Protection of ultra long HVDC transmission lines.
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Date
2005
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Abstract
HVDC transmission is today widely used in modem Power Systems as an alternative to HVAC.
Current trends indicate that many future conventional HVDC systems will be systems of
increasing power ratings, delivered over larger distances as well as multi-terminal systems. In
order to ensure the security and dependability of such systems, the current protection schemes
need to be evaluated to assess their ability to provide adequate protection for the envisaged
HVDC systems. This research work firstly reviews the present HVDC transmission line protection
systems, and highlights their advantages and disadvantages, including factors that adversely
influence their performance. The author critically evaluates the current protection schemes and
reveals the drawbacks and other factors that render them unsuitable for the protection oflong
dc transmission lines. The author then goes on to propose and develop an HVDC line protection
system that will be able to provide adequate protection for proposed long HVDC transmission
lines. The proposed protection system is able to make decisions based solely on local detection
increasing its overall reliability. The author then recommends that the proposed protection
system be used in conjunction with the existing main protection system in order to optimise the
protection response times for both close in and distant faults. The author also proposes and
develops a method of further enhancing the reliability of the protection system by the use of
the telecommunication infrastructure when available. Finally the performance and feasibility of
the proposed protection system is evaluated using the results obtained from the extensive fault
simulations performed in EMTDC and Matlab. The simulations are performed using a bipole model
of an HVDC System on which the required line and protection systems are modelled. The
simulation results obtained are very favourable and promote the use of this proposed protection
system, for the protection of long HVDC transmission lines.
Description
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.
Keywords
Electric power transmission--Direct current., High voltages., Theses--Electrical engineering.