Summary
Read more on ELECTRAIt is important that the current rating calculations of power cables are reliable and trustworthy. However, setting-up a current rating calculation according to the IEC 60287 standards is difficult and requires making decisions regarding the selection of the equations to use and the parameters to adopt, often in the absence of guidance provided by the standards. This often leads to different calculation results for similar cable installations depending on the engineer and the tool used to make the calculation, even in straightforward situations. CIGRE WG B1.56 has now developed both guidance on how to deliver consistent calculation results and has developed a procedure with which any calculation spreadsheet, tool, own or commercial software can be verified as recommended by CIGRE TB 640. The verification procedure comprises 11 case studies ranging between MV and EHV and comprising DC, XLPE, SCFF and pipe type cables for both land and submarine installations, against which the calculation tool can be verified in full detail. The key benefit which is provided is that with such a verification in place, current rating calculations for power cables become demonstrably reliable, trustworthy and consistent.
Table of content
Executive summary
1. Introduction
1.1. Background
1.2. Key benefits
1.3. This brochure and the standards
1.4. This brochure and other work on cable current ratings
1.5. Referencing this brochure in technical specifications
1.6. How to use this brochure
2. Guidance
2.1. Overview
2.2. Rounding and accuracy
2.3. The standard to be used in the current rating calculations
2.4. Common pitfalls
2.5. Iteration in calculations
2.6. Simplifications in the IEC standard
2.7. Current rating calculations of HVDC cables
2.8. Deduction of dimensions (interpretation of datasheet values)
2.9. Properties of materials
2.10. Electrical capacitance
2.11. AC and DC conductor resistance calculations
2.12. Calculation of losses in metallic screens, sheaths and armours
2.13. Calculations for sheaths and screens
2.14. Calculations for armour
2.15. Thermal resistance calculations
2.16. Thermal resistance of fillers in three core submarine cables
3. Interpretation of differences
Read more Read less4. Introductory case study 0
4.1. Introduction
4.2. Case #0: Input data
4.3. Case #0: Guidelines for the iterative calculation
4.4. Case #0-1: Results independent of the temperature
4.5. Case #0-1: Results dependent on the temperature
4.6. Case #0-1: Possible variations
4.7. Case #0-2: Sub-case study with touching HDPE ducts
4.8. Case #0-3: Sub-case study with PVC ducts in flat formation embedded in concrete
4.9. Case #0-4: Sub-case study with cables laid in free air directly exposed to solar radiation
4.10. Case #0-5: Sub-case study with cables in an unfilled trough
4.11. Case #0: Summary table
5. Case study 1: Direct buried 132kV cables
5.1. 132 kV cables in direct buried trefoil formation
5.2. 132 kV cables in directly buried flat formation
6. Case study 2: A 30kV submarine array cable
6.1. Introduction
6.2. Calculation of lay-up factor of the cores
6.3. Calculation of the conductor AC resistance at operation temperature
6.4. Dielectric losses
6.5. Loss factor for sheath
6.6. Loss factor for armour
6.7. Thermal resistance T1 between conductor and screen
6.8. Thermal resistance T2 of the sheath around each core, fillers and bedding
6.9. Thermal resistance T3 of outer covering
6.10. External thermal resistance T4
6.11. Permissible current rating
6.12. Calculation of losses
7. Case study 3: A 230kV HPFF cable
7.1. Introduction
7.2. Physical dimensions of cable system
7.3. Calculation of the conductor AC resistance at operation temperature
7.4. Dielectric losses
7.5. Loss factor for taped screen
7.6. Loss factor for skid wire
7.7. Loss factor for pipe loss increment
7.8. Thermal resistance T1 between conductor and screen
7.9. Thermal resistance T2 between the cable surface and inside of pipe
7.10. Thermal resistance T3 of outer covering (pipe coating)
7.11. External thermal resistance T4
7.12. Permissible current rating
7.13. Calculation of losses
7.14. Calculation of cable temperatures
8. Case study 4: A 33kV land cable
8.1. Introduction
8.2. Installation conditions
8.3. Calculation of the conductor AC resistance at operation temperature
8.4. Dielectric losses
8.5. Loss factor for screen
8.6. Thermal resistance T1 between conductor and screen
8.7. Thermal resistance T2 between screen and armour
8.8. Thermal resistance T3 of outer covering
8.9. External thermal resistance T4
8.10. Permissible current rating
9. Case study 5: A 400kV LPOF cable
9.1. Introduction
9.2. 400 kV LPOF cable in trefoil
9.3. 400 kV LPOF cable in flat formation
10. Case study 6: A 400kV single core AC submarine cable circuit
10.1. Introduction
10.2. Calculation of the conductor AC resistance at operation temperature
10.3. Dielectric losses
10.4. Loss factor for screen, lead alloy sheath and armour
10.5. Thermal resistance T1 between conductor and screen
10.6. Thermal resistance T2 between lead alloy sheath and armour
10.7. Thermal resistance T3 of outer covering
10.8. External thermal resistance T4
10.9. Permissible current rating
10.10. Calculation of losses
11. Case study 7: A 320kV HVDC submarine bipole
11.1. Introduction
11.2. Introduction to rating calculation of HVDC cables
11.3. Calculation of the conductor DC resistance at operation temperature
11.4. Thermal resistance T1 between conductor and the screen
11.5. Thermal resistance T2 between lead sheath and the armour
11.6. Thermal resistance T3 outer serving
11.7. External thermal resistance T4
11.8. Permissible current rating-thermally limited
11.9. Calculation of temperature drop across the insulation
11.10. Calculation of field limited conductor temperature
11.11. Permissible current rating-field limited
12. Case study 8: A 220kV 3-core submarine export cable
12.1. Introduction
12.2. Core layup effect
12.3. Calculation of the conductor AC resistance at operation temperature
12.4. Dielectric losses
12.5. Loss factor for sheath
12.6. Loss factor for armour
12.7. Thermal resistance T1 between conductor and screen
12.8. Thermal resistance T2 between screen and armour
12.9. Thermal resistance T3 of outer covering
12.10. External thermal resistance T4
12.11. Current rating
12.12. Iteration
12.13. Final result
12.14. Calculation of losses
13. Case study 9: A 110kV retrofitted cable
13.1. Introduction
13.2. Calculation of the conductor AC resistance at operation temperature
13.3. Calculation of core layup factor
13.4. Dielectric losses
13.5. Loss factor for sheath
13.6. Loss factor for armour
13.7. Thermal resistance T1 between conductor and screen
13.8. Thermal resistance T2 between sheath and amour
13.9. Thermal resistance T3 of outer covering
13.10. External thermal resistance T4
13.11. Current rating
13.12. Iterative calculation of current rating
13.13. Final result
13.14. Calculation of losses
14. Case study 10: A 10kV three core PILC cable
14.1. Introduction
14.2. Calculation of the conductor AC resistance at operation temperature
14.3. Dielectric losses
14.4. Loss factor for lead sheath
14.5. Loss factor for the armouring
14.6. Thermal resistance T1 between conductor and screen
14.7. Thermal resistance T2 between sheath and armour
14.8. Thermal resistance T3 of outer covering
14.9. External thermal resistance T4
14.10. Permissible current rating
14.11. Calculation of losses
15. References
Additional informations
| Publication type | Technical Brochures |
|---|---|
| Reference | 880 |
| Publication year | |
| Publisher | CIGRE |
| ISBN | 978-2-85873-585-3 |
| Study committees | |
| Working groups | WG B1.56 |
| File size | 9 MB |
| Pages number | 331 |
| Price for non member | 300 € |
| Price for member | Free |
Authors
Frank de Wild, Convenor (NL), Jos van Rossum, Secretary (NL)
George Anders (CA), Rusty Bascom (US), Stefie Cray (UK), Jaeyun Joo (KR), Woulèye Kamara (CA), Queeneth Khumalo (ZA), Thomas Kvarts (DK), Frédéric Lesur (FR), Abbas Lotfi (NO), Wael Moutassem (US), James Pilgrim (UK), Kyrre Pinkert (DE), Varvara Rizou (GR), Ola Thyrvin (SE)
Corresponding Members
Roberto Benato (IT), Sebastian Dambone Sessa (IT), Antony Falconer (OM), Ying Liu (CN), Fabio Gabriel Oliveira (BR), Tsuguhiro Takahashi (JP)
