DEVICE FOR MONITORING SHORT CIRCUIT IN ALTERNATING CURRENT OVERHEAD SYSTEM Russian patent published in 2009 - IPC G01R31/02 

FIELD: electrical engineering.

SUBSTANCE: invention relates to a system for automating electric power supply to electric railways. The device has a residual voltage transformer, the primary winding of which is connected to one switch of the overhead system, and the secondary winding to a filter of high harmonics of residual voltage through a delayed closing contact of a crank relay. The first input of the crank relay coil is connected through series-connected closing contacts of the protection slave relay of the switch to the negative terminal and the second input directly to the positive terminal of the power supply. The input of the low-pass filter (LPF) with transmission band of 0-40 Hz is connected to the output of the high harmonics filter. The output of the low-pass filter is connected to the input of an amplifier, whose output is connected to the input of an output relay. The device also contains a comparator and a time-delay relay with a delayed closing contact. The switch has a slave relay for its open state with a closing contact. The circuit from series-connected time-delay relay coils and closing contact of the slave relay for the open state of the switch is connected in parallel to the crank relay coil. The input of the comparator is connected to the output of the high harmonics filter through the delayed closing contact of the time-delay relay, and the output is connected to the input of the amplifier.

EFFECT: increased reliability of operation due to detection of short circuit in a switched off overhead system in the absence of an electric train.

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