GB2512101A

GB2512101A - Loop break detection and repair

Info

Publication number: GB2512101A
Application number: GB1305123.0A
Authority: GB
Inventors: Nicholas Healey; Graham Hawks
Original assignee: Tube Lines Ltd
Current assignee: Tube Lines Ltd
Priority date: 2013-03-20
Filing date: 2013-03-20
Publication date: 2014-09-24
Also published as: GB201305123D0

Abstract

An inductive loop break detector has two connectors to provide connections between a detector and two inductive loop wires. Signal LED indicators 312, 314 show whether a signal is present on each wire and phase LED indicator 310 shows whether the signals are in phase or out of phase, on the basis of microprocessor analysis. Also described is a Wire repair connector with ahousing402 having a bore for end sections of broken wire, and at least one aperture 406 for a fastener 408 to secure the ends of broken wire.

Description

I

Loop Break Detection and Repair The present invention relates to a communications-based automatic train control (CBTC) loop break detection device and a method to detect a loop rupture in a communications-based automatic train control (CBIC). The present invention also relates to a loop wire connector device. In particular, but not exclusively, the present invention relates to a device for detecting ioop breaks in a SelTrac (RIM) system loop and a method therefor and a device to re-connect wires in a SelTrac (RTM) system loop.

In the railway industry, signalling is used to control railway traffic safely to prevent rail vehicles from colliding as the use of fixed rail tracks makes these vehicles susceptible to collision. Further, rail vehicles are typically heavy and the friction between the wheels and the track is low. In view of the low friction coefficient between the wheels and the rails, rail vehicles cannot stop quickly. Thus, safety systems for providing traffic control are essential to the operation of a line.

Most safety systems are based on the principle that vehicles cannot collide with each other if they are not permitted to occupy the same section of a track at the same time.

Accordingly, railway lines are divided into sections or blocks and only one vehicle is allowed to be located in each block at any given time.

Historically, block lengths were fixed, i.e. they were defined by two discrete fixed structural points, for example a first and a second station, each point being capable of providing a signal. The length of each block was calculated according to the line speed, train speed, track gradient or slope, brake type and reaction time of the driver. Thus, in a railway line using a fixed block system, a vehicle is prevented from entering a block defined by two fixed points until a signal indicating that it is safe to proceed was generated and transmitted to the vehicle. However, it was not possible for the safety system to know exactly where the vehicle was located within any given block. Thus, a fixed block system will only allow a subsequent vehicle to travel into the last unoccupied block. An additional disadvantage of fixed block safety systems is that for fast trains each defined block must be fairly long to allow the trains to stop safely within the block; thus, line capacity is decreased.

In contrast, in modern moving block CBTC systems the safety zone for each vehide is not statically defined by the infrastructure; in these safety systems processors are used to calculate a salety zone around each moving rail vehicle while location and speed of any given vehicle is calculated by using train sensors and markers on the track. Specificafly a vehicles braking curve is continuously calculated to establish a safety zone. Accordingly, signals can be transmitted directly to each vehicle and track capacity is increased by allowing vehicles to safely run closer.

CBTC systems are railway signalling systems which use telecommunications between a train and track equipment for traffic management and infrastructure control.

These systems are based on continuous communication between a train and a traffic-controfling computer and/or other device, hereinafter referred to as vehicle control centre (VCC). One of the main advantages of these systems is the increase in transport capacity achieved by safely reducing the time interval or headwa' between trains travelling along a line.

In present CBTC systems, a rail vehicle continuously communicate its status via radio signals including information on, amongst other parameters, exact position, speed.

travel direction and braking distance to the track equipment which transmits the signals to the VCC. This information enables the area potentially occupied by the vehicle on the track to be calculated. Further, it allows the system to define points on the line that must not be crossed by other vehicles on the same track; information on these defined points is sent automatically and continuously to relevant rail vehicles so that speed can be adjusted according to predetermined safety requirements.

CBTC systems use closed inductive loops for providing a communications channel and electromagnets on rail vehicles and/or stations for inducing current signals in the inductive loops; these current signals are sent by transmitting antennae to a VCC at a first frequency, for example 56 kHz. The relevant VCC then sends data to rail vehicles at a second Irequency, for example 36 kHz through receiving antennae. Systems which operate in the 30-60 KHz frequency have been widely adopted by metro, subway or underground cperators.

The inductive loops typically comprise two wires which conduct direct current (DC) and run parallel through a loop section, for example 25 metres; the two wires are transposed at the end of each loop section to thereby form another loop section. Each wire in the loop emits a 36 kHz which is received by antennae in the rail vehicles. When the loop is closed, i.e. the loop is Iunctoning normafly; the phase of an individual signal is asynchronous or out of phase with the signal from the parallel wire as shown in Figure 1, which is described in more detail be!ow. Accordingly. the wire transpositions can be detected by the vehicle onboard systems; these use transposition points to determine the exact position of the train as when a vehicle passes through a crossover point, the two electrical signals switch. This allows a transmitting antenna to send a detection signal to a VCC and/or the onboard processor to determine the loop section in which a vehicle is positioned. Generally, an individual ioop is 1 kilometre in length and therefore comprises over 2 km of wire. However, there are certain rail lines, such as London's Docklands Light Railway (DRL), which use loops of up to 3.2 km in length transposed into loop sections every 25 metres.

An individual VCC can control up to 15 loops. Once the relevant VCC or onboard processor has received the exact position and speed of the train, a safe distance and speed for a following vehicle can be calculated. If the calculation is performed by a VCC, a return signal including the calculated safe distance and speed is sent to the relevant vehicle via the communications link.

A VCC can store, for example, a geographical map of the complete line including the position of transposition points, track loops, stations, track gradient, maximum line speed and in which increased braking distance is advised so that this information can be used for controlling vehicle movement and overall line traffic.

SelTrac (RTM) is a widely used (CBTC) system in which the VCC sends data to relevant vehicles at 1200 bit per second on a 36 kHz frequency while the vehicles transmit signals at 600 hit per second on a 56 kHz frequency. Separate antennae are used for transmission and reception; signal amplifiers connected to transmission or reception antennae may also be used.

One of the main advantages of CBTC systems is that the technology associates to them have been evolving for around 30 years and therefore modern CBTC systems are reasonably reliable, retrofitable and widely supported. CBTC signalling is the most widely adopted signalling technology for metro operators across the globe as around 90% of metro signalling systems use it.

The two-wire set up inductive 1oop described above has some disadvantages, particularly as the exposed loop is susceptible to damage by external objects such as stones, haflstones, tree branches, etc; therefore, in some of the latest systems the wires are located within the running tracks. Nevertheless, in systems in which space between the tracks is limited or the running tracks are not easily accessible, for example underground rail systems, the two-wire visible loop arrangement is still preferred.

The main disadvantage of CBTC systems is that communication links must be maintained for the system to work normally; if the connection between a vehicle and the VCC is disrupted in any way, the entire system might enter an emergency (failsafe) state until the problem is fixed. A signal interruption may lead to automatic application of the service brake or emergency brake and thus signalling failures seriously impact service.

Depending on the severity of the communication loss, the emergency state ranges from vehicles temporarily reducing speed to completely halting until the link is re-established.

Some emergency modes allow vehicle drivers to manually override a stopping signal and operate a vehicle in a degraded mode or in fixed block mode so that a station may be reached and passengers can be evacuated.

Communications failures may arise from equipment malfunction, electromagnetic interference, weak signal strength or saturation of the communications nevork. However, ri most systems communication links are broken as a result of a breakage of the inductive loop. As the inductive loop has a maximum length of 1 km and potentially 40 transposition points, a cable break could be anywhere within the 1 km length of cable and on either wire, that is the break could be anywhere in a length of cable measuring at least 2 km.

Currently, time domain reflectometer (TDR) meters are used to locate faults.

Although TOR meters are generally effective in locating faults in most settings they are rather inadequate in railway signalling settings because using a TDR meter to locate a fault in the approximately 2 km of cable which form an individual loop is extraordinarily time consuming1 typically taking over 2 hours. During this time, services have to be interrupted so that the cable is fully accessible to technical personnel. Further, the entire length of the cable must be checked as the TDR meter does not include any means to narrow down the location of a fault within a loop.

Under current practice, once the fault has been located, technical personnel must be called in to re-attach the broken sections of the wire by soldering one wire section to the other. This step can be relatively slow and thus increases the amount of superfluous fime spent in locating and repairing a fault which inevitably increases disruption to the service.

The present invention therefore aims to provide a device which allows a loop break location to be detected quickly and more accurately. The present invention also aims to provide a method for detecting a loop break location to be detected quickly and more accurately. Moreover, the present invention aims to provide a device which allows broken sections of wire to be repaired promptly.

According to a first aspect of the present invention there is provided inductive loop wire break detector comprising: a first connector arranged to provide an operative connection between a first inductive loop wire and the inductive loop break detector to enable a first leg signal to be generated; a second connector arranged to provide an operative connection between a second inductive loop wire and the inductive oop break detector to enable a second leg signal to be generated; an analysing unit to analyse the first and second leg signals from the first and second inductive loop wires; signal indicator means arranged to indicate whether at least one leg signal of the first or second leg signals is present or absent; phase indicator means arranged to indicate whether the first and second leg signals are in or out of phase; wherein, in use, the first and second connectors are operatively connected to a respective first and second inductive loop wire so that the analysing unit determines whether the first and second leg signals are being generated by the inductive loop, whether at least one leg of the first and second leg signals is present and whether the first and second leg signals are in or out of phase.

Advantageously, the First and second connectors have a clip for gripping an inductive loop wire.

Preferably, the inductive loop break detector further comprises display means and or wire indicator means.

In a preferred embodiment, the signal indicator means, the phase indicator means, the display means or the wire indicator means is an LED.

Advantageously, a microprocessor is adapted to determine sign& strength and phase direction of a signal generated by an inductive loop wire.

In another preferred embodiment, the display means is arranged to provide information on signal strength and phase direction of a signal generated by sri inductive loop wire.

According to a second aspect of the present invention there is provided an inductive loop wire repair connector comprising a connecting housing having a through bore with first and second open ends, each open end being arranged to receive an end section of a broken wire, the housing further having at least one aperture arranged to receive a fastener adapted to secure the two ends of the broken wire together electrically.

Advantageously, the inductive loop wire repair connector further comprises a sheath arranged to be placed over a repaired connection defined, in use, by the substantially tubular connecting housing.

According to a third aspect of the present invention there is provided an inductive loop break location method comprising the steps of: providing an inductive loop break detector having an analysing unit comprising a microprocessor adapted to analyse a signal from an inductive loop, a first connector arranged to provide an operative connection between a first inductive loop wire and the inductive loop break detector; a second connector arranged to provide an operative connection between a second inductive loop wire and the hop break detector; signal indicator means and phase indicator means; dividing the inductive loop into intervals having a predetermined length; attaching either the first or second connector to a first inductive loop wire in a first interval and attaching the remaining first or second connector to a second inductive loop wire in the first interval; determining whether an nductive loop break is present in the first interval by analysing the signal indicator means and/or phase indicator means; if the inductive loop break was not present in the first interval, attaching either the first or second connector to a first inductive loop wire in a second interval and attaching the remaining first or second connector to a second inductive loop wire the second interval; determining whether an inductive loop break is present in the second interval by analysing the signal indicator means and/or phase indicator means; repeating steps e. to f. above on n number of intervals until an inductive loop break is present.

Advantageously, the inductive loop break location method further comprises the steps of: determining whether the first or second inductive loop wire emits a weaker signal so that a broken inductive loop wire is identified; and repeating steps b. to g. above on the broken inductive loop wire and the relevant interval to find an accurate inductive loop break location.

More advantageously, the inductive loop break location method comprises the steps of: providing a substantially tubular connecting housing having open ends and at least one aperture arranged to receive a fastener; repairing the inductive loop break by a placing a first section of a broken inductive wire in the substantially tubular connecting housing, placing a second section of a broken inductive wire in the substantially tubular connecting housing and securing the first and second sections of the broken inductive wire to the substantiafly tubular connecting housing with a fastener to define a repaired connection; and placing a sheath over the repaired connection defined by the substantially tubular connecting housing.

Preferred embodiments of the present invention will now be described, by way 0 example only, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic representation of a moving block signalling system; Figure 2 is a diagrammatic representation of a typical CBTC system architecture; Figure 3 is a perspective view of a representative two-wire inductive loop used in CBTC systems; Figure 4 is a top view of loop sections and transpositions in a two-wire induction loop; Figure 5 is a schematic representation of the communications links between the an inductive loop and transmitting and receiving antennae; Figure 6a is a representation of two out of phase signals in an inductive loop; Figure Sb shows the signals of Figure Ba in phase; Figure 7 is a top view of the main components of a detector device according to a preferred embodiment of the present Invention: Figure 8; is a partial view of the user interface of the detector device of Figure 7; Figure 9 is a is a top view of the main components of a re-connecting device according to another aspect of the present invention; Figure 10 is a diagrammatic representation of the re-connecting device of Figure 9 in use; Figure ha shows a first step for using the re-connecting device according to the present invention; Figure lIb shows a second step for using the re-connecting device according to the present invention; Figure 11 c shows a third step for using the re-connecting device according to the present invention; and Figure lid shows a wire after repair with a re-connecting device according to the present invention.

Referring now to Figure 1, there is shown a diagram of a moving block system including a first inductive loop 1 and a second inductive loop 2, each loop comprising two wires arranged to conduct DC current and to generate an out of phase signal. A first rail vehicle 10 and a second rail vehicle 20, each rail vehicle 10, 20 having a controller 101 and an electromagnet 30 arranged to induce a current change in a relevant inductive loop 1, 2 are also shown. The current change is used to generate a location signal 40 which is detected and transmitted by a transmitting antenna at 600 bits per second on a 56 kHz carrier so that it can be read remotely by a VCC 100. Once the VCC 100 receives a location signal 40, it uses information stored therein to calculate a target point so that, for example, when the second rail vehicle 20 is scheduled to stop at a predetermined operational stopping point S, i.e. a station, the VCC 100 calculates a target point I which defines the limit of a block for the first rail vehicle 10. Next, a target point signal 60 which identifies the relevant target point S,T for each rail vehicle 10, 20 is sent from the VCC 100 to the relevant controller 101 at 1200 bits per second on a 36 kHz carrier. In the example shown, the controller 101 in the first rail vehicle 10 will analyse the target point signal 60 and adjust rail vehicle speed according to the deFined target point T and other parameters such as track slope, track layout, line maximum speed, direction and type of braking system used by the rail vehicle 10 so that a safe distance A is always maintained between the first and second rail vehicles 10, 20.

Referring now to Figure 2, there is shown a diagrammatic representation of a representative system architecture wherein a VCC 100 is connected though a signal 110 to adjacent VCCs 100 and a standby direct signal 120 to a scheduler 140 and a system management centre 200. The system management centre 200 controls aH VCCs 100 in a rail line and includes a central database 150 which central database 150 stores information on the line schedule, rail line, type of train, track slope, relevant braking system, planned engineering works and other programmed service disruptions. In fully integrated embodiments, if a controller 101 detects that a rail vehicle is approaching an operational stopping point S or a target point T at an over-speed, the controller 101 generates a driver alert and monitors response. In the event the driver does not react appropriately, the controller 101 activates the emergency braking system.

Normally, a rail vehicle 10 is controlled by moving target points T along a route so that has the controller 101 will search for operational stopping point S or a target point T and always maintain a predetermined safety distance A, for example 50 metres. The target point T is defined as an inductive loop number, for example 2; the rail vehicle 10 wiLl approach the target point I at maximum line speed and, if the target point T is not moved forward along the line, the rail vehicle 10 will slowly brake and stop just before the target point T is reached. In the event the VCC 100 loses contact with a rail vehicle 10, the signalling system is unable to obtain information on the location of the rail vehicle 10 and is therefore unable to send a target point signal 60 to the rail vehicle 10. Further, the VCC can no longer use location data to communicate with the controller 101 to control the rail vehicle 10. The onboard controller 101 detects that the relevant VCC target point signal has not been received and uses the emergency braking system to bring the rail vehicle 10 to a halt. The system onboard the train detects this situation and puts the train to an emergency stop.

In certain signalling CBTC systems, such as the one used in London's DLR which is shown in Figure 2, a rail vehicle 10 may be manually removed from the VCC's control and therefore the rail vehicle will be undetectable by the VCC as described above, in this system, in the event the emergency braking system is activated outside an operational stop point S, the CBTC system further comprises a fixed block signalling system including an axle counter head 106, an axle counter amplifier 104 and an axle counter evaluator 108. When a non-communicatlig rail vehicle 10 passes an axle counter head 106, the VCC 100 determines location of a non-communicating rail vehicle 10 and is able to advance relevant target points I of subsequent rail vehicles. The VCC 100 can keep track of a defective rail vehicle 10 in this manner until an operational stopping point S is reached or until the rail vehicle is cleared from the tracks.

Referring now to Figure 3 there is shown an installed inductive loop 1 havIng two wires Ia and lb which are paraiiei through a loop section 5 and transposed at an intersection point 6. The wires Ia, lb. run parallel to one another and to the track through the loop sections 5. The track shown in this figure is a four-rail system comprising two smaller running rails 7,8, a top-contact third rail 9 on the outermost right position and a top-contact fourth rail 4 placed between the running rails 7,8; sleepers 11 and track ballasts 12 are also provided, in this instance, the top-contact third rail 9 is energised at +420 VDC and the top-contact fourth rail 4 is energised at -210 V DC to provide a combined traction voltage of 630 V DC. The inductive wires I a and lb are placed between the top-contact fourth rail 4 and the running rails 7, 8. The illustrated track has a standard track gauge (i.e. 1435 mm) and as a result there is very little space between the top-contact fourth rail 4 and each running rail 7, 8. Further in busy metro systems, such as the London Underground, the space between the top-contact fourth rail 4 and the running rails 7, 8 is reduced further by using this space as materials storage. Accordingly, location of a loop break using of a TDR meter is unrealistic in practical terms In this type of track because technical personnel cannot reach the inductive wires Ia, Ia with ease. Moreover, the stored material may damage the inductive wires.

FIgure 4 illustrates five loop sections 5, each measuring about 25 meters in length, and four intersection points 6. In the system archftecture described in relation to Figure 2 position of a rail vehicle 10 within a specific loop section 5 is calculable by counting axle revolutions. A rail vehicle 10 communicates the position Information into the inductive loop sections 5.

* Referring now to Figure 5 there is shown an inductive loop 1 having two wires Ia, lb running parallel to a pair of running rails 7, 8 in a loop section 5. Each wire Ia, lb allows current to flow through and when a rail vehicle 10 passes over a given intersection point 6 in the loop; a location signal 40 is generated and sent to a VCC 100 by a transmitting antenna 14 on a 56 kHz frequency channel. A VCC analyses the location signal 40, calculates a target point and generates a target point signal 60 which is sent to a receiving antenna 16 on a 36 kHz frequency channel. Communication between a VCC and transmitting or receiving antennae 14, 16 is through open-standard single integrated networks which comply with widely recognised industry standards and protocols; accordIngly, It will not be discussed further.

Referring now to Figures 6a and 6b, the loop break detection device analyses the 36 kHz signal of the Inductive loop to determine the phase of each leg (i.e. the signal produced by each individual wire I a, or I b). If the inductive loop Is closed and each leg is measured the two legs will be 180° out of phase as seen In Figure 6a. However, If the loop is open, that is one of the wires has been broken, both legs will be on the same phase when measured as shown In Figure 6b.

Refenlng to Figure 7, there is shown a loop break detection devIce 300 comprising an analysing unit 302, a first connector 304 and a second connector 306 arranged to provide an operative connection between the wires la,lb and the loop break detection device 300, each connector 304, 306 havIng clip 308 for gripping a wire la,lb. The analysing unit comprises a microprocessor adapted to analyse the inductive loop signal, phase indicator means 310, frst signal indicator means 312, second signal indicator means 314, first and second wire indicator means 318, 320 and display means 316. In this particular example, the phase 310, first signal 312, second signal 314 and wire Indicator 318, 320 means are LEDs. In use, the loop break detection device 300 Is connected to the wires Ia, lb of the inductive loop I by the first and second connector 304,306 at a given feed RLB connection point and then at a test point or points. The analysing unit 302 will detect the 36 kHz signal produced by each wire Ia, lb so that the microprocessor can analyse the signals to determine whether each leg Is In or out of phase and to establish the signal strength.

in the embodiment shown in Figures 7 and 8, the first and second signal indicator means 312, 314 are arranged to show whether an electrical signal is being transmitted through each wire Is, Ib; as a result, each signal indicator LED 312, 314 will light in a first colour, for example green, if a valid signal is detected in the relevant wire Ia, lb and to be illuminated in a second colour, for example red, if a valid signal is not detected in the appropriate wire la, lb. In the event both signal indicator LEDs 312, 314 indicate that a valid signal is undetectable the fault or break must be located between the test point and the relevant feed RLB. On the other hand, the phase indicator LED 310 is arranged to provide an indication of whether the signals are in phase or out of phase so that if the signals are out of phase the phase indicator LED 310 will light in a first colour, for example green, and if the signals are in phase the phase indicator LED 310 will light in a second colour, for example red, to indicate that the inductive top 1 is broken at a point between the feed RLB connection point and the test point. Accordingly, if the phase indicator LED 310 is lit in the first colour, the signals from the wires la, lb are 1800 out of phase from one another and the break in the loop must be located between the test point and a terminating RLB. On the other hand, if the phase indicator LED 310 is lit in the second colour, the signals from the wires la, lb are in phase and the fault must be located between feed RLB and the test point.

Each wire indicator LEDs 3182 320 corresponds to either the first or second connector 304, 306 and is arranged to provide a user with an indication of which wire 1 a or lb is broken, For example, when the phase indicator LED 310 is lit up in the second colour (red) and the wire indicator LED 318 for the first connector 304 is lit in a third colour, for example blue, the fault is located on the vire connected to the first connector 304. The display means 316, for example an LED screen, is arranged to provide data on the signal strength and phase direction of each leg. The signal strength is measured in a numeric range of between 0 and 1023 and a higher value is indicative of higher signal strength.

As the oop break detection device 300 essentially mimics the principles of communication between the rail vehicle, antenna and the controller 101, faults in the system are much easier to locate and then narrow down to a specific point than if a TDR meter were used. Further, the loop break detection device 300 described is compact and portable and can therefore be carried as standard equipment by trackside personnel. In addition, the first and second connectors 304, 306 are easily attachable and detachable from the cable; thus, the loop break detection device 300 can be used quickly. The loop break detection device 300 described can be deployed around every 250 m or 500 m to identify the signal phase and strength of the signal.

According to a preferred method of use, a user would be able to find a oop break by following the steps below: a. attaching either the first or second connector 304, 306 to a wire 1 a, lb of the loop I and attaching the remaining first or second connector 304, 306 to the other wire Ia, lb; b. confirming that the trackside equipment? and loop break detection device are working by confirming that a signal is being transmitted from the SER to the loop 1; c. dividing the inductive loop into quarters or intervals measuring approximately 250 m each; d. attaching the either the first or second connector 304, 306 to a wire 1 a, lb of the loop 1 and attaching the remaining first or second connector 304, 306 to the other wire 1 a, lb in the first quarter of the inductive loop1; e. if the break was not located in the first quarter, attaching the first and second connectors 304, 306 to the second quarter of the inductive loop 1 and determining whether a break is present; f. in the event a break was not located in the second quarter, attaching the first and second connectors 304, 306to the third quarter of the inductive loop 1 and determining whether a break is present; g. if a break was not present in any of the previous quarters, attaching the first and second connectors 304, 306 to the fourth quarter of the inductive loop; ft once the location of the fault to the nearest quarter has been established, determining which one of the two wires la, lb emits a weaker signal to determine which wire is broken; i. repeating the detection process on the broken wire and the relevant break quarter to find the exact location of the break.

Referring now to Figures 9 to 11, there is shown a inductive loop wire repair connector 400 comprising an external sheath 404 and a connecting housing 402 having a through bore with first and second open ends for receiving end sections of a broken wire, and at least one aperture 406 arranged to receive a fastener 408 (i.e. bolts, screws, nails or pins). In use, a broken cable or wire section is placed in the connecting housing 402 as shown in Figure 1 la; subsequently, the other broken wire section is placed inside the connecting housing 402 as shown in Figure lIb. Next, a fastening tool 410, such as an Allen key, screwdriver or a hammer, is used to secure the broken wire sections to the connecting housing 402 with fasteners 408 so that the electrical connection between both sections of the wire is re-established. This step of the repair process is shown in Figure lic. Once the electrical connection has been repaired, external sheath 404 is placed over the repaired connection defined by the connecting housing 402 and ties 412 are used to secure the sheath 404 over the repaired connection. This oop cable repair connector 400 allows broken cables to be repaired extremely quickly without the need of soldering wires back together so that rail service may be re-established promptly. Moreover, as the sheath 404 is distinctly visible, technical personnel can easily locale the repaired connection at an opportune time, for example during night maintenance works, and solder one broken section of the wire to the other to permanently re-establish the connection. The advantage of using the inductive loop wire repair connector 400 is that disruption to the service is minimised at inopportune times such as rush hour. Further, it is not essential to call upon a specialised technician to use the inductive loop wire repair connector 400 to temporarily repair the electrical connection.

Although the track discussed in the description is a four-rail system, it should be clear to skilled readers that the invention is equally applicable to two-and three-rail systems. The four-track example is merely used to highlight the fact that the inductive wires may be inaccessible or damaged by routine use of the space between the rails.

Further, it should also be apparent that the loop break detection device described above can be used with any CBTC systems and is not limited to SelTrac (RTM) systems nor is it limited to more complex system structures such as that described in Figure 2.

Moreover, it should be clear to the skilled person that the first and second connectors described above may be replaced with electromagnetic sensors, probes or any other means which provides an operative connection, which need not be physical, between the wires and the loop break detection device.

In addition, it should be apparent that the phase indicator means, first and second signal indicator means and wire indicator means described above need not be LEDs. For example, the relevant indicators could be provided on the display means, on a separate screen or through other types of lights. Moreover, the embodiment described above is a preferred embodiment but features such as the wire indicator means, first AND/OR??? second signal indicator means and the data on the signal strength and phase direction of each leg are not essential to the invention.

Aflhough depoyment of the cop break detecfion device every 250 m or 500 m ntervals is preferred, a user rriay choose to depoy the oop break detection device at random intervars or at different predetermined intervas.

Claims

Claims 1. An Inductive loop break detector comprising: a first connector arranged to provide an operatIve connectIon between a first Inductive loop wire and the inductive loop break detector to enable a first leg signal to be generated; a second connector arranged to provide an operative connection between a second inductive loop wire and the inductive loop break detector to enable a second leg signal to be generated; an analysing unit to analyse the first and second leg signals from the first and second Inductive loop wires; signal Indicator means arranged to indicate whether at least one leg signal of the first or second leg signals Is present or absent phase Indicator means arranged to indicate whether the first and second leg signals are in or out of phase; wherein, In use, the first and second connectors are operatively connected to a respective first and second Inductive loop wire so that the analysing unit determines whether the first and second leg signals are being generated by the inductive loop, whether at least one leg of the first and second leg signals is present and whether the first and second leg signals are in or out of phase.
2. An inductive loop break detector according to claim 1, wherein the first and second connectors each has a dip for gripping an inductive loop wire.
3. An inductive loop break detector according to claim 1 or claim 2, further comprising display means.
4. An inductive loop break detector according to any preceding claim, further comprising wire indicator means.
5. An inductive loop break detector according to any preceding claim, wherein the signal indicator means is an LED.
6, An inductive loop break detector according to any preceding claim, wherein the phase indicator means is an LED.
7. An inductive loop break detector according to claim 3, wherein the display means is an LED screen.
8. An inductive loop break detector according to claim 4, wherein the wire indicator means is an LED.
9. An inductive loop break detector according to claims 3 or 4 to 8, when dependent on claim 3, wherein the microprocessor is adapted to determine signal strength and phase direction of a signal generated by an inductive oop wire.
10. An inductive loop break detector according to cLaim 9, wherein the display means is arranged to provide information on signal strength and phase direction of a signal generated by an inductive loop wire.
11 An inductive loop wire repair connector comprising a connecting housing having a through bore with first and second open ends, each open end being arranged to receive an end section of a broken wire, the housing further having at least one aperture arranged to receive a fastener adapted to secure the two ends of the broken wire together electricafly.
12. An inductive loop wire repair connector according to claim 11, further comprising a sheath arranged to be placed over a repaired connection defined, in use, by the connecting housing.
13. Use of an inductive loop wire repair connector according to claim 11 or claim 12.
14. An inductive loop break location method comprising the steps of: a. providing an inductive loop break detector having an analysing unit comprising a microprocessor adapted to analyse a signal from an inductive loop, a first connector arranged to provide an operative connection between a first inductive loop wire and the inductive loop break detector; a second connector arranged to provide an operative connecUon between a second inductive oop wire and the mop break detector; signal indicator means and phase indicator means; b. dividing the inductive oop into intervals having a predetermined length; c. attaching either the first or second connector to a first inductive loop wire in a first interval and attaching the remaining first or second connector to a second inductive loop wire in the first interval; d. determining whether an inductive cop break is present in the first interval by analysing the signal indicator means and/or phase indicator means; a if the inductive loop break was not present in the first interval, attaching either the first or second connector to a first inductive loop wire in a second interval and attaching the remaining first or second connector to a second inductive loop wire the second interval; f. determining whether an inductive loop break is present in the second interval by analysing the signal indicator means and/or phase indicator means; g. repeating steps e. to f. above on n number of intervals until an inductive loop break is present.
15. An inductive loop break location method according to claim 14, further comprising the steps of: a. determining whether the first or second inductive loop wire emits a weaker signal so that a broken inductive loop wire is identified; and b. repeating steps b. to g. above on the broken inductive loop wire and the relevant interval to find an accurate inductive loop break location.
16. An inductive loop break location method according to claim 14 or claim 15, further comprising the steps of: a. providing a connecting housing with a through bore having open ends and at least one aperture arranged to receive a fastener; b. repairing the inductive loop break by a placing a first section of a broken inductive wire in the connecting housing, placing a second section of a broken inductive wire in the connecting housing and securing the first and second sections of the broken inductive wire to the connecting housing with a fastener to define a repaired connection; and c. placing a sheath over the repaired connection defined by the connecting housing.
11, An nducLEve bop break detector substanflay as described herehi with reference Ic, and as illustrated in, the accompanying drawings.
18. A method to locate a break ri an inductive loop substantially as described herein with reference to, and as illustrated in, the accompanying drawings.

19 An inducthte loop wire repair oonriector substent y as described herein with referenceto, and as iUustrMed in, the accompanying drawings.