Robert and Allen are of course absolutely on point! Take this pieces of equipment out of service immediately, perform a "hi-pot" or high potential test on the various elements of the switchgear and attempt to locate the area that is "leaking" to ground (or between phases). Inspect closely for indications of tracking on insulators from corona discharge and replace any compromised components. After component replacement, installation of new SF6 gas and other repairs, re-run the Hi-Pot test
to confirm that the switchgear is able to withstand voltages at least 50% greater than the name-plate rating. Of course all of this advice is worthless if the unit has already failed. Good Luck Benard!