Failure Investigation of Gas-Insulated Switchgear at 110-500 kV Substation, Maintenance and Repair

The paper presents an analysis of the reliability, maintenance practices, and failure statistics of 110–500 kV gas-insulated switchgear (GIS) operated by Rosseti FGC UES. Over the past 12 years, the company has replaced more than 500 aging oil-filled current transformers with SF₆insulated units. Although SF₆-based equipment offers improved insulation and reduced maintenance, failures still occur, driven by mechanical weaknesses, manufacturing defects, inadequate installation, poor-quality gas, and insufficient servicing.