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Evaluation of Gas Insulated Lines (GIL) for long distance HVAC power transfer

Elnaddab, Khalifa 2014. Evaluation of Gas Insulated Lines (GIL) for long distance HVAC power transfer. PhD Thesis, Cardiff University.
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Offshore wind power is a key element in EU policies to reduce the greenhouse effect and secure energy sources. In order to accomplish the EU’s target of a 20% share of energy from renewable sources by 2020, some of the planned projects have to be placed far away from the shoreline to benefit from the high wind speeds in the open sea area. However, a traditional transmission system for offshore wind farms based on a High Voltage Alternating Current (HVAC) utilizing conventional cables is not appropriate for long distances. In contrast, a High Voltage Direct Current (HVDC) can transmit electrical power over such distances, but the complicated concept of converting the HVAC offshore generated power into DC and then converting the DC power at the onshore grid back to AC requires sophisticated and expensive converter stations at both ends. Therefore, developing a new infrastructure solution based on HVAC transmission technology, which has been in operation for more than a century and which runs almost entire electrical systems, to support and advance the development of offshore wind energy is a highly desirable outcome. This research work was conducted to examine and determine the suitability of using an HVAC gas-insulated transmission line (GIL) as a long-distance transmission system for offshore wind farms in terms of technical and economic costs. A computer model of GIL has been built using the Electromagnetic Transient Program (EMTP) to assess the suitability of GIL and quantify the voltage, current and power transfer characteristics of the GIL under different steady state conditions. Furthermore, a suitable model has been developed for the simulation of the switching transient during energisation of the GIL transmission system and various wind farm components. The development concept of GIL as a submarine Power Transmission Pipeline (PTP) is described, and the practical side of installing the PTP technology and the special design requirements of the offshore wind farms were illustrated. The PTP components, the maximum transmission capacity of the PTP system and the layout options were addressed. In addition, the challenges facing this technology were discussed. An economic comparison of the total cost for both HVAC-GIL and HVDC-VSC transmission systems is made, including annual costs (operation, maintenance, and losses) during the lifetime of the projects. The initial investment costs are added to the annual costs in order to obtain the total cost for the assumed project. Furthermore, the Power Transmission Cost (PTC) is calculated for each MVA-km being delivered to the receiving end of the GIL transmission line.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Uncontrolled Keywords: Gas Insulated Transmission Line (GIL); GIL; Steady state power flow; Offshore wind farm; Switching transients; Alternative transmission neutrals.
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:56

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