Special technical features of dead-tank design. The distinguishing feature of dead-tank technology is that the interrupter chamber is accommodated in an earthed metal housing. With this arrangement the SF6 gas filling insulates the high voltage live parts of the contact assembly from the housing. Outdoor bushings connect the interrupter chamber with the high-voltage terminals.
reference : siemens (siemens\Power Transmission\high voltage products\Circuit-Breaker)