EP2183126A1

EP2183126A1 - Construction element for supllying electrical power to a rail vehicle and electrical power supply system comprising such a construction element

Info

Publication number: EP2183126A1
Application number: EP08779004A
Authority: EP
Inventors: Bastiaan Gravendeel; Frank Van Overbeeke
Original assignee: Em Power Systems BV
Current assignee: Em Power Systems BV
Priority date: 2007-07-25
Filing date: 2008-07-22
Publication date: 2010-05-12
Also published as: NL1034189C2; WO2009014426A1

Abstract

A construction element (2) for supplying electrical power to a rail vehicle comprises an elongate profiled section (4) which is provided with a supply conductor (7) which is to be fitted parallel to the profiled section. The construction element furthermore has a compensating conductor (8) which is electrically insulated with respect to the supply conductor and extends parallel to the profiled section. The supply conductor and the compensating conductor are designed to carry oppositely directed currents. The profiled section is a hollow profiled section, the compensating conductor (8) being arranged in a hollow space of the profiled section (4).

Description

CONSTRUCTION ELEMENT FOR SUPPLYING ELECTRICAL POWER TO A RAIL VEHICLE AND ELECTRICAL POWER SUPPLY SYSTEM COMPRISING SUCH A CONSTRUCTION ELEMENT

The present invention relates to a construction element for supplying electrical power to a rail vehicle. The present invention furthermore relates to an electrical power supply system comprising such a construction element, and to a coupling element for use in an electrical power supply system of this type.

In the prior art, the use of a supply conductor for supplying power to electrical vehicles which move on rails (trains, trams, underground trains, and the like) in the form of an electrical overhead wire or a third rail is generally known. The vehicle is, on the one hand via the overhead wire or third rail and on the other hand via the rails, connected to a power supply, such as one or more power supply stations. Such supply conductors usually carry a high direct voltage or alternating voltage, applied from the power supply station, compared to the associated rails which are kept at or near earth potential for safety reasons. If an electrically driven vehicle moves over the rails, electrical power is drawn from the power supply via the supply conductor, via one or more current collectors which are located on the vehicle, in which case the circuit to the power supply closes via the rails. The supply conductor is connected to a power supply station at certain regular intervals, for example at the location of a gantry (in the case of an overhead wire) or another supporting structure (in the case of a third rail) by means of which the overhead wire or third rail is arranged near the rails. The rails are also connected to a power supply station at certain regular intervals. The location where the supply conductor is connected to a power supply station and the location where the rails are connected to a power supply station do not have to be one and the same, viewed along the rails.

The known systems have two conductors for supplying power which have to be at a certain distance apart due to their potential difference. This distance depends inter alia on the insulating value of the intermediate medium and the magnitude of the potential difference, taking into consideration any voltage peaks which may, for example, occur in the case of lightning voltages.

Both in the case of direct current power and in the case of alternating current power, the voltage comprises varying components. In the former case, a direct voltage for electrical traction is usually generated by rectifying an alternating voltage, with a ripple remaining on the rectified alternating voltage.

Each current-carrying wire is surrounded by an (electro)magnetic field which behaves according to the laws of Maxwell with regard to properties and magnitude. In a conventional arrangement of the power supply conductor and rails in air, the magnitude of the field is directly proportional to the magnitude of the current through the wire (in the case of electrical traction, the wire is formed by the supply conductor and the rails). The field which is thus generated is not utilized when driving the vehicle, but can have a disruptive effect on equipment in the vicinity of the railway.

The degree of the electromagnetic effect which the magnetic field of a railway exerts on an object depends on the distance between the electrical conductors (supply conductor and rails) and the object, and furthermore depends on the distance between the electrical conductors. If the distance between an outward current from a power supply station to a rail vehicle and a return current from the rail vehicle to the power supply station becomes smaller, the magnetic field at a certain distance from the railway also becomes smaller: the fields of the outward and return currents compensate one another better as the distance between the conductors becomes smaller. However, in the prior art, the conductors cannot be arranged very close to one another for practical reasons.

It is an object of the invention to provide measures by means of which the generation of a disruptive magnetic field by an electrical power supply system for a rail vehicle can be prevented to a high degree.

To this end, the invention in one embodiment provides a construction element for supplying electrical power to a rail vehicle. The construction element comprises an elongate profiled section and a supply conductor which is attached to the profiled section and extends parallel to the profiled section. The construction element furthermore comprises a compensating conductor which is electrically insulated with respect to the supply conductor, is mechanically connected to the profiled section and extends parallel to the profiled section. The supply conductor and the compensating conductor are designed to carry oppositely directed currents. The construction element, the profiled section of which may have a substantially O- shaped, l-shaped, U-shaped or H-shaped cross section, makes it possible to minimize a magnetic field which is generated by an electrical power supply system of which the construction element forms part, as a result of which the disruptive influence thereof is reduced or rendered negligibly small. The supply conductor and the compensating conductor may be arranged at a very small distance from one another. In one embodiment of the invention, the profiled section is a hollow profiled section and the compensating conductor is arranged in a hollow space of the profiled section. This makes it possible to provide a very high degree of compensation for an effect which disrupts the environment around a magnetic field which is generated by the supply conductor.

A further embodiment of the invention provides an electrical power supply system for a rail vehicle, comprising a construction element according to the invention and a rail. The supply conductor of the construction element and the rail are each connected to a power supply station, with the compensating conductor of the construction element being connected to the rail.

In a further embodiment of the invention, a coupling piece is provided for the electrical power supply system according to the invention. This coupling piece is designed to be mechanically coupled to the construction element and comprises a first conductor which is designed to be coupled electrically to the supply conductor and/or comprises a second conductor which is designed to be coupled electrically to the compensating conductor.

The invention will be explained below in more detail with reference to a non-limiting example of an embodiment, as illustrated in the attached figures, in which:

Fig. 1 shows a cross section of an embodiment of a construction element according to the present invention; Fig. 2 shows a cross section of another embodiment of a construction element according to the present invention;

Fig. 2a shows a cross section of an embodiment of a coupling piece according to the present invention;

Fig. 3 shows a diagram of a representation of a network of an electrical power supply system for a rail vehicle;

Fig. 4 shows a diagram of a representation of a network of an electrical power supply system in an embodiment of the present invention;

Fig. 5 shows a diagram of a representation of a network of an electrical power supply system in a subsequent embodiment of the present invention; Fig. 6 shows a diagram of a representation of a network of an electrical power supply system in another embodiment of the present invention; and Fig. 7 shows a diagram of a representation of a network of a component of the electrical power supply system from Fig. 4, 5 or 6.

In the various figures, the same reference symbols refer to identical or similar components or components having the same or a similar function.

Fig. 1 shows a construction element 2 having an elongate sleeve-shaped profiled section 4 which is known per se from NL1027142. On a side which in use is to be directed down (underside), the profiled section 4 is provided with a longitudinal gap 6, into which a supply conductor or contact wire 7 (indicated by a dotted line) for current takeoff by a current collector of a rail vehicle can be fitted. Such a profiled section 4 is used in locations where the height is limited, such as in tunnels, or where this is deemed necessary for other technical or for aesthetic reasons.

The profiled section 4 comprises a duct or hollow space for accommodating a conductor 8 (compensating conductor) which is insulated with respect to the contact wire 7. In the case illustrated in Fig. 1 , the conductor 8 is formed by a cable 10 which is provided with an insulating sheath 12. The conductor 8 may either be flexible, such as the cable 10, or stiff, for example be in the shape of a metal rod. The conductor 8 may be provided with an insulating sheath along its length, or be supported with respect to the profiled section 4 by means of insulating spacers (not shown) at discrete locations. The conductor 8 may have a length which substantially corresponds to the length of the profiled section 4 or may have a greater length.

Fig. 1 furthermore diagrammatically shows an electrical lead-through 14 by means of which an electrical contact with the conductor 8 can be established which is accessible from outside the profiled section 4. If the profiled section is made of metal, the lead-through comprises a conductive core, surrounded by insulating material. The insulating material may be omitted if the profiled section is made of an insulating material. The lead-through 14 may be arranged at any desired location along the length of the construction element. In one embodiment, lead-throughs 14 are provided both at a first end of the construction element and at a second, opposite end of the construction element, which are respectively connected to the ends of the conductor 8 which are situated opposite one another. Conductors 8 of various series-connected construction elements can be connected to one another via the lead-throughs 14 of the various construction elements, but a conductor 8 or an end of a conductor 8 can also be connected to another conductive element, such as a rail. Alternatively, an electrical connection with a conductor 8 or between conductors 8 of adjacent construction elements 2 can be established by means of a coupling piece 20 which is shown in Fig. 2a and is designed to be mechanically coupled to a construction element 2 and comprises a coupling device 22 which is designed to couple electrical conductors to one another. In the embodiment illustrated in Fig. 2a, a coupling piece 20 having a profiled section 4a of a short length comprises a coupling device 22 which comprises electrically conductive clamping blocks 24 which can clamp cables 10 of adjacent construction elements 2 together by means of bolts 26 and nuts 28 in order to establish an electrical connection between conductors 8.

As Fig. 2 shows, the profiled section 4 may be provided with openings 16, provided, for example, along the length of the profiled section in walls thereof, in order to improve the removal of heat generated in the conductor 8 by means of the circulation of air, if the conductor 8 carries current.

The profiled section may also have a cross section which differs from the substantially O- shaped cross section illustrated, such as an l-shaped, a U-shaped or an H-shaped cross section, or any other suitable cross section which allows the profiled section and the conductor to be connected to one another mechanically and a contact wire 7 or another conductor suitable for this purpose to be attached.

In use, a contact wire 7 arranged in the gap 6 carries a current originating from a power supply for supplying power to a rail vehicle which moves along the contact wire, with the conductor carrying a return current which is essentially of equal magnitude but directed in the opposite direction to the power supply. As a result of such an arrangement, in which two oppositely directed, essentially equal currents flow at a very close distance to one another, a magnetic disturbance of the surroundings by the currents is eliminated to a large degree.

Fig. 3 shows a representation of a network of a conventional electrical power supply system 30 for a rail vehicle. From a power supply station OS, a current I is supplied to a rail vehicle RV via an overhead wire 32. Via one or more rails 34, the current returns to the power supply station OS. The distributed electrical resistance of the overhead wire is shown in concentrated form in the form of resistance R_B, while the distributed electrical resistance of the rail/rails is shown in concentrated form in the form of resistance R_s. The current circuit from power supply station OS via overhead wire 32, rail vehicle RV, rail/rails 34, back to power supply station OS forms a loop covering a relatively large surface area resulting in a magnetic field, in particular due to the currents flowing through the overhead wire 32 and the rail/rails 34. The magnetic field can be disruptive for the environment of the power supply system.

Fig. 4 illustrates how the magnetic field which is generated by the supply current circuit of the rail vehicle RV can be essentially compensated by a passive form of compensation when the construction elements 2 according to the invention are used. In an embodiment, a compensating conductor 36 of the construction element is to this end connected to the rail 34 below the latter at predetermined locations which are a distance apart. Between these locations, compensating conductors 36 of adjacent construction elements can be electrically connected in series, for example by means of the abovementioned lead-throughs 14 (Fig. 1) on the construction elements or by means of coupling pieces 20 (Fig. 2a) between the construction elements. Thus, current paths are created which run electrically parallel to the rails. If the conductors of the construction elements have a lower electrical resistance than the rails, a significant portion of the current I will not flow through the rails, but through the conductors of the construction elements. Thus, the magnetic fields which are generated by the currents in the overhead wire 32 and the conductor 36 compensate one another to a high degree, so that a magnetic disturbance of the surroundings of the railway by the supply current circuit of the rail vehicle RV is minimized.

Fig. 5 illustrates how the magnetic field which is generated by the supply current circuit of the rail vehicle RV can be substantially compensated through an active form of compensation. In one embodiment, a current I' is to this end passed through a compensation loop 40 by means of a power source 42, which current I¹ is equal, but directed opposite to, the current 1. The compensation loop 40 may comprise one or more windings and may comprise the rail 34. In the case of several windings, the current per winding is equal to the current I' divided by the number of windings.

The current I' is generated by means of a controllable power source. Control is based on an input signal which can be obtained in various ways.

As is illustrated in Fig. 6, a first input signal can be obtained by measuring a voltage across a length of a rail 34, with the length being substantially equal to the length (viewed in the longitudinal direction of the rail 34) of the compensation loop. Taking into account the resistance R_s, the voltage across the rail 34 is a direct measure for the current I + I' which flows through the rail 34. According to Fig. 6, the compensation loop extends between two overhead wire gantries B (which do not necessarily follow one another on the railway track) and the potential of the rail is measured at the location of the overhead wire gantries B. The rail 34 forms part of the compensation loop. A voltage difference is determined from the potential measurements at the location of the overhead wire gantries B and supplied to a control circuit for the power source 42 illustrated in Fig. 5 and accommodated in a control cabinet RK.

Fig. 7 shows some basic components of a control circuit 60 for the power source 42. In a first comparator 44, a voltage U1 measured at the location of a first measuring point is compared to a voltage U2 at the location of a second measuring point, which is at a distance from the first measuring point. In a second comparator 46, the difference voltage U1-U2 which is emitted at the output of the comparator 44 is compared to a zero potential, with the difference between the difference voltage and the zero potential which is emitted at the output of the second comparator 26 being used in a manner which is not shown in any more detail for controlling the power source 42 in such a manner that the difference voltage U1-U2 becomes zero.

The part 50 of the compensation loop illustrated in Fig. 6 can be formed by the conductor 8 shown in Figs. 1 and 2 of one or more construction elements 2 in series.

Rather than using the measurement of a voltage difference across the rail 34, as explained above, the power source 42 can also be controlled based on the measurement of a magnetic field (using a suitable magnetic field sensor) at a distance from the compensation loop, if desired at a specific location where magnetic disturbance fields have to be compensated. The current provided by the power source 42 is set such that the magnetic field at the location of the magnetic field sensor becomes essentially zero.

Due to the presence of a rail vehicle RV which forms a path for (a part of) the current from the supply conductor to the rails or vice versa, the current to be compensated is not of equal magnitude at every location along a section of the railway line. Therefore, the respective section of the railway line can be divided into successive portions, each having its own compensation loop. For practical reasons, the ascending and descending part of the compensation loop are arranged at the overhead wire gantries, which are already present, but this is not essential. If the space between the power supply and the rail vehicle comprises several compensation loops, each loop will carry (substantially the same) current separately. The magnetic fields of the ascending and descending portions of the successive compensation loops are of equal magnitude and opposite to one another. Together, they therefore do not contribute to the magnetic field outside the power supply system.

In practice, the magnetic field to be compensated does not have to be proportional to the traction current. This may be caused by the fact that, for example, the vehicle itself causes a certain degree of magnetization or by the fact that magnetic structures are situated in the vicinity of the train which influence the magnetic field. In that case, the magnitude of the current through the compensation loop has to be adjusted to the local situation.

In practical embodiments, the loop has a small electrical resistance, as a result of which the voltage drop across the loop is limited and not as large as the potential difference between the supply conductor and the rails.

The practical embodiment of the compensation loop can be produced in various ways. The compensation loop may, for example, be brought substantially to supply conductor potential. In this case, the conductor which compensates the magnetic field, which is generated by the current through the rails, has to be electrically insulated well with respect to the rails. It is also possible to bring the compensation loop essentially to rail potential. In that case, attention should be paid to the insulation of the compensation loop with respect to the supply conductor.

It should be understood that the embodiments described are only examples of the invention, which may be embodied in various embodiments. Therefore, the specific structural and functional details which have been disclosed herein should not be regarded as being limiting, but only as forming a basis for the claims and as a representative basis to provide sufficient information to the person skilled in the art to be able to perform the invention. The terms and phrases which have been used in the present application are not intended to be limiting, but only to provide a clear description of the invention.

The terms "a" and "an", as used in this application, are defined as one or more than one. The term "number", as used in this application, is defined as two or more than two. The term "another", as used in this application, is defined as at least a second or more. The term "comprising" and/or "having", as used in this application, does not exclude other components which have not been mentioned (that is to say is non-limiting).

Claims

C L A I M S

1. Construction element (2) for supplying electrical power to a rail vehicle, comprising an elongate profiled section (4), a supply conductor (7) which is attached to the profiled section and extends parallel to the profiled section, and a compensating conductor

(8) which is electrically insulated with respect to the supply conductor, is mechanically connected to the profiled section and extends parallel to the profiled section, the supply conductor and the compensating conductor being designed to carry oppositely directed currents.

2. Construction element according to claim 1 , wherein the profiled section has a substantially O-shaped, l-shaped, U-shaped or H-shaped cross section.

3. Construction element according to claim 1 or 2, wherein the profiled section is a hollow profiled section and the compensating conductor (8) is arranged in a hollow space of the profiled section (4).

4. Construction element according to claim 3, further comprising at least one electrical lead-through (14) arranged in a wall of the profiled section (4) and connected to the compensating conductor (8).

5. Construction element according to any of the preceding claims, wherein the compensating conductor (8) comprises an insulated cable.

6. Construction element according to any of the preceding claims, wherein the profiled section (4) is perforated.

7. Construction element according to any of the preceding claims, wherein the profiled section (4) is made of plastic.

8. Construction element according to any of claims 1-6, wherein the profiled section (4) is made of metal.

9. Electrical power supply system for a rail vehicle, comprising a construction element (2) according to any of the preceding claims and a rail, a supply conductor (7) of the construction element and the rail each being electrically connected to a power supply station, and the compensating conductor (8) of the construction element being connected to the rail (34).

10. Electrical power supply system according to claim 9, wherein the compensating conductor (8) is connected to the rail (34) by a first end thereof at a first location, and wherein the compensating conductor is connected to the rail by a second end thereof at a second location, with the interposition of a controllable power source (42), the first location being situated at a distance from the second location.

11. Electrical power supply system according to claim 10, wherein the power source (42) is controlled by a control circuit (60) which is configured to measure a voltage difference between the first location and the second location, and to control the current of the power source on the basis of said voltage difference in order to minimize said voltage difference.

12. Electrical power supply system according to claim 10, wherein the power source is controlled by a control circuit which is configured to measure a magnetic field near the power supply system, and to control the current of the power source on the basis of said magnetic field in order to minimize said magnetic field.

13. Electrical power supply system according to any of claims 9-12, further comprising a coupling piece which is designed to be mechanically coupled to the construction element and comprises a first conductor which is designed to be coupled electrically to the supply conductor and/or comprises a second conductor which is designed to be coupled electrically to the compensating conductor.

14. Coupling piece for the electrical power supply system according to any of claims 9- 12, wherein the coupling piece is designed to be mechanically coupled to the construction element and comprises a first conductor which is designed to be coupled electrically to the supply conductor and/or comprises a second conductor which is designed to be coupled electrically to the compensating conductor.