EHV/HV Underground Cable Systems for Power Transmission

Research output: Book/ReportPh.D. thesisResearch

Abstract

Power transmission is facing its largest challenges ever with regards to handling a transition from today’s fossil‐based power production into renewable sources of generation. We can no longer place power plants close to centres of consumption; they must be located where the natural resources are to be found. One very good example of this is offshore wind power plants.

The current transmission system is laid out in a traditional manner, which is based on the idea of not transporting power over longer distances as the power plants have been located near centres of consumption. It has merely played the role of interconnecting these generation/load centres, ensuring fair reliability and redundancy of supply.

Nowadays, the power transmission system must be able to handle the various sources of renewable generation in a flexible electricity market. This has the consequence that the original layout of the transmission system must be re‐thought in order to accommodate the transmission needs for the future. New lines have to be constructed.

Transmission lines are usually laid out as overhead lines, which are large structures, i.e. a 400 kV power pylon is 50 meters high. According to public opinion, such power lines are undesirable. Therefore, we must come up with an alternative, acceptable to the public.

Underground cables fulfil the above mentioned need to be more publically acceptable, but, for long transmission lines, they are in many ways unproven. Guidelines for their design are needed.

This thesis presents the results of a decade of underground cable research studies performed in Denmark by Danish TSO Energinet.dk and the Department of Energy Technology.

The thesis is based upon a number of selected publications and summarises the results of these at a presentation level intended to have an easier, possibly less scientific touch. The results are taken from their scientific embedding in the papers and made more easily accessible to readers of the thesis. The full theoretical background is to be found in the papers and their references.

Firstly, an introduction to the challenges when using underground cables is given, and secondly, the modelling approach and validation of this is discussed. Thirdly, making up the main core of the work presented, dynamics of underground cable systems are discussed and important cases to study are highlighted, and next, protection and fault location are discussed. The thesis ends with conclusions and future works, a bibliography and the publications upon which it is based.

It is concluded that underground cable systems are technically possible for power transmission, although the maturity of the consequences of the newly made design guidelines are still in its youth. Many interesting research topics are still open, especially with regards to asset management tools.
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Power transmission is facing its largest challenges ever with regards to handling a transition from today’s fossil‐based power production into renewable sources of generation. We can no longer place power plants close to centres of consumption; they must be located where the natural resources are to be found. One very good example of this is offshore wind power plants.

The current transmission system is laid out in a traditional manner, which is based on the idea of not transporting power over longer distances as the power plants have been located near centres of consumption. It has merely played the role of interconnecting these generation/load centres, ensuring fair reliability and redundancy of supply.

Nowadays, the power transmission system must be able to handle the various sources of renewable generation in a flexible electricity market. This has the consequence that the original layout of the transmission system must be re‐thought in order to accommodate the transmission needs for the future. New lines have to be constructed.

Transmission lines are usually laid out as overhead lines, which are large structures, i.e. a 400 kV power pylon is 50 meters high. According to public opinion, such power lines are undesirable. Therefore, we must come up with an alternative, acceptable to the public.

Underground cables fulfil the above mentioned need to be more publically acceptable, but, for long transmission lines, they are in many ways unproven. Guidelines for their design are needed.

This thesis presents the results of a decade of underground cable research studies performed in Denmark by Danish TSO Energinet.dk and the Department of Energy Technology.

The thesis is based upon a number of selected publications and summarises the results of these at a presentation level intended to have an easier, possibly less scientific touch. The results are taken from their scientific embedding in the papers and made more easily accessible to readers of the thesis. The full theoretical background is to be found in the papers and their references.

Firstly, an introduction to the challenges when using underground cables is given, and secondly, the modelling approach and validation of this is discussed. Thirdly, making up the main core of the work presented, dynamics of underground cable systems are discussed and important cases to study are highlighted, and next, protection and fault location are discussed. The thesis ends with conclusions and future works, a bibliography and the publications upon which it is based.

It is concluded that underground cable systems are technically possible for power transmission, although the maturity of the consequences of the newly made design guidelines are still in its youth. Many interesting research topics are still open, especially with regards to asset management tools.
Original languageEnglish
PublisherDepartment of Energy Technology, Aalborg University
Number of pages472
ISBN (Print)978‐87‐92846‐54‐9
Publication statusPublished - 2015
Publication categoryResearch

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