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Design optimisation of bare conductors for overhead line applications.

The South African economy is an emerging market and as such there is a continued and
growing need for the efficient supply of cost effective electricity. The capital investment
involved in the design, construction, installation and commissioning of overhead
transmission line networks are high and so too are the subsequent maintenance and operation
costs, incurred over their life cycle periods. The need to improve the electrical operating
efficiency of existing and future electrical transmission networks, through the reduction of
electrical losses, focused and motivated the research in this particular area.
The results and findings produced by this research study show that the magnetic induction
produced by the steel core in ACSR (Aluminium conductor, steel reinforced) conductors
cause in increase in the ac power losses, associated ac-dc resistance ratio and the effective ac
resistance of the conductor, whilst the conductor is energised during normal operation. More
specifically, the key parameters that cause this increase in the effective ac resistance of the
conductor, as a result of the magnetic induction produced by the steel core, are those of
hysterisis and eddy current power losses in the steel core and an added power loss caused by
the non-uniform redistribution of current in the layers of aluminum wires, due to the
‘transformer effect’. Therefore the addition of the conductor dc resistance value to the
component resistances produced by the current redistribution and magnetic hysterisis & eddy
current power losses, form the total effective ac conductor resistance. This is contrary to
standard practice where assumption is made that the conductor ac and dc resistance values
are equal.
The factors which influence the magnetic induction, include amongst others; the ferromagnetic
properties of the steel core, the physical construction of the conductor, the
conductor operating/core temperature and the load current. In order to calculate the effective
ac-resistance of multi-layer ACSR conductors a computer simulation program was
developed, which was largely based on determining the impact of varying these key factors,
by evaluating its effect on the ac resistance of the conductor. It was found through
manipulation of these factors that the total effective ac resistance of the conductor could be
reduced and significantly so with higher load currents. The conductor sample used in this
research study is commonly known as TERN ACSR conductor in the South African market
and it was shown that with practical changes in lay ratios or lay lengths, one is able to reduce
the total effective ac resistance of the conductor and associated power losses.
Several software simulation exercises were performed using the developed software
simulation program, to ultimately produce a set of optimised lay-lengths (lay-ratios) for the
TERN ACSR conductor, with the intention that these simulated parameters would be
employed in the production of actual conductor samples. The intention going forward after
the planned production trial runs would be to test these conductor samples to verify
compliance, in meeting both electrical and mechanical performance requirements.
It should be noted that the planned production trials and relevant conductor-testing processes
did not form part of the scope of this research report but are processes that have been
planned for in the near future. Although testing to IEC 61089 are post processes that are
planned for outside of this research scope, the specification requirements of IEC61089 were
incorporated into the various computer simulation exercises. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.
Date January 2009
CreatorsMunilall, Anandran.
ContributorsIjumba, Nelson M., Muftic, Dzevad.
Source SetsSouth African National ETD Portal
Detected LanguageEnglish

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