CORROSIVE-SULFUR PROBLEMS RESURFACE

摘要

Corrosive sulfur in oil causes problems in large power transformers and shunt reactors. LARGE POWER TRANSFORMERS AND SHUNT REACTORS HAVE FAILED in part because of corrosive sulfur in the electrical insulating mineral oils. This has occurred even though the oils, in most or all cases, passed internationally recognized industry specifications. The problem occurs because the corrosive sulfur reacts with copper conductors (Fig. 1) and silver contacts to form metal sulfides that contaminate the insulating paper. Since the metal sulfides are conductive, the dielectric breakdown strength of the paper is reduced. Under some conditions, a breakdown occurs through the insulation between conductor strands on a disk or between disks (Fig. 2). This ultimately leads to the failure of the apparatus. Although the number of failures has been small (double digits), the assets lost have been substantial. Examples have included the failure of a 500-kV shunt reactor and a 450-MVA autotransfbrmer. The problem, which has been reported by many countries, tends to develop undetected in the appara-