A new approach for compaction of HVDC transmission lines and the assessment of the electrical aspects
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Date
2016, 2015-05
Authors
Salimi, Maryam
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Abstract
This thesis proposes a novel consolidated approach for substantial compaction of HVDC
lines that includes both new tower geometries as well as novel control concepts. This is
based on a thorough discussion on the basic overhead line design parameters and their
impact on the right of way width and tower height. Then the electrical aspects of the new
approach such as dc overvoltage assessment and lightning performance are investigated.
The required horizontal clearances between pole conductors and tower members, as a component of the right of way width, depend on the maximum expected overvoltages. Detailed electromagnetic transient models for the point to point MMC HVDC with different transmission configurations, all including the proposed dc overhead line, are developed for this thesis. The models are used to assess fault contingencies that result in the most significant overvoltage stresses on the HVDC transmission line for finding minimum air clearances and for the design of overvoltage limiting devices, such as surge arresters. New control approaches are proposed that significantly reduce the dc side overvoltage and consequently minimize the required air clearances for maximum compaction of the HVDC overhead lines and also reduce the required surge arrester size for line insulation.
Because power transmission lines are the most exposed component within a power system, they are subject to lightning strikes which, in turn, are the main cause of disruption to power flows. This thesis will include an analysis of lightning occurrence on the proposed compact transmission line in order to assess the risk of pole faults. The focus of this analysis is mainly on evaluation of the critical lightning currents that cause fast front overvoltage stresses that may result in insulation failure.
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Keywords
Compact dc transmission, MMC HVDC
Citation
M. Salimi, L. Barthold, D. Woodford and A. Gole, "Prospects for Compaction of HVDC Transmission Lines," in CIGRÉ, Montreal, Canada, 2016.
M. Salimi, X. Chen, D. Woodford and A. Gole, "Fast Reduction of DC Voltage for Half-Bridge MMC HVDC Systems with Symmetrical Monopole during the Nonpermanent Pole to Earth DC Fault," in CIGRÉ Symposium , Lund, Sweden, May 2015.
M. Salimi, X. Chen, D. Woodford and A. Gole, "Fast Reduction of DC Voltage for Half-Bridge MMC HVDC Systems with Symmetrical Monopole during the Nonpermanent Pole to Earth DC Fault," in CIGRÉ Symposium , Lund, Sweden, May 2015.