Test For SF-6 Circuit Breakers 72-5 Class

This does not sound like you have any problem. All HV equipment has a (usually minimal) amount of electrical discharge / corona. It usually is hardly or not noticeable, depending on environmental conditions. The discharge you saw when the rain started was probably due to residue from the soap used to clean the bushings, until it washed off. A real problem would probably have flashed over the bushing to ground.

You didn't mention what testing was done during the maintenance, if any. Recommended for HV breakers would be insulation power factor (or alternatively, tan-delta or dissipation factor), contact resistance, and possibly open/close timing tests (depending on age of bkr). The SF6 could be sampled and tested for moisture, breakdown products, etc.

For future cleaning, you would do well to get some proper insulator / porcelain cleaner. There is a line of cleaner and wax products by Collinite (www.colliniteindustrial.com) just for this purpose. My company also used isopropyl alcohol (90% conc or more) previously with good results, as it left no residues and cleaned dirt, grease, and other contaminants well. However, in some conditions it's hydrophilic, causing more moisture to condense on the porcelain after cleaning and throwing off insulation test results.

Good luck!

Dear PeterT,

Thank you, yes you are alright in your coments, after we saw the the chain of discharges open the system and clean all the insulator with Isopropyl alcohol,, and close again the efect was worse for few seconds and then dissapear just we note for some time the tipical sound of bzzzz, but now we don't hear and see anything, Thanks for you information about the test that would be necessry just in case if we saw something durant the operation of the CB by the way this unit only have 192 operations..

Regards Mario