EP3772132B1 - Arrangement for high-frequency potential compensation - Google Patents

Description

From the document WO 2011/039002 A1 a rail vehicle with at least one vehicle antenna of a train protection system directed towards the track is known.

The document US 5,351,018 A discloses a television receiver having a coaxial cable connected to a radio frequency signal source. Interference signals are discharged to ground potential via at least one suction or series resonant circuit connected to the outer shielding conductor of the coaxial cable.

The disclosure document EP 0 778 683 A2 discloses telecommunications equipment with human-machine interface.

The invention is based on the object of specifying an arrangement for a rail vehicle which helps to minimize or at least reduce the negative effects of interference currents on data transmission.

This object is achieved according to the invention by a rail vehicle with an arrangement according to patent claim 1. Advantageous refinements of the arrangement according to the invention are specified in the dependent claims.

An essential advantage of the potential equalization provided according to the invention is that this data transmission taking place via the antenna protects against the influence of interfering external currents.

The absorption or series resonant circuit is preferably low-impedance for the carrier frequency used by the antenna or at least also for the carrier frequency used by the antenna. The absorption circuit or series resonant circuit preferably has low impedance in a range between 3.9505 MHz and 4.5165 MHz in order to achieve a sufficient bandwidth of the absorption circuit characteristic for ETCS-compatible FSK signal transmission. It is particularly advantageous if a further suction or series resonant circuit is arranged between a wheel set arranged in the bogie and the car body.

In addition, it can advantageously be provided that a further absorption circuit or series resonant circuit is arranged between the outer conductor of the antenna cable and the antenna shielding plate and/or the electronic assembly or its housing.

The absorption or series resonant circuit preferably has at least one series circuit made up of an inductance of an electrical conductor and a capacitance.

The absorption or series resonant circuit preferably also has a resistor which is connected in series with the inductance and the capacitance.

The at least one vehicle antenna is preferably a vehicle antenna of the European train control system ETCS. The rail vehicle is preferably designed as an electric multiple unit or as a locomotive.

The absorption or series resonant circuit is preferably low-impedance for the carrier frequency used by the antenna or at least also for the carrier frequency used by the antenna. The absorption or series resonant circuit is preferably low-impedance in a range between 3.9505 MHz and 4.5165 MHz in order to achieve a sufficient bandwidth of the absorption circuit characteristic for ETCS-compatible FSK signal transmission.

The invention is explained in more detail below with reference to drawings and exemplary embodiments.

The European train control system ETCS (European Train Control System) uses, among other things, antennas for the exchange of information between rail vehicles and the route or infrastructure, which are mounted under the floor on the vehicle. The vehicle antenna sends electromagnetic energy into the track bed at high frequency (27 MHz), thereby energizing an antenna installed in the track bed (also referred to as a balise or Eurobalise), which is thereby activated. The energized balise modulates its information onto a high-frequency carrier (4.2 MHz) (FSK modulation) and sends information to the vehicle antenna. Information can be transmitted up to a rail vehicle speed of 500 km/h with a data transmission rate of 565 kbit/s.

For shielding reasons, the vehicle antenna itself preferably has a metal plate on the side facing the underbody of the vehicle, which is intended to prevent interference from the antenna generated by the vehicle (=from above). In order to prevent this shielding plate from acting as a receiving antenna for interference fields that are present in the vicinity of the antenna, it must be connected to the car body with low impedance (low-impedance equipotential bonding). In the ideal case, this takes place via a direct, extensive, electrically conductive contact between this plate and the car body, for example by means of bare metal screwing surfaces.

Furthermore, the outer conductor of the usually coaxial connecting line between the antenna and the connected electronic system is usually electrically connected on both sides to the car body or, if the antenna is installed in the bogie, to the bogie frame. A low-impedance equipotential bonding is also required to avoid interference.

However, such a low-impedance equipotential bonding is often not achieved for high frequencies, particularly in the range of the carrier frequencies of the ETCS, for various reasons. Electromagnetic transient currents, such as those generated by sparking, for example, caused by main switch switching operations, jumpers, driving through separation points, etc., can therefore cause disadvantageous faults in the ETCS system due to equipotential bonding that is not sufficiently low-impedance for high frequencies.

Two problems were identified, with a first problem relating to the low-impedance equipotential bonding of the antenna shielding plate.

If the antenna is installed in the bogie, a large-area, electrically conductive connection between the antenna and the car body is not possible, since the necessary flexible equipotential bonding between the bogie and the car body is usually implemented using electrically conductive round cables or flat strips.

However, these equipotential bonding conductors have the disadvantage that they have a non-negligible impedance in the MHz frequency range because of the complex, predominantly inductive resistance that increases with the frequency. The inductive resistance of a 0.5 m long potential equalization conductor has a value of approximately 13 ohms at the ETCS reception frequency of 4.2 MHz (assuming an assumed inductance per unit length of approximately 1 µH/m of the potential equalization conductor).

Since the antenna 10 - as an example FIG 1 shows - is usually not mounted directly on the bogie frame 21 of a bogie 20, but on antenna supports or add-on parts, the impedances add up from the antenna 10 via add-on parts to the bogie frame 21 up to the car body 30. FIG 1 shows a related example for a potential equalization from the antenna 10 to the car body 30 of the rail vehicle 40. Components A and B are mechanical Constructions, such as consoles or antenna mounts made of electrically conductive material. In order to establish potential equalization, either bare metallic contact surfaces are required, or potential equalization conductors which electrically connect the individual components to one another are used. In the latter case, the potential equalization takes place via a chain of potential equalization conductors with the total inductance L1+L2+L3+L4, plus a relatively small inductance of the mechanical components themselves. Even if all contact surfaces are electrically conductive, the impedance of the inductance L1 still affects the high-frequency equipotential bonding between antenna 10 and car body 30.

A second problem (cf. FIG 2 ) relates to the grounding of the outer conductor 51 of the coaxial antenna cable 50, which is usually used as a transmission cable between the vehicle antenna 10 and the electronics of the train protection system. In a coaxial cable, the outward current Ih flows in the inner conductor 52 and the return current Ir in the coaxial, tubular outer conductor 51 .

This outer conductor 51 is now electrically conductively connected on the side of the vehicle antenna 10 to the rear antenna shielding plate 11 of the vehicle antenna 10, and thus in turn to the bogie frame 21. On the side of the electronics cabinet 60 or electronics container, which is usually in or is arranged on the car body 30, the outer conductor 51 is usually connected to the car body 30. The outer conductor 51 thus forms an electrical connection between the bogie 20 and the car body 30. Electrically speaking, this connection is a parallel connection to the equipotential bonding conductor between the bogie 20 and the car body 30, see FIG FIG 2 .

In particular, main switch switching operations represent high-frequency interference generators due to the spark formation and the resulting spark break. The resulting high-frequency Interference current Iemv can flow back to the main switch via car body 30 - bogie 20 - rail 70 - mains impedance. An example path of the interference current through the vehicle is in FIG 2 shown. FIG 2 shows the exemplary superimposition of the transient interference current Iemv (thick arrows) to the useful current of the signaling system (thin arrows) in the connecting line 50 between antenna 10 and electronics cabinet 60. Due to the additional connection between car body 30 and bogie 20 through the coaxial outer conductor 51, not the entire flows Part of the high-frequency interference current Iemv via the protective connection between car body 30 and bogie 20 or bogie frame 21, but part flows via the coaxial outer conductor 51. This high-frequency transient interference current Iemv is directly superimposed on the antenna current flowing on it and is therefore galvanically coupled to the useful signal . Due to this galvanic coupling, the train protection system can be disturbed by even small transients.

Even if the antenna cable 50 is only grounded on one side and is not electrically conductively connected to the bogie 20 on the antenna side, for example, parasitic capacitances between the antenna 10 or the connector plug and the antenna shielding plate 11 are often sufficient for 4 .2 MHz a relevant current can flow over it.

The same applies if the bogie 20 is electrically isolated from the rail 70 and has no ground contact. Here, too, the parasitic capacitances between the bogie frame 21 and the wheel set 80 or wheel set rocker are sufficient to allow high-frequency interference currents to flow from the bogie frame 21 to the rail 70 . This is in the FIG 2 specified as impedance Z1 by way of example. In the figures, Z1 designates the equivalent impedance between the wheelset 80 and the bogie frame 21; In the figures, Z2 designates the equivalent impedance of line 31 (cf. 3 ) between the bogie frame 21 and the car body 30.

The situation is also more critical because the impedance Z2 of the potential equalization conductor between the bogie 20 and the car body 30 can no longer be neglected in the MHz frequency range, as already explained above.

If the coaxial cable or antenna cable 50 is routed at the jump-off point to the car body 30 to the bogie 20, for example via an adapter plug (in FIG 2 not shown) and the coaxial outer conductor 51 is connected there with relatively low impedance to the car body 30, the impedance of the then relatively short coaxial outer conductor 51 between antenna 10 and adapter plug is reduced again with the result that an even higher proportion of the high-frequency interference current via the coaxial Outer conductor 51 flows.

Vehicle antennas 10 are preferably mounted directly on the car body 30 . A very good, low-inductance and thus low-impedance connection between shielding plate 11 and car body 30 can be established via a screw connection between the shielding plate 11 attached to the rear of the antenna 10 and the car body 30, especially if the mechanical contact surfaces of the screwing are bare metal.

If this is not the case, grounding can be achieved using grounding lines that are as short as possible, as is shown in the example in 3 is shown. However, this type of grounding is less advantageous than surface grounding due to the resulting parasitic inductances of the grounding lines at high frequencies.

3 shows an exemplary arrangement of a vehicle antenna 10 on the car body 30. If the antenna support 12 is metallically bare via its screwing surfaces and the associated mounting surfaces on the car body 30 and on the antenna 10, a very good, low-inductive grounding of the antenna 10 is given. If this is not the case, the antenna 10 is appropriate shown to be grounded via ground lines with associated parasitic inductances L1 and L2.

When mounted on the car body 30, the two problems discussed above occur to a significantly lesser extent than when the vehicle antenna 10 is mounted in the bogie 20. As a rule, a sufficiently low-impedance potential equalization can be achieved by means of an electrically conductive connection on the mounting surfaces, so that the system has sufficient interference immunity (EMC).

The present invention assumes that the antenna 10 is arranged on a bogie 20 of the rail vehicle 40, as exemplified in FIG 5 is shown. This can be necessary for various reasons, in particular due to a lack of available space in the underfloor area outside the bogies 20 of the rail vehicle 40 .

For high-frequency equipotential bonding, a resonant circuit, in particular in the form of a series resonant circuit, is used instead of a normal electrical conductor. Such an absorption circuit can be implemented, for example, by connecting a capacitor and, if necessary, a damping resistor in series with an electrical conductor, for example a wire, a round cable or a flat strip, and tuning the absorption circuit to the receiving frequency of the vehicle antenna 10 .

5 shows an example of a first trap circuit formed by an equivalent inductance Ls1 of the line connected to the grounding point (here the wheelset 80) and a discrete capacitance Cs1 connected in series with the equivalent inductance Ls1; in addition, a discrete resistor that is in 5 is not shown, be looped in series with the equivalent inductance Ls1 and the discrete capacitance Cs1.

5 Fig. 12 further shows, by way of example, a second trap circuit formed by an equivalent inductance Ls2 of the line connected to the antenna faceplate 11 and a discrete capacitance Cs2 connected in series with the equivalent inductance Ls2; in addition, a discrete resistor placed in 5 is not shown, be looped in series with the equivalent inductance Ls2 and the discrete capacitance Cs2.

FIG 4 shows, by way of example, schematic representations of an exclusive equipotential bonding conductor 90 (left) between connection points 91 and 92, high-frequency equipotential bonding by means of a capacitor Cs connected in series with the equipotential bonding conductor 90 (centre), with the capacitance Cs of the capacitor together with the parasitic inductance Ls of the conductor being an LC absorption circuit 100 or series resonant circuit acts. According to the third or right representation, an additional resistor Rs can be additionally provided, which is connected in series with the capacitor Cs.

The inductance Ls of the line 90 acts with the capacitance Cs of the capacitor as an LC absorption circuit 100. This absorption circuit 100, also referred to as a series resonant circuit, acts like a short circuit in the range of the resonant frequency, ie it has a very low impedance here. The capacitance value is selected in such a way that the resulting series resonant circuit consisting of line inductance Ls and capacitance Cs has a resonant frequency which, for example, corresponds to the center frequency of the ETCS reception signal f=4.2 MHz. If necessary, a resistor Rs can be switched on as an attenuator in addition to the capacitor Cs in order to achieve a sufficient bandwidth of the absorption circuit characteristic and the two maxima in the spectrum of the FSK signal (3.9505 MHz and 4.5165 MHz at 565 kbit/s data transmission rate of the ETCS -FSK antenna signal) completely. However, the additional resistance Rs has the disadvantage that it disadvantageously increases the minimum impedance of the trap circuit 100. In which case the ohmic resistance of line 90 and capacitance Cs at the absorption circuit resonant frequency is already sufficient as a resistance value.

This arrangement advantageously means that any components for high frequencies, in particular in the range of the ETCS reception frequency of 4.2 MHz, can be connected to one another with low impedance.

The use of absorption circuits is again given as an example below using the 5 explained. Based on the embodiment of FIG 2 the following measures have been implemented.

A path from the car body 30 directly to the rail 70 that is as low-impedance as possible is to be offered to the transient high-frequency currents Iemv. For this purpose, a wheel set contact or grounding contact is provided on the wheel set 80 of the bogie 20, on which the vehicle antenna 10 is arranged, if this is not already present. A supply line with the equivalent inductance Ls1 and a capacitance Cs1 in series with it are connected to this wheelset contact. The resulting series resonant circuit is tuned to the reception center frequency of 4.2 MHz of the ETCS system. As a result, the high-frequency interference current Iemv flows from the car body 30 directly to the rail 70 in the area of the reception center frequency.

It should be noted that the series oscillating circuit consisting of Ls1 and Cs1 is not able to conduct low-frequency equalizing currents or operating currents, for example reverse current for 16.7 Hz or 50 Hz of the single-phase alternating current of the traction power system. The low-frequency equipotential bonding and the operating current feedback thus remain unaffected by the present invention. Existing grounding contacts can, however, also be used if necessary. For example, grounding contacts usually offer the possibility of connecting two lines.

Furthermore, the antenna shielding plate 11 should find potential equalization with the car body 30 that is as low-impedance as possible. This is achieved in that a line with the equivalent inductance Z2 and a series-connected capacitance Cs2 connects the antenna screen plate 11 above the antenna 10 directly to the car body 30. A low-impedance connection between the antenna 10 and the car body 30 is also achieved here by tuning to the reception center frequency of 4.2 MHz of the ETCS system.

Finally, the coaxial outer conductor 51 of the antenna cable 50 should have a low-impedance equipotential bonding to the car body 30 on both sides. This is achieved in that the outer conductor 51 is connected to the antenna shielding plate 11 on one side, ie on the antenna side. If the outer conductor 51 is already electrically conductively connected to the antenna shielding plate 11 in the antenna 10, the above measure with regard to the antenna shielding plate 11 is already sufficient. If, however, the outer conductor 51 is insulated from the antenna shielding plate 11, the coaxial outer conductor 51 is connected, for example at the entrance to the antenna 10, directly to the car body 30 via a further, third absorption circuit (not specifically in 5 shown).

If the coaxial outer conductor 51 is connected on the other side via the electronics cabinet 60 with a high-frequency, low-impedance connection to the car body 30, this is sufficient. However, in the event that the connection in the high-frequency range on the side of the electronics cabinet 60 is also not sufficiently low-impedance, an absorption circuit can also be provided here.

The use of absorption circuits described above with the aim of equipotential bonding for high-frequency transient interference currents in the operating frequency range of train protection systems represents an alternative or supplement to the known extensive high-frequency equipotential bonding in order to To avoid the disadvantage of line inductances with their respective non-negligible impedance.

Irrespective of the above statements based on the European train protection system ETCS, the present invention is suitable for all systems in which there is a need for equipotential bonding that works in the high-frequency range. These include, in particular, the French train protection system KVB (Contröle de vitesse par balises) and the Swedish train protection system ATC, which is also based on passive balises.

The configurations described above by way of example relate to the equipotential bonding for high frequencies and primarily serve to ensure adequate electromagnetic compatibility (EMC), in particular the interference immunity of the ETCS systems used in rail vehicles. This high-frequency equipotential bonding using a series resonant circuit has a different objective than the usual equipotential bonding for electrical safety. Accordingly, an additional equipotential bonding for electrical safety should be considered if necessary.

Although the invention has been illustrated and described in detail by means of preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention, which results from the appended claims.

Claims (9)

1. Rail vehicle (40), having a railcar body (30), a bogie (20), an antenna (10), arranged in or on the bogie (20), with a shield plate (11), an antenna cable (50) with an external conductor (51), and an electronic assembly (60) with a housing, wherein the electronic assembly (60) is connected by way of signalling by means of the antenna cable (50) to the antenna (10),
   and wherein for high-frequency potential compensation an absorption circuit or series resonant circuit is connected electrically between the shield plate (11) of the antenna (10) and the railcar body (30), said circuit being adjusted with respect to a carrier frequency used for a signal transmission by means of the antenna (10).
2. Rail vehicle according to claim 1, wherein the absorption or series resonant circuit is low resistance for the carrier frequency used by the antenna (10).
3. Rail vehicle according to claim 1 or 2, wherein the antenna (10) is a vehicle antenna (10) of the European Train Control System ETCS.
4. Rail vehicle according to one of the preceding claims, which is embodied as an electrical drive train or as a locomotive.
5. Rail vehicle according to one of the preceding claims, wherein a further absorption or series resonant circuit is arranged between a wheel set (80) arranged in the bogie (20) and the railcar body (30).
6. Rail vehicle according to one of the preceding claims, wherein a further absorption or series resonant circuit is arranged between the external conductor (51) of the antenna cable (50) and the antenna shield plate (11) of the antenna (10) .
7. Rail vehicle according to one of the preceding claims, wherein a further absorption or series resonant circuit is arranged between the external conductor (51) of the antenna cable (50) and the electronic assembly (60) or its housing.
8. Rail vehicle according to one of the preceding claims, wherein the absorption or series resonant circuit has at least one series circuit comprising an inductance of an electrical conductor and a capacitance.
9. Rail vehicle according to claim 8, wherein the absorption or series resonant circuit further has a resistance, which is connected in series with the inductance and the capacitance.

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