Railway Signalling& Interlocking International Compendium Editors: Gregor Theeg . Sergej Vlasenko
Authors: Dr.-Ing. Enrico Anders, Thales Rail Signalling Solutions GmbH, Technische Universität Dresden Prof. Dr.-Ing. Thomas Berndt, Fachhochschule Erfurt Prof. Dr. Igor Dolgij, Rostov State Transport University Prof. Dr. Vladimir Ivančenko, Rostov State Transport University Dr. Andrej Lykov, Petersburg State Transport University Ing. Peter Márton, PhD., University of Žilina Dr.-Ing. Ulrich Maschek, Technische Universität Dresden Dott. Giorgio Mongardi, Ansaldo STS Dr. Oleg Nasedkin, Petersburg State Transport University Prof. Dr. Aleksandr Nikitin, Petersburg State Transport University Prof. Dr.-Ing. Jörn Pachl, FIRSE, Technische Universität Braunschweig Prof. Dr. Valerij Sapožnikov, Petersburg State Transport University Prof. Dr. Vladimir Sapožnikov, Petersburg State Transport University Dr. Andreas Schöbel, Technische Universität Wien Dipl.-Ing. Eric Schöne, Technische Universität Dresden Dr. Dmitrij Švalov, Rostov State Transport University David Stratton MA CEng MIRSE, Alstom Transport Dipl.-Ing. Gregor Theeg, Technische Universität Dresden Dipl.-Inform. Heinz Tillmanns, Thales Rail Signalling Solutions GmbH Prof. Dr.-Ing. Jochen Trinckauf, FIRSE, Technische Universität Dresden Dr. Sergej Vlasenko, Omsk State Transport University Dipl.-Ing. CarstenWeber, Technische Universität Dresden Thomas White, Transit Safety Management Editors: Dipl.-Ing. Gregor Theeg, Technische Universität Dresden Dr. Sergej Vlasenko, Omsk State Transport University Railway Signalling & Interlocking International Compendium
Bibliographic information published by the Deutsche Nationalbibliothek: The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie, detailed bibliographic data are available in the Internet at http://d-nb.de Publishing House: DVV Media Group GmbH | Eurailpress Postbox 101609 · D-20010 Hamburg Nordkanalstraße 36 · D-20097 Hamburg Telephone: +49 (0) 40–2371402 Telefax: +49 (0) 40–23714236 E-Mail: info@eurailpress.de Internet: www.dvvmedia.com, www.eurailpress.de, www.railwaygazette.com Publishing Director: Detlev K. Suchanek Editorial Office: Dr. Bettina Guiot, Ulrike Schüring Advertisements: Silke Härtel Distribution and Marketing: Riccardo di Stefano Cover Design: Karl-Heinz Westerholt Layout and Production: Axel Pfeiffer Print: TZ-Verlag & Print GmbH, Roßdorf Copyright: © 2009 by DVV Media Group GmbH | Eurailpress, Hamburg This publication is protected by copyright. It may not be exploited, in whole or in part, without the approval of the publisher. This applies in particular to any form of reproduction, translation, microfilming and incorporation and processing in electric systems. 1st Edition 2009, ISBN 978-3-7771-0394-5 Printed in Germany A DVV Media Group publication DVVMediaGroup
Contents 3 Contents Preface.................................................................................................................15 1 Basic Characteristics of Railway Systems and the Requirements for Signalling............................................................................17 1.1 Introduction...........................................................................................................17 1.2 Specific of Railway Systems ................................................................................17 1.3 Railway Signalling and Control ............................................................................18 1.3.1 Definitions...............................................................................................................18 1.3.2 The Safety-related Railway Theory ..........................................................................18 1.3.3 Functional Structure................................................................................................21 2 Safety and Reliability in Signalling Systems................................................24 2.1 Safety Basics ........................................................................................................24 2.1.1 What is RAMS(S)? ..................................................................................................24 2.1.2 Safety/Security .......................................................................................................24 2.1.3 Availability, Reliability and Maintainability..................................................................25 2.1.4 Role of the RAMS Components in the Railway System ...........................................26 2.2 Safety Principles in Railway Operation................................................................27 2.2.1 Dealing with Errors, Failures and Disturbances (E/F/D) ............................................27 2.2.2 Analysis of Errors, Failures and Disturbances (E/F/D) by System States ..................29 2.3 Conception of Safety and Reliability of Railway Signalling Equipment .............30 2.4 Characteristics of Reliability and Safety..............................................................31 2.5 Evaluation of Safety Level of Signalling Equipment ...........................................32 2.6 Rating of Safety Parameters ................................................................................35 2.7 Calculations of the Safety Parameters ................................................................36 2.8 Methodology of Safety Case for Railway Signalling Equipment ........................38
Contents 4 3 Railway Operation Processes.........................................................................39 3.1 Historical Background..........................................................................................39 3.2 Classification of Tracks, Stations and Signals ....................................................42 3.2.1 Main Tracks and Secondary Tracks.........................................................................42 3.2.2 The Role of Signals .................................................................................................43 3.2.3 Definitions of Stations and Interlocking Areas ..........................................................44 3.2.4 Signal Arrangement on Double Track Lines .............................................................47 3.3 Movements with Railway Vehicles.......................................................................48 3.3.1 Train Movements ....................................................................................................48 3.3.2 Shunting Movements ..............................................................................................49 3.4 Principles of Train Separation ..............................................................................51 3.4.1 Signalled Fixed Block Operation..............................................................................52 3.4.2 Cab Signal Operation..............................................................................................55 3.4.3 Non Signal-controlled Operation .............................................................................58 3.5 Dispatching Principles..........................................................................................58 3.5.1 Decentralised Operation .........................................................................................58 3.5.2 Centralised Traffic Control .......................................................................................60 4 Interlocking Principles......................................................................................61 4.1 Overview ...............................................................................................................61 4.1.1 Introduction ............................................................................................................61 4.1.2 Basic Requirements................................................................................................61 4.1.3 Basic Principles of Safeguarding a Train’s Path .......................................................62 4.2 Element Dependences .........................................................................................63 4.2.1 Classification...........................................................................................................63 4.2.2 Coupled Elements ..................................................................................................63 4.2.3 Unidirectional Locking.............................................................................................64 4.2.4 Simple Bidirectional Locking ...................................................................................65 4.2.5 Conditional Bidirectional Locking ............................................................................65 4.3 Routes ...................................................................................................................66 4.3.1 Introduction ............................................................................................................66 4.3.2 Extension of Routes and Related Speed Restrictions..............................................67
Contents 5 4.3.3 Basic Route Locking Functions...............................................................................70 4.3.4 Route Selection by the Signaller..............................................................................75 4.3.5 Flank Protection......................................................................................................76 4.3.6 Overlaps and Front Protection ................................................................................79 4.3.7 Route Elements in the Start Zone............................................................................83 4.3.8 Life Cycle of Routes................................................................................................84 4.3.9 Principles of Route Formation in the Track Layout...................................................89 4.3.10 Shunting Routes .....................................................................................................91 4.3.11 Automation of Route Operation...............................................................................93 4.4 Block Dependences .............................................................................................94 4.4.1 Introduction ............................................................................................................94 4.4.2 Geographical Assignment of Block Sections ...........................................................96 4.4.3 Classification of Block Systems...............................................................................97 4.4.4 Process of Block Working in Token Block Systems .................................................99 4.4.5 Process of Block Working in Tokenless Block Systems .........................................100 4.4.6 Locking Functions of Tokenless Block Systems ....................................................102 4.4.7 Returning Movements...........................................................................................103 4.5 Special Issues.....................................................................................................105 4.5.1 Overlaying Block and Route Interlocking Systems.................................................105 4.5.2 Protection of Trains by a Signal at Stop in Rear.....................................................106 4.5.3 Several Trains between two Signals ......................................................................106 4.5.4 Degraded Mode Operation ...................................................................................107 5 Detection...........................................................................................................113 5.1 Requirements and Methods of Detection .........................................................113 5.1.1 Introduction ..........................................................................................................113 5.1.2 Types of Objects ...................................................................................................113 5.1.3 Safety Requirements.............................................................................................113 5.1.4 Detection Purposes ..............................................................................................114 5.2 Technical Means of Detection............................................................................116 5.2.1 Classification.........................................................................................................116 5.2.2 Spot Wheel Detectors...........................................................................................116 5.2.3 Linear Wheel and Axle Detectors ..........................................................................120 5.2.4 Linear and Area Detectors for Vehicles and External Objects.................................121 5.2.5 Three-Dimensional Detection ................................................................................123 5.2.6 Systems with Active Reporting from the Train........................................................124 5.2.7 End of Train (EOT) Detection Systems...................................................................127
Contents 6 5.3 Track Circuits ......................................................................................................128 5.3.1 Basic Structure of Track Circuits ...........................................................................128 5.3.2 Geometrical Assembly of Track Circuits ................................................................130 5.3.3 Treatment of Traction Return Currents...................................................................132 5.3.4 Additional Functions of Track Circuits....................................................................135 5.3.5 Immunity against Foreign Currents........................................................................135 5.3.6 Electrical Parameters and Dimensioning................................................................136 5.3.7 Application of the Types of Track Circuits ..............................................................139 5.4 Axle Counters .....................................................................................................143 5.4.1 General Structure and Functioning........................................................................143 5.4.2 The Rail Contact ...................................................................................................145 5.4.3 Treatment of Counting Errors ................................................................................146 5.5 Comparison of Track Circuits and Axle Counters .............................................147 5.5.1 Advantages and Disadvantages............................................................................147 5.5.2 Application............................................................................................................147 6 Movable Track Elements................................................................................149 6.1 Kinds of Movable Track Elements and their Geometry ....................................149 6.1.1 Overview...............................................................................................................149 6.1.2 Simple Points........................................................................................................149 6.1.3 Other Solutions for Connection of Tracks ..............................................................152 6.1.4 Arrangements of Several Movable Track Elements ................................................153 6.1.5 Derailing Devices ..................................................................................................155 6.2 Safety Requirements at Movable Track Elements ............................................156 6.3 Track Clear Detection at Points and Crossings ................................................156 6.4 Point Machines ...................................................................................................157 6.4.1 Overview...............................................................................................................157 6.4.2 Electric Point Machines.........................................................................................159 6.4.3 Supervision of Point Position on the Example of SP-6...........................................161 6.5 Point Locking Mechanisms................................................................................163 6.5.1 External Locking Mechanism: Clamp Lock............................................................163 6.5.2 Internal Locking Mechanism .................................................................................164
Contents 7 6.5.3 Monitoring of Locking Mechanism ........................................................................165 6.5.4 Mechanical Key Lock............................................................................................167 6.6 Circuitry of Point Operation and Control in Relay Technology.........................167 6.6.1 General Overview..................................................................................................167 6.6.2 Example with Type N Relays: Russian Five-Wire Point Circuitry .............................168 6.6.3 Example with Type C Relays: GS II DR (Germany) .................................................171 7 Signals ...............................................................................................................179 7.1 Requirements and Basic Classification.............................................................179 7.2 Technical Characteristics of Trackside Signals.................................................181 7.2.1 Structure of Light Signals ......................................................................................181 7.2.2 Optical Parameters ...............................................................................................184 7.2.3 Retro-Reflection of Passive Signal Boards.............................................................184 7.2.4 Control and Supervision of Signal Lamps..............................................................185 7.3 Principles of Signalling by Light Signals ...........................................................187 7.3.1 Utilisation of Signal Colours...................................................................................187 7.3.2 Stop Aspects........................................................................................................188 7.3.3 Signalling of Movement Authorities........................................................................188 7.3.4 Signalling of Speed Reductions.............................................................................192 7.3.5 Combination of Main and Distant Signals..............................................................195 7.3.6 Shunting Signals ...................................................................................................196 7.4 Redundancy and Degraded Mode Operation ...................................................197 7.5 Signal System Examples....................................................................................198 7.5.1 German Mechanical and ‘H/V’ Light Signals .........................................................198 7.5.2 Belgian Mechanical Signals...................................................................................199 7.5.3 British Light Signals...............................................................................................200 7.5.4 OSŽD Signals .......................................................................................................201 7.5.5 Modern Dutch Signal System................................................................................202 7.5.6 German System ‘Ks’.............................................................................................204 7.5.7 Signal System on Japanese Commuter Lines .......................................................205 7.5.8 NORAC Signals ....................................................................................................205
Contents 8 8 Train Protection................................................................................................208 8.1 Requirements, Classification and Conditions for Application..........................208 8.1.1 General Overview..................................................................................................208 8.1.2 Cab Signalling Functions.......................................................................................208 8.1.3 Supervision Functions...........................................................................................209 8.1.4 Intervention Functions...........................................................................................211 8.1.5 Role in the Railway Operation Process..................................................................212 8.1.6 Automation of Train Operation...............................................................................212 8.2 Technical Solutions for Data Transmission........................................................213 8.2.1 Overview over Forms of Transmission ...................................................................213 8.2.2 Spot Transmission ................................................................................................214 8.2.3 Linear Transmission ..............................................................................................216 8.3 Particular Systems..............................................................................................219 8.3.1 Classification of Systems ......................................................................................219 8.3.2 Group 1: Systems with Intermittent Transmission and without Braking Supervision ...219 8.3.3 Group 2: Systems with Intermittent Transmission at Low Data Volume and with Braking Supervision................................................................................223 8.3.4 Group 3: Systems with Continuous Transmission of Signal Aspects by Coded Track Circuits........................................................................................227 8.3.5 Group 4: Systems with Intermittent Transmission at High Data Volume and Dynamic Speed Supervision ..........................................................................235 8.3.6 Group 5: Systems with Continuous Transmission at High Data Volume and Dynamic Speed Supervision .........................................................................238 8.4 ETCS ...................................................................................................................240 8.4.1 History + Motivation ..............................................................................................240 8.4.2 Application Levels and Technical Components......................................................242 8.4.3 Functional Concepts.............................................................................................245 8.4.4 Operation Modes..................................................................................................249 8.4.5 Data Structure ......................................................................................................251 9 Interlocking Machines ....................................................................................252 9.1 Classification ......................................................................................................252 9.2 Mechanical Interlocking .....................................................................................253 9.2.1 Historical Development .........................................................................................253 9.2.2 System Safety in Mechanical Interlocking..............................................................253
Contents 9 9.2.3 Structure of Mechanical Interlocking Systems .......................................................254 9.2.4 Example: British Origin Mechanical Interlocking.....................................................255 9.2.5 Example: German Type ‘Einheit’............................................................................258 9.3 Relay Interlocking ...............................................................................................263 9.3.1 Historical Development .........................................................................................263 9.3.2 System Safety in Relay Interlocking.......................................................................263 9.3.3 Design of Relay Interlocking Systems....................................................................267 9.3.4 Example: SGE 1958 (Britain) .................................................................................270 9.3.5 Example: SpDrS60 (Germany) ..............................................................................271 9.3.6 Example: UBRI (Russia) ........................................................................................276 9.4 Electronic Interlocking........................................................................................280 9.4.1 Historical Development .........................................................................................280 9.4.2 System Safety in Electronic Interlocking ................................................................281 9.4.3 Structure of Electronic Interlocking Systems..........................................................282 9.4.4 SSI (Britain) ...........................................................................................................285 9.4.5 SMILE (Japan) ......................................................................................................289 9.4.6 Simis and L90 with Derivates (German origin) .......................................................291 9.4.7 Ebilock..................................................................................................................294 9.4.8 EC-EM (Russia).....................................................................................................298 9.4.9 ACC (Italy).............................................................................................................300 9.4.10 Local-electrical Operated Point Switches (LOPS) ..................................................302 9.5 Hybrid Technologies ...........................................................................................303 9.5.1 Hybrid Mechanical and Electrical/Pneumatic/Hydraulic Forms ..............................303 9.5.2 Hybrid Relay and Electronic Forms .......................................................................305 10 Line Block Systems ........................................................................................306 10.1 Classification ......................................................................................................306 10.2 Safety Overlays for Staff Responsible Safety Systems ....................................306 10.3 Decentralised Block Systems ............................................................................307 10.3.1 Overview...............................................................................................................307 10.3.2 Token Block Systems............................................................................................308 10.3.3 Systems with Singular Unblocking upon Clearing..................................................309 10.3.4 Systems with Continuous Unblocking ...................................................................316
Contents 10 10.4 Centralised Systems for Safety on Open Lines.................................................321 10.4.1 Overview...............................................................................................................321 10.4.2 Centralised Block Systems for Secondary Lines....................................................323 10.4.3 Radio Electronic Token Block................................................................................323 10.4.4 Open Line Controlled from Neighbouring Interlockings..........................................324 10.4.5 Train Control Systems for High Speed Lines..........................................................325 10.5 Moving Block Systems.......................................................................................326 11 Remote Control and Operation Technology..............................................328 11.1 Remote Control and Monitoring ........................................................................328 11.1.1 Types of Dispatcher Control/Monitoring ................................................................328 11.1.2 Centralisation of Interlocking Control.....................................................................330 11.1.3 Flexible Allocation of Control Areas .......................................................................330 11.2 Processes in Operation Control.........................................................................331 11.2.1 Information Input and its Viewing ..........................................................................331 11.2.2 Evaluation of Operational Situation........................................................................333 11.2.3 Command Output.................................................................................................334 11.3 Data Transmission in Remote Control Systems................................................335 11.3.1 Types of Communication between CTC and Stations............................................335 11.3.2 Interface between CTC and Relay Interlockings on the Relay Technology..............336 11.3.3 Interface between CTC and Relay Interlockings on the Electronic Technology.......339 11.4 Operator’s Workload...........................................................................................339 11.4.1 Influence of Technology.........................................................................................340 11.4.2 Influence of Size of Infrastructure ..........................................................................340 11.4.3 Influence of Operation Programme........................................................................341 11.4.4 Influence of Moving Vehicles .................................................................................341 11.4.5 Influence of Disturbances......................................................................................342 11.4.6 Results and Conclusions of Calculating Operator’s Workload................................343 11.5 Examples for Operation Control Systems .........................................................343 11.5.1 Centralised Traffic Control in the USA....................................................................343 11.5.2 Operation Control Centres in Germany..................................................................346 11.5.3 Operation Control Centres in Russia .....................................................................349
Contents 11 12 Safety and Control of Marshalling Yards....................................................351 12.1 Principles of Marshalling of Trains.....................................................................351 12.2 Parts of Marshalling Yards and their Function ..................................................351 12.2.1 General Structure and Functioning........................................................................351 12.2.2 Layout Variants .....................................................................................................352 12.2.3 Automation ...........................................................................................................354 12.3 Control of Marshalling Yards..............................................................................355 12.3.1 Introduction ..........................................................................................................355 12.3.2 Retarders..............................................................................................................356 12.3.3 Handling Systems for Freight Wagons...................................................................360 12.3.4 Points ...................................................................................................................361 12.3.5 Sensors ................................................................................................................362 12.3.6 Track Clear Detection............................................................................................363 12.3.7 Yard Management Systems ..................................................................................363 13 Level Crossings ...............................................................................................369 13.1 Requirements and Basic Classification.............................................................369 13.2 Static Roadside Signs ........................................................................................370 13.3 Passive Level Crossings.....................................................................................371 13.4 Active Level Crossings .......................................................................................375 13.4.1 Overview...............................................................................................................375 13.4.2 Dynamic Roadside Safeguarding ..........................................................................376 13.4.3 Opening and Closing of Level Crossings ...............................................................380 13.4.4 Supervision of Level Crossings..............................................................................384 13.4.5 Possibilities of Degraded Mode Operation.............................................................389 13.4.6 Combination with Road Junctions.........................................................................390 13.5 Removal of Level Crossings...............................................................................391 14 Hazard Alert Systems .....................................................................................393 14.1 Hazards in Railway Systems ..............................................................................394 14.1.1 Safety Related Hazards.........................................................................................394 14.1.2 Security Related Hazards......................................................................................395
Contents 12 14.2 Solutions for Hazard Detection..........................................................................395 14.2.1 Ways of Inspection................................................................................................396 14.2.2 Fault States to Monitor..........................................................................................397 14.2.3 New Approach of Inspection – The Checkpoint Concept ......................................398 14.2.4 Extract of Available Technologies and Products.....................................................399 14.3 Choice of Location .............................................................................................405 14.3.1 Operational Handling ............................................................................................405 14.3.2 Classification of Risky Elements ............................................................................407 14.3.3 Strategies for Infrastructure Manager ....................................................................408 References ..........................................................................................................409 Glossary ..............................................................................................................416 Explanation of Symbols in Track Layout Schemes...........................................435 The Authors.........................................................................................................437 Index....................................................................................................................443
3 Railway Operation Processes 44 cleared by the train ahead. The principle is no more than one train, in any one block, at any one time. In a territory with lineside signals, block sections are limited by signals which govern train movements. A signal that controls entry to a block section is called a block signal. 3.2.3 Definitions of Stations and Interlocking Areas Generally, stations are all places designated in the timetable by name. Regarding the schedule, stations are the points where time applies. On British railways, only places where trains stop for load/unload passengers or freight are referred to as stations. In North American usage, each station is designated by a station sign that designates the specific point at which an instruction using only the name of the station applies. On European railways, station signs are mainly used at passenger stations for the purpose of passenger information. In extended and complex terminal areas, some railways place station signs at interlockings outside passenger stations to support the driver in local orientation. But this is usually only be done at places without a local interlocking station, so that the station cannot be identified by the interlocking station’s ID. Some railways use the term station only for places where trains have regular stops. The term station is not necessarily associated with the term station track which is used by several railways to separate sections of main track where station rules apply from the block sections of the open line. Rules on station tracks are closely related to the interlocking rules of a specific railway. An interlocking is an arrangement of points and signals interconnected in a way so that each movement follows another in a proper and safe sequence. Signalled routes for trains on main tracks are usually interlocked (chapter 4.3). Signals that govern train movements through an interlocking are called interlocking signals. An interlocking signal can also be a block signal. The points and signals within interlocking limits are controlled either by a local interlocking station or from a remote control centre. Local interlocking stations are called interlocking towers in North America, and signalboxes or signal cabins on railways that follow British principles. The block signals between controlled interlockings are often called intermediate block signals. In Britain, this term is used only in older systems for a block signal that is controlled from the interlocking station in rear. Concerning interlockings and stations, the railways designated different names and limits in accordance to their individual operating practice. In particular, there is a big difference between North American railways and those elsewhere. In North America, the block system that protects train movements is not interrupted in interlocking areas. There is no station track separated from the open line. Figure 3.3 demonstrates the essential difference at the example of a track arrangement with several loop tracks. In North America, the point zones at both sides of the loop tracks would form separate small interlockings. These are limited by opposing interlocking signals in a way that each interlocking does normally not contain any consecutive interlocking signals. Station names refer to these small interlockings but not to the entire loop track layout. In Europe and on other railways outside North America, the entire loop track layout would be a station designated by name. The tracks between the outer point zones are station tracks. On station tracks, there are consecutive interlocking signals, which form station track sections. Train movements on these sections are protected by the interlocking system but not by a block system. Thus, the entire layout that may even contain more than just two point zones forms one interlocking area. Figure 3.4 gives a more detailed example of how interlocking limits are established on North American railways. At each track that leads into interlocking limits, there is a signal that may authorise train movements, even at tracks that are not used for regular train movements (this
3.2 Classification of Tracks, Stations and Signals 45 is an essential difference from European signalling). These signals are called home signals. A speed indication at an interlocking signal applies until the train has passed the first opposing interlocking signal, which is called the exit signal of that interlocking. On European railways, there is still a difference between the traditional British practice and the continental railways that followed more the German principles. In traditional British interlocking systems, there are designated ‘station limits’. Station limits are the tracks between the home signal and the last main signal of the same direction (the section, or starting signal), controlled from the same signalbox (interlocking station). The section signal permits trains to leave the station limits and enter the next block section. There are different station limits for each direction. In most British installations, this signal is placed behind the last points of the interlocking (then also called an advance signal or formerly an advanced starter signal), thus usually requiring additional interlocking signals before the points (figure 3.5). Figure 3.4: Interlocking limits (North American practice) Figure 3.3: Different principles of assigning interlocking and station names to a track layout on North American and European railways
4.3 Routes 83 4.3.7 Route Elements in the Start Zone In some cases, movable track elements which are situated in rear of the route entrance signal in the start zone have to be included into the route functions (figure 4.29). In particular, this occurs with station exit routes in situations where the train starts the route from a scheduled stop, with the previous route of this train already released (chapter 4.3.3.6). Many railways try to avoid such situations in track layout planning by not placing movable track elements in tracks where trains will stop regularly. But particularly in areas with a restricted availability of space, these situations cannot always be avoided. Figure 4.30: Points of the start zone influencing the route speed Figure 4.29: Examples of route elements in the start zone In cases where the movable track element is already occupied by the starting train (figure 29 a and b), locking functions are already fulfilled by the track occupation: However, depending on the interlocking system, additional locking of this element in the route can be applied. In cases where the element can be situated between the train front end position and the route entrance signal (figure 4.29, c and d), this element must always be included in the route locking functions. Additional special requirements in interlocking logic can occur to determine the exact position of the starting train in this context, and in the case of converging tracks to determine the track from which the train starts. The solutions are particular for the interlocking systems and are not be discussed in detail here. A controversial problem of speed signalling occurs if the train uses an element in the start zone in the diverging track (figure 4.29, b and d) and the speed permitted by this element is lower than the speed the route would permit without this element (figure 4.30). The solutions depend on the regulations about the local validity of the speed indication of the signal in rear and which speed has been signalled there (chapter 4.3.2.3). The case that the speed signalled at the station home signal is valid through the whole station (figure 4.9, case 1) is the simpler case in this context. In case of separate speed restrictions for each route (figure 4.9, cases 2a-e), particular attention has to be paid to the element of the start zone concerning speed regulation:
5 Detection 122 These technologies are mainly applied to detect occupancy of level crossings by road users (chapter 13.4.4.4) and in other cases with increased probability of objects other than rail vehicles occurring, e. g. at platform tracks, particularly in automatic metropolitan railways. In other applications, systems of this type are also suitable for indirect detection of occupancy by trains. An example is the disruption of a ray with sender and receiver on opposite sides of the track by each wagon of a train. The evaluation principle is similar to that for axle counters, but wagons are counted instead of axles. This principle is applicable mainly to metropolitan railways (Barwell 1983). By using the Doppler effect, the speed of trains and, calculated from speed and occupation time of a certain position, the train length can be measured (Fenner/Naumann/Trinckauf 2003). 5.2.4.2 Mechanical Technologies Mechanical supervision of the limiting areas of the clearance profile is applied by some railways. A net of wires or a single horizontal wire stretches outside the limits of the clearance profile and carries a low voltage current (figure 5.14). If an object of not too small extension breaks through this area with a certain minimum force, the wires break, disrupting the current. This disruption of current is evaluated by the interlocking or block system which can hold signals at red in this case. As repair works are necessary after such events, this technology is only useful to detect occurrences which seldom occur. Examples are: – Detection of avalanches and earthslides in mountainous areas. – Detection of road vehicles fallen from a bridge above a railway line, as applied on French high speed lines. – In situations where a railway is situated in proximity of an airport, to protect against an aircraft overshooting the runway and obstructing or destroying the railway line. Figure 5.14: Example of an installation to detect avalanches mechanically (France) Another mechanical technology is contact mats placed on and beside the track to detect the presence of persons, vehicles or other objects by their weight. This technology is applied on some automatic metropolitan railways, e. g. in Vancouver. 5.2.4.3 Magnetic Inductive Loops Such detectors consist of a resonant circuit with the inductivity situated in the track (figure 5.15). When a rail vehicle passes over the loop, the inductivity L changes due to the iron mass of the vehicle. According to the formula of the resonant circuit 1 (2 · f)2 = L · C (with f being the
5.2 Technical Means of Detection 123 Figure 5.16: Remote visual supervision of a level crossing Figure 5.15: Inductive loop for vehicle detection frequency, L the inductance of the coil and C the capacity of the capacitor), this changes the frequency of the resonant circuit. This shift of frequency is evaluated to detect the vehicle. To compensate inductive effects of traction return currents in the rails, symmetrical double loops are normally used (figure 5.15). By this technology, directions cannot be distinguished (unless using two double loops) and axles cannot be counted. It is applied for initiating the opening and closing of level crossings in some systems. It can also be used to detect road vehicles on level crossings, with the disadvantage that due to lack of iron mass, pedestrians and animals are not detected and cyclists rarely. In road traffic management, such loops are widely used. 5.2.5 Three-Dimensional Detection 5.2.5.1 Visual Observation The simplest and historically oldest form of detection is visual observation of the respective track by staff. The ability of human to also evaluate unexpected observations is the main advantage over all technical systems. Disadvantages are the relatively high probability of human error and the high costs of staffing. Therefore, the usage of visual observation is decreasing, especially in highly developed countries. Another version is remote visual observation via camera and monitor (figure 5.16). The number of people required for observation can be much reduced by this method. It is used especially in situations where not only rail vehicles have to be detected. Examples are the conflicting areas of level crossings with roads, the tracks in platform areas, but also passenger areas for security purposes.
6.4 Point Machines 161 The generalised block diagram is shown in figure 6.14: – In an electro-mechanical point machine, electric power is transformed into mechanical by means of an AC or DC electric motor M. The motor rotation is spread on to the reduction gear R meant to strengthen the angular momentum and to reduce the rotary speed of the motor. The motor is connected with reduction gear via branch sleeve which allows an insignificant radial displacement of shafts while retaining a parallel position of their axes. To protect the motor from overloads, e. g. if the blades do not reach their end position due to an obstacle, and to ensure the braking of the revolving parts of the EPM after the end of switching the points, a friction gear is inserted into the gear. The rotating movement is transferred into the progressive motion of the throw bar TB in the last cascade of the reduction gear. – In an electro-hydraulic point machine, the electric motor M rotates the pump of the hydraulic gear R. This pump pumps oil from one cylinder into another and causes a relative movement between the cylinder and a piston. Either the cylinder or the piston is mechanically connected with the throw bar TB, the other is fixed. In both forms, the throw bar impacts upon the blades of the points through the point drive rod. The detection contacts DC provide checking of point positions and commutate the electric controlling circuits. Obtaining the checking signal about of point end position is only possible if the position of the detection bars DB conforms to that of the throw bar. An important factor for exchangeability of EPM's of different manufacturers is compatibility of two kinds: – Electrical compatibility of the EPM in the operation and supervision circuitry. An example for a standard is the German four-wire point circuitry (chapter 6.6.3.1). – Mechanical compatibility at the interface between EPM and point drawbar, regarding mechanical connections, switching length and others. Often compatibility is provided in one country, but not internationally. For degraded mode operation and for maintenance, EPM shall enable the possibility of switching the points by the hand crank. During hand cranking, electrical movement must be prevented for safety. The EPM influences directly the safety of train movements, since is checks the actual position of a set of points. The idea of supervision of point position is to verifiy the conformity between the detection bars and the throw bar. In order to check point position, one checking drawbar is attached to each blade. These drawbars are connected with the detection bars which move inside the EPM. 6.4.3 Supervision of Point Position on the Example of SP-6 To illustrate the principle of proving the point position, let us examine the checking block of the Russian EPM SP-6 (Reznikov 1985, Sapožnikov et al. 2008). According to the classification given in chapters 6.4.1 and 6.4.2, this EPM is electro-mechanical with possibility of using Figure 6.14: EPM block diagram (R is a mechanical gear in electro-mechanical and a hydraulic gear in electro-hydraulic point machine)
ihr-emagazin.deRkJQdWJsaXNoZXIy MjY3NTk=