WO2015083190A1 - Coded current automatic block system without the use of insulated joints - Google Patents

Abstract

One of the fundamental problems of Coded Current Automatic Block (Bacc) system currently in use in about 5000 miles of the RFI (Rete Ferroviaria Italiana) network is the need to use insulated joints to separate various sections of track that are one of the most frequent causes of track breakage. The basic idea of this invention is the separation of the different sections of the line not through galvanic isolation of the rails but through short circuits between the rails. This allows greater consistency along the rails, eliminating completely the delicate isolated joints. Short circuits isolate an electrical circuit that "shifts" in accordance with the movement of the train so that in front of the train there is always a generator present which is able to generate the coded current that is read on-board in accordance with specific railway protocol. The presence of rolling stock can be detected by special current sensors placed in specific places along the rail. The sensors detect the train arrival by means of the short circuits generated by the axles of the train eliminating, at the sensors, the current impressed by generators. Signal transmission to the train remains unchanged compared to previous systems so that no changes in on-board subsystems are required. The achievement of the required safety integrity level is easily obtained because the system has the possibility to re-read what is transmitted to the train It is possible to install the proposed system in specific tracks of the line. The coexistence of tracks traditionally equipped (with isolated joints) and tracks equipped with the new system in the same line allow a gradual transition between the two systems. The system also allows the observation of electrical parameters of the rails, raising alarms in the case of specific types of breakage or damage of the rail.

Description

CODED CURRENT AUTOMATIC BLOCK SYSTEM WITHOUT THE USE OF

INSULATED JOINTS

INTRODUCTION:

The invention subjected to patenting relates to the earth electric "equipment" useful both for rail traffic control and for status of the line monitoring. In particular, the invention can be used to identify the presence of a railway rolling stock, to transmit continuously on board train signals (RSC) and to ensure the continuity of physical/status of the rails, everything in a manner consistent with the current Bacc system (automatic blocking system with codified currents) in use in Italy and in other parts of the world (See RFI specification document of the SCMT system requirements-coding: RFI TC.PATC SR CM OB M 93 and other similar).

BACKGROUND ART:

The system currently in use is characterized by a separation of tracks into isolated sections. The term CdB track circuit is traditionally used to indicate tracks section electrically equipped bounded by isolated joints upstream and downstream within which can be identified the presence of a rolling stock.

As better described below thank to the electrical separation between the C.d.B and the placement of generators and current sensors, current are established on the rail when the train is present and the train presence on C.d.B. can so be detected.

Within the sections there are coded signal generators. The presence of the train on rail closes the circuit allowing the passage of coded currents that are detected by onboard train equipment, while the same short imposed by train axis prevents the signals to be captured by ad hoc detectors on the opposite ends of rail sections (track circuit -C.d.B.) reporting to the ground equipment the presence of the convoy.

In order to comply with the first two of the three objectives Bacc systems currently in use are now placed on approximately 5000 Km of Italian Railway network while the third objective is not pursued to date.

In relation to the first two above indicated goals the systems currently adopted are not fully satisfactory and one of the main problems that characterize them are the need to use insulated joints to separate the various track circuits. The presence of these joints is, in fact, one of the most common causes of broken rails and this, in addition to heavy financial commitment for their maintenance, can generate potentially dangerous situations.

The replacement of the current coding technology with other technologies is in many cases impractical (it is made for modem routes developed ex novo where, most of the time, over the air ground-train communications are used and coded currents are not used for the purpose) as it would entail changes not only to the infrastructure but also to all circulating vehicles equipped today for "dialogue" with the Bacc on earth equipment. The proposed system aims to provide an answer to the problems indicated in a very "transparent" way in respect of the on board systems today present in most of the circulating vehicles.

To explain the invention and represent its easy capability to work in the railways context currently present we consider a track equipped with the automatic block coded currents in the traditional way, represented in Figure 1.

BRIEF DESCRIPTION OF DRAWINGS IN FIG 1 - TRADITIONAL SYSTEM Along the track equipped in a traditional way (T), elements 01 , 02, are the different traditional voltage detectors, element 03 is the different traditional voltage generators, X are isolation joints between sections (track circuits) in which the line is divided. The generators and detectors are connected to the rail control system (in Italy SCMT) whose link is not explicitly indicated in the drawings. The control system sends signals to generators to be repeated through Coded train Currents.

In traditional operation when the train moves on and occupies the subsequent sections of the line, once it is passed over the isolated joints X, the set constituted by its axes/wheels, short-circuit the rails at the point of contact of the wheels removing the voltage imprinted by the generator. In Figure 1 the train moves in the direction of the arrow and once it has passed over the detector 01 eliminates the voltage imprinted by the generator 03. This absence of voltage generated by short circuit created by train is used to signal the occupation of track to the central control system. The short circuit imposed to generator 03 creates a current flow that must be detected by special sensor located under the train ahead on the first axis which forces the short. Being the current imprinted by generator 03 coded, it is possible to broadcast to train some codes/commands related to his march.

The railway routes are divided into "subsequent" circuits, in which the indicated process happen, which are galvanically isolated with special joints (whose problems above mentioned).

DISCLOSURE OF INVENTION:

To overcome the situation described above, the basic idea of the system that we intend to patent is to electrically separate the different track sections through "short circuit" points rather than through galvanic isolation. These points of short circuit between the rails are made with switches. A carefully orchestrated opening and closing of the switches creates on the Rails electrically identifiable circuits that are not rigidly fixed (as in previous situations) but can be identify as "shifting" C.d.B. In the case of presence of rolling stock within C.d.B. defined above the presence of current in electric circuits identified in part of C.d.B circuits (delimited by the generator on one side and train axis on the other one) allows you to localize the presence of the train in C.d.B. itself.

Similarly to isolation, short circuits do not allow the passage of signals (voltage presence) downstream and upstream allowing the identification of different tracks where the current of Baac system flows with different codes for different tracks. This concept lets to eliminate the problematic isolated joints.

The presence of the vehicle can be detected with current detectors similar to those present on today vehicles and placed on the appropriate near rail zone. In the absence of vehicles the detectors reveal the currents impressed by generator / short-circuit allowing real sent code verification as well as the detection of possible alteration of the electrical parameters of the rail (the alteration can indicate problems on the rail). The presence of coming vehicle is detected when the detector does not receive the code anymore, due to the presence of a convoy between generator and detector, the currents impressed by the generator are in fact short-circuited from one or more of the train's axes indicating the occupancy of the track (0.1 - 0.2 ohms typical short-circuit impedance between the Rails sets from an axis). Signal transmission to train board also remains unchanged with the care of generating a current of sufficient power so that its distribution from the generator to the subsequent short circuit and upstream toward coming train is sufficient so that it can be detected by the onboard subsystem (minimum allowed value 2.7A for 50 Hz, 1, 7A for 178Hz).

95 The main advantages of the present system are the overcoming of the problems connected to the presence of joints, the easiness in being applied in the present railway context, security, usability for the verification of the integrity of the rails, low cost.

To better understand how the innovative system is constituted let us consider a binary equipped in accordance to the new innovative dictates, represented in Figure 2.

100 BRIEF DESCRIPTION OF DRAWINGS IN FIG 2 - NEW SYSTEM:

Long Track innovatively equipped is indicated with N; elements 07, 08, ... are the current codified detector sensors of the new system, elements 04, 05, 06, ... are the current generators of the new system, each of which has a specific switch 09,10,11 associated in parallel. Generators, switch and sensors are connected to the control

105 signaling network.

The System that you can see in the figure is repeated on all subsequent track circuits that have to be taken under control.

When the train moves in the direction of the arrow occupies one after the other the subsequent sections of the line,

no Lefs suppose that at the starting time the generator 04 is switched off and the connected switch in parallel is open; so the generator 05 is active with the right code generation and the associated switch in parallel is open while the generator 06 is switched off and the switch associated to is closed.

The vehicle, moving on as indicated by the arrow, creates a short circuit in the loop lis identified by the generator 05, the first vehicle axis and the Rails interposed between them. The current generated by generator 05 is detected by sensor located under the vehicle before the first axis, as in the case of traditional system, allowing the proper reception of codes on the rolling stock. The presence of a short-circuit beyond generator 05 constituted by the closing of the switch in parallel to generator 06 limits downstream and upstream the circuit and does not cancel the current towards the vehicle (it imposes only a greater power generation - generator 05).

When the train overcomes the sensor 07 the short circuits generated by the vehicle will inhibit reception of the signal generated by the generator 05 to sensor 07 informing the system of track occupancy. At this point the control logic will activate generator 06, opening the associated parallel switch and will shut off the generator 05, no longer useful, leaving open the associated switch. In order to avoid the propagation of the signal on the subsequent track the switch in parallel to the generator following generator 06, not shown in Figure 2, will be held close (the generator will be switched off). The dosing of the switches downstream and upstream is used to prevent the code generated by the generator 06 propagates in the line (upstream this is anyway guaranteed by the presence of rolling stock and its axis/wheels), identifying the single track not with the four insulated joint but with two "shifting" short circuits.

In order to ensure correct operation, considering the electrical typical and extreme values of parameters of the rails we must pay attention to necessary low impedance of switches and short-circuit in the ON status to ensure proper separation of adjacent track circuits.

This process is repeated as the train advances in the different subsequent tracks circuit identified by the presence of the subsequent generators, switches and sensors. According to this operating model the generators will come into operation in sequence 140 as the train overcomes the current sensor placed upstream of the generator of interest while an electric circuit is identified by the "short circuit" driven upstream and downstream of the sensors.

Because the short circuits imposed by control system are not fixed as it happen in the insulated joint case you can vary, depending on the situation, the number and the length

145 of the track (rail sections).

Of course other types of implementation are possible, for example, using systems for train presence detection as axis counter system, audio-frequency track circuits system and so on. Even the topology is quite indicative, i.e. the position of the switches do not need to be near to a generator but it could be in the midway between two generators,

150 similarly you can expect implementations with different numbers and arrangements of the different current sensors.

One of the most interesting topology can be implemented associating to each switch/generator two magnetic sensors, one slightly upstream and one slightly downstream the track (close to the end and the start of the track) instead than

155 positioning one sensor in the middle of the track (as shown in the diagram).

This topology, in case of application on track where it had already installed a traditional Bacc system would use only existing cables without the need of new ones. Using this topology it is possible to shut down the generator, not when the train is arriving to it but immediately after the train overcomes it (and this is detected by the sensor displaced

160 slightly after the generator or by sensor displaced slightly before the subsequent generator); also the following generator can be activated immediately after to generate the correct current code to and the connected switch can be shut off. The system can be installed also on short sections of a line allowing the coexistence of insulated joints track - C.d.B. and track equipped with the innovative system. So the migration to the 165 new system can be done gradually without much initial investment (as an example it is possible to update the tracks where maintenance action is required due to breakage of a joint).

The proposed system allows continuous monitoring of some parameters of the line allowing direct control of the integrity of the signals transmitted to the train and the line

170 facilitating the achieving of the necessary level of safety integrity.

BEST MODE FOR CARRYING OUT THE INVENTION:

In the proposed topology the system is able to handle two-way traffic.

In order to save current when no train is passing, but with the objective of continuous occupancy verification and integrity check of the rail, the system can work in the

175 described, following configuration (or other similar): short circuit switches closing alternately; active generators at open switches characterized by pulsed emission with a very low duty cycle to check the presence of vehicles in their coverage thank to the presence of adjacent sensors as shown in Figure 2 (Ax). This would make possible to check vehicle presences along the line and the integrity of the line structure with a

180 minimum of dissipation, generating the appropriate encoded currents only in a fixed range of neighboring sections where the convoy is passing.

In the tracks in "waiting state", tracks in which can be used pulse signal to detect the possible train presence it is convenient to change cyclically closed switches and active generators to keep under control all the involved features, and not just half of them, as 185 can be easily understood observing the design in Figure 2. During the "waiting period" the use of different signals from the classic codes ensures the absence of enabling movement codes (SCMT or equivalent protocol).

In the "waiting state", you may join multiple track sections (opening more adjacent switches).

190 Taking into consideration the procedures above reported to continuously detect the presence of vehicles in the "waiting period" or "waiting state" it is clear that those procedures can be used to perform a remote diagnosis of the line.

It is Obvious that a breakage of a rail involves the interruption of circuit where impulses pass through and it can be immediately detected.

195 Considering the recent evolution of the equipment used for analysis, it is also quite simple and not expansive to measure the electrical parameters of each track circuit of interest and to see if variations of the values of those parameters are compatible with the present climatic variations, suggesting more accurate control where it can be assumed that something not usual (like damage of the rails) that does not involve the

200 total interruption of current flow can be happen.

Ad hoc generators used in the new system (used in every track circuit or in specific one) can be developed to be able to generate in the "waiting state" signals different from those used today, able to verify in the best way the rail status (as above described); this generators can be applied also in traditional joint insulated system but in this case the

205 analysis have to be performed internally the single track.

Obviously different topologies, configurations, modes of operation can be hypothesized introducing additional elements referring anyway to the described technology. CONSIDERATION OF POSSIBLE MODE FOR CARRYING OUT THE INVENTION: The proposed system is fully compatible with the present one because the magnetic

210 fields in front of the train are equivalent to current ones, so that an observer on the train cannot functionally distinguish if the train is moving in the new or in the old system. On the same line some tracks equipped in the traditional way (with insulated joints) and some other equipped with the innovative system can be present, this possibility allows the migration form the old situation (with insulated joints) to the new one (without

215 insulated joints) gradually.

The submitted system was designed specifically to meet the security requirements required in the rail.

In fact the detection of the occupancy of track is operated by current sensors, which by the way can be of the same type as those mounted on board, and the system is able to

220 re-read by the ground sensors the same code read on board verifying that the signals that have to be read by the rolling stock are the same that was generated.

In addition the continuous alternation between open and closed switches and active generators with the current generated signal reread by ground sensors, improve the security of the system and facilitate the possibility of testing it.

225 CONCLUSION:

In this document we described a system of Automatic Block Coded Current which is based on separation between the various sections of track, not through isolated joints but using shifting short circuit created in fixed sections in front of the train which has the following important features: 230 · It overcomes some issues that heavily impact existing traditional systems in relation to the presence of insulated joints (that weaken the rail causing high maintenance costs).

• It allows to detect mechanical failures thank to the analysis of the electrical parameters of the Rails.

• It is absolutely equivalent to the present system in relation to the ground to board 235 communication.

• It has the possibility to re-read the generated codes which involves a simplified way to achieve the level of safety and integrity required for railway applications.

Claims

CLAIMS 240 "CODED CURRENT AUTOMATIC BLOCK SYSTEM WITHOUT THE USE OF INSULATED JOINTS COMPATIBLE WITH ON BOARD SUBSYSTEM TODAY INSTALLED ON RAILWAY VEHICLE"

1. Codified current automatic block system without the use of insulated joints (BACCRC), compatible with the on board codified current equipment used

245 today for continuous signal repetition, characterized by a presence of codified current generators (fig.2 04-05-06) useful for ground-train communication by rail transmission in accordance to protocols used in Italy and in other countries (we refer to SCMT coding: RFI TC.PATC SR CM 0B M 93 E for Italy and similar protocols used in other countries) and a sequence low impedance switches (fig.

250 2 09-10-11) (low impedance in relation to typical frequencies of codified current in automatic block system) placed on the rails to electrically separate the various "track circuits¹¹ and current sensors used mainly to detect train presence

2. System consisting of one of the "track circuits" claimed above governed by a logic of moving short circuit determined by the switches on the railway, in sync 255 with the advancement of vehicles on Rails during the passage of individual

"track circuits" that are dynamically defined with opening and closing switches.

3. System consisting of one of the BACCRC described claimed above, but with two or more current detectors (fig.2 07-08), placed between subsequent generators / switches to improve the precision of train localization and optimize the cabling. 260 It is possible to place two sensors at short distance of few meters for example 10 meters from the generator one before and one after instead that placing it in the middle between two generators (fig.2 04-05-06-09-10-11)

4. System consisting as claimed above equipped with generators able to emit also pulse with low Duty cycle or width (fig.2 04-05-06) to save energy when verifying possible presence of the unexpected vehicles on the line. When a train is present the codified current protocol requests a specified minimum energy.

5. System consisting of one of the "track circuits" claimed above with addition of integration modules with other railways traffic control system like audiofrequency circuits, axes counters, etc.) used to detect the train presence.

6. System consisting as claimed above equipped by specific devices able to detect magnetic fields generated by the coded current flowing on the track circuits and to compare them with the generated signals in order to verify the integrity of the transmitted codes, the presence of unexpected signals and detect possible anomalous situations or breakage of the Rails all with security level SIL4. We consider in particular train wrong coding reading in situation of breakage of mass connection point (generically named third binary problem).

7. System consisting of systems claimed above characterized by generators, (fig.2

04-05-06), switches (fig. 2 09-10-1 ), transducers (fig.2 07-08) displaced on the rails with different topology as for example the presence of a greater numbers of switches between generators.