Aleksandar Damjanovic
Transformer losses, no load losses, accuracy, error in measurements,penetration of error
The objective of this study is to determine and compare the accuracy and errors of power transformer loss measurements under load conditions, using two different methods, the power in minus power out, in–out method and the voltage and current difference, VA difference method. As the in–out method of measurement of power transformer losses is inherently erroneous (in the range of 50–60%), a new method called the VA difference method was developed in the early 1990s with apparent superior accuracy. Based on these published articles, we built an embedded instrument and system for the measurement of power transformer losses under load conditions, which measures the transformer losses with both methods simultaneously. It turns out that the total losses measured with both methods are exactly the same. Hence, there was no improvement in measurement of accuracy of power transformers losses under load conditions, the conclusions from previous articles and publications, which state that the error in the VA difference method is much less than in the in–out method are absolutely wrong.
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