Method for detection of rail breaks on occupied blocks to support reduced train spacing

Abstract

A method for detecting broken rail and track occupancies measures both the electrical current and voltage on each end of the block of track. This allows a broken rail to be detected even with a shunting axle (occupancy) in the same detection block. The method also provides broken rail detection capability to support modes of operation in which a following train maintains safe spacing from a leading train without the use of track circuit information for train location, allowing for reduced train spacing. The current and voltage measurements are used to make binary decisions, in order to minimize the sensitivity to variations in track impedance characteristics. When combined with train location information, this method also allows for identifying the location of a rail break.

We claim: 
     
         1 . A method for detecting rail breaks in a block of track having first and second ends, said method comprising
 applying a voltage across the tracks at the first end and detecting the resulting voltage and current at the second end;   applying a voltage across the tracks at the second end and detecting the resulting voltage and current at the first end; and   determining the existence of broken rail from the combination of voltages and currents detected at the first and second ends.   
     
     
         2 . The method of  claim 1  wherein the block of track is determined to be unoccupied by a vehicle and to have no broken rail if the magnitudes of all of the detected voltages and currents exceed predetermined threshold values. 
     
     
         3 . The method of  claim 1  wherein the block of track is determined to have a broken rail if the block of track is unoccupied by a vehicle and the magnitudes of all of the detected voltages and currents do not exceed predetermined threshold values. 
     
     
         4 . The method of  claim 1  wherein, if the block of track is occupied by a vehicle, the block of track is determined to have a broken rail between the first end and the vehicle, and a broken rail between the second end and the vehicle, if the magnitudes of all of the detected voltages and currents do not exceed predetermined threshold values. 
     
     
         5 . The method of  claim 1  wherein the block of track is determined to be occupied by a vehicle and to have no broken rail if the magnitudes of the detected voltages at both ends are do not exceed predetermined threshold values, and the magnitudes of the detected currents at both ends exceed predetermined threshold values. 
     
     
         6 . The method of  claim 1  wherein the block of track is determined to be occupied by a vehicle and to have a broken rail between the first end and the vehicle if the magnitude of the current detected at the second end exceeds a predetermined threshold value and the magnitudes of the other detected voltages and currents do not exceed predetermined threshold values. 
     
     
         7 . The method of  claim 1  wherein the block of track is determined to be occupied by a vehicle and to have a broken rail between the second end and the vehicle if the magnitude of the current detected at the first end exceeds a predetermined threshold value and the magnitudes of the other detected voltages and currents do not exceed predetermined threshold values. 
     
     
         8 . The method of  claim 1  wherein the block of track is determined to have a broken rail if the magnitude of the current detected at either the first end or the second end does not exceed a predetermined threshold value. 
     
     
         9 . The method of  claim 1  wherein the block of track is determined to be occupied by a vehicle if the magnitude of the detected voltage at either the first end or the second end does not exceed a predetermined threshold value. 
     
     
         10 . The method of  claim 1  further comprising limiting the movement authority of a following vehicle behind a leading vehicle on the block of track by determining the location of the leading train on the block of track when the magnitude of the current detected behind the leading vehicle falls below a predetermined threshold value. 
     
     
         11 . The method of  claim 1  further comprising limiting the movement authority of a following vehicle behind a leading vehicle on the block of track by determining the location of the leading train on the block of track when the following train enters the block. 
     
     
         12 . The method of  claim 1  wherein the block of track has a length determined by the braking distance plus a warning distance for trains operating on the track. 
     
     
         13 . The method of  claim 1  further comprising determining the location of the rail break in a block of track having a vehicle moving along the block of track by determining the location of the vehicle when the magnitude of the current detected behind the vehicle falls below a predetermined threshold value.