DEVICE FOR IDENTIFYING CAUSE OF CIRCUIT-BREAKER OFF- OPERATION Russian patent published in 1997 - IPC

FIELD: protection of contact systems, such as those of trams and trolleybuses. SUBSTANCE: device has controlled signal meter connected to power feeder and having its output connected to first inputs of first and second threshold units. The latter have their second inputs connected to first and second reference-voltage sources, respectively. Outputs of threshold units are connected to respective inputs of flip-flop and the latter has its output connected to circuit warning about cause of circuit-breaker opening. With device in operation, voltage across power feeder of contact system is recorded in advance at transients occurring in case of short circuits or overloads on line. Then, depending on transient amplitude in line at short circuit and overload, two opposite-polarity reference voltages are generated and compared with voltage across power feeder. Differential signals are shaped in the process, their sequence being used to shape alarm signal. EFFECT: simplified identification of cause of circuit-breaker off-operation in urban transport contact system power circuit; improved reliability of data on cause of circuit opening. 3 dwg