Corrosion analysis of switchgear moving contacts in a 66 kV substation of shenyang

Abstract A serious burn accident occurred in the 10 kV secondary switchgear of a 66 kV substation in Shenyang. The moving contacts of other switchgear that were replaced at the same time showed corrosion and blackening. In order to analyze the causes of the corrosion of the switchgear moving contacts, macroscopic morphology observation, chemical composition analysis, metallographic structure observation, and scanning electron microscopy were utilized. The results indicated that the thickness of the silver plating layer on the contact parts of the switchgear met the standard requirements, and the chemical composition of the spring used for fixing the contacts met the requirements of non-magnetic stainless steel chemical composition. A uniform and continuous corrosion product layer was observed on the outer side, with the presence of sulfur elements detected. The main reason for corrosion was attributed to the presence of a large number of microorganisms and sulfides in the sewage entering the cable tunnel. These elements generated hydrogen sulfide gas under the influence of alienation, which entered the substation along the cable tunnel and reacted with the silver plating layer on the switchgear contacts, resulting in the production of corrosion products such as silver sulfide. This process led to an increase in contact resistance and overheating of the contacts, ultimately causing the burnout of the switchgear.