Analysis and Discussion on a Maloperation of Transformer Backup Protection Caused by Inrush Current
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Abstract
In order to study the effect of inrush current to the backup protection of transformer, a maloperation of transformer backup protection is presented in this paper, which is caused by inrush current emerged during the no-load switching of the new transformer in a 220 kV substation. The equivalent circuit model of the no-load switching transformer is established which derives the differential equation of the transformer magnetic flux. The mechanism of inrush current and the factors related to amplitude and attenuation are analyzed. Then some conclusions are presented. The theoretical results are verified by the real fault recorder data. According to the slow attenuation of inrush current, some measures are proposed to avoid the maloperation of backup protection, which have been verified in practice.
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