GB2595905A - Methods and apparatus for electrically isolating a section of railway track or similar - Google Patents

Abstract

A method for remotely controlling electrical isolation of a conductor 10, 20 (in embodiments the powerline or third rail of an electric railway). The method involves creating a script (fig. 5 and 6) comprising a time-ordered sequence of instructions for operating remotely controlled equipment 6, 7, 9 and 26, loading the script into a controller 24, and executing the script on the controller to apply the instructions to the remotely controlled equipment to disconnect a voltage from the conductor. The script may include further instructions for reconnecting the voltage to the conductor (fig. 6). The script may be stored with an identifier in a library to enable future re-use. Physical tokens 19a may be removed from some trackside equipment to prevent the voltage being re-applied. Reconnection may include replacing the physical tokens prior to running the script. An authorisation code may be requested from a signaller before running the script, and the code may be stored in the library with the script. A further authorisation code may be required before executing the script. The script may be tested on a simulator model. A claim is also made to an apparatus for performing the method.

Description

METHODS AND APPARATUS FOR ELECTRICALLY ISOLATING A SECTION OF RAILWAY TRACK OR SIMILAR

The present invention relates to methods and apparatus for 5 electrically isolating a section of railway track or similar.

Electrified railways addressed by the present invention include a high voltage power conductor running along the railway track. In embodiments particularly discussed herein, the high voltage power conductor is an overhead line. In other arrangements, a conductor is provided at ground level -such conductor may be known as a "third rail". Other arrangements may be employed within the scope of the present invention.

For maintenance, repair or intervention in trackside incidents, it is from time to time necessary to remove the voltage from a section of track, by isolating that section.

In conventional arrangements, safely isolating a section of track, and safely restoring the voltage once the required intervention is complete can take a significant amount of time. Such sequence of operations is referred to herein as 'an isolation'. Preferably, such interventions take place overnight in order to reduce the disruption to passenger traffic on the railway. However, with known isolation and restoration of voltage methods, most of the time available on a night shift is often taken up with safely isolating a section of track, and safely restoring the voltage, meaning that a very restricted amount of work can be performed in a night shift.

The present invention seeks to provide improved methods and apparatus for performing an isolation, that is to say, isolating a stretch of track and for later restoring high voltage to the stretch of track, to enable such operation to be performed in much shorter time and so to enable a longer time to undertake work during a predetermined time frame, such as a night shift. This means that any required work may be completed in fewer shifts, reducing disturbance to the functioning of the railway.

Safety considerations also dictate that a rapid isolation and 5 rapid reconnection are in the interests of trackside workers, who will accordingly spend less time in a vulnerable location establishing and removing isolation equipment.

Fig. 1 illustrates a conventional arrangement of a railway track with high voltage conductors and equipment for disconnecting ("isolating") a section 100. Substations 1, 2, 3, 4 are shown. A first conductor 10, which may be an overhead line, a third rail or equivalent, extends from substation 1 to substation 2. A second conductor 20, which similarly may be an overhead line, a third rail or equivalent, extends from substation 3 to substation 4. Each substation includes a circuit breaker 7 and an earthing isolator 6. In use, a control signal from communication channel 22 or manual operation may be applied to the substation in order to cause circuit breaker 7 to open, to remove a supply voltage VT from the associated conductor 10; 23. Isolator 6 may then be opened to prevent inadvertent re-application of supply voltage VT to the conductor. Adjacent each substation, on the conductor side, is an earthing switch 8. Once the circuit breaker 7 has been opened, and Isolator 6 has also been opened, earthing switch 8 is closed, to remove from the conductor 10; 20 any residual voltage which may for example remain due to capacitive effects, and to ensure that the conductor 10; 20 remains at earth voltage. A fixed earthing device 9 may be provided for each conductor. This is a further conductive path from the conductor to ground. In a conventional arrangement, the fixed earthing device 9 may be a large metal strap which is manually attached to the associated conductor at one or more relevant locations along the conductor.

The action of temporarily removing supply voltage VT from conductors 10; 20 over a section such as shown at 100 in the drawings may be referred to as "an isolation": representing a geographical area bounded and protected by circuit breakers 7 at each end. The circuit breakers are typically located within substations. The substations include means for disconnecting a high voltage power supply and applying a local earth to the conductors 10, 20. Although such equipment may be remotely controlled to apply earths to conductors in the isolation, trackside workers are conventionally required to walk alongside the length of the track in the isolation, manually applying earth straps and using personal earths as appropriate for safety considerations. The manual application of earthing straps is employed as a guarantee of effective earthing in the isolation, a protection against errors in the remote controlling of earthing devices.

Conventionally, control signals are applied to substations 14 and fixed earthing devices 9, over a communication channel 22. Communication channel 22 may be embodied as a twisted copper pair, an optic fibre, a GSM-R or other mobile telephone connection, radio link, or other conventional communication 20 channel.

In the conventional method, over one hundred mouse clicks are typically required at a control system user interface for an operator to operate all the required devices to perform a single section isolation. After each remote device action, the state of the respective controlled device is verified. If any further manual tasks are required, these are performed before continuing.

Instructions are sent to the substations 1-4, the earthing switches 8, and the fixed earthing devices 9. These instructions command these devices to perform the switching outlined above: 1) Open circuit breakers 7 to remove voltage VT from 35 conductors 10; 20 in the section 100; 2) Open isolators 6, and close earthing switch 8 to prevent inadvertent re-application of voltage VT by unintentional operation of circuit breaker 7; 3) Apply fixed earthing device 9 to ensure that conductors 10, 20 remain at ground voltage.

It can take many minutes of operator time to effect a single isolation. Indeed, each step carries a risk of human error. Accordingly, trackside workers are required to walk the length of the isolation to install temporary manual straps to ensure that appropriate earthing is in place along the isolated section. Such temporary manual straps serve to ensure that power supply voltage VT cannot unintentionally be restored while work is performed on the railway in the isolated section. Significant time is required to perform the manual strapping phase of the works, and this also carries a manual handling risk to the workers, due to the need to handle large straps of some 25-30kg and install it, for example to an overhead power line, connecting to a trackside earth connection. Such operations to secure the isolation are accordingly reliant on many human operations and interventions: each of which carries a risk of human error. These steps must be performed in reverse to remove the manual straps at the end of the working shift.

Aside from the manual interventions required, the remotely controlled operations outlined above are manually commanded and time consuming.

Conventionally, the remotely controlled operations are commanded by a single operator at a control centre, using display screen equipment. In current processes, the isolation of a typical section, such as illustrated in Fig. 1, requires the operator to make in the region of one hundred to one hundred and fifty mouse clicks on a display screen equipment interface. This is time consuming and each click carries a risk of operator error. To mitigate the possibility of operator error, local checks are performed onsite trackside at 35 the isolated section to ensure that the section is actually isolated, and manual earthing is applied as described.

The present invention seeks to provide methods and equipment for reducing the time taken to perform such isolation of a section of track; and to perform such isolation in a reliable, secure manner.

The present invention accordingly provides methods and equipment as defined in the appended claims. The above, and further, objects characteristics and advantages of the present invention will become more apparent from the following description of certain embodiments thereof, in conjunction with the accompanying drawings, wherein: Fig. 1 shows a typical conventional arrangement for electrical isolation of a track section; Fig. 2 shows an arrangement of equipment for performing 15 electrical isolation of a track section according to an embodiment of the present invention; Fig. 3 shows a simplified flow chart representing a general sequence of events of an isolation method of the present invention; Fig. 4 shows an example graphic user interface GUI as may be presented by an editor useful in composing scripts for use in a method of the present invention; and Tables 1 and 2 illustrate example sequences of commands and 25 may be provided by a method according to the present invention.

Fig. 2 schematically illustrates an example of equipment which may be used according to an embodiment of the present 30 invention.

Preferably, the fixed earthing devices 9 are enabled for remote control. In the method of the present invention, operation of such remotely-controlled fixed earthing devices may remove the 35 need for manual trackside intervention to install earth straps.

In preferred embodiments of the present invention, arrangements are provided in which physical tokens, located at trackside equipment, may be removed for the duration of the works, and the absence of these physical tokens ensures that power supply voltage VT cannot be reapplied to the conductors 10, 20, 10', 20' until the physical tokens are replaced. The physical tokens preferably have an interlock arrangement, whereby it is not possible to remove the tokens unless the supply voltage VT has been removed from the associated conductor(s) 10, 20, 10', 20'. Such physical tokens may be located at each substation and at a further point of access within the section 100 to be Isolated. In the illustrated embodiment, this is at the fixed earth device 9. Preferably, the substations 1, 2 and fixed earth devices 9 are arranged such that, with the physical token removed, remote control of the device is not possible. Preferably, the system is arranged such that removal of any one physical token in the isolation is sufficient to prevent re-connection of the power supply voltage VT, but the power supply voltage VT is not reestablished until all physical tokens have been replaced.

With further reference to Fig. 2, a trackside fixed earthing device controller 24 is illustrated. According to the specific section in question, second and further trackside fixed earthing device controllers 24 may be provided within the section 100. Each fixed earthing device controller 24 is connected to communication channel 22 to receive commands from, and provide status indicators to, a control centre (not illustrated). The, or each, trackside fixed earthing device controller 24 may include a rotary switch 19 with physical token 19a as discussed above, or similar apparatus, in which the physical token 19a may be removed from the trackside fixed earthing device controller 24 once the conductors 10, 20, 10', 20' are isolated and a fixed earth path established between the conductors 10, 20, 10', 20' and a ground voltage. A responsible person should keep such physical token about their person until the required intervention is complete. This provides added assurance that the conductors 10, 20, 10', 20' are at ground potential. Once the intervention is complete and the trackside workers are all safely removed from any isolated electrical equipment, the responsible person may replace the physical tokens 19a, and operate the rotary switches 19 (or equivalent apparatus). In this way, the responsible person who is on site trackside may be confident that conductors 10, 20, 10', 20' remain at ground voltage at least until the responsible person has replaced the physical tokens 19a into the rotary switch 19, or equivalent.

In the example illustrated in Fig. 2, four conductors 10, 20, 10', 20' are represented. Each corresponds to a track on the section 100 of railway. Depending on the planned intervention, it may be necessary to isolate the conductor of any one, or more, or all, of the tracks.

Each conductor 10, 20, 10', 20' is provided with a fixed earthing device 9 which provides a secure earth connection. This is typically a mechanically activated switch, which receives commands over a communication channel 22. A trackside fixed earthing controller 24 is provided, and receives control signals from the communication channel 22, and issues corresponding commands to motor operated switch devices 26 each controlling a fixed earthing device 9 provided for a corresponding track.

Depending on the length, or other features, of the section 100, second and further track side controllers 24 may be provided along the length of the track within the section 100. Each further track side controller 24 will be arranged to issue corresponding commands to corresponding motor operated switch devices 26 each controlling a fixed earthing device 9 as described.

The composition of each substation 1-4; track side controllers 24; motor operated switch devices 26; and fixed earthing 35 devices 9 may be conventional in themselves, and so will not be described in detail here.

The present invention provides a method for controlling steps of an isolation, generating a control script into a library which may be used to provide "scripted" automation. The associated system may be referred to as an Isolation Planning 5 Module, and may work with a central control system to provide isolation selection by an automated switching sequence. In a particular embodiment, substation circuit breakers are controlled via the IEC61850 standard. Typically, each substation 1-4 has a local control unit: akin to a PLC, 10 although this is not illustrated in the drawings.

Remotely controlled fixed earthing devices 9 are required: in the absence of these, manual earthing will still be required.

Although the fixed earthing devices may remove the need for installing a manual strap, a manual trackside isolator may be employed, for additional security of isolation, such that an on-site responsible person may prevent voltage being applied to conductors 10, 20 while trackside workers are in the vicinity of the track. Such manual trackside isolator may use conventional Castellg, keys, or equivalent; or some other isolation means managed by physical tokens.

In an arrangement using Castell keys, a rotary switch 19 or similar may be used to further isolate a conductor 10, 20, 10', 20' from voltage VT. This may only be performed when the rotary switch 19 or similar is enabled -for example, when a solenoid is activated in response to voltage VT being disconnected from the conductor 10, 20, 10', 20'. When the rotary switch 19 is moved into position of further isolating an associated conductor, a physical token 19a (e.g. a Castell key) becomes removable. With the physical token removed, it is not possible to return the rotary switch to its closed position, so that the associated conductor remains isolated, at least by this switch, until the physical token is returned.

In the present invention, such equipment may be deployed in each of the substations 1, 2, 3, 4, such that in each case, once the circuit breaker 7 is opened and the isolator 6 is also opened to provide isolation of the conductors 10, 20, 10', 20', then a solenoid or similar enabling device may be operated to enable the rotary switch 19 to be used to further isolate a conductor 10, 20, 10', 20' from the supply voltage VT. Operation of the rotary switches 19 is performed by a responsible person, and that responsible person removes physical tokens 19a from each rotary switch and keeps them safe until the required intervention is complete, and trackside workers are all safely removed from any isolated electrical equipment. The rotary switches 19, controlled by physical tokens 19a such as CastellY keys or similar, interact with a Control Inhibit signal, which prevents local or remote operation from a current state.

Once the intervention is complete and the trackside workers are all safely removed from any isolated electrical equipment, the responsible person may replace the physical token(s) 19a, and operate the rotary switch(es) 19. In this way, the responsible person who is on site trackside may be confident that the high voltage VT will not be applied to conductors 10, 20, 10', 20' at least until the responsible person has replaced the physical token(s) 19a into the rotary switch(es) 19, or equivalent. Optionally, but preferably, a visual indicator 12 such as an illuminated beacon or rotating barber pole may be provided, to provide reassurance that the section is isolated.

Rather than employing the conventional time-consuming and labour-intensive practice of manual strapping, the method of the present invention may only require one responsible person to travel to the isolation, where that person may operate a series of switches, and remove CastellS keys 19a from rotary switches 19 or equivalent. These switches 19 and keys 19a are usually provided at trackside substations 1-4, and these substations are located at a safe distance from the track, hence the method and apparatus of the present invention reduces the risk to maintenance staff as there is no requirement for workers to undertake manual operations on site at the track.

This reduces the labour costs for on-site workers, reduces down-time of the railway for any given operation, and improves safety by removing the need for workers to intervene on site at the track during establishment of the isolation.

The Castel:J.' keys 19a cannot be removed without being "enabled", for example by a solenoid, which is only energised in response to the associated circuit breaker 7 being in an earthed position, through earthing isolator 6 and/or earthing switch 8. So, the Castell'1) key 19a can only be removed from its switch 19 after the high voltage VT is disconnected from the conductor 10, 20, 10', 20' and the high voltage can only be reconnected to the conductor 10, 20, 10', 20' if the Castell' key is in place. Provided that the responsible person does not allow any work to be carried out on the track unless the Casten® keys have been removed into their possession, then workers on the track are safe from contacting the high voltage VT.

In summary, circuit breakers 7 are closed; earthing isolators 6 are connected to earth; fixed earthing devices 9 are closed to remove residual voltage from conductive materials of conductors 10, 20, 10', 20'. Process logic in a central controller and / or in substations 1-4 inhibits re-connection of the high voltage VT. Removal of the appropriate Castell® keys 19a is enabled. Castell® keys 19a are then removed from rotary switches 19 or equivalent to prevent re-energisation of the track section conductors 10, 20, 10', 20' until the Castell® keys 19a are replaced.

Substations 1-4 and earth switches 9 are operated by remote control in accordance with signals transmitted over the communication path 22. In this manner, according to an aspect of the present invention, an operator in a remote control room can compose a script for automated device operation to effect an isolation, test the script on a simulator model, store and perform the script as required.

II

In an embodiment of the present invention, a script for device operations to perform a required isolation is defined in advance. Such script is then stored for later use, and may be kept in a library of such scripts for performing different isolations. A simulator model may be used to tesb a defined sequence of device operations to ensure that a script is correctly written.

As the script has been tested on the simulator model, the 10 operator can have confidence that the isolation will be correctly performed. By knowing that a predetermined, preferably tested, sequence of steps is performed, it becomes less important to install temporary manual earth straps 9 for the duration of works on the line.

Fig. 3 shows a simplified sequence of events according to a method according to an embodiment of the present invention.

In step 301, a request is received to perform an isolation. 20 This is identified in the drawings as "IDF Received", where IDF represents an Isolation Detail Form.

A check may be performed to examine whether a suitable script is already available to perform the requested isolation. If such a script exists already, step 302 is omitted; in the absence of a suitable existent script, a script is composed at step 302 to define a time-ordered sequence of operations of remotely controlled equipment suitable to perform the requested isolation. That script is saved at step 303 into a library, so that it may be retrieved in future when the corresponding isolation is requested on a future occasion. An authorisation is received from a signaller at step 304. In UK parlance, this authorisation may be referred to as "Form AE". The script for the appropriate isolation sequence is loaded into a controller at step 305 -which script may be one created in step 302, or one retrieved from a library.

When an isolation is to be performed, by operation of the stored script, the script may be passed to a control system database, in the form of a sequence of instructions, for action.

With the script loaded, permission for executing the script is sought from a signaller or other appropriate authority at step 306. With the correct permission granted, the script is run on the controller, to execute the isolation sequence in step 307. In some embodiments of the invention, a local check of the isolation is performed at step 308 to ensure that the required conductor(s) have been grounded. The securing of the isolation will not take place if the required devices are not in the correct position.

A responsible person, having checked that the isolation has become effective, may remove one or more physical token(s) 19a, such as a Castelle' key, from trackside equipment at step 309 to ensure that the conductors cannot inadvertently be re-energised until the physical token(s) is/are replaced.

The responsible person can thereafter be confident that the isolation has been performed correctly and that the high voltage VT cannot inadvertently be re-applied. The required intervention may then be performed, with work carried out on the track at step 310.

Once the work is completed, and all workers have left the vicinity of the track, the responsible person can replace the 30 physical token(s) previously removed, such as CastelP) keys, at step 311.

A further part of the script, or a second script, may then be performed at step 312, thereby to execute a closure sequence defined by the script. Once that is performed, the task is complete and the system may be brought back into service, at step 313 which concludes the procedure.

This method involves very little on-site manual operation, is therefore safer and much faster than the conventional methods for performing the isolation.

Fig. 4 shows an example layout of a GUI (Graphical User Interface) of an editor which may be used in an embodiment of the present invention in preparing scripts of actions to be performed to establish an isolation. Of course, many other layouts may be employed with embodiments of the present invention, but the arrangement shown is a possible example.

A user is presented with a list 40 of circuit breakers 7 and fixed earth devices 9, and possibly other types of equipment, available on an associated railway network, and which can be controlled remotely by signals transmitted over the communication path 22. The list 40 of circuit breakers may be arranged such that the operator may sort the list as required, for example by name or mnemonic, or by geographical location, or a logical subset.

In the example illustrated in Fig. 4, a user is creating a new script 42 for performing a certain isolation. In the illustrated GUI screen, the list 40 of circuit breakers may be accompanied by a separate empty list 44, which may be referred to as an "isolation list", which may be used to contain a new script 42 to define a required isolation sequence.

Typically, the operator may compose a script 42 by selecting circuit breakers from the list 40 of circuit breakers, and by copying, selecting or drag-and-dropping labels representing certain circuit breakers into the isolation list 44; and for each of those circuit breakers, and at each corresponding time point, a corresponding action 46 is defined: typically "open" or "close" or "earth". The resulting script 42 is a time-ordered sequence of operations of remotely controlled equipment suitable to perform the required isolation. Any one circuit breaker may appear multiple times, at different times represented in the script 42. For example, a single circuit breaker may be controlled to "open", then to "earth" then to "close" at respective time points during an isolation sequence. As is common with GUI file editing software, once an isolation list 44 is populated, the individual entries 48, each representing a time-ordered list of operations at defined circuit breakers or other pieces of equipment, may be duplicated, re-ordered or deleted. Other operations available for inclusion within the script may typically include control inhibits (which block a circuit breaker from acting on further commands until the inhibit is removed) and reading of line voltages, using sensors incorporated into the circuit breakers, fixed earth devices or other remote equipment.

Provision may be made to include authorisation codes 50 from a signaller (e.g. that which may be known in the UK as a Form AE reference) to enable operators using the script later to verify which isolation is carried out by the script 42, and that the script is known to perform a sequence of operations approved by a signaller.

Once the script 42 has been completed, verified for example by testing on a simulation model and provided with an authorisation code 50 from the signaller, it can be stored in a library of such scripts. A suitable identifier is added and a database, or a reference listing, or some other arrangement, is preferably provided so that the stored scripts can be identified by the identifier and recalled when the corresponding isolation is to be formed.

In normal operation, a system operator will receive a request for an isolation e.g. step 301 in Fig. 3. The operator will consult the database, listing or other arrangement in search of a script for performing the requested isolation. Should the system operator locate a corresponding script, the script is loaded into an operational control system. In embodiments where an authorisation code is associated with the script, that authorisation code is checked to ensure that the script is currently approved for use on the section of track which is the subject of the planned isolation. If any such authorisation code is found to be valid, the script may be run on a central control system to perform the required isolation, in which case the method illustrated in Fig. 3 is not pursued further. If such an authorisation code is found to be invalid, then the operator may request re-validation of the script from the signaller, or other authority as appropriate, or may delete the stored script from the library and begin work on a replacement script to perform the required isolation.

Should the operator find no appropriate script within the library, then the operator may compose a new script using the editor as described above and may follow a method outlined by the flow chart of Fig. 3. Each time the operator composes a new script 42, that script may be stored in the library, and a reference to it may be placed in the database or reference list to enable the script to be found again when the same isolation is required again. Where required in a certain embodiment, an authorisation code is sought for each new script, from a signaller or other appropriate authority. Once granted, such authorisation code 50 is stored in or with the script 42.

The operator may compose a new script 42 by amendment of an existing script. This may be performed by opening an existing script into an editor such as the editor discussed above. The operator may add, remove and amend operations in The script, and may save the amended script under a new name. Once the operator begins to edit the script, the editor should remove or invalidate any authorisation code 50 which was stored with the existing script. Once the operator has completed the new, revised, script, it can be stored in the library under a new name, and a corresponding reference added into the database, reference listing, or other arrangement, so that the script can easily be located and used again another time if required to perform the corresponding isolation. A new authorisation code SO may be obtained and stored with, or within, the new script.

If an error should occur during execution of an isolation 5 script, an alarm will be generated and/or the execution of the script may be aborted.

Preferably, the system is arranged such that execution of the script will not proceed to a next command until the previous command has been completed and verified. For example, the state of the voltage at conductors 10, 20, 10', 20' may be monitored, and execution of the script will not continue if one of the conductors involved is found to still be carrying the supply voltage VT.

Table 1 shows typical steps performed in execution of a script for an isolation sequence. In it, all four substations 1-4 illustrated in Fig. 2 are operated to perform the isolation.

In a first step, an authorisation code, here referred to as and AE Form Ref may be entered, to ensure that the operator is authorised to instruct the isolation represented by the script loaded into the system.

Once that step is successfully passed, "open" instructions are sent to the circuit breakers 7 in each of the substations 14. A verification step may be performed, and a further check is shown in that the conductor voltage is measured to ensure that none of the conductors 10, 20, 10', 20' involved in the isolation are still connected to the supply voltage VT. Once that step is successfully passed, and none of the conductors are found to be carrying the supply voltage VT, instructions are sent to each substation to open the earthing isolators 6. The operation of that step may be checked by an appropriate step that will be apparent to those skilled in the art. Next, instructions are sent to close the earth switch 8 (Circuit Main Earth CME) of each substation 1-4. Once those steps are performed and tested, the conductors 10, 20, 10', 20' will be connected to earth voltage, at least at each of the substations 1-4. Next, commands may be sent to close circuit breakers 7. The circuit breakers are closed at the end to provide earth continuity. Finally, "inhibit" instructions may be sent to each substation to prevent further remote operation of the equipment until the "inhibit" command is cancelled. Further steps may be added, as will be apparent to those skilled in the art, to bring about the closure of the fixed earth device switches 9, providing a further path to ground for the conductors 10, 20, 10', 20'.

Table 2 shows typical steps performed in execution of a script for removal of an isolation. In particular, it illustrates a sequence for removing the isolation set up by the operations of Table 1. As such, all four substations 1-4 illustrated in Fig. 2 are operated to remove the isolation.

Not illustrated in Table 2, an authorisation code, similar to the AE Form Ref mentioned above may be entered, to ensure that the operator is authorised to instruct the removal of isolation represented by the script loaded into the system. Then "cancel inhibit" instructions are sent to each substation to re-enable remote operation of the equipment. The switches of fixed earth devices 9 are opened before undertaking any other operations.

Cancelling the inhibit must be undertaken before opening switches of fixed earth devices 9 as they would otherwise also be inhibited.

Once that step is successfully passed, "open" instructions are 30 sent to the circuit breakers 7 in each of the substations 1- 4. The order of switching the circuit breakers 7 in the substations may be determined such that, if there is a fault whilst switching the voltage back on then there is no impact on the system. A verification step may be performed, and a further check is shown in that the conductor voltage is measured to ensure that none of the conductors 10, 20, 10', 20' involved in the isolation are still connected to the supply voltage VT. Once that step is successfully passed, and none of the conductors are found to be carrying the supply voltage VT, instructions are sent to each substation to open the earth switch 6. The operation of that step may be checked by an appropriate step that will be apparent to those skilled in the art. With that step performed, and in the absence of any other electrical connections, the conductors 10, 20, 10', 20' will be at a floating voltage. Next, instructions are sent to close the isolator 6 of each substation 1-4. After a suitable checking step, further instructions are sent to close the circuit breakers 7. Once those steps are performed and tested, the conductors 10, 20, 10', 20' will be once again connected to supply voltage VT, and the isolation will be over.

After the trackside work is complete, control of substations, fixed earth devices and so on will not be enabled until all Castell® keys or other physical tokens have been replaced. The replacement of the Castell® keys or other physical tokens at the trackside by an authorised person represents the completion of trackside work, and represents the taking of responsibility by the authorised person for the re-application of the supply voltage VT by operation of a script approved for ending the corresponding isolation.

Preferably, when the Castell® key(s) or other physical token(s) is/are removed, a beacon 12 or other audible or visible indication is activated, to assure trackside workers that the supply voltage VT has been removed from conductors 10, 20, 10', 20'.

When any Castell® key is removed, all remotely controlled devices within the section are notified. The operator is notified. The notified remotely controlled devices are inhibited when a Castell® key within the section is removed, and those remotely controlled devices cease to react to commands applied over the communication channel 22. The remotely controlled devices are re-enabled once all of the Castell® keys have been replaced.

Preferably, the operator has a facility to manually override the establishment of an isolation, such that an operator can remove an established isolation, provided that no CastellP keys have been removed from the relevant substation yet.

Preferably, the operator has a facility to manually override the removal of the isolation, for example if communication between substations has failed, but a Castell''' key is missing (for example). Preferably, this can only be done from within 10 the relevant substation, not remotely.

The method of the invention allows remote establishment and removal of an isolation, while use of physical tokens such as Casten® keys provides assurance that the high voltage VT will not be re-established to the conductors 10, 20, 10', 20' until the physical tokens are replaced.

Claims (10)

1. CLAIMS1.A method for electrically isolating a conductor, comprising the steps of: (a) creating a script for performing an isolation, the script comprising a time-ordered sequence of instructions for operations of remotely controlled equipment; (b) loading the script into a controller; (c) executing the script on the controller, resulting in the time-ordered sequence of instructions being applied to the remotely controlled equipment, resulting in the disconnection of a voltage (VT) from the conductor.
2. 2.A method according to claim 1, further comprising the step of: (d) removing a physical token from trackside equipment, thereby preventing the voltage (VT) being applied to the conductor.
3. 3.A method for re-establishing connection of a voltage (VT) to a conductor, comprising the steps of: (a) performing electrical isolation of the conductor in a method according to claim 1; further comprising the steps of: (b) further executing the script on the controller, resulting in further application of the time-ordered sequence of instructions to the remotely controlled apparatus, resulting in the re-connection of the voltage (VT) to the conductor.
4. 4.A method for re-establishing connection of a voltage (VT) to a conductor, comprising the steps of: (a) performing electrical isolation of the conductor in a method according to claim 2; further comprising the steps of: (b) replacing the physical token to the trackside equipment, thereby enabling the voltage (VT) being applied to the conductor.(c) further executing the script on the controller, resulting in further application of the time-ordered sequence of instructions to the remotely controlled apparatus, resulting in the reconnection of the voltage (VT) to the conductor.
5. 5. A method according to ant preceding claim, further comprising the step of storing the script in a library together with an identifier to enable the script to be located for future re-use.
6. 6.A method according to ant preceding claim, further comprising the step of requesting authorisation from a signaller, and receiving an authorisation code from the signaller.
7. 7.A method according to claim 6, further comprising the step of storing the authorisation code with the script.
8. 8.A method according to claim 3 further comprising requesting further authorisation from the signaller prior to executing the script.
9. 9.A method according to any preceding claim, wherein the step (a) of creating a script comprises the step of testing the script on a simulator model.
10. 10. Apparatus for electrically isolating a conductor, arranged to perform a method according to any preceding claim.