P35.007: Line Design
Objective
Considering the anticipated growing demand for transmission capacity, which is fueled by a combination of changing generation patterns and emerging electricity-intensive technologies, utilities will find value in producing higher performing overhead lines that feature increased performance in terms of capacity, transmission efficiency, and reliability. The goals of this project are closely aligned to the EPRI vision of producing safe, affordable, environmentally responsible, and reliable electricity. This mission is reflected in the transmission line design space where multiple aspects of system performance converge in the design process.
The objectives of this project are to facilitate the engineering and construction of higher performing transmission lines, to enhance the knowledge and skill of engineers performing line design, and to assist in the research and development of tools and solutions that complement the line engineering effort.
This project provides:
- Red, Orange, and Blue reference books, which are updated periodically to serve as living documents for the body of knowledge relating to transmission line design
- Electrical and mechanical design software, including TLW, Red Book Applications, and Op10
- Red Book seminars and Orange Book seminars, which provide fundamental and problem-specific training
- Design guidebooks, which are updated periodically and include the Overhead Line Design Guide and the Guide for Coordination of Overhead Line Designs for Construction and Maintenance
- Forums for information sharing across utilities to share best practices and lessons learned
- Additional topical workshops for focused training
Research Value
Research in overhead transmission design provides guidance on proper selection and application of line components to ensure optimal line design, which ensures:
- Increased performance and efficiency
- Reduction of capital and operational expenditures
- Increased safety
- Increased reliability
Planned 2025 Research
Fundamental research and laboratory testing is undertaken to enhance the industry body of knowledge. As knowledge levels for a research question reach maturity, these are translated into actionable recommendations and recorded in reference books.
Both existing and emerging tools and technologies are tested and performance validated to facilitate application. Development and continuous enhancement of line design tools is undertaken, and training workshops are held to facilitate adoption into engineering divisions.
This project aims to enhance overhead design capability in utilities throughout the spectrum of expertise and experience. This is achieved by a focus on continuing education for line design professionals, aimed at both early career as well as seasoned engineers.
EPRI Transmission Line Reference Book: Conductor and Structure Motion. EPRI intends to expand the initial research into the efficacy of anti-vibration fasteners to include more systems and additional testing to validate results. In addition, the project aims to improve the guidance on design for magnetic attraction between sub-conductors in a bundle in 2025.
Optimal Pole Material Selection Guide . In partnership with P35.005, Ductile Iron and Composite Structures Project, EPRI intends to publish a new guide comparing the five primary materials used for utility structures: wood, steel, concrete, fiber-reinforced polymer (FRP) composites, and ductile iron. In 2025, EPRI aims to produce representative structural designs of all five materials under various loading conditions. This will help engineers make more informed decisions to select an optimal pole material for their application.
Overhead Line Design Guide: Extra-High-Voltage Line Design Checklist. Last produced in 2018, EPRI’s AC Overhead Line Design Guide helps engineers navigate the multi-faceted tasks associated with transmission line design. In 2025, EPRI aims to update the guide with an extra-high-voltage (EHV) line design checklist. This addition will serve as a roadmap for engineers unfamiliar with EHV design and will include topics such as phase geometry design, corona, audible noise, and minimum approach distance (MAD) calculations.
Safe Design Tension of ACSS Conductor. Determining a safe conductor tension is a multi-faceted problem that requires understanding of the self-damping performance and fretting fatigue endurance of a conductor. This new initiative, which is a collaborative effort with P35.015, aims to help solve this problem for aluminum conductor steel supported (ACSS) conductor because its self-damping and fatigue properties vary significantly from those of aluminum conductor steel reinforced (ACSR) conductor.
Online Training for Orange Book: EPRI aims to start the production of selected training modules covering key chapters in the Orange Book. These events will be held in conjunction with EPRIU4T.
Online Training/Workshop: Calculation of Overhead Line Loads: Training on the fundamentals for the quantification of overhead line design loads will be hosted in conjunction with EPRIU4T, with reference to National Electric Safety Code (NESC) and American Society of Civil Engineers (ASCE) recommendations.
Transmission Line Workstation Gen 2: Design Modules Vibration (TLW-Gen2) v13.0: The EPRI software tool was developed to facilitate engineers in evaluating different design options effectively. Algorithms in some of the design programs may require updating based on EPRI research. Updating of this software may also be required to improve user features, add new functionalities, or be compatible with other industry software used by the design engineers.
Anticipated Deliverables
In 2025, a mix of ongoing research initiatives together with new research areas will be undertaken.
| Deliverable | Type | Date |
|---|---|---|
| Conductor and Structure Motion Reference Book (The Orange Book) | Reference Book | December 2025 |
| AC Transmission Line Reference Book: 200 kV and Above (The Red Book) | Reference Book | December 2025 |
| AC Transmission Line Reference Book: 115–400 kV Compact Line Design (The Blue Book) | Reference Book | December 2025 |
| Optimal Pole Material Selection Guide | Technical Update | December 2025 |
| Overhead Line Design Guide: Extra-High-Voltage Line Design Checklist | Technical Update | December 2025 |
| Safe Design Tension of ACSS Conductor | Technical Update | December 2025 |
| Online Training Seminar: The Orange Book | Workshop | December 2025 |
| Calculation of Overhead Line Loads Workshop | Workshop | December 2025 |
| Transmission Line Workstation Gen 2 (TLW-Gen2) v13.0: Design and Vibration Modules | Software | December 2025 |
Past EPRI Work on Topic
| Product ID | Title | Description | Published Date |
|---|---|---|---|
| 3002026982 | EPRI AC Transmission Line Reference Book: 200 kV and Above: 2023 Edition (The Red Book) | Updated reference book | December 2023 |
| 3002021493 | Guide for the Application and Selection of Aerial Warning Devices | Wind tunnel testing and computational fluid dynamics (CFD) modeling to enable accurate structural modeling and address issues relating to installation | December 2021 |
| 3002019001 | Guide for Coordination of Overhead Line Designs for Construction and Maintenance | Significant revision and expansion of the guide to include design features facilitating construction | December 2020 |