Summary
This Technical Brochure presents the joint CIGRE and IEEE recommendations for selecting conservative weather parameters used in overhead line thermal rating calculations. Its objective is to define practical methodologies ensuring that conductor temperatures remain within safe operating limits while maintaining required clearances, mechanical integrity, and system reliability under adverse weather conditions.
The brochure is based on an extensive international literature review and utility experience, providing guidance for static ratings, study-based ratings, and variable or real-time ratings. It highlights the importance of the correlation between wind speed, ambient temperature, and solar radiation, as well as the influence of terrain and local environmental conditions on conductor cooling performance.
The document recommends default “Base Rating” assumptions for use when no field measurements are available and describes the conditions under which higher ratings may be justified through dedicated weather studies or real-time monitoring systems. It also provides recommendations regarding measurement methods, conductor sag and temperature monitoring, and operational practices required to maintain adequate safety clearances and reliable line operation.
Table of content
1. Executive summary
1.1. Objective
1.2. Technical background
1.3. History and current practices
1.4. Organization of the project
1.5. Selection of weather parameters
1.6. Reasons for recommendations and recommended further work
2. Assumptions and definitions
2.1. Underlying assumptions
2.2. Common terminology
3. Recommendations regarding weather parameter selection for rating calculations
3.1. Technical background
3.2. Selection of weather parameters
3.3. Reasons for recommendations
4. Condensed findings based on literature review
4.1. Overview
4.2. General principles of ratings
4.3. Impact of major variables on ratings calculations
4.4. Impact of variables other than weather in rating calculations
4.5. Special rating methods
4.6. Consequences of too optimistic rating assumptions
4.7. Specific rating observations in literature
5. Recommendations for weather and rating measurements
5.1. Common requirements
5.2. Meteorological measurements and equipment
5.3. Using tension/sag monitors to determine ratings
5.4. Data collection and analysis
5.5. Combination of weather and line monitor ratings
5.6. Establishing Enhanced Ratings based on the studies
6. Acknowledgements
Appendices
Additional informations
| Publication type | Technical Brochures |
|---|---|
| Reference | 299 |
| Publication year | |
| Publisher | CIGRE |
| Study committees | |
| Working groups | WG B2.12 |
| File size | 4 MB |
| Pages number | 57 |
| Price for non member | 120 € |
| Price for member | Free |
Authors
Tapani Seppa, Convenor (US), Afshin Salehian, Secretary (US)
Kresimir Bakic (SI), William Chisholm (CA), Nicholas DeSantis (US), Svein Fikke (NO), Dale Douglass (US), Michelle Gaudry (FR), Anand Goel (CA), Sven Hoffmann (UK), Javier Iglesias (SP), Andrew Maxwell (SE), Dennis Mize (US), Ralf Puffer (DE), Jerry Reding (US), Jimmy Robinson (US), Rob Stephen (ZA), Woodrow Whitlatch (US)
Keywords
overhead line rating, bare overhead conductor, thermal rating, dynamic line rating, transmission line ampacity, weather parameters, conductor temperature, real-time line rating, transmission line monitoring, power line sag
