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DC grid discriminating protection

Dantas, Rui 2017. DC grid discriminating protection. PhD Thesis, Cardiff University.
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High-voltage direct current (HVDC) has been proven an affordable and technically capable solution to bring vast amounts of power over long distances, though overhead lines, underground or undersea cables. As a result, a large number of point-to-point HVDC links appeared in several locations over the last decades. The technological step currently going on is the connection of point-to-point links to form a multi-terminal dc (MTDC) grid, a configuration that would bring several advantages. The construction of MTDC grids faces a few technical challenges, where the most notorious one might be dc grid protection. This thesis presents protection strategies for MTDC grids equipped with different dc fault clearance and isolation devices. These include ac circuit breakers (ACCBs), converters with fault blocking (FB) capability, dc circuit breakers (DCCBs) and fast dc disconnectors (only for isolation purposes). Each of these strategies in presented in a chapter, where the steps of the protection strategy are described and overvoltage suppression methods are proposed. The protection strategies include dc fault detection and dc fault discrimination algorithms. In literature, extensive research is available regarding dc fault discrimination, potentially the "hottest" topic in dc protection. In this thesis, discrimination algorithms are proposed being those based on analysis of local currents and voltages. Thus, link communication channels are not required, which reduces the overall decision-making time. The performance of the developed protection strategies is tested in PSCAD/EMTDC environment. DC faults are applied on two MTDC grids, including a 4-terminal meshed grid and the CIGRE 11-terminal dc grid. The main outcomes of this thesis include the discriminative fault criteria and the tailored protection strategies for dc grids equipped with either ACCBs, FB converters or DCCBs as main fault current clearance devices.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: DC Protection, HTDC Network, DC Circuit Breakers, HVDC Grids, Fault Blocking Convectors, Fault Detection and Discrimination.
Date of First Compliant Deposit: 1 February 2018
Last Modified: 10 Nov 2021 16:44

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