Method for detecting a fault on a section of the electrical power supply of a railway network and associated device
Patent Information
- Application Number
- FR2023002370
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-03-14
- Publication Date
- 2025-02-21
- Estimated Expiration
- 2043-03-14
Smart Images
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Abstract
Description
Title of the invention: Method for detecting a fault on a section of the electrical power supply of a railway network and associated device
[0001] The field of the present invention relates to the electrical supply networks of a railway network and more particularly to a method of detecting a fault on a section of electrical supply of a railway network, a protection method and associated devices.
[0002] In the context of railway networks, overhead power supply lines for a vehicle are known, also called overhead contact lines when they consist of only one or two contact wires.
[0003] An overhead power line is called a catenary when it consists of one or two contact wires suspended by droppers from one or two carrier cables. The carrier cable is itself supported at regular intervals by brackets. Under its own weight, the carrier cable takes the form of a catenary, and the droppers are positioned at heights adapted so that the contact wire is suspended substantially horizontally.
[0004] The electric vehicle, for example a motor car, electric locomotive or tram, is then powered by capturing the current flowing on the contact wire by means of a pantograph mounted on the roof of the vehicle and deployed to make contact with the contact wire.
[0005] According to another example, electric current can be supplied to the electric vehicle via a friction pad which is in contact with a specific electric power supply rail.
[0006] In this document, the term "electric vehicle" means any vehicle capable of collecting current from such an electric power line, either by overhead contact line or via an electric power rail. Examples include guided electric vehicles (trains, trams, subways, etc.) or unguided electric vehicles (trolleybuses, cars, etc.).
[0007] For the safe operation of the power supply network and more particularly for the safety of drivers, passengers and people in the immediate vicinity of the installation, it is important that the power supply network be monitored and can be quickly interrupted in the event of a malfunction.
[0008] Such a malfunction could, for example, be a break in the contact wire of an overhead contact line, a fault in the insulation at the catenary attachment point, or, for example, a tree falling on the catenary. This constitutes a generally dangerous incident that can occur, in particular, at level crossings or through melting at the pantograph of a stopped train.
[0009] Once broken, the contact wire hangs or falls to the ground. Being carried to a high potential, it then presents a significant risk of electrocution for people in the area near the point of breakage.
[0010] Such an incident can be characterized in certain cases, particularly when the catenary touches the rails for a 1.5kV DC network, by a transient phenomenon which leads to a very large and very rapid rise in current.
[0011] To overcome this problem, supply sections of the power supply lines of a railway network are equipped with protection devices which measure the current flowing and cut off the current on the entire section in question if the current is too high compared to nominal values.
[0012] However, it has been observed that protection cannot always be reliably ensured when the fault is located far from a substation because the impedance presented by the catenary itself limits both the amplitude of the fault current and its rate of increase.
[0013] On the other hand, there are other transient phenomena, such as the detachment of a pantograph from a catenary, which in some cases can trigger the installed protection systems. Another example is the starting of older locomotives without an inverter. However, in most cases, these are not phenomena requiring a power outage in a section of the electrical supply.
[0014] The present invention relates to an improved method for detecting a fault on a section of a power supply line of a railway network.
[0015] To this end, the present invention relates to a method for detecting a fault on a section of an electrical power line supplying a railway network, comprising the following steps: - A current is measured across the section as a function of time during a measurement window of predefined duration. - parameters are determined for at least one parameterizable modeling function modeling the current measurement curve as a function of time, this parameterizable modeling function having an asymptotic increasing component with at least one parameter defining the asymptotic value of the current in steady state and at least one parameter corresponding to a time constant defining a duration of establishment of the steady state, - the presence or absence of a defect is determined from at least some of the said parameters determined from said parametric modeling function.
[0016] The detection method may further comprise one or more of the following aspects taken alone or in combination:
[0017] The time window has, for example, a duration of less than 200ms in particular less than 100ms and for example between 30ms and 50ms, in particular equal to 40ms.
[0018] The asymptotic increasing component of the function can be described by a function of the type / , where represents the parameter defining the value asymptotic of the current in steady state and T represents the parameter corresponding to a time constant defining a duration of establishment of the steady state.
[0019] The parameterizable modeling function further includes in particular an additional oscillatory component.
[0020] The parameterizable modeling function of the current ip(t) as a function of time is defined by t ip(t) = Pi -h [ / o - P3 - Pile + p3sïn(2Kp4t + p5)
[0021] With T
[0022] where Iœ represents the parameter corresponding to the current established at the end of the transient regime, r represents the parameter corresponding to the time parameter used to define the duration of the transient phenomenon, Ih represents a parameter corresponding to an amplitude of the current harmonic of the transient phenomenon in the oscillatory term, which can be equal to 1, fh represents a parameter corresponding to a frequency in the oscillatory term describing the transient phenomenon and ah represents a fifth parameter corresponding to a phase of the oscillatory term describing the transient phenomenon.
[0023] The function of the current ip(t) as a function of time can be defined by taking into account more parameters by: ip ( 0 = PA + [ / () - / oo - Pt ] + ^=iP3yin ( p^t + p5J< )
[0024] J _yn n 1 100 - L^PySm P5k )
[0025] with: pi = P3 ~ r and p3>k, p4>ket p5jk, parameters corresponding respectively to current amplitudes, frequencies, and phase shifts.
[0026] According to the process, the determined parameters P2 ~ T and p3 > k can be applied, p4>ket p5jkune principal component analysis to obtain new uncorrelated variables and we determine the presence or absence of a defect from at least one of said new uncorrelated variables.
[0027] According to the method, before determining the presence or absence of a defect, it is checked in particular whether Iœ>I0 and Io> 0, if one of these inequalities is not verified, it is determined that there is no defect.
[0028] The modeling of the measurement curve by the parameterizable modeling function can be carried out by applying a least squares method.
[0029] The start of the measurement time window can be triggered when the measured current crosses a predefined threshold.
[0030] According to a variant or as an additional condition, the start of the measurement time window is triggered for example when the time derivative of the measured current crosses a predefined threshold.
[0031] The presence or absence of a fault is determined by determining, for example, the membership of at least one given parameter in a fault region obtained by a learning and / or classification process, from real measurements or obtained by simulation of faults on a model of a power supply section between two monitored substations or by a combination of both.
[0032] The invention also relates to a device for detecting a fault on a section of an electrical power supply line of a railway network comprising a current measurement sensor and being configured to implement a protection method as defined above.
[0033] The invention further relates to a method of protecting a section of a power supply line of a railway network, in which each section is equipped with several protection devices, each protection device comprising a current measurement sensor and is configured to implement a fault detection method as defined above, and in which all the protection devices of the same section are triggered when a fault has been determined by at least one protection device.
[0034] Finally, the invention relates to a device for protecting a section of an electrical supply line of a railway network comprising a current measurement sensor and being configured to implement a protection method as defined above.
[0035] Other features and advantages of the invention will become apparent from the following description, given by way of example and without limitation, with reference to the accompanying drawings in which:
[0036] [Fig. 1] [Fig. 1] shows a simplified diagram of a direct current power supply line for a railway network,
[0037] [Fig.2] [Fig.2] shows a diagram similar to that of [Fig.1] with devices protection
[0038] [Fig.3] [Fig.3] is a graph of the current as a function of time to illustrate the method of the invention,
[0039] [Fig.4] [Fig.4] is a flowchart to illustrate certain steps in the process of the invention,
[0040] [Fig. 5] [Fig. 5] is a first example of the result obtained with the process according to the invention,
[0041] [Fig.6] [Fig.6] is a second example of the result obtained with the process according to the invention,
[0042] [Fig.7] [Fig.7] is a third example of the result obtained with the process according to the invention, and
[0043] [Fig.8] [Fig.8] is a fourth example of a result obtained with the process according to the invention.
[0044] In all figures, elements having identical functions bear the same reference numbers.
[0045] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features from different embodiments can also be combined or interchanged to provide other embodiments.
[0046] In principle, the railway electric traction system consists of fixed installations (substations, catenaries, rails) and rolling stock (freight or passenger train pulled by a locomotive). In most cases, the locomotive's electrical power supply is provided via an overhead line called the catenary. A pantograph, equipped with a contact shoe, allows the electric vehicle to collect the current.
[0047] Fig. 1 shows a simplified diagram for supplying at least one, in this case two, power supply lines IA and IB of a railway network with direct current.
[0048] Reference 2 refers to the public electricity network of an electricity supplier, for example alternating current at several tens of kV at a frequency of 50Hz.
[0049] The public network 2 is connected to substations 3. More specifically, this refers, for example, to a transformer / rectifier unit 4 located in substation 3. The transformer / rectifier group 4 has the function of converting the high voltage alternating current from the public network 2 into a medium voltage direct current, for example 1.5kV or 3kV.
[0050] The output of a transformer / rectifier group 4, in particular with power diodes, is connected to the overhead lines IA and IB (the catenaries) via current interruption devices 7 such as circuit breakers.
[0051] Overhead line 1A is for example intended to supply electric vehicles on a first track, for example an outbound track and overhead line IB is for example intended to supply electric vehicles on a second track, parallel to the first, for example a return track.
[0052] To balance the supply voltage between the outbound and return tracks, parallel switching stations 8 and mixed parallel switching and sub-sectioning stations 9 are provided, for example every 10 to 15 km. For line protection against a catenary-rail short circuit, fast circuit breakers are installed in the parallel switching stations 8, in the mixed parallel switching and sub-sectioning stations 9 and at the output of the substations 3.
[0053] Overhead lines IA and IB between two substations 3 or between a substation 3 and a combined paralleling and sub-sectioning substation 9 form part of the same section S of the railway power supply network. A section S of a power supply line IA or IB may be electrically isolated from other sections by switches or circuit breakers.
[0054] On [Fig.1] sections SI, S2 and S3 are shown as examples.
[0055] Finally, in [Fig.1] reference 10 represents rails (two tracks) which are connected to a low voltage pole and on which electric vehicles will travel.
[0056] Figure 2 shows a diagram similar to that of Figure 1, with protective devices designated in this example by P1, P2, and P3, which protect the same section S2 of the power supply line, in this case line IA. The protective device P1 can be integrated into a substation 3, the protective device P2 into a paralleling substation 8, and the protective device P3, for example, into a combined paralleling and sub-sectioning substation 9. In Figure 2, the rails 9 and the public network 2 are not shown.
[0057] As can be seen in [Fig. 2], the protection devices PI, P2, and P3 are equipped with communication means (schematically represented by arrows), for example, wired, optical, or aerial, so that they can communicate with a central monitoring station (PC). Furthermore, there is also a common interlock between the protection devices PI, P2, and P3 so that if one of the circuit breaker protections supplying the line trips, this opens not only the local circuit breaker but also the other circuit breakers through which this section is powered.
[0058] In particular, each protection device PI, P2 and P3 is configured to, on the one hand, implement a fault detection process which will be detailed below, communicate the opening request to the other protection devices of the same electrical supply section and, on the other hand, if necessary, communicate the fault detection to the central station PC.
[0059] When at least one of the protection devices, for example PI, detects a fault on the section, for example S2 to be protected, it is configured to send a signal to the other protection devices, for example P2 and P3 of the same section S2, which has the effect of also triggering the latter and thus quickly isolating the power supply section S2 where the fault was detected.
[0060] Each protection device PI, P2 or P3 is equipped with a current sensor (represented on [Fig.2] by a current measurement loop) which is for example located near a switch which can be controlled (schematically represented by arrows) by the protection device.
[0061] Thus, a current sensor is for example placed on the power supply line downstream of a switch to measure a current IPi which will then be processed by the PI device and depending on the result, the PI device is configured to open the switch in question in case of fault or to leave it closed if the detected transient is not considered a fault requiring isolation of the section S2 of the power supply line IA.
[0062] The method for detecting a defect will be detailed below with reference to figures 3 and 4.
[0063] Figure 3 schematically and simplified in dotted line with reference 100 shows an example of a measurement of the current I as a function of time t.
[0064] This measurement is carried out during a measurement time window of a predefined duration Tw for example by one of the protection devices PI, P2 or P3 which are all equipped with current sensors for this purpose as previously described.
[0065] Transient phenomena are disturbances on a railway power line generally characterized by an abnormally rapid rise in current, followed by reaching a high and relatively constant current value. Depending on the nature of the transient phenomenon, for example, a catenary wire breaking or the pantograph of the electric vehicle detaching / bouncing from the power line, electrical isolation, for example, of a section S2 by actuation of the protection devices PI, P2, and P3 may or may not be necessary.
[0066] The time window Tw has, in particular, a duration of less than 200 ms, specifically less than 100 ms, and for example between 30 ms and 50 ms, in particular equal to 40 ms. The duration of the measurement time window Tw is a compromise between on the one hand the accuracy that we want to obtain for the modeling of this measurement curve 100 and on the other hand the speed with which we want to trigger the protection devices PI, P2 and P3 of the electrical supply section S2 in order to electrically isolate this section S2 to remove the dangers for people who may be near the fault.
[0067] As can be seen in [Fig. 3], initially, before the measurement window Tw is triggered, the current I is constant and equal to Io. This is a nominal current Io that flows, for example, in the overhead line IA under normal operating conditions. Of course, the value of the nominal current Io depends on the operating conditions, in particular on whether and how many electric vehicles are being powered simultaneously by the same power supply section S.
[0068] The start of the measurement time window Tw is determined by the detection of a triggering event that may be a precursor to the occurrence of a fault. A triggering event may be a significant rise in the derivative of the current dl(t) / dt, or a combination with another triggering event.
[0069] Thus, after measuring the current on the section as a function of time during a measurement time window of a predefined duration Tw, the measurement curve of the current I(t) as a function of time is modeled.
[0070] To achieve this, parameters are determined for at least one parameterizable modeling function modeling the current measurement curve as a function of time. This parameterizable modeling function 102 has an asymptotic increasing component with at least one parameter defining the asymptotic value of the current in steady state and at least one parameter corresponding to a time constant defining a duration for the establishment of the steady state.
[0071] In [Fig.3], such a function which is a continuous function for the window of Time Tw is represented by a solid line and referenced by 102.
[0072] More specifically, the asymptotic increasing component of the function 102 can be described by a function of the type
[0073]
[0074] where Iœ represents the parameter defining the asymptotic value of the steady-state current and r represents the parameter corresponding to a time constant defining the duration of the steady-state establishment. In this function, IA can be IA = Iœ - Io and corresponds in some way to the amplitude of the current rise.
[0075] The modeling accuracy can be improved by adding to said continuous function an additional oscillatory component.
[0076] In this case, according to a first simplified embodiment, the function of the current ip(t) for a protection device as a function of time is, for example, defined by
[0077] t ip(t) = 4- [Jq — p3 sinCp5) - Pile Ps + p3sm(2jrp4t + p s )
[0078] with '7L ™ Z®
[0079] where Iœ represents the first parameter and corresponds to the current established at the end of the transient regime,
[0080] r represents the second parameter and corresponds to a time parameter allowing the duration of the transient phenomenon to be defined,
[0081] Ih represents a third parameter corresponding to an amplitude of the current harmonic of the transient phenomenon in the oscillatory term which can be equal to IA,
[0082] fh represents a fourth parameter corresponding to a frequency in the oscillatory term describing the transient phenomenon and
[0083] ah represents a fifth parameter corresponding to a phase of the oscillatory term describing the transient phenomenon.
[0084] For modeling and therefore to determine the parameters of the modeling function, the difference between the current measurement and the function 102 in the time window Tw is minimized, for example by applying a least squares method.
[0085] Then the presence or absence of a defect is determined from at least some of said parameters determined from said parameterizable modeling function 102, in particular by determining whether at least one of the parameters belongs to a defect region called Q (see last step represented on the flowchart of [Fig.4]).
[0086] The fault region Q can be determined for example by a learning and / or classification process, from real measurements or obtained by simulation of faults on a model of a power supply section between two monitored substations or by a combination of both.
[0087] If the fault region Q is determined by simulation, the topology of the power supply network to be monitored is modeled as closely as possible.
[0088] The electrical system infrastructure must accurately represent the actual electrical power supply network. Therefore, all the simulations mentioned below must take into account the different configurations.
[0089] In particular, the electrical power supply network to be monitored is simulated in numerous different operating conditions to represent as many possible situations as possible in order to delimit the fault region as precisely as possible.
[0090] To achieve this, the simulations must take into account faults at different locations on the power supply network, particularly when no trains are running and when one or more trains are running. Different values of the power absorbed by the substations 3 must also be considered. Non-fault events, such as pantograph bounces at different positions on the power supply line and for different power values, must also be simulated. Within this fault region delimitation, simulations of electric vehicle starts at different locations on the network and transients triggered, for example, by a train passing through a substation 3, a parallel-connection substation 8, or a mixed substation 9, are also performed at different speeds and power levels.
[0091] It may be advisable to check before determining whether, for example, the first parameter / second parameter pair is within a fault region Q, if the following conditions are cumulatively met:
[0092] L> Io, and
[0093] Io> 0.
[0094] Indeed, if one of these two inequalities is not verified, it is determined that there is no defect (see first step represented on the flowchart of [Fig.4]).
[0095] For even greater precision in modeling the measured curve 100, said function 102 of the current ip(t) as a function of time can be defined more generally by:
[0096]
[0097] 4s = &=!
[0098] with: p^ — Iw P2 ~ T and p3jk, p4jket p5jk parameters corresponding respectively to current amplitudes, frequencies and phase shifts.
[0099] In this case, a multitude of parameters can be determined, and to determine whether, for example, at least the first and second parameters are in the fault region, a principal component analysis (a well-known mathematical method) is applied to the determined parameters p = P2~T and p3>k, p4>ket, p5>k to obtain new uncorrelated variables, and the presence or absence of a fault is determined from at least one of these new uncorrelated variables. The fault region can be depending on the number of parameters taken into account (multidimensional).
[0100] Figures 5 to 8 show examples of results obtained with the process described above.
[0101] In these figures 5 to 8, the first parameter Iœ in kA is represented on the abscissa and the second parameter r in ms is represented on the ordinate.
[0102] The defect region Q is delimited in these graphs by a solid line 200 having a part 202 substantially parallel to the ordinate axis and to the value of r = 2.5 ms and a part 204 substantially parallel to the abscissa axis and to the value Iœ = lOkA.
[0103] It should be noted that parts 202 and 204 may also have curved shapes.
[0104] In these graphs, a pair (Iœ / r) is included in a fault region called Q to detect a fault if in the example Iœ > lOkA and r > 2.5 ms.
[0105] The pairs of first and second parameters (Iœ / r) determined by the modeling are represented by circles (see arrow 206 as an example).
[0106] Figure 5 shows the detachments of a vehicle pantograph. electrical fault in the IA power supply line. Even though such a detachment results in a significant current surge, it is not a fault that requires the safety measures / isolation of the affected power supply section. Figure 5 shows that, indeed, the first and second parameter pairs (Iœ / r) determined by the modeling are not in the fault region Q.
[0107] In [Fig.6] catenary pull-outs are shown as defects having as a result the wires are in contact with the earth - no electric vehicle is connected to the IA overhead power line.
[0108] It can be seen on [Fig.6] that indeed, the pairs of first and second parameters (Iœ / r) determined by the modeling are in the defect region Q.
[0109] We can see that the second parameter r is substantially the same for all pairs (Iœ / r), while Iœ can have very large amplitudes up to 18kA.
[0110] On [Fig.7] catenary pull-outs are shown as defects so that the wires are in contact with the earth - in this situation a train is located 12km from the fault in a nearby power supply section S3, the fault being present on section S2.
[0111] The results are similar to those of [Fig.6].
[0112] We can see that the second parameter r is substantially the same for all pairs (Iœ / r), while Iœ can have very large amplitudes up to 18kA.
[0113] In [Fig.8] catenary pull-outs are shown as defects with wires that are in contact with the earth - in this situation an electric vehicle is located 6km from the fault in the same electrical supply section S2.
[0114] The results in this specific case are much more dispersed than in the previous figures, but it is still observed that the determination of the pair of parameters (Iœ / r) allows us to determine the nature of the defect and the pairs of first and second parameters (Iœ / r) determined by the modeling are in the defect region Q.
[0115] Many other situations have been simulated and tested, for example with two electric vehicles in the same electrical supply section S with pantograph detachment or catenary tear-off for example.
[0116] The fault detection method is distinguished by its reliability and the fact that it can be implemented locally, without requiring intervention from a central PC monitoring and protection system. Because the method described above allows for the classification of observed transients, it is possible to avoid, in particular, unintended interruptions of the power supply sections.
Claims
Claims
1. Method for detecting a fault on a section (S) of an electrical supply line (IA) of a railway network, comprising the following steps: - a current is measured on the section (S) as a function of time during a measurement time window of a predefined duration, - parameters of at least one parameterizable modeling function (102) are determined modeling the measurement curve (100) of the current as a function of time, this parameterizable modeling function (102) having an asymptotic increasing component with at least one parameter defining the asymptotic value of the current in steady state and at least one parameter corresponding to a time constant defining a duration of establishment of the steady state, - the presence or absence of a fault is determined from at least some of said determined parameters of said parameterizable modeling function (102).
2. Detection method according to claim 1, according to which the time window has a duration of less than 200ms, in particular less than 100ms and for example between 30ms and 50ms, in particular equal to 40ms.
3. Detection method according to claim 1 or 2, according to which the asymptotic increasing component of the function is described by a function of the type _ , where represents the parameter defining the asymptotic value of the current in steady state and T represents the parameter corresponding to a time constant defining a duration of establishment of the steady state.
4. Detection method according to any one of claims 1 to 3, according to which said parameterizable modeling function further comprises an additional oscillatory component.
5. Detection method according to claim 4, according to which said parameterizable modeling function of the current ip(t) as a function of time is defined by ip(£) = 4- [Z8 — Ps sin(p5) — p^ je P* 4- p3sm(27ip4t + p5) with where Iœ represents the parameter corresponding to the current established at the end of the transient regime, r represents the parameter corresponding to the time parameter used to define the duration of the transient phenomenon, Ih represents a parameter corresponding to an amplitude of the current harmonic of the transient phenomenon in the oscillatory term which can be equal to / a, fh represents a parameter corresponding to a frequency in the oscillatory term describing the transient phenomenon and ah represents a fifth parameter corresponding to a phase of the oscillatory term describing the transient phenomenon.
6. A detection method according to any one of claims 1 to 5, wherein said function of the current ip(t) as a function of time is defined by: ^(0 = P. + Pc - -F 4 p^). k=l = S : A. with: = 7 ™ / 4 = r and p3>k, p4>k and p5jk parameters corresponding respectively to current amplitudes, frequencies and phase shifts.
7. Method according to claim 6, according to which a principal component analysis is applied to the determined parameters Pl — IP^~T and p3jk, p4jk and p5jk to obtain new decorrelated variables and in that the presence or absence of a defect is determined from at least one of said new decorrelated variables.
8. Method according to any one of claims 1 to 7, according to which before determining the presence or absence of a fault, it is checked whether Iœ>I0 and Io> 0, if one of these inequalities is not verified, it is determined that there is no fault.
9. Method according to any one of claims 1 to 8, according to which the modeling of the measurement curve by the parameterizable modeling function is carried out by applying a least squares method.
10. Method according to any one of claims 1 to 9, according to which the start of the measurement time window is triggered when the measured current crosses a predefined threshold.
11. Method according to any one of claims 1 to 10, according to which the start of the measurement time window is triggered when the time derivative of the measured current crosses a predefined threshold.
12. Method according to any one of claims 1 to 11, according to which the presence or absence of a fault is determined by determining the membership of at least one determined parameter in a fault region (Q) obtained by a learning and / or classification process, from real measurements or obtained by simulation of faults on a model of an electrical supply section between two monitored substations or by a combination of the two.
13. Device for detecting a fault on a section (S) of an electrical supply line (IA) of a railway network comprising a current measurement sensor and being configured to implement a protection method according to any one of claims 1 to 12.
14. Method for protecting a section of an electrical supply line of a railway network, in which each section is equipped with several protection devices (PI, P2, P3), each protection device (PI, P2, P3) comprising a current measurement sensor and is configured to implement a method for detecting a fault according to any one of claims 1 to 12, and in which all the protection devices (PI, P2, P3) of the same section (S2) are triggered when a fault has been determined by at least one protection device.
15. Protection device (PI, P2, P3) for a section (S2) of an electrical supply line of a railway network comprising a current measurement sensor and being configured to implement a protection method according to claim 14.