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Characterisation of HVDC gas insulated systems

Li, Haoluan 2023. Characterisation of HVDC gas insulated systems. PhD Thesis, Cardiff University.
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This research investigated a challenging objective related to the future needs of transmission networks. To develop an environmentally friendly gas insulated system for HVDC applied voltage, extensive simulation and experiments have been done before the proposed solution could be deployed in industry. The electric field distribution under DC applied voltage using an initial design of the spacer with and without temperature gradient was first introduced. When calculating with the initial design, different conductivity models with linear and nonlinear characteristics were used to explore the electric field distribution under DC steady state conditions controlled by the conductivity of the material. Fundamental investigations on the properties of spacer shapes including increasing the spacer thickness, introducing a small gas gap at the spacer-flange interface, increasing the radius of the flange corner, varying the radius of the spacer edge near the ground side, increasing the spacer inclination angle, varying the distance between the spacer and the end of the flange radius, and the spacer materials using different conductivity models with linear and nonlinear characteristics were researched. A finite element model combining steady-state and transient solvers was used to simulate the electric field distribution and space charge distribution in a gas-insulated system under DC superimposed lightning impulse voltage, which revealed the ion transportation law under lightning excitation. C4-PFN and CF3I based gas mixtures were tested electrically for withstand tests in a reduced scale gas insulated system and PDIV tests under DC applied voltages with positive and negative polarities at different pressures from 1 to 5 bar (abs.) with different electrode shapes and different gap distances. A list of more detailed conclusions and discussion points are presented at the end of each chapter, and which are further developed in the last chapter of this thesis. Suggestions that can potentially be implemented in future works, experimental and theoretical, are also listed.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: 1) HVDC 2) Spacer 3) Gas insulated systems 4) Shape optimization 5) PDIV 6) Withstand test
Date of First Compliant Deposit: 2 February 2024
Last Modified: 06 Feb 2024 13:16

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