Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B61—RAILWAYS
  • B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
  • B61L23/00—Control, warning or like safety means along the route or between vehicles or trains
  • B61L23/06—Control, warning or like safety means along the route or between vehicles or trains for warning men working on the route

Definitions

• the invention relates to a detection device for a short circuit link to be applied between or across the rails of a section of railway track, comprising a source of electrical energy and a monitoring device connected to the rails for measuring and monitoring the short circuit resistance caused by the short circuit link.
• a detection device for a short circuit link to be applied between or across the rails of a section of railway track, comprising a source of electrical energy and a monitoring device connected to the rails for measuring and monitoring the short circuit resistance caused by the short circuit link.
• the protection of a network of railways by automatic signalling of the presence of trains is generally known.
• the tracks of the network are divided into electrically insulated sections, which are connected to the so- called track circuiting loop, by which it can be established if there is a train on this section.
• This track circuiting loop consists of a source of alternating current connected to the rails at one end of the section and a relay (the so-called track circuit relay) connected to the rails at the other end of the section.
• the object of the invention is to avoid the disadvantages described above and improve safety during work on the track.
• the electrical energy source is an alternating current source and the monitoring device comprises a resonant circuit and an evaluation device for the evaluation of the resonance produced in the resonant circuit.
• This system itself can indicate that the short circuit resistance meets the requirements imposed and can provide a local signal of this to the person applying the short circuit. There is a local continuous signal, so that it is not necessary to walk regularly to the signal to check that the signal is at danger, which could easily be forgotten when busy with the work. Safety is thus improved considerably and there is not complete dependence on test protocols.
• the source of electrical energy preferably provides alternating current, which works together with a resonant circuit in the monitoring device; this allows very low short circuit resistances to be measured reliably. These measurement results are fed to an evaluation device for the evaluation of the resonance produced by the resonant circuit. Moreover, by using a resonant circuit it is always observed when this circuit, across which it is measured, is defective. For, both a short circuit and an interruption will de detected.
• a reliable choice for the frequency of the alternating current source can be made between 15 and 25 kHz. This frequency is preferably 17 kHz.
• the resonant circuit comprises an inductance and a capacitor in series and is connected at one end to an output terminal of the alternating current source, the other output of which is connected to one rail.
• the other end of the resonant circuit is connected to the other rail.
• the inductance is connected to a comparator for the comparison of the inductance output signal with a reference signal.
• the level of the resonant voltage across the inductance is measured, for which the inductance is connected to the comparator through an RMS converter. Thereby an additional reliability is achieved by using an extra selection criterion, i.e. the enrgy contents.
• a pulse generator is provided to control the intermittent switching of the series connection of the alternating current source and the resonant circuit formed by the inductance and capacitor onto the rails, when the comparator is connected to a pulse decoder.
• the intermittent operation not only saves energy, but by using the pulse generator produces measurements at regular intervals. This frequency can also be used as an additional safety criterion. Moreover, by using the intermittent operation the measurement is insensitive for EM interferences.
• the detection equipment is also connected to a signalling device that can, if required, provide an external signal.
• FIG. 1 - a part of the track of a railway network
• Fig. 2 - a preferred version of the detection device according to the invention.
• the part of the track shown in Fig. 1 is divided into sections electrically insulated from each other, of which only sections a, b and c are shown in Fig. 1.
• Fig. 1 illustrates the track circuit for section b only, this track circuit consists of an alternating current source Wl whose output terminals are connected at one end of section b to rails SI and S2 respectively.
• a track circuit relay Rl is connected to these rails SI and S2 at the other end of this section.
• section b When work has to be carried out on section b, this section has to be made safe or protected reliably. This protection is achieved, by simulating the presence of a train on the section, for which a short circuit link is placed across the rails SI and S2.
• a track can be short-circuited in the following ways.
• the short circuit lance in its simplest form, consists of a metal rod whose ends make contact with the rails SI and S2 with the lowest possible transition resistance by, for example, penetration of the corrosion layer of the rails.
• a test procedure can, for example, include walking regularly to the signal and checking that the signal is at danger.
• - Short-circuiting cable with magnets Such a cable is used, for example, by drivers when they observe that an unsafe situation exists on another track. This method is less reliable. Only when the first method is used does the track remain accessible to any works trains.
• the invention provides a self-signalling short circuit lance, which enables continuous, reliable, local signalling that the conditions for short circuit resistance are being met.
• the preferred version of a circuit of a short circuit lance is shown in Fig. 2.
• Fig. 2 shows a part of a section b with the rails SI and S2. Between the rails SI and S2 a short circuit lance KL is fitted.
• the detection device DT associated with the short circuit lance KL is connected to the rails SI and S2. While a short circuit lance is shown in the version illustrated, the detection device is also suitable for a short-circuiting cable with rail clamps. This method is used when a short circuit lance cannot be used, as for example, at points systems. It is also possible to check if a stationary (works) train, for example a fitting vehicle, produces an adequate short circuit. In addition, adequate short-circuiting by a short-circuiting cable with magnets can also be checked.
• the detection device DT has an electrical energy source providing alternating current connected by one terminal to the rail SI.
• This alternating current source W2 places a nearly constant alternating voltage on the rails SI and S2.
• Measurements have shown voltages of various amplitudes and with frequencies up to 5 kHz on the track.
• OTC sections are also used for protection, using a voltage with a frequency of 10 kHz. Tramways also use frequencies of from 9.5 to 14.5 kHz for train detection.
• the frequency of the alternating current source W2 has therefore been selected as higher than 15 kHz. It is advantageous to select a frequency below 25 kHz for the alternating current source W2, to avoid high frequency problems caused by self inductances and capacities in the system. Seventeen kHz is an exceptionally suitable frequency, it is relatively low and does not occur in the track. Moreover, there are no frequencies in the track that have 17 kHz as a higher harmonic. At the same time there is some tolerance around 17 kHz, this allows standard components to be used.
• the other output terminal of the alternating current source W2 is connected to the other rail S2 through a resonant circuit, this consists of the inductance L and the capacitor C.
• a resonant circuit this consists of the inductance L and the capacitor C.
• the level of the output voltage from the band-pass filter B can be measured and compared with a reference value that has been previously set to correspond to a short circuit that meets the requirements imposed. It is certainly preferable to base the comparison on the resonated voltage, since this will result in a measurement and comparison of greater accuracy and reliability. For this reason the output of the band-pass filter B is connected to an RMS converter RMSC, this generates the effective value of the output voltage from the band-pass filter B.
• the RMS converter output voltage is fed to the comparator CO for comparison with a reference signal REF. When the short circuit meets the applicable conditions, the comparator input signal CO will be greater than the reference signal applied to the comparator. A signal will then appear at the comparator output that indicates a safeguarded situation.
• a switch SW is inserted in the connection between the LC circuit and the rail S2, this is controlled by a pulse generator that is not shown. By means of this switch SW the measurement is performed intermittently. Two measurements per second is a suitable choice. Since the measurement is carried out twice a second the adequacy of the short circuit will also be determined twice a second. If this is the case the pulse detector PD connected to the comparator CO gives a safe signal to the signalling device SI. The pulse detector will be operated synchronously with the switch SW. The pulsed detection measurement is described below.
• the measurement circuit consisting of the capacitor C and the inductance L is brought into resonance, this causes an increase in the voltage across the inductance.
• the level of the voltage increase is a measure of the short circuit value.
• the voltage across the inductance is measured. It is applied to the input of a 17 kHz band-pass filter, this filters out the 17 kHz signal. Thus, only signals at a frequency of 17 kHz can appear at the output of the band-pass filter.
• the alternating voltage occurring at the band-pass filter outlet is converted to its RMS value by the RMS converter RMSC.
• This converter determines the energy content of the 17 kHz voltage appearing across the inductance.
• the signal from the RMS converter is a direct current voltage whose level corresponds to the actual effective value of the alternating voltage of 17 kHz voltage. Interfering voltages with a frequency of 17 kHz will be reduced to a very low level and later rejected.
• the RMS converter output signal will also be alternated with the 2 Hz of the pulsed measurement.
• the RMS value from the converter is applied to the comparator CO and compared within it to the value set in advance for the comparator.
• the output of the comparator will be high when the measurement voltage is switched on and the short circuit is satisfactory.
• the comparator output will be low. With a proper short circuit the comparator output will also be alternately high and low.
• the pulse detector PD is connected to the output of the comparator CO. Only if the output is a square wave can the safe signal be given. All other situations produce an alarm.
• Pulsed measurement is used for the following reasons: - To save energy, a smaller battery;
• the entire detection circuit is switched at the rate of interruption of the measurement voltage.
• the comparator determines if the signal is sufficiently high and low at the pulse rate used, which is checked.
• the output is also controlled at the same rate, which must also receive an alternating voltage, if it is to deliver a safety signal. In this way the reliability of the system is increased greatly.
• a continuous or intermittent light signal can be used that is clearly visible to the personnel carrying out the work.
• the signalling device can also be so constructed that external signalling is possible, for example to the traffic controller. Transmission and reception are also possible. In an alarm situation, both light and audible warning signals could be generated.
• An electronic solution could be considered, such as a reliable transistor or FET circuit, but switching of light and audible signals through the break contacts of a so-called B relay is another possible method. In a safe situation the self-signalling short circuit lance should hold the B relay in the powered state. An electronic solution could be preferable for various reasons.
• An additional test button will be included in the detection device circuit to test that an alarm signal will be given.
• connection and attachment of the self-signalling short circuit system and the short circuit lance should only be removed using one unique key.
• a reliable short circuit measurement is guaranteed by the increase in the voltage across the inductance. This increase only takes place if there is a circuit of sufficiently low ohmic value between the measuring unit, the short circuit lance and the rails.
• the following faults can appear in a properly placed short circuit: loss of the supply voltage loss of the 17 kHz alternating voltage defective pulse generator (continuously open or closed) open circuit in the LC circuit short circuit in the capacitor or inductance defective RMS converter defective pulse detector. In all these cases no safety signal will be given.
• the detection device can possibly be constructed with the additional feature of indicating that the short circuit is unsatisfactory or that the measuring unit is defective.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Train Traffic Observation, Control, And Security (AREA)
• Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
• Electric Propulsion And Braking For Vehicles (AREA)
• Protection Of Static Devices (AREA)
• Refuge Islands, Traffic Blockers, Or Guard Fence (AREA)
• Curtains And Furnishings For Windows Or Doors (AREA)
• Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=19761263

Family Applications (1)

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• 1995
  • 1995-06-30 NL NL1000713A patent/NL1000713C2/xx not_active IP Right Cessation
• 1996
  • 1996-06-28 DE DE69606297T patent/DE69606297T2/de not_active Expired - Fee Related
  • 1996-06-28 DK DK96937115T patent/DK0835202T3/da active
  • 1996-06-28 PL PL96324261A patent/PL324261A1/xx unknown
  • 1996-06-28 HU HU9900325A patent/HUP9900325A3/hu unknown
  • 1996-06-28 AT AT96937115T patent/ATE188929T1/de not_active IP Right Cessation
  • 1996-06-28 EP EP96937115A patent/EP0835202B1/de not_active Expired - Lifetime
  • 1996-06-28 TR TR97/01747T patent/TR199701747T1/xx unknown
  • 1996-06-28 WO PCT/NL1996/000268 patent/WO1997002169A1/en not_active Ceased
• 1997
  • 1997-12-29 NO NO976089A patent/NO976089L/no not_active Application Discontinuation

Non-Patent Citations (1)

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