ES2949846T3 - High frequency potential compensation device - Google Patents

Abstract

The invention relates to an arrangement for equalizing high frequency potential between an antenna (10) arranged in or on a bogie (20) of a railway vehicle (40) and a body (30) of the railway vehicle (40), and/or between an external conductor (51). an antenna cable (50) and the antenna (10), in particular the antenna protective plate (11) of the antenna (10), and/or between an outer conductor (51) of the antenna cable (50) and a electronic assembly (60), which is responsible for signaling, is connected to the antenna (10), or to the housing of the assembly (60), the potential equalization being carried out through a suction or series resonant circuit, which is tuned to with respect to a carrier frequency used for the transmission of signals through the antenna (10). (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

High frequency potential compensation device

From WO 2011/039002 A1, a railway vehicle with at least one vehicle antenna of a train control system directed towards the track is known.

US 5,351,018 A describes a television receiver comprising a coaxial cable connected to a radio frequency signal source. Interference signals are dissipated to ground potential through at least one suction or series resonant circuit connected to the outer shield conductor of the coaxial cable.

Disclosure document EP 0778683 A2 discloses telecommunications equipment with a human-machine interface.

The invention is based on the task of specifying an arrangement for a railway vehicle that helps to minimize or at least reduce the negative influences of interference currents on data transmission.

This object is solved according to the invention by a railway vehicle with an arrangement according to patent claim 1. Advantageous embodiments of the arrangement according to the invention are indicated in the subclaims.

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

Preferably, the suction or series resonant circuit is of low impedance for the carrier frequency used by the antenna or at least also for the carrier frequency used by the antenna. Preferably, the suction or series resonant circuit is low impedance in a range between 3.9505 MHz and 4.5165 MHz to achieve sufficient bandwidth of the suction circuit characteristic for ETCS compatible FSK signal transmission. It is especially advantageous to provide another suction or series resonant circuit between a set of wheels arranged on the bogie and the car body.

Furthermore, another suction or series resonant circuit may advantageously be arranged between the outer conductor of the antenna cable and the shielding plate of the antenna and/or the electronic assembly or its housing.

The suction or series resonant circuit preferably has at least one series circuit comprising an inductance of an electrical conductor and a capacitance.

The suction or series resonant circuit preferably comprises a resistor connected in series with the inductance and capacitance.

The at least one onboard antenna is preferably a European Train Control System (ETCS) onboard antenna. The railway vehicle is preferably an electric multiple unit or a locomotive.

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

The invention is explained in more detail below with reference to the drawings and embodiment examples.

The European Train Control System (ETCS) uses, among other things, antennas mounted under the vehicle for the exchange of information between railway vehicles and the track or infrastructure. The vehicle's antenna transmits electromagnetic energy at high frequency (27 MHz) to the roadbed, which activates an antenna installed on the roadbed (also known as a beacon or eurobeacon). The energized beacon modulates its information onto a high frequency (4.2 MHz) carrier (FSK modulation) and sends the information to the vehicle's antenna. Information can be transmitted at a speed of up to 500 km/h with a data transmission rate of 565 kbit/s.

For shielding reasons, the vehicle's own antenna preferably has a metal plate on the side facing the underbody of the vehicle, intended to keep interference generated by the vehicle (= from above) away from the antenna. To prevent this shielding plate from acting as a receiving antenna for interference fields present in the vicinity of the antenna, it must be connected to the vehicle body with low impedance (low impedance potential compensation). Ideally, this should be done through direct, electrically conductive contact between this plate and the car body, for example through bare metal bolted surfaces.

Furthermore, the outer conductor of the connecting cable, usually coaxial, 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 on the bogie, to the bogie frame. To avoid interference, low impedance potential compensation is also necessary.

However, such low impedance potential compensation is usually not achieved for high frequencies, especially in the ETCS carrier frequency range, for several reasons. Transient electromagnetic currents, such as those generated, for example, by sparks, produced by, for example, switching operations of the main switch, ring bridges, passage through separation points, etc., can, therefore, cause adverse disturbances in the ETCS system due to insufficient compensation of low impedance potential for high frequencies.

Two problems were identified, the first of which concerns compensation for the low impedance potential of the antenna shield plate.

When the antenna is installed on the bogie, a large-area electrically conductive connection between the antenna and the car body is not possible, since the necessarily mobile potential equalization between the bogie and the car body is usually carried out using round cables electrical conductors or flat strips.

However, these potential compensation conductors have the disadvantage that they present a non-negligible impedance in the MHz frequency range due to the complex, predominantly inductive, resistance that increases with frequency. The inductive resistance of an equipotential bonding conductor 0.5 m long, for example, has a value of approx. 13 ohms at the ETCS receive frequency of 4.2 MHz (assuming an inductance coating of approx. 1 |jH/m of the equipotential conductor).

Since the antenna 10, as illustrated in Fig. 1, is usually not mounted directly to the frame 21 of a bogie 20, but rather on antenna brackets or accessories, the impedances of the antenna 10 through the frame accessories 21 from the bogie to the car body 30 are added. FIG. 1 shows an example of compensation of the potential from the antenna 10 to the body 30 of the wagon of the railway vehicle 40. Components A and B are mechanical constructions, for example, consoles or antenna supports made of electrically conductive material. To establish potential compensation, bare metal contact surfaces or potential compensation conductors are required that electrically connect the individual components to each other. In the latter case, potential compensation is achieved by a chain of potential compensation conductors with the total inductance L1+L2+L3+L4, plus a relatively small inductance of the mechanical components themselves. Although all contact surfaces are electrically conductive, the impedance of the inductance L1 still impairs the high-frequency potential compensation between the antenna 10 and the car body 30.

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

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

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

Although 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, the stray capacitances between the antenna 10 or the connector and the plate 11 of Antenna shielding is usually sufficient for a relevant current to flow through it at 4.2 MHz.

The same applies if the bogie 20 is electrically isolated from the rail 70 and has no ground contact. In this case, the stray capacitances between the bogie frame 21 and the wheel axle 80 or the wheel axle rocker arm are sufficient to allow high frequency interference currents to flow from the bogie frame 21 to the rail. 70. This is exemplified in FIG. 2 as impedance Z1. Z1 in the Figures denotes the equivalent impedance between the wheel axle 80 and the bogie frame 21; Z2 in the Figures denotes the equivalent impedance of line 31 (comp. FIG. 3) between the frame 21 of the bogie and the body 30 of the wagon.

The situation becomes even more critical due to the fact that the impedance Z2 of the potential compensation conductors between the bogie 20 and the car body 30 can no longer be neglected in the MHz frequency range, as explained above. .

If the coaxial cable or antenna cable 50 is routed to the bogie 20 at the jump point to the car body 30, for example, through an intermediate connector (not shown in FIG. 2), and the conductor 51 outer coaxial conductor is connected there to the car body 30 with a relatively low impedance, the impedance of the then relatively short outer coaxial conductor 51 between the antenna 10 and the intermediate connector is reduced again, with the result that an even greater proportion of The high frequency eddy current flows through the coaxial outer conductor 51.

Preferably, the vehicle antennas 10 are mounted directly to the car body 30. A very good, low induction and therefore low impedance connection can be established between the shield plate 11 and the car body 30 by a bolted connection between the shield plate 11 mounted on the rear of the antenna 10 and the vehicle body 30, especially if the mechanical contact surfaces of the bolted connection are metallically shiny.

If this is not the case, grounding can be done through grounding lines that are as short as possible, as shown as an example in FIG 3. However, this type of grounding is less advantageous than an area ground due to the resulting parasitic inductances of the ground lines at high frequency.

FIG. 3 shows an example arrangement of a vehicle antenna 10 in the car body 30. If the antenna bracket 12 is metallically bare across its bolted surfaces and the associated mounting surfaces on the car body 30 and on the antenna 10, very good, low induction grounding of the antenna 10 is provided. If this is not the case, the antenna 10 must be grounded according to the illustration via grounding lines with associated parasitic inductances L1 and L2. Otherwise, the antenna 10 must be grounded according to the illustration using grounding lines with associated parasitic inductances L1 and L2.

By mounting on the wagon body 30, the two problems mentioned above occur to a significantly lesser extent than when mounting the vehicle antenna 10 on the bogie 20. As a rule, a compensation of the impedance potential can be achieved. low enough by an electrically conductive connection at the mounting surfaces, so that the system has sufficient immunity to interference (EMV).

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

For high-frequency potential compensation, instead of a normal electrical conductor, a suction circuit is used, in particular in the form of a series resonant circuit. Such a suction circuit can be realized, 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 band, and tuning the suction circuit at the reception frequency of the vehicle's antenna 10.

FIG. 5 shows, by way of example, a first suction circuit formed by a spare inductance Ls1 of the line connected to the ground point (here, the wheel axle 80) and a discrete capacitance Cs1 connected in series with the spare inductance Ls1; furthermore, a discrete resistor, which is not drawn in FIG. 5, can be connected in series with spare inductance Ls1 and discrete capacitance Cs1.

FIG. 5 further shows, by way of example, a second suction circuit formed by a spare inductance Ls2 of the line connected to the antenna shielding plate 11 and a discrete capacitance Cs2 connected in series with the spare inductance Ls2; furthermore, a discrete resistor, which is not drawn in FIG. 5, can be connected in series with spare inductance Ls2 and discrete capacitance Cs2.

FIG. 4 shows examples of the principle of a dedicated potential compensation conductor 90 (left) between connection points 91 and 92, a high-frequency potential compensation by means of a capacitor Cs (middle) connected in series with the potential compensation conductor 90, so the capacitance Cs of the capacitor together with the parasitic inductance Ls of the conductor acts as an LC suction circuit 100 or series resonant circuit. According to the third illustration or illustration on the right, an additional resistor Rs can be provided, which is connected in series with the capacitor Cs.

The inductance Ls of line 90 acts with the capacitance Cs of the capacitor as LC suction circuit 100. This suction circuit 100, also called series resonant circuit, acts in the range of the resonance frequency as a short circuit, that is, it acts here with very low impedance. The value of the capacitance is selected so that the resulting series resonant circuit, formed by the line inductance Ls and the capacitance Cs, has a resonant frequency corresponding, for example, to the center frequency of the ETCS - receive signal f = 4.2 MHz. If necessary, a resistor Rs can be connected as an attenuator in addition to the capacitor Cs to achieve a sufficient bandwidth of the suction circuit characteristic and to completely cover the two maxima in the FSK signal spectrum ( 3.9505 MHz as well as 4.5165 MHz at a data transmission rate of 565 kBit/s of the ETCS FSK antenna signal). However, the additional resistance Rs has the disadvantage that it negatively increases the minimum impedance of the suction circuit 100. If necessary, the ohmic resistance of line 90 and the capacitance Cs at the resonance frequency of the suction circuit are sufficient as a resistance value.

This arrangement makes it advantageous that any components for high frequencies, in particular in the ETCS receive frequency range of 4.2 MHz, can be connected together with low impedance.

The use of suction circuits is explained again below by way of example using FIG. 5. Based on the example of FIG. 2, the following measures have been implemented.

High frequency transient currents lemv must be offered a path with the lowest possible impedance from the car body 30 directly to the rail 70. To do this, on the axle 80 of the bogie 20 on which the antenna 10 of the vehicle, a wheel contact or a ground contact is provided, if it does not already exist. A power line with substitution inductance Ls1 and a capacitance Cs1 in series with it is connected to this contact of the wheel axle. The resulting series oscillator circuit is tuned to the 4.2 MHz receiving center frequency of the ETCS system. As a result, the high-frequency interference current lemv in the range of the receiving center frequency flows out of the body 30 directly into the rail 70.

It should be noted that the series resonant circuit formed by Ls1 and Cs1 is not capable of carrying low-frequency compensation currents or operating currents, for example return current for 16.7 Hz or 50 Hz single-phase AC mains current. of traction current. Therefore, the present invention does not affect low-frequency potential compensation or service current return. However, existing ground contacts can be used if necessary. For example, grounding contacts usually offer the possibility of connecting two lines.

Furthermore, the antenna shielding plate 11 must find a potential equalization with the body 30 with as low an impedance as possible. This is achieved by connecting a line with replacement inductance Z2 and a series connected capacitance Cs2 directly between the antenna shield plate 11 above the antenna 10 and the car body 30. By tuning to the central reception frequency 4.2 MHz of the ETCS system, a low impedance connection between the antenna 10 and the car body 30 is also achieved here.

Finally, the coaxial outer conductor 51 of the antenna cable 50 will have low impedance potential compensation with respect to the car body 30 on both sides. This is achieved by connecting the outer conductor 51 on one side, i.e. on the antenna side, to the antenna shielding plate 11. If the outer conductor 51 is already electrically conductively connected to the antenna shield plate 11 on the antenna 10, the above measurement is already sufficient with respect to the antenna shield plate 11. However, if the outer conductor 51 is insulated from the antenna shield plate 11, the coaxial outer conductor 51 is connected directly to the car body 30, for example, at the entrance of the antenna 10 through a third additional suction circuit (not specifically shown in FIG. 5).

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

The described use of suction circuits for potential compensation for high-frequency transient disturbing currents in the working frequency range of train protection systems represents an alternative or complement to the zone-based high-frequency potential compensation known for avoid the disadvantage of line inductances with their respective non-negligible impedance.

Regardless of the above explanations based on the European train control system ETCS, the present invention is suitable for all systems where potential equalization operation in the high frequency range is necessary. This includes, in particular, the French train protection system KVB (Contróle de vitesse par balises), as well as the Swedish train protection system ATC, which is also based on passive beacons.

The designs described above as examples relate in summary to potential compensation for high frequencies and mainly serve to ensure adequate electromagnetic compatibility (EMV), in particular interference immunity of ETC systems used in railway vehicles. This High frequency potential compensation using a series resonant circuit has a different objective than the usual potential compensation for electrical safety. Therefore, if necessary, additional potential compensation for electrical safety must be considered.

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 those skilled in the art can derive other variations thereof without departing from the scope of protection of the invention that emerges from the attached claims.

Claims (9)

1. Railway vehicle (40), which has a wagon body (30), a bogie (20), an antenna (10) that is arranged in or on the bogie (20) with an armor plate (11), a antenna cable (50) with an outer conductor (51), and an electronic assembly (60) with a housing, wherein the electronic assembly (60) is connected to the antenna (10) in terms of signaling by means of the cable ( 50) of antenna, and where, for a high frequency potential compensation between the shielding plate (11) of the antenna (10) and the body (30) of the vehicle, a suction resonant circuit is electrically connected or in series, which is tuned with respect to a carrier frequency used for signal transmission through the antenna (10). 2. Railway vehicle according to claim 1, wherein the suction or series resonant circuit for the carrier frequency used by the antenna (10) is of low impedance. 3. Railway vehicle according to claim 1 or 2, wherein the antenna (10) is a vehicle antenna (10) of the European Train Control System ETCS. 4. Railway vehicle according to one of the preceding claims, which is designed as an electric multiple unit or as a locomotive. 5. Railway vehicle according to one of the preceding claims, wherein another series suction or oscillation resonant circuit is arranged between a wheel axle (80) arranged in the bogie (20) and the body (30) of the wagon. 6. Railway vehicle according to one of the preceding claims, wherein another suction or series resonant circuit is arranged between the outer conductor (51) of the antenna cable (50) and the antenna shield plate (11). the antenna (10). 7. Railway vehicle according to one of the preceding claims, wherein another series suction or oscillation resonant circuit is arranged between the outer conductor (51) of the antenna cable (50) and the electronic assembly (60) or its housing. . 8. Railway vehicle according to one of the preceding claims, wherein the suction or series resonant circuit has at least one series circuit of an inductance of an electrical conductor and a capacitance. 9. Railway vehicle according to claim 8, wherein the suction or series resonant circuit further has a resistance connected in series with the inductance and the capacitance.