The present application discloses a method and device suitable to perform the method for operating Voltage Indication system (VIS) and partial discharge module (PD) for medium-voltage or high voltage apparatuses, comprising: monitoring, with the partial discharge-module (PD), provided in low-voltage section, whether partial discharge occurs within a dielectric of the high-voltage or medium-voltage apparatus or system, the partial discharge-module or VIS being electrically connected to a coupler provided in the medium-voltage or high-voltage apparatus; indicating with the Voltage Indication System (VIS), provided in a low-voltage portion, the presence of operating voltages in high-voltage or medium-voltage apparatus or system, Voltage Indication System (VIS) being electrically connected with partial discharge-module (PD) and deactivating by deactivation module connected to Voltage Indication System and partial discharge-module (PD) an optical display in the Voltage Indication System (VIS) during partial discharge measurements.