Ampacity and thermal equivalent modeling of subsea power cables for long distance power transmission and optimization

One of the defining aspects of life in the modern world is the convenience of access to a dependable and plentiful supply of electricity. This essential utility is delivered to consumers from power generating stations via an extensive and intricate network of cables. Submarine power cables are be...

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Main Author: Duraisamy, Nishanthi
Other Authors: Gooi Hoay Beng
Format: Thesis-Doctor of Philosophy
Language:English
Published: Nanyang Technological University 2021
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Online Access:https://hdl.handle.net/10356/153225
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Institution: Nanyang Technological University
Language: English
id sg-ntu-dr.10356-153225
record_format dspace
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Electrical and electronic engineering::Electric power::Production, transmission and distribution
spellingShingle Engineering::Electrical and electronic engineering::Electric power::Production, transmission and distribution
Duraisamy, Nishanthi
Ampacity and thermal equivalent modeling of subsea power cables for long distance power transmission and optimization
description One of the defining aspects of life in the modern world is the convenience of access to a dependable and plentiful supply of electricity. This essential utility is delivered to consumers from power generating stations via an extensive and intricate network of cables. Submarine power cables are becoming increasingly important to modern power transmission strategies. There has been a large amount of recent investment in projects such as offshore wind farms and international “megagrid" initiatives, of which submarine power cables are essential components. The installation and maintenance costs of such buried cables are far higher than the overhead lines due to the complexity involved. The cable construction and cooling system for the cables are not interchangeable with their overhead counterparts. The maximum allowable cable conductor temperature is limited to avoid cable failures. The maximum current carrying capacity (ampacity) of power cables depends on the heat transferability of its surrounding medium. Submarine power cable ampacity is calculated conventionally following the international standards defined for underground cables. This conservative approach results in the system over design and under-utilization of the cable capacity. In reality, the thermal behavior of submarine environments differs significantly from its underground counterpart as the porous sediments are constantly water-saturated. The research aims to model the electrical and thermal characteristics of such long distance cables for accurately determining the effect of the factors that influence the ampacity and optimize the power flow. The cable ampacity analyses were carried out using the standards defined in IEEE 835 and IEC 60287. Unrealistic simplifications used for calculating the heat dissipation from the cable limited the validity of the calculation to specific cable geometries. Consequently, the first challenge in this work was developing a general reliable numerical procedure for the analysis of thermal field characteristics of the subsea cable systems of any system geometry, backfill and submarine environment. The effect of the thermal circuit parameter variations was the main concern as it has a higher effect on the cable’s thermal behavior and it may result in a significant difference in the cable ampacity . In this regard, special attention was paid in developing a sensitivity methodology of thermal field with respect to the thermal parameter changes. The difficulties have arisen since the model developed here was based on the exact finite element implementation and did not involve any simplification for the thermal heat modeling. The finite element method (FEM) was used for determining the factors affecting ampacity of submarine power cables cable using the COMSOL Multiphysics software program. Complex multiple layered co-axial cables were analysed to determine the effect of sediment properties on the cables ampacity. Considerations of sediment properties to calculate external thermal resistance resulted in ampacity values significantly different from standard values. Lab-scale experimentation was conducted to validate the results. The inclusion of convective heat transfer obtained a more precise ampacity estimate compared to that of the standard methods. The findings are significant for submarine power cables where the occurrence of convective cooling is neglected in general.
author2 Gooi Hoay Beng
author_facet Gooi Hoay Beng
Duraisamy, Nishanthi
format Thesis-Doctor of Philosophy
author Duraisamy, Nishanthi
author_sort Duraisamy, Nishanthi
title Ampacity and thermal equivalent modeling of subsea power cables for long distance power transmission and optimization
title_short Ampacity and thermal equivalent modeling of subsea power cables for long distance power transmission and optimization
title_full Ampacity and thermal equivalent modeling of subsea power cables for long distance power transmission and optimization
title_fullStr Ampacity and thermal equivalent modeling of subsea power cables for long distance power transmission and optimization
title_full_unstemmed Ampacity and thermal equivalent modeling of subsea power cables for long distance power transmission and optimization
title_sort ampacity and thermal equivalent modeling of subsea power cables for long distance power transmission and optimization
publisher Nanyang Technological University
publishDate 2021
url https://hdl.handle.net/10356/153225
_version_ 1772825726667456512
spelling sg-ntu-dr.10356-1532252023-07-04T17:42:18Z Ampacity and thermal equivalent modeling of subsea power cables for long distance power transmission and optimization Duraisamy, Nishanthi Gooi Hoay Beng School of Electrical and Electronic Engineering EHBGOOI@ntu.edu.sg Engineering::Electrical and electronic engineering::Electric power::Production, transmission and distribution One of the defining aspects of life in the modern world is the convenience of access to a dependable and plentiful supply of electricity. This essential utility is delivered to consumers from power generating stations via an extensive and intricate network of cables. Submarine power cables are becoming increasingly important to modern power transmission strategies. There has been a large amount of recent investment in projects such as offshore wind farms and international “megagrid" initiatives, of which submarine power cables are essential components. The installation and maintenance costs of such buried cables are far higher than the overhead lines due to the complexity involved. The cable construction and cooling system for the cables are not interchangeable with their overhead counterparts. The maximum allowable cable conductor temperature is limited to avoid cable failures. The maximum current carrying capacity (ampacity) of power cables depends on the heat transferability of its surrounding medium. Submarine power cable ampacity is calculated conventionally following the international standards defined for underground cables. This conservative approach results in the system over design and under-utilization of the cable capacity. In reality, the thermal behavior of submarine environments differs significantly from its underground counterpart as the porous sediments are constantly water-saturated. The research aims to model the electrical and thermal characteristics of such long distance cables for accurately determining the effect of the factors that influence the ampacity and optimize the power flow. The cable ampacity analyses were carried out using the standards defined in IEEE 835 and IEC 60287. Unrealistic simplifications used for calculating the heat dissipation from the cable limited the validity of the calculation to specific cable geometries. Consequently, the first challenge in this work was developing a general reliable numerical procedure for the analysis of thermal field characteristics of the subsea cable systems of any system geometry, backfill and submarine environment. The effect of the thermal circuit parameter variations was the main concern as it has a higher effect on the cable’s thermal behavior and it may result in a significant difference in the cable ampacity . In this regard, special attention was paid in developing a sensitivity methodology of thermal field with respect to the thermal parameter changes. The difficulties have arisen since the model developed here was based on the exact finite element implementation and did not involve any simplification for the thermal heat modeling. The finite element method (FEM) was used for determining the factors affecting ampacity of submarine power cables cable using the COMSOL Multiphysics software program. Complex multiple layered co-axial cables were analysed to determine the effect of sediment properties on the cables ampacity. Considerations of sediment properties to calculate external thermal resistance resulted in ampacity values significantly different from standard values. Lab-scale experimentation was conducted to validate the results. The inclusion of convective heat transfer obtained a more precise ampacity estimate compared to that of the standard methods. The findings are significant for submarine power cables where the occurrence of convective cooling is neglected in general. Doctor of Philosophy 2021-11-15T07:17:53Z 2021-11-15T07:17:53Z 2021 Thesis-Doctor of Philosophy Duraisamy, N. (2021). Ampacity and thermal equivalent modeling of subsea power cables for long distance power transmission and optimization. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/153225 https://hdl.handle.net/10356/153225 10.32657/10356/153225 en This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0). application/pdf Nanyang Technological University