U.S. patent application number 16/031863 was filed with the patent office on 2018-11-15 for method for detection of rail breaks on occupied blocks to support reduced train spacing.
This patent application is currently assigned to Transportation Technology Center, Inc.. The applicant listed for this patent is Transportation Technology Center, Inc.. Invention is credited to Joseph David Brosseau, Joel Donald Kindt, Alan Lee Polivka.
Application Number | 20180327008 16/031863 |
Document ID | / |
Family ID | 64097629 |
Filed Date | 2018-11-15 |
United States Patent
Application |
20180327008 |
Kind Code |
A1 |
Kindt; Joel Donald ; et
al. |
November 15, 2018 |
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.
Inventors: |
Kindt; Joel Donald;
(Colorado Springs, CO) ; Polivka; Alan Lee;
(Pueblo West, CO) ; Brosseau; Joseph David;
(Pueblo, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Transportation Technology Center, Inc. |
Pueblo |
CO |
US |
|
|
Assignee: |
Transportation Technology Center,
Inc.
Pueblo
CO
|
Family ID: |
64097629 |
Appl. No.: |
16/031863 |
Filed: |
July 10, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62534307 |
Jul 19, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B61L 2205/02 20130101;
B61L 25/025 20130101; B61L 1/18 20130101; B61L 23/044 20130101 |
International
Class: |
B61L 23/04 20060101
B61L023/04; B61L 25/02 20060101 B61L025/02 |
Goverment Interests
GOVERNMENT LICENSE RIGHTS
[0002] This invention was made with government support under work
sponsored by the Federal Railroad Administration of the U.S.
Department of Transportation. The government has certain rights in
the invention.
Claims
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.
Description
RELATED APPLICATION
[0001] The present application is based on and claims priority to
the Applicant's U.S. Provisional Patent Application 62/534,307,
entitled "Method for Detection of Rail Breaks on Occupied Blocks to
Support Reduced Train Spacing," filed on Jul. 19, 2017.
BACKGROUND OF THE INVENTION
Field of the Invention
[0003] The present invention relates generally to the field of
methods for detecting rail breaks on railroad tracks. More
specifically, the present invention discloses a method for
detecting rail breaks in occupied blocks of track.
Statement of the Problem
[0004] The following definitions apply to the following terms in
this disclosure:
[0005] "Detection block" means a section of track with defined
limits in which broken rails or occupancies can be detected, but
that is not limited to a signal block.
[0006] "Signal block" means a section of track with defined limits
that utilizes conventional wayside or cab signals and may refer to
an intermediate, controlled, or absolute permission block.
[0007] "Intermediate (automatic) block" means a section of track
associated with a single track circuit for automatic block
signaling within a controlled block.
[0008] "Controlled (absolute) block" means a section of track
spanning between control points, the movement into which is
controlled by a dispatcher or control operator and may include
multiple intermediate blocks.
[0009] "Moving block" means a type of train control in which train
separation is determined dynamically according to the braking
distance of the following train. A moving block is related to a
virtual block.
[0010] Track circuits are one of the basic components of
conventional fixed block railroad signaling systems. Conventional
signal systems typically use track circuits to perform two
functions: (1) Detect occupancy and broken rails in each block; and
(2) Communicate the status of each block to adjacent blocks. Track
circuits utilize the steel rails as a path for electrical current
flow. The track is separated into electrically isolated sections,
or blocks, using insulated joints in the rails to isolate each
block. A voltage is placed across the rails at one end of the block
and the presence or absence of electrical current is detected at
the opposite end of the block. Electrical continuity throughout the
length of the block provides information on whether the block is
clear of shunting vehicles and broken rails or not. When a train is
occupying a block, the wheels and axles of the train shunt the
rails together so there is no longer sufficient electrical current
at the end of the block to indicate the block is unoccupied.
Similarly, a broken rail will result in an open circuit, preventing
any current flow through the track circuit. Consequently, track
circuits are utilized to detect train occupancy and broken
rails.
[0011] In conventional signaling systems, signal aspects are
determined by the status of the block over which the signal governs
movement, as indicated by the track circuit in that block, as well
as the status of adjacent blocks. Information about the status of
each block is typically transmitted to adjacent blocks through the
use of coded track circuits, although there are other methods used
in some cases. With coded track circuits, the electrical signal
that is transmitted through the rails is coded using different
pulse rates to indicate the signal aspect that block is currently
displaying. This information is interpreted by the equipment at the
adjacent block and used in determining the proper aspect to display
for the signal governing movement over that block.
[0012] The minimum required length of the track circuit is based on
braking distances at track speed and the number of signal aspects
that can be displayed. For example, with 4-aspect signaling, the
blocks are spaced such that two blocks represent no less than the
distance of normal service braking for the worst-case braking
train. This creates safe separation between trains as seen in FIG.
1. If a train is detected on a given block, the signals for the
preceeding blocks will be ordered by restrictiveness: red (stop),
yellow (approach), flashing yellow (advance approach), and green
(proceed). Flashing yellow can be used to indicate proceed and
prepare to stop at the second signal, or proceed and reduce speed
before passing the next signal.
[0013] Modern track circuits for freight applications typically use
DC coded track circuits. The DC signals sent through the track are
pulsed to form codes, providing aspect information that is
communicated between the blocks. To allow for bi-directional
traffic, DC circuits work in both directions with coordinated pulse
timing to avoid interfering with one another. Additional features
often include a handshaking protocol to send and receive data
within a block, and alternating polarity current to prevent code
detection from an adjacent block.
[0014] The railroad industry is interested in identifying new
technologies that use the rails as the broken rail and track
occupancy sensing medium and have potential to support new methods
of train control (e.g., communications-based). New train control is
intended to improve the capacity of the line with moving block
operation and variants thereof. The potential capacity improvement
with a moving block (or similar) train control system is limited if
conventional fixed blocks are still required to maintain broken
rail detection.
[0015] Conventional track circuits cannot detect a broken rail that
occurs in the same block that a train is occupying since the axles
will be shunting the block. The broken rail can then be detected
after the train has left that particular block. Also, conventional
track circuits do not detect or indicate where within a block a
broken rail or occupancy is located. Hence train control systems
must protect the entire block when a break or occupancy has been
detected. This is the primary limitation in their ability to
support moving block operation.
Solution to the Problem
[0016] In contrast to the prior art, the present system detects
both the current and voltage at the ends of the track circuit. The
combination of current and voltage can be used to detect a broken
rail even if the block is occupied by a train.
SUMMARY OF THE INVENTION
[0017] This invention provides a method for detecting rail breaks
in occupied blocks of track by measuring both the current and
voltage at the ends of the track circuit. The combination of
current and voltage allows detection of a rail break even if the
block is occupied.
[0018] These and other advantages, features, and objects of the
present invention will be more readily understood in view of the
following detailed description and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The present invention can be more readily understood in
conjunction with the accompanying drawings, in which:
[0020] FIG. 1 is a diagram illustrating track circuits in a
4-aspect block network.
[0021] FIG. 2 is a diagram showing conventional track circuit
interfaces.
[0022] FIG. 3 is a diagram showing next generation track circuit
interfaces for PTC and train control.
[0023] FIG. 4 is a diagram illustrating examples of a next
generation track circuit with transmitting (Tx) current with and
without a rail break.
[0024] FIG. 5 is a diagram illustrating a next generation track
circuit with transmitting current from both ends of a block.
[0025] FIG. 6 is a diagram illustrating fixed versus moving block
operations.
[0026] FIG. 7 is a series of diagrams showing next generation track
circuits with broken rail (BR) between trains.
[0027] FIG. 8 is a series of diagrams illustrating movement
authority when the following train enters an occupied block with no
rail break.
[0028] FIG. 9 is a series of diagrams corresponding to FIG. 8
illustrating movement authority with a broken rail between
trains.
[0029] FIG. 10 is a diagram depicting several types of signaled
territories.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Interfaces and Detection Methods.
[0031] Track circuits typically provide binary information for a
fixed block. The track circuit can either be clear (i.e., no
occupancy and no broken rail) or not clear (i.e., occupancy and/or
broken rail). FIG. 2 illustrates a conventional track circuit for a
bi-directional track. Each side of the track circuit will transmit
(Tx) and receive (Rx) a signal through the track. The conventional
track circuit will identify the block as being clear at location A
if Rx2 receives from Tx3. Similarly, the track circuit will
identify the block as being clear at location B if Rx3 receives
from Tx2. This usually includes track signal coordination so only
one side of the block is transmitting at a time. The status
information for this block is transmitted through the rails to
adjacent track circuits with signals Tx1 and Tx4. An adjacent block
uses this status information along with what it detects within its
own block to determine which signal aspect to display.
[0032] With today's PTC (Positive Train Control) and other newer
proposed train control systems (especially those that are
communications-based), the track circuit information may be
transmitted to a server (that may be located in the office) or
directly to the locomotive's onboard computer as seen in FIG. 3. In
the next generation track circuit, broken rails are similarly
detected by monitoring the transmission current. FIG. 4 provides an
example of the current loop with the transmitted Tx2 signal. If the
signal Tx2 is being transmitted and the current in the loop is
substantial (i.e., I.noteq.0), then the track circuit is clear of
broken rails within that current loop. If the signal Tx2 is being
transmitted and the current loop is near zero (i.e., I=0), then
there is a broken rail. There is likely a negligible amount of
current flowing through the ballast. Consequently, this method
allows for the detection of broken rails, even with a shunting axle
on the block, but does not distinguish if the track circuit is
occupied or unoccupied if no further information is available.
[0033] Monitoring of the transmission current can be performed on
each side of the track circuit. FIG. 5 provides an example of the
current loops from both the transmitted Tx2 and Tx3 signals.
Further considerations regarding the monitoring of transmission
current include: (1) A broken rail can be detected anywhere between
a shunting axle and the respective end of the block; (2) Since the
Tx2 and Tx3 signals are being time-coordinated, so will the
monitoring of the transmission current through the track as
detected at each end of the block; (3) Binary information is
obtained from monitoring the transmission current (i.e., broken
rail or not); and (4) Even though broken rail information is
provided both in front of and behind a train, the relevant
information for that train will be ahead of it. Technology is
available in which a track database plus an onboard positioning
system can be used to process the location and direction of a
vehicle.
[0034] In the present methodology, additional information is
obtained by also monitoring of voltage by the next generation track
circuit. If the voltage detected at A and/or B drops to
approximately zero, but the current in the block is substantial,
then an occupancy can be determined to be present in the block.
This produces additional binary information from each end of the
block. Table 1 presents the various combinations of information
provided by voltage and current for each end of the block. The next
generation track circuit can also be used to detect an open or
shunt caused by a device (e.g., turnout or track obstruction
detector) interfaced with the track circuit.
TABLE-US-00001 TABLE 1 Possible combinations of voltage and current
for ends A and B of the block |V.sub.Rx| |I.sub.Tx| (A) |V.sub.Rx|
(A) |I.sub.Tx| (B) (B) Indication >0 >0 >0 >0 Clear 0 0
0 0 Broken Rail - No Occupancy Or Occupied - Broken Rail Between A
and Occupancy; and Broken Rail Between B and Occupancy Note: The
ambiguity is resolved when the locomotive onboard system knows it
is occupying the block. >0 0 >0 0 Occupied - No Broken Rail 0
0 >0 0 Occupied - Broken Rail Between A and Occupancy >0 0 0
0 Occupied - Broken Rail Between B and Occupancy Note: In the
table, 0 means near zero or within a defined threshold.
[0035] Moving Blocks.
[0036] In this disclosure, modern train control is understood to be
a moving block or similar (e.g., virtual block) operation. The
advantage of moving blocks compared to fixed block operation is
seen in FIG. 6. Fixed blocks with 4-aspect signaling are spaced
such that the length of two blocks represent no less than the
distance of normal service braking for the worst-case braking
train. A following train that is slightly less than three blocks
from the rear of the train ahead and operating at or near track
speed will have to reduce speed. Therefore, the minimum
steady-state train separation that can be maintained between two
trains operating at track speed is three blocks, using 4-aspect
signaling. Moving block operation will theoretically allow the
following train to be at its braking distance, with some additional
warning distance and margin, from the leading train.
[0037] Detection Blocks.
[0038] The concept for next generation track circuits is to perform
as detection blocks that provide broken rail identification and
roll-out protection against unexpected or unmonitored occupancies.
The next generation control system can use the binary track circuit
status information for these functions but does not require it for
train location determination and separation, all of which are
available functions with conventional track circuits.
[0039] Next generation track circuit technology will improve the
spatial and temporal resolution of rail breaks compared with
conventional track circuit technology. The proposed next generation
track circuit method utilizes both electrical voltage and current
on both ends of the detection block as described above. This
improves the spatial resolution as a broken rail can be detected
between a shunting axle and one end of the block. The spatial
resolution of rail break location can be improved even more
significantly if the train control system uses rear-of-train
location reported by a leading train in conjunction with the next
generation track circuit information described here. Furthermore,
temporal resolution is improved in the sense that a broken rail can
be detected while there is a shunting axle in the block.
Conventional technology can only detect a broken rail once the
signal block is unoccupied.
[0040] In conventional fixed block signaling systems, the minimum
length of the signal block is determined by the braking distance of
the trains operating over the territory at the maximum allowable
speed. This provides safe separation of trains. In a modern train
control system with next generation track circuits, safe separation
of trains is provided by a moving block train control method.
Furthermore, the track circuits communicate status to trains in the
area through a wireless communications system or to a server via
any of various communications media, as opposed to only
communicating status via signal aspect to trains approaching the
block. In this concept, longer detection blocks may be practical
but can reduce the potential capacity gained through the moving
block train control system. Therefore, it is the maximum detection
block length that needs to be specified, in order to optimize the
capacity of the operation with a modern train control system.
[0041] In other words, while in conventional fixed block signal
systems, the minimum length of the signal block is determined to
provide safe train separation for a specified number of available
signal aspects, in this system, the maximum length of the detection
block is determined to provide the desired balance between track
circuit cost and line capacity. For the next generation track
circuit, the length of the track circuit is still driven by the
braking distance of the train, including the desired warning
distance: (1) If the braking distance plus warning distance is less
than the detection block length, train separation is dictated by
the detection blocks; or (2) If the braking distance plus warning
distance is greater than the detection block length, train
separation is dictated by the moving block train control system.
Therefore, with this system, an analysis of the utilization of each
specific line where it is to be implemented and the typical braking
distance plus warning distance of the trains operating on the line
should be conducted to optimize the length of the detection blocks
on the line.
[0042] Broken Rails Between Trains.
[0043] The next generation track circuit detects broken rails
between trains, albeit before they simultaneously occupy the same
block. The proposed concept is for broken rails to be detected by
the received voltage signal as well as monitoring the current in
the loop, as described above. Monitoring the current in the loop
allows a broken rail to be detected, even if an axle is shunting in
the same detection block, as long as the train is not spanning
across the broken rail. FIG. 7 provides illustrations of a broken
rail and how it would be detected between trains using this
concept.
[0044] Once the broken rail is detected, the information will be
transmitted to the office (or other off-board system) and/or
locomotive. Enforcement braking will occur in time to stop the
train before reaching the rail break. If a train is following
another train as closely as the moving block control system will
allow (i.e., by the warning distance), and the broken rail occurs
directly beneath the leading train, the break will be detected as
soon as the leading train is no longer over the break, leaving
sufficient time for the following train to receive the broken rail
notification and stop short of the broken rail as long as the
following train has not yet entered the block.
[0045] Movement Authorities.
[0046] The context for the next generation track circuit is that
train separation is controlled by modern methods of train control
(e.g., moving block). The train control system will separate the
following train from the rear of the leading train by the following
train's braking distance plus warning distance and margin. Modern
train control systems use movement authorities and/or stop targets
to ensure train separation. In order to apply the proposed next
generation track circuit the following rules should be
considered.
[0047] A movement authority rule could be designed into the system
to account for the case when a following train enters an occupied
detection block, thereby masking the broken rail protection between
trains. See FIG. 8, which illustrates movement authority when the
following train enters an occupied block with no rail break. This
case is possible if the braking distance for the following train is
less than the detection block length. To restore broken rail
detection, a stop target is held corresponding to the last reported
end-of-train location of the leading train at the time when the
following train enters the occupied block, when no rail break has
been detected in the occupied block up to that time. Entering an
occupied block can be determined by a database with detection block
boundary locations and the known head of train location.
[0048] The stop target would be replaced with a new stop target
behind the latest reported leading train location once the leading
train clears the block and the track circuit determines there is no
rail break in the block in advance of the following train. Clearing
an occupied block can be determined by a database with detection
block boundary locations and the known rear of train location
[0049] The proposed movement authority rule would be designed into
the system to protect the following train in the case of broken
rails between trains. See FIG. 9, which illustrates movement
authority with a broken rail between trains. The office/server
would need to process the following pieces of information: (A) last
reported end-of-train location of the leading train at the time
when (B) the transmission current behind the leading train changes
to I=0 amps. Once this state change occurs, the corresponding
location becomes the limit of the movement authority for the
following train. Note that additional broken rails could occur
underneath the leading train. The first detected broken rail will
remain as the limit of the movement authority since that is the
only possible instance when the transmission current Tx changed to
I=0 amps.
[0050] Deployment.
[0051] Next generation track circuits may also need to support
current methods of operation in different types of signaled
territory, as seen in FIG. 10. With Centralized Traffic Control
(CTC), the dispatcher manages traffic remotely between Control
Points (CPs). The intermediate blocks between CPs are automatically
controlled with track circuits and provide for train separation.
Ensuring train separation between CPs may eventually migrate to
modern train control. Therefore, next generation track circuits
should provide the two functions of conventional signal systems:
(1) Detect occupancy and broken rails in each block; and (2)
Communicate the status of each block to adjacent blocks. Migration
to modern train control may eventually eliminate the need for the
second function. However, next generation track circuits could keep
the function of communicating status to adjacent blocks as a
fallback function. PTC territory and high capacity lines are
examples of territories that may benefit from modern train control
and next generation track circuits. High capacity lines can take
advantage of modern train control to increase volume and reduce
delay
[0052] The above disclosure sets forth a number of embodiments of
the present invention described in detail with respect to the
accompanying drawings. Those skilled in this art will appreciate
that various changes, modifications, other structural arrangements,
and other embodiments could be practiced under the teachings of the
present invention without departing from the scope of this
invention as set forth in the following claims.
* * * * *