Full-range Design And Implementation Of Point Track Insulation Fault Detector

The railway is playing the extremely vital role in the national economy development.The railway signal system that is used for adjusting train orbit is the base equipment of auto-control and long-range control system . It uses two tracks as electrical wire , both end are physical insulation (or electric rail insulation) . The system which is completed by using wire to connect the signal equipments and two tracks is used to examine whether the orbit is busy or not, transfer a track occupancy information and transfer information between the control center and the train.The reliability of its work has direct impact on the safety and the efficiency of the train operation .The insulation broken malfunctions are often found . They could be divided into two parts—the short circuit malfunctions and the leakage of electricity malfunctions—according to the location where malfunction occur . When the malfunction happens, the red lights is always on and the green lights is always off. The signal Lights has no way to carry out the right information. The circuit is disconnected . Trains must be forbidden to go through before the trouble is removed . Detecting malfunction spot contains a lot of work. To accomplishe a trouble removal within short time is indispensable.The available domestic orbit signal styles are 50HZ , 25 HZ phase-sensitive, domestic shift frequency (550 HZ , 650 HZ , 750 HZ , 850 HZ) , UM71 (1700 HZ , 2000 HZ , 2300 HZ , 2600 HZ), domestic 2000 (the same frequent point with UM71) 10 kinds frequency in total. Be to adapt to detect insulation broken spot of diversity style track and diversity frequency in one style track , multiple frequency insulation broken spot detector has been designed here. It applies to 10 frequencies in the homeland.To take electromagnetic induction principle as basis , it abstracts the faint signal from the tack circuit by the inductance coil . The signal size of different frequency is coordination by amplifier circuit . Band filtering depending on programmed filter chip MAX262 is used for weaking the external disturbance . Then the signal through precise commutation and the peak value detecting circuit. At last it is changed into digital signal by inside A/D . The Software accomplishes anti-interference in A/D sampling and the judgement of malfunction .The malfunction spot is judged according to signal size by software .Experiments at railway scene show that this instrument can resist the disturbance of non-homogeneous magnetic in the tack and no error or fault alarm.The frendly interface request a little specialized knowledge of user.