Analysis of converter insulation characteristics and selection of restraint resistors

Abstract

Abstract The commutation structure is a composite insulation structure composed of oil, paper and cardboard. The converter transformer usually adopts positive and negative adjustment, and the polarity selector generates a recovery voltage and a breaking circuit between the opened contacts during the switching process. It is usually necessary to use a tie resistor to make a potential connection to the voltage regulating winding to limit the recovery voltage. At the same time, in order to shorten the time of the potential resistance access and reduce the no-load loss of the transformer, a potential switch is required to be used in conjunction with the tie resistor. In this paper, the characteristics of the floating potential and the capacitor current during the switching of the positive and negative voltage-regulating windings are analysed. The relationship between the arrangement of the commutating windings and the recovery voltage is given. The positive and negative floating suspension breaking capabilities of the contacts are analysed by examples. The calculation basis for the selection of the binding resistor is given, and relevant conclusions are given.