| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 87 === The major purpose of this thesis is to examine the definitions of voltage unbalance factor. After carefully reviewing the related standards, research reports, journals and others, two types of definitions of voltage unbalance factor were found, one based on the magnitudes of phase voltages and the other on the symmetrical components of the phase voltage, and three common used definitions were detected. The relationship between these three definitions was explored in general and then the comparison between them was made according to their capability of evaluating the impact of the voltage unbalance, such as increment of system loss, interference of communication systems, malfunction of protective relays, etc. The advantages and disadvantages of these definitions can therefore be assessed based on the comparison results. Some unbalance cases were used to demonstrate the difference of them. The difference should be properly emphasized. The misuse of the definitions may lead to incorrect conclusions and increase significantly the investment cost of electric power engineering.
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