SF6 purity requirement in 66kV switchgear

[ahhie]

hi,

I am working on 66kV switchgear maintenance. I like to know what is the minimum requirement for the SF6 purity (% volume). I cannot find it on the manual, it only give dew point requirement like -5 degree C for switchgear and -10 degree C for circuit breaker. Thank you.

 

[DTR2011]

This may help.
Your text to link here...

 

[ahhie]

Thank you. I measured the SF6 purity in our switchgear compartment (15 years old) using RH SF6 Analyzer 973, some are as low as 95%. Does this means we need to replace the gas? What is the minimum SF6 purity requirement for 66kV GIS switchgear?

 

[Marmite]

I can't see there being a definitive answer to your question as the amount of decomposed gas depends on the type of enclosure, the type of metallic electrodes and the arcing energy. The concentration of decomposition products is also affected by absorption at the surface of the vessel wall and by the alumina absorbant which is usually enclosed within each gas filled section. You would also need the purity at commissioning as a reference point.
Regards
Marmite