Monitoring device for detecting fault arcs in encapsulated, gas-insulated switching installations

摘要

A semi-reflecting window (3) is located in the wall (2) of a gas-insulated, encapsulated switching installation. Ending on its outside is an optical fibre cable (5). Located behind this is an optical filter (6). Located in one beam path (7) of the filter (6) is an evaluation device (8) having an amplifier (9) downstream from which there is arranged a device (10), which contains a timer, for detecting earth shorts, and a tripping element (11). The evaluation device (6) with the amplifier (9) is connected to a circuit arrangement (12a) of a generator (12). With a transmitter (13), said generator (12) forms a light-pulse unit. Periodic pulses from the transmitter (13) pass to the optical filter (6), to the window (3) and to the evaluation unit (8) as well as, converted into electrical return signals, to the circuit arrangement (12a). The latter emits a defect indication if the return signals are absent. The light from a fault arc passes from the window (3) through the optical fibre cable (5) to the evaluation device (8). An interference signal is produced here which energises the tripping element (11) when there is at the same time an earth short on the device (10) and the time set in the timer has been exceeded. IMAGE