SF6 in oil – Bushing seal defects

Bushings in oil and SF6 The "SF6 in oil – Bushing seal defects" criticality does not concern transformers directly, but rather bushings, accessories that allow conductors to pass from inside the transformer to the outside without coming into contact with the casing. In generation step-up transformers (GSU), 14% of the failures are due to bushings (>100KV). CIGRE WG A2. 37Read more

The "SF6 in oil – Bushing seal defects" criticality does not envisage a real treatment; the criticality can only be resolved through replacement of the bushing. The life cycle management of the accessory calls for constant monitoring of the content of SF6 in oil (see prevention) in order to minimise the risk of failure as much as possible and schedule aRead more

Sulfur hexafluoride (SF6)Sulfur hexafluoride (SF6) is an inorganic, colorless, odorless, non-flammable, extremely potent greenhouse gas, which is an excellent electrical insulator From Wikipedia [source]New sulfur hexafluoride (SF6)SF6 complying with IEC 60376, and never used previously Published in: IEC 60480, ed. 2.0 (2004-10) – Reference number: 3.3.2 [source]Unused sulfur hexafluoride (SF6)SF6 never been introduced into electrical equipment (e.g. gas having been transferredRead more

For diagnosis of "SF6 in oil – Bushing seal defects", Sea Marconi uses its own diagnostic metrics, namely: visual signs on the bushing are interpreted; through analysis of the oil, the symptoms- that is, the symptomatic indicators (SF6 in oil, dissolved gases, dissolved water) and their characteristic values - are identified; the database is used to study family or subjective case histories (in the search,Read more

Since there is no real treatment for this criticality, prevention is the only viable strategy for correct life cycle management of the bushing and the transformer to which it is connected. Prevention actions during the life cycle of the insulator Monitoring symptomatic indicators (see symptoms above). If the first symptoms of criticality, such as a high SF6 content in oil,Read more

Signs (visual inspection) The "SF6 in oil – Bushing seal defects" does not show any characteristic signs; however, through visual inspection, it is possible to: assess the general condition of the accessory (corrosion) and the presence of leaks, check the dilation of the bellows (oil/SF6), an indicator of the amount of oil present in the insulator; check in particular theRead more

Oil sampling in the insulator must be carried out according to the manufacturer's specifications: using appropriate procedures for the purpose and specific sampling devices using staff with specific skills and training relying on operators able to demonstrate an extensive application case history and able to certify interventions carried out with quality assurance (ISO 9001) Supplementary informationDiagnostics of HV bushings throughRead more

The "SF6 in oil – Bushing seal defects" criticality is mainly caused by sealing defects between the insulator (insulated with oil) and the metallic casing (containing SF6) that encloses the top of the insulator itself. Sealing defects can result from physical chemical degradation of materials, electrical, thermal and/or mechanical stress. Taken together, these factors lead to a migration of SF6 inRead more

Symptoms (analysis) The specific symptom of the "SF6 in oil – Bushing seal defects" criticality is correlated with values that do not conform for the following diagnostic indicator: SF6 in oil* There are other co-factors useful for completing the diagnostic picture: Dissolved water (IEC 60814) Dissolved gases (IEC 60567) [oxygen, nitrogen, carbon dioxide, carbon monoxide, hydrogen, methane, ethane, ethylene, acetylene]Read more