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Analysis for electrical energy and overall efficiency in distribution networks with harmonic distortion

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009 / Traditionally, harmonics are ignored in overall efficiency and energy usage studies. However,
in the modern era, power systems contain levels of harmonics which can no longer be
ignored by engineers, planners, energy conservationists and economists. The directions of
power flows have to be considered when harmonics are present in the power network.

A methodology and new formulae for individual and overall efficiency and energy usage is
developed at each frequency (f1, h and H) and forms the main contribution to research in this

Two case studies were conducted; a measurement based laboratory experiment set-up and a simulated case study. In the set-up, measurements of current, voltage and power at different points in the network for the 1st, 5th and 7th frequencies were taken. Current and voltage results were used for hand calculations to prove the measured power flows and directions. The measurements were taken with a Fluke 345 three-phase harmonic power quality analyzer. For the simulated case study, a network was investigated using the DIgSILENT and SuperHarm software packages. Their results were compared and it was found that DIgSILENT is the preferred package for power results.
It was found that the total harmonic distortion limit for voltage in the simulated network
exceeded an acceptable level. The harmonic mitigation solution chosen was to design a
passive filter to decrease the distortion by shifting the resonance point of the network. The
method to design the passive filter and its impact on efficiency and energy usage is included
in the thesis.

Unique power flow direction diagrams are developed as part of the methodology and form an
essential step in the derivation of the new formulae. Efficiencies, power losses and energy
usage at individual and combined frequencies were determined. Results showed the
negative effects of harmonics on overall efficiency, energy usage and power losses of the
system. The methodology and new formulae developed was found to be effective and their
application is recommended for use by industry.
Date January 2009
CreatorsNegumbo, Rosalia
PublisherCape Peninsula University of Technology
Source SetsSouth African National ETD Portal
Detected LanguageEnglish

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