Research On Frequency Shift Track Circuit Parameters On Line Testing Technology In Electrified Block

Safety is the life-line of railway transportation. Track circuit signal can ensure railway transport. Rails are used as transmission line to enable train communicate with signal processing equipment. The two rails are not only signal lines of track circuits, but also loop line for locomotive traction current in electrified railway block. Industrial frequency traction current may have significant interference with FSK signal. The electric parameters of track circuit such as current, voltage, phase must be measured periodically to make sure track circuits and signal equipments run normally in order to avoid accident.The content of this theme is as follow: without time, without open, without stopping railway transport, and without interrupting traction current of block tested, track circuit parameters in electrical and no electrical blocks is measured with on-line, dynamic and real-time. These parameters include voltage, current and phase of FSK signal.This paper shows in detail about how to resolve some technical problems for on-line testing circuits parameters in electrical railway.In this paper, signal conversion method (processing before analogue) are used including RC active and on active notching filters, RC low pass filters, double T filters, switched capacitor filters and heterodyne measurement method, etc.According to the characteristics of frequency shift track circuits, this paper has analyzed signal acquisition methods of voltage and current measurement on line. In phase measurement, the instrument used zero-crossing shaping circuit, zero-drift compensation circuit and software burr rejection technique. It has solved problems of dead-zone and filter circuits errors in phase measurement.The whole system has been used 8098 microprocessor as control unit.