Abstract: There are various types of through-wall insulation sleeve faults used in 35kV fixed metal enclosed switchgear, and most of them require long-term operation to develop into faults. The risks and hidden dangers leading to faults are also diverse and difficult to identify. This article analyzes the possible faults caused by various types of risk hazards in the casing, proposes preventive and governance measures, improves the operating conditions of the equipment, and lays a good foundation for the safe and stable operation of the equipment.