STRAY CURRENT CURRENTTRACTION RETURN The railway authority is responsible for any damaged or corrosion to other companies’ equipment due to effects of stray or leakage currents from the railway. With new railway electrification projects this has to be addressed during the design period, to minimise any modifications that may be required in operation of the railway. CENELEC European Standard EN50122-2 Part 2 ‘Protection against the effects of stray current caused by D.C. Traction Systems indicates that in Light Rail systems the stray current will be minimised if the return conductor system is allowed to float, and if the negative busbars are deliberately not connected to earth or to a stray current conductor via diodes. The total stray current at a particular location is dependent on the design of the infrastructure and in particular whether this includes slab or ballasted track. Figure 28 Double Insulated Rail Clips Floating Negative or Diode Earthed Railway This normally includes a rectifier drainage panel located at the Rectifier Substation for those assets within close proximity, and remote rectifier cubicles for those assets requiring protection that are remote from the Rectifier Substation. A drainage system to protect Utilities and the railway infrastructure normally includes a drainage diode, a current limiting resistor, and surge arrestor. Where it is identified that stray current protection is required, cables are bonded from the infrastructure to drainage diodes mounted in cabinets at the track side or in the Rectifier Substation. Running Rail Insulation The Running Rail is normally insulated from the sleeper / concrete pad by the use of single and double insulation pads placed under the rails with an insulation value in line with the European Standard EN 50122-2. [Table 1 Page 6; No added rail insulation 0.5 S/km for open formation and 2.5 S/km for closed formation]. This level can be improved with the application of track insulation mounting pads or polymeric insulation. This value of insulation however will reduce over time due to degradation of the track insulation. For closed formation, improved levels of insulation can be achieved where the rail is to be embedded in the road. The level of insulation is determined not only by the installation but the maintenance of the track bed. Every effort should be made to minimise the risk of ballast from coming into contact with the rails, since ballast, especially when wet will reduce the insulation value of the rails to earth. Provision of Stray Current Control Where monitoring indicates that there is a high level of leakage current from the D.C. electrification system, and therefore potential damage to metallic structures, arrangements must be made to provide the appropriate form of cathodic protection to railway infrastructure, utilities and non railway property. The only condition when the track earth may be connected to true earth is by means of a short circuiting device, which operates for a pre-determined short period of time when the track potential exceeds a specified direct contact of 60V D.C. as specified in EN 50121-1 Section 4.1.1 271 DC GROUND COLLECTION SYSTEMS Figure 29 Relationship of Conductor Rail to Running Rail Network Rail Southern Zone The conductor rails for ground collection systems are mounted on porcelain insulators and laid at the side of each electrified track. Current collection in the UK is mainly by shoes in contact with the top surface of the conductor rail, and the docklands where it is under running contact. The fourth rail system (LUL UK) provides a power distribution system that is able to control the current paths taken. The power rails are supported by insulators to provide electrical isolation. The power is supplied via the rail (+ve) positioned close to one of the running rails with the return current located on the centre rail (-ve). Using this circuit layout the current pathway is controlled. This has the main advantage in that the current is contained and therefore it is able to control the generation of electro-magnetic interference. This layout of the power system is therefore also able to reduce the corrosion in pipes and cables belonging to third party and other railway systems In the third rail system the power distribution is traditionally located to one side of the running rail, with either one or both of the running rails are used for return path to the sub station. Side Rail Contact [ Vancouver Skytrain] The side rail is supported by insulators and brackets from the trackside leaving the side surface open for contact by the vehicle pick-up shoes. This system has not been widely adopted, however it offers a reasonable level of protection and has the advantage of better conductor layout at points and a reduction in the frequency of gaps in the conductor rail. Under Rail Contact [ Docklands] THIRD RAIL CONTACT SYSTEMS This subject is covered in D Hartland’ Lecture Pantograph, Shoegear and Conductor Rail Interface. Top Rail Contact [Network Rail] The conductor rails are electrically connected to the feeder station and rest on insulators mounted on the track with the top surface is exposed. The shoes on the vehicle draw current from the conductor rail due to the downward force by the shoe on the rail. This system is used by British Rail and London Transport and is also used extensively in the United States. The live conductor rails require gapping at point-work and crossovers. It is inevitable that the system is rather vulnerable to snow, ice and falling leaves. The weakness of the top rail contact system is its exposure; the rail is particularly dangerous for permanent way staff, passengers and trespassers walking along the track. It is possible to incorporate a cover to protect the live conductor and insure a higher degree of safety for personnel. With this system the rail is hung from insulated brackets beside the track enabling the current to be collected from underneath. The electrical shoe collector presses up from below, making it possible to have a continuous insulating cover over the length of the third rail. This significantly improves the safety for personnel on the line and prevents the build-up of ice or debris at the current collection interface. The weight of the rail is supported by cantilever supports and it is inevitable that the design is more complicated than for top running system. Under running systems are becoming more popular with the inherent safety factor and are now widely used in Europe, Singapore Mass Transit Railway and Docklands Light Railway. 272 Figure 30 Underneath Contact System The cross section of the rail is determined by a number of factors, the resistance of the conductor, the ease with which the conductor rail can be laid during construction, the ease that the conductor rail can be handled during maintenance The ability to engage and obtain good collection by the collector shoe on the traction vehicle has to take into consideration the width of the shoe and the possible variations of position due to the dynamic effects and lateral tolerances that are attributed to the conductor rail geometry, track geometry and train position. Conductor rail cross sectional area does govern its resistance (R = *length/area). Conductor rails have flat bottom flanges to facilitate mounting on the insulators but usually have a larger top section than the running rails, with a somewhat thinner web section. Conductor rail weights in use are: Construction of the Conductor Rail 25 kg m-1 - mostly used in sidings 52 kg m-1 - main lines 74 kg m-1 - main lines at busy junction With a standard 52 kg m-1 conductor rail the equivalent copper section is 10.32 sq cm, which gives an electrical resistance / km / rail is 0.001606 ohms. Conductor rails have been traditionally manufactured from steel, this has the advantage of long established mechanisms of manufacturing, installing and maintaining normal processes familiar to the railway operator. The main disadvantage with steel when used as a supply and return conductor is its electrical resistance; the conductivity of the rail is such that it limits the distance between substations due to the voltage drop produced by the load current. Developments have enabled higher conductivity rails, which produce less voltage drop and hence allow an increase in distance between substations. With the introduction of regenerative equipment on board traction vehicles it provides a greater scope for redistribution of energy. A number of railway and metro systems are evaluating or implementing the use of aluminium conductor rails. Conductor resistance values in the range 0.038 ohms down to 0.007 ohms per kilometre are fitted with a stainless steel contact face for the power collector. Conductor rail cross section 273 Continuously Welded Conductor Rail Conductor Rail Materials Two-hole fishplates were used to form the mechanical joint between each rail length, but most conductor rails are now continuously welded lengths with expansion gaps every 500 metres. Where gaps in the conductor rail occur, e.g. expansion gaps, Level Crossings and Junctions, electrical continuity is maintained by jumper cables. Until recently conductor rails have been made of steel due to the costs and strength of the materials. Steel however does not have an exceptionally low resistance when compared with other metals. To improve electrification system performance D.C. composite conductor rails are being used. Aluminium Stainless steel composite conductor rail offers: steel interface for strength and reduced electrical corrosion lower resistance due to the aluminium construction to improve losses in the supply and improve electrical supply performance reduced weight providing ease if installation and maintenance of the permanent way DESIGN OF THIRD ARRANGEMENT RAIL TRACK With the knowledge of the performance of the traction equipment and the scheduled timetable it is possible to determine the current level and hence the specification of the distribution equipment which will deliver the required amount of power to the train. On D.C. electrification systems the conductor rail is a major component in determining the performance of the electrification system, the choice of conductor rail is a vital aspect in the design of each electrification system. Support Insulators Insulators are vital to the success of any third rail system, they appear passive to the onlooker however they are necessary to separate the supply system voltage from the earth. It is also necessary that they operate under severe traction vibration, pollution and impact. For under rail contact system each insulator must be capable of withstanding cantilever stresses. The Geometry of the Conductor Rail The position of the conductor rail is an issue that has to decide at the outset of any electrification system. It must fulfil a number of specific requirements: The conductor rail must provide a position such that it is given the highest performance of uninterrupted contact with the traction vehicle shoe gear. The geometry of the conductor rail should be such that it provides the highest degree of safety for maintenance staff and public, this will normally mean that any new schemes will utilise underneath contact systems. The position of the conductor rail should stay within acceptable tolerances to ensure a good level of current collection, this will take into consideration the following factors take into consideration the movement of the track due to ballast deformation the wear of rolling stock wheel tread and flange wear of the traction vehicle collector shoe mechanism variation in the track geometry wear of the running and conductor rail contact surfaces dynamic behaviour of the traction vehicle suspension system. Expansion Joints The conductor rail will expand and contract due to variation in temperature. The conductor rail is supported at specific points and must therefore be allowed to move freely, with the expansion being taken up by ramp gaps or with special sliding splice joints. It is necessary in both cases to allow smooth passage of the conductor shoe and traction current across the gap. Track Bed Arrangement The track bed arrangement is conventionally concrete sleepers on ballast with insulators supporting the conductor rail secured to the sleepers on the ends for third rail, and additionally in the centre for fourth rail systems. There are a number of lengths of paved concrete layouts this is commonly found in tunnelled metro railway. In surface railway systems concrete layouts is less common. 274 Alignment of the Conductor Rail. The collector shoes need to be carefully guided, including smooth transitions onto and off the rail at various parts of the network switches etc. Often a track layout which appears to give simple train movements for the operating department, may be quite unsuitable for third rail layout and leave large gaps in the current collection as the trains traverse the track work. Such 'gapping' of trains will be very serious for train operation. The question of third rail layouts must be considered at an early stage in the design of the main track work, especially at complicated junctions and depot siding areas. A careful study will ensure that conductor rails are placed so that trains can collect current under all conditions. The geometry of the rail system is dependent on: the position of the switches, the vehicle curving characteristics, radius of curves, maximum/minimum permitted lengths of conductor rails the design of the train and position of shoe gear the position of fixed structures including lineside equipment, station platforms electrical sectioning of electrification systems the need to provide safe clearance for public at level crossing, footpath, animal crossings, access for staff, The positioning of ramps depends on a number of factors: the geometry of the switches the radius of the curves Often the track layout which appears to give simple train movements for the operating department may be quite unsuitable for the conductor rail layout and leave large gaps in the current collection as the train traverses the track-work. This is liable to produce ‘gapping’, and will be serious for train operation. The design of the conductor rail layout must be considered at an early stage in the design of the main track-work, especially at complicated junction sand depot siding areas. Design of Conductor Rail Ramps. Conductor rail ramps are a vital characteristic to ensure that the conductor rail is ramped down adequately in the facing direction. This is to ensure that any approaching shoe is engaged and then guided to the required level of the conductor rail without damage to the collector shoe mechanism, at the same time ensuring good electrical contact. The trailing ramp is designed to return the traction vehicle collector shoe to its designed free height position safely. It is vital that the ramp and the conductor rail is maintained within the specified tolerance if consistent shoe gear engagement is to be maintained. In the design of end ramps it is necessary to take into consideration the following factors: the vehicle curves characteristics the free height of the collector shoe, the choice of the ramp profile will be dependant on the speed restriction of the line, and the dynamic performance of the shoe gear on impact with the conductor rail. Gradients that are typically used vary from 2 to 3% The positioning of the ramps depends on the geometry of the track and the gaps that are necessary to ensure safe operation. Clearances of the Conductor Rail. The clearances of the conductor rail are determined by the system voltage and the policy of the railway operators. Conductor Rail Terminations: The terminations of the conductor rail need to be specified so as to establish standards and ensure that the ends of lines, or gaps required at crossings and point works, are adequate to provide enough electrical clearance necessary to provide under extreme conditions of expansion. It is also a requirement to provide adequate safe electrical and mechanical passage of the traction vehicle shoe at points and crossovers. Conductor Rail Ramping. The collector shoes need to be carefully guided including smooth transitions onto and off the rail at various parts of the network. A careful study will ensure that conductor rails are placed so that trains can collect current under all conditions. PERFORMANCE OF THIRD RAIL CURRENT COLLECTION Experience has shown that there are two major problems in the collection of high direct currents from a 750 V system; a flashover to the running rail or the bogie frame can occur at low speeds when the trailing shoe of a vehicle leaves the conductor rail at a gap. Secondly, the sparking that occurs in icing conditions becomes excessive. Tests have shown that it is undesirable to exceed a value of 2000 amperes per 275 shoe. Hence there is a limit to the power of a vehicle for use on this type of system. The contact force generates friction at the interface and this friction force causes wear. The higher the contact force, the higher the wear. The friction force obviously depends on the coefficient of friction and therefore the materials in contact, and may be improved by providing a lubricant on the power collector in the form of liquid or powder. The current collecting surface must be allowed and encouraged to properly follow undulations in the conductor surface without losing contact, and preferably while maintaining constant force. This means that the contact head and linkage must have the minimum possible inertia and therefore mass. Current Collection Arcing The arcing that is produced at the ramp ends is of concern and must be minimised if the level of maintenance is to be minimised especially that between the conductor rail, shoe gear and traction bogie or track side equipment. An arc is generated between the last shoe to loose contact with the conductor rail due to the inductance of the traction equipment and the supply system. The arc is drawn as the vehicle moves away from the ramp, and then may arc to traction bogie or track side equipment. Arcing is also produced as the traction vehicle destabilises power, due to the dynamic performance ( or lack of) of the collector shoe as it remakes contact with the leading ramp end. The mechanisms that can be used to minimise arcing on making or breaking electrical load are as follows: To ensure that where the traction vehicle do not undergo areas of track where there are gaps in the conductor rail and therefore total loss of power. To ensure that during a loss of line voltage that the control system on the traction vehicle automatically returns the traction load to zero. Provide shielding at points and where clearances are minimised such that the arc is discouraged from arcing to track side equipment. force which will give equal electrical and mechanical wear, and minimum overall wear. In practical systems it is usual to run in a state with a higher proportion of electrical wear than mechanical. Icing Conditions Experimental work on current collection has shown that current sharing between parallel shoes is often poor and not always in accordance with the resistance characteristics of the circuits. Under icing conditions the leading shoe tends to act as a rail cleaner, leaving the succeeding shoes to collect the current. The ice that forms on the rail surface is very difficult to remove other than by chemical means. The remedy to the problem is to apply an oily fluid which adheres to the rail and prevents the ice 'sticking' to the rail, even when it forms. Snow, on the others hand, is no longer a serious problem, since the adoption of radial shoe gear with square fronted shoes which have a ploughing action and remove dry snow from the rail surface before it becomes compacted into ice. Traction Shoe Gear Design The main characteristic of the shoe gear is that it must remain in contact with the conductor rail under all dynamic conditions of the vehicle, and provide a sound electrical path for the supply of the traction power. The shoe gear material must be designed for a number of specific duties: Slide with minimal resistance, Provide minimal electrical resistance under the passage of the traction load current. Shoe gear must be able to operate in such a way as to minimise the dynamic behaviour of the bogie or traction vehicle .Shoe must be designed to provide adequate contact area with the conductor rail. Shoe must be able to assist in the clearance and breaking of ice from the conductor rail head. Electrical Erosion. As current flows between two surfaces there are minute local areas of high current density which cause material to be removed from both surfaces in contact. The contact force will affect the resistance at the interface, and determine how closely the materials are in contact. The higher the contact force, the lower is the current density in the local areas and the lower the electrical wear. Lubricant at the interface will have the effect of raising the resistance and increasing the electrical wear. There is an optimum Shoe gear Damage. The collector shoe must be strong enough to withstand the forces seen in service, for third rail systems the shoe-gear sees impacts with ramps, and the severe vibration levels associated with bogie or axle box-mounted equipment. The shoe arm is designed with a "weak spot" which enables the shoe to break clear of the running gear should it hit an obstruction. Maximum permissible speed with standard shoe gear 144 km hr-1. 276 DC OVERHEAD CONTACT SYSTEMS mounted on the line side masts [open route] or drop tubes [tunnel metro systems]. Figure 31 MTRC Hong Kong 1500V Overhead Line contact System For D.C. systems the cross sectional area of the conductors is determined from the substation spacing, the characteristics of the proposed locomotives and multiple units together with the anticipated train schedule. A variety of arrangements for the overhead conductors are available for the systems detailed below: 750 V city tram/metrolink where the voltage is limited due to the proximity of buildings/public 1500V metro and main line railway systems 3000V main line passenger and freight Single Contact Systems Single contact wire (also known as tramway construction). On D.C. lines, this type of construction was limited to minor sidings. It requires short spans, in the order of 37.5 m and is limited to slow running. Compound Contact Systems A main catenary supporting an auxiliary catenary and one contact wire. Other compound systems that are used but support two contact wires instead of one. The advantage claimed is that improved current collection is obtained with two contact wires. The main and auxiliary catenaries installed were usually stranded cables of hard-drawn copper, to give maximum conductivity for minimum weight of conductor. In sidings, where conductivity of the catenary is not so important, cadmium copper was often used, but in corrosion free area galvanised steel stranded wire has been used. Traction Power Auxiliary Feeds The level of traction power of a typical 1500V DC traction substation is 3 MW [usually double banked]. A traction load of 3MW the total line current [typically] 1000A per traction unit. Typically a track section will have two trains in section with total of 2000A per substation. To provide this level of line current it is necessary to provide parallel feeds to the overhead line. This is provided by parallel conductors 277 Bibliography British and European Regulations: 5. 6. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. The Railways Act 2005 EMC Regulations 2005 Requirements for Electrical Installations (BS 7671) Railway Safety Principles and Guidance – Part 2 Secti on B: Guidance on Stations Construction (Design and Management) Regulations 2007. Construction (Health, Safety and Welfare) Regulations 1996. Management of Health and Safety at Work Regulations 1999. Railways (Safety Critical Work) Regulations 1994 Railways (Safety Case) Regulations 1994 Control Of Substances Hazardous to Health (COSHH). Transport and Works Act, 1992 Electricity at Work Regulations 1989. Health and Safety at Work Act 1974. SRA Code of Practice – Train and Station Services for Disabled Passengers Dr R J Hill Power Electric Railway Traction Part 1-7 Traction Systems, Power Engineering Journal 1997. Seminar D.C. Traction Stray Current Control 21.10.99, IEE Railway Industry Group. IEE and IRSE Conference and Proceedings 1. 2. 3. 4. IRSE ASPECT 2003; Signs of the Times for Train Control; London. IRSE ASPECT 2006; Quality of service through Signalling And Communication; London. IEE Residential Railway Electrification Infrastructure School, 2005; ISBN 0-86341-511-3. Systems’ IRSE Seminar Railway Interfaces; IEE Savoy 18 November 2006. IEE and IRSE Conference Papers 1. White R. D. 2005, ‘Induced Longitudinal Voltage and screening of lineside Cables’; IEE International Conference on Railway Engineering Development into the 21st Century, Miramar Hotel Hong Kong. White R.D. 2006 November Atkins Rail ‘Electrification Interfaces and Electromagnetic Compatibility with Railway Control Systems’ IRSE Seminar Railway Interfaces; IEE Savoy White R.D., Zhang Z., Cox J., Armstrong D, Price S, Sept 2003 ‘Induced Longitudinal Voltage into Lineside Cables for WCRM’ IRSE ASPECT Signs of the Times for Train Control; London. Lilley M ‘Signalling systems compatibility at radio frequencies’ IEE 6th Residential Course on Electric Traction System, Wrightsons. Chapter D4. ISB 0-86341-452-4. Hewitt M 2005, ‘Impact of Electrification systems on signalling’ The IEE Second Residential Course on REIS Wrightsons. Chapter D4. ISBN 0 – 86341 –511 – 3. T Loades, 2005 ‘Practical considerations of EMC compatibility on Railtrack WCRM’ The IEE Second Residential Course on REIS Wrightsons. Chapter D4. ISBN 0 – 86341 –511 – 3. D Bradley 2005 ‘Compatibility between railway electrical systems’ IEE Residential Railway Electrification Infrastructure School, , ISBN 086341-511-3. White R.D. ‘GTO and IGBT three phase traction inverter drives’; IEE ‘Power Electronics and Variable Speed Drives’ 7th International Conference 1998. White R.D. ‘Fault Currents on AC Electrified Railways, Rail Potentials and Interference with Track Circuits; IRSE YM Conference 2000 July 00; ISBN 1356-1448. 2. Bibliography: Books Publications 3. 1. White R. D, Chapter O5, 2000, Railway Electrification, Kemps Engineering Handbook Miller Freeman pp 2473 -2489, ISBN 086382 442 0. Williams T Armstrong 2000, ‘EMC for Systems and Installations’ , Newnes ISBN 0-7506-4167-3. Technical Specification for Interoperability relating to energy subsystems of the Trans European high speed rail system. 2002; Office of the Journal of the European Union. Marshman C; ‘Guide to the EMC Directive’; EPA Press; ISBN 0-9517362-7-2. 4. 2. 3. 5. 4. 6. Journal Publications 7. 1. Dr R J Hill Feb 1997 IEE Power Engineering Journal Part 6 Electromagnetic Compatibility Sources and Equipment. Dr R J Hill Electric Railway Traction Part 7 Electromagnetic interference in traction systems Power Engineering Journal Dec 97; Vol 11; No 6. Carson JR ‘Wave Propagation in Overhead wires with ground return’. 1926 Bell System Technical Journal 5 p539-554. Mellitt B ‘Simulation shows how choppers can save energy’ Railway Gazette International 135(4) p300-304 1997’. 2. 8. 3. 9. 4. 278 10. White R.D. ‘Power Supply Design Issues for 25kV AC Electrification Systems’ Conference on Traction Power Supplies IMechE Headquarters, London 22nd January 2006. 11. R D White WS Atkins Rail 1999, , 'Modelling for EMC Studies on High Performance Railway Systems'. AIC Electrification and Power Supply Conference London March 99. 12. Chew TC ‘Chopper Control Equipment for Singapore MRT ’ Electric Railway System for a new Century London 1987 pp6-12, ISBN 085296351-3. 13. Mellitt B, Johnston W.B., Allan J, Shao Z Y, Denley M 1989, ‘Whole System Compatibility measurement on 50 kV New Zealand Railway’, International Conference on Main Line Electrification York pp 246-251, ISBN 85296384. X. IEE Conference on 'Main Electrification' Publication 312: Line Railway Other DC Electrification Publications 1. R. J. Kemp, R. W. Sturland GEC ALSTHOM publication 'Integrated Design of D.C. railway systems'. Influence of Commutating Reactance on the Design of D.C. Power Supply Converters, L. L. Denning GEC ALSTHOM Publication. Protective Relays For Rail Transport System GEC ALSTHOM Protection and Control. J.G.Yu “The Effect of earthing strategies on rail potential and stray currents in DC transit railways” CEGELEC Projects Ltd UK. “Stray Current Design Parameters for D.C. Railways” Proc of the ASME/IEEE Joint Railroad Conference pp 19-28 1992;. J G Yu and C J Goodman “Computer Analysis of touch and step voltages for D.C. Railways”., Proc. of the third International Conference on Computer Aided Design, Manufacture and Operation in the Railway and other Advanced Mass Transit System Washington 1992. 2. 3. 4. 5. 6. IEE Conference on 'Electric Railway Systems for a New Century'. Publication 279: 1. Y.Yoshiki, T.Jinzenji, T. Kodor, H.Inokuchi "Static Power Supply for D.C. 1500 V Transit System" IEE Conference on 'Main Line Railway Electrification' Publication 312. J Bouley "Electrification: why not?" IEE Conference on 'Electric Railway Systems for a New Century' Publication 279. Professor S Sone; University of Tokyo, Japan S Ishizu; Japanese Railways, Tokyo, Japan The International Union of Railways, France "Reassessment of power feeding systems at introducing regenerative trains". "Contribution to energy saving in D.C. railways", R Filliatre IEE Conference on 'Electric Railway Systems for a New Century' Publication 279. P O Barnwell, Professor B Mellitt and Dr C J Goodman W B Johnston "Assessment of voltage controlled substations for D.C. traction applications" IEE Conference on 'Electric Railway Systems for a New Century' Publication 279. H Puntis, P Strubin "Determination of protection requirements for D.C. traction systems and the development of a solid state protection relay to optimise current availability" IEE Conference on 'Electric Railway Systems for a New Century'. Publication 279. J E Buttery, D N Ebenezer and B P McCormick "Electromechanical and electronic falling voltage track impedance devices for fault detection on D.C. track systems", IEE Conference on 'Electric Railway Systems for a New Century' Publication 279. 2. 3. 4. 5. 6. 7. 279 British Standards BS EN 501231:1996 BS EN 501231:2003 BS EN 501232:1996 BS EN 501232:2003 BS EN 501233:1996 Railway applications. Fixed installations. D.C. switchgear. General Railway applications. Fixed installations. D.C. switchgear. General Railway applications. Fixed installations. d.c. switchgear. d.c. circuit breakers Railway applications. Fixed installations. D.C. switchgear. D.C. circuit breakers Railway applications. Fixed installations. d.c. switchgear. Indoor d.c. disconnectors and switch-disconnectors Railway applications. Fixed installations. D.C. switchgear. Indoor d.c. disconnectors, switchdisconnectors and earthing switches Railway applications. Fixed installations. d.c. switchgear. Outdoor d.c. in-line switchdisconnectors, disconnectors and d.c. earthing switches Railway applications. Fixed installations. D.C. switchgear. Outdoor d.c. disconnectors, switch-disconnectors and earthing switches Railway applications. Fixed installations. d.c. switchgear. Surge arresters and low-voltage limiters for specific use in d.c. systems Railway applications. Fixed installations. D.C. switchgear. Surge arresters and low-voltage limiters for specific use in d.c. systems Railway applications. Fixed installations. D.C. switchgear. D.C. switchgear assemblies Railway applications. Fixed installations. D.C. switchgear. D.C. switchgear assemblies Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Measurement, control and protection devices for specific use in d.c. traction systems. Application guide Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating current transducers and current measuring devices. Isolating current transducers and other BS EN 50123-72:2003 BS EN 50123-73:1999 BS EN 501233:2003 BS EN 50123-73:2003 BS EN 501234:1999 BS EN 501231:1996 BS EN 501231:2003 BS EN 501232:1996 BS EN 501232:2003 BS EN 501233:1996 BS EN 501234:2003 BS EN 501235:1999 BS EN 501235:2003 BS EN 501233:2003 BS EN 501236:1999 BS EN 501236:2003 BS EN 50123-71:2003 BS EN 501234:1999 BS EN 501234:2003 BS EN 501235:1999 BS EN 50123-72:1999 BS EN 501235:2003 BS EN 50123- current measuring devices Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating current transducers and other current measuring devices Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating voltage transducers and other voltage measuring devices. Isolating voltage transducers and other voltage measuring devices Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating voltage transducers and other voltage measuring devices Railway applications. Fixed installations. D.C. switchgear. General Railway applications. Fixed installations. D.C. switchgear. General Railway applications. Fixed installations. d.c. switchgear. d.c. circuit breakers Railway applications. Fixed installations. D.C. switchgear. D.C. circuit breakers Railway applications. Fixed installations. d.c. switchgear. Indoor d.c. disconnectors and switch-disconnectors Railway applications. Fixed installations. D.C. switchgear. Indoor d.c. disconnectors, switchdisconnectors and earthing switches Railway applications. Fixed installations. d.c. switchgear. Outdoor d.c. in-line switchdisconnectors, disconnectors and d.c. earthing switches Railway applications. Fixed installations. D.C. switchgear. Outdoor d.c. disconnectors, switch-disconnectors and earthing switches Railway applications. Fixed installations. d.c. switchgear. Surge arresters and low-voltage limiters for specific use in d.c. systems Railway applications. Fixed installations. D.C. switchgear. Surge arresters and low-voltage limiters for specific use in d.c. systems Railway applications. Fixed 280 6:1999 BS EN 501236:2003 BS EN 50123-71:2003 BS EN 50123-72:1999 BS EN 50123-72:2003 BS EN 50123-73:1999 BS EN 50123-73:2003 BS EN 501231:1996 BS EN 501231:2003 BS EN 501232:1996 BS EN 501232:2003 BS EN 501233:1996 BS EN 501233:2003 installations. D.C. switchgear. D.C. switchgear assemblies Railway applications. Fixed installations. D.C. switchgear. D.C. switchgear assemblies Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Measurement, control and protection devices for specific use in d.c. traction systems. Application guide Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating current transducers and current measuring devices. Isolating current transducers and other current measuring devices Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating current transducers and other current measuring devices Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating voltage transducers and other voltage measuring devices. Isolating voltage transducers and other voltage measuring devices Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating voltage transducers and other voltage measuring devices Railway applications. Fixed installations. D.C. switchgear. General Railway applications. Fixed installations. D.C. switchgear. General Railway applications. Fixed installations. d.c. switchgear. d.c. circuit breakers Railway applications. Fixed installations. D.C. switchgear. D.C. circuit breakers Railway applications. Fixed installations. d.c. switchgear. Indoor d.c. disconnectors and switch-disconnectors Railway applications. Fixed installations. D.C. switchgear. Indoor d.c. disconnectors, switchdisconnectors and earthing BS EN 501234:1999 BS EN 501234:2003 BS EN 501235:1999 BS EN 501235:2003 BS EN 501236:1999 BS EN 501236:2003 BS EN 50123-71:2003 BS EN 50123-72:1999 BS EN 50123-72:2003 BS EN 50123-73:1999 switches Railway applications. Fixed installations. d.c. switchgear. Outdoor d.c. in-line switchdisconnectors, disconnectors and d.c. earthing switches Railway applications. Fixed installations. D.C. switchgear. Outdoor d.c. disconnectors, switch-disconnectors and earthing switches Railway applications. Fixed installations. d.c. switchgear. Surge arresters and low-voltage limiters for specific use in d.c. systems Railway applications. Fixed installations. D.C. switchgear. Surge arresters and low-voltage limiters for specific use in d.c. systems Railway applications. Fixed installations. D.C. switchgear. D.C. switchgear assemblies Railway applications. Fixed installations. D.C. switchgear. D.C. switchgear assemblies Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Measurement, control and protection devices for specific use in d.c. traction systems. Application guide Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating current transducers and current measuring devices. Isolating current transducers and other current measuring devices Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating current transducers and other current measuring devices Railway applications. Fixed installations. d.c. switchgear. Measurement, control and protection devices for specific use in d.c. traction systems. Isolating voltage transducers and other voltage measuring devices. Isolating voltage transducers and other voltage measuring devices IEE ETS Supply AC & DC 2010 281
Report "Stray current traction return current.pdf"