance: The repair or replacement of the line components to restore or improve their performance or reliability. Maintenance can be done by preventive, corrective or predictive methods. Maintenance can help extend the life and serviceability of the line components and reduce the probability and consequence of failure or damage.



  • Reinforcement: The addition or modification of the line components to increase or enhance their performance or reliability. Reinforcement can be done by strengthening, stiffening, damping, anchoring or other means. Reinforcement can help increase the capacity and safety margin of the line components and reduce their stress and strain.



Detailed design of line components




IEC 60826 does not cover the detailed design of line components such as supports, foundations, conductors or insulator strings. However, it provides some guidance and references for these aspects in some informative annexes. It also refers to other standards and documents that deal with these aspects in more detail. In this section, we will briefly introduce the main components of overhead transmission lines and how they are designed using IEC 60826 and other sources. Supports




Supports are the structures that hold and carry the conductors and insulator strings of an overhead line. They also provide the necessary clearances and alignments for the line. Supports can be classified into different types according to their function, shape, material and configuration. Some common types of supports are:


  • Towers: Tall and rigid structures that are usually made of steel or concrete and have lattice or tubular shapes. Towers are used for long spans, high voltages, heavy loads and complex configurations.



  • Poles: Shorter and more flexible structures that are usually made of wood, steel or concrete and have cylindrical or polygonal shapes. Poles are used for shorter spans, lower voltages, lighter loads and simpler configurations.



Portals: Horizontal structures that are usually made of steel or concrete and have two or more legs connected by


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