TWO-STAGE SHUT-OFF DEVICE

摘要

The invention relates to a two-stage shut-off device for a varistor (1), comprising a first switching unit (2), which is suitable to be switched in the event of a fault, wherein the first switching unit (2) is an opening contact which is connected in series to the varistor (1), a PTC thermistor (3) that is connected in parallel to the first switching unit (2), wherein the resistance of the PTC thermistor in the cold state is smaller than the comparable resistance that would form at the first switching unit (2) in the event of a switch arc, and a second switching unit (4), wherein the second switching unit (4) is an opening contact that is connected in series to the varistor (1), wherein the second switching unit is controlled by the PTC thermistor (3).