Partial discharge measurements are used to validate the integrity of the insulation system at the end of the production line or when commissioning gas insulated switchgear and lines (GIS, GIL). On the other hand, an increasing population of service aged GIS equipment has reached its originally projected lifetime. On-line partial discharge measurements utilizing acoustic as well as UHF sensors help keeping such equipment in service. External ring antennas, window sensors, or embedded sensors allow survey type measurements and monitoring of the partial discharge activity in the UHF range. Acoustic measurements offer excellent sensitivity with so-called bouncing particles. Field experience applying a compact instrument that combines the application of UHF and ultrasonic measurements is presented.