Method for monitoring the evolution of stray currents in a railway infrastructure and railway infrastructure monitored by such a method

Abstract

Method for monitoring the evolution of stray currents of a railway infrastructure and railway infrastructure monitored by such a method This method for monitoring the evolution of stray currents applies to a railway infrastructure comprising rails (2) laid on a ground (3), insulated from the ground by an insulation system (21) and defining at least one section (S, S') of track, substations (5) generating a direct voltage for supplying a vehicle, a monitoring system (7) comprising at least one rail-ground voltage sensor (73) and at least one calculation unit (77, 79) and at least one stabilized current source (71).The monitoring method comprises an operating phase comprising at least the emission of a stabilized current by each current source in at least one of the rails; the measurement of the voltage generated by the stabilized current between the rails and the ground by at least one rail-ground voltage sensor; the analysis by the calculation unit of the voltage measured by the rail-ground voltage sensor and the detection of a possible degradation of the insulation between the rails and the ground. Figure for the abstract: 1.

Description

Title of the invention: Method for monitoring the evolution of stray currents in a railway infrastructure and railway infrastructure monitored by such a method

[0001] The present invention relates to a method for monitoring the evolution of stray currents in a railway infrastructure and a railway infrastructure monitored by such a method.

[0002] It is known from US2004104723A1 to propose a method for identifying the risks induced by insulation defects on a railway infrastructure by stray currents generated by the passage of trains, this method consisting of analyzing the voltage generated by the stray currents at numerous measurement points distributed over the infrastructure and comparing these measurements with reference values. Due to the variability of the stray currents generated by the trains, this method has the disadvantage of requiring a very large number of measurements, and therefore of having to resort to a complex and expensive analysis.

[0003] It is these drawbacks that the invention more particularly intends to remedy by proposing a method for monitoring the evolution of stray currents in a railway infrastructure that is simpler to implement and less expensive.

[0004] To this end, the invention relates to a method for monitoring the evolution of stray currents in a railway infrastructure, the railway infrastructure comprising:

[0005] - rails laid on a ground and insulated from the ground by an insulation system, the rails defining at least one section (S, S') of track; - substations generating a voltage, preferably direct current, to supply a railway vehicle; and - a monitoring system comprising at least one rail-to-ground voltage sensor and at least one computing unit.

[0006] According to the invention, the railway infrastructure further comprises at least one stabilized current source and the monitoring method comprises an operating phase comprising at least the following steps:

[0007] - emission of a stabilized current by each current source in at least one of the rails; - measurement of the voltage generated by the stabilized current between the rails and the ground by at least one rail-ground voltage sensor; and - analysis by the calculation unit of the voltage measured by the rail-ground voltage sensor and detection of possible degradation of the insulation between the rails and the ground.

[0008] Thanks to the invention, it is possible to propose a method for monitoring the evolution of stray currents in a railway infrastructure based on an analysis of the voltages generated by a controlled stabilized current, which reduces the costs of this analysis and simplifies the implementation of the monitoring.

[0009] According to advantageous, but not mandatory, aspects of the invention, this monitoring method may incorporate one or more of the following characteristics, taken in any technically admissible combination:

[0010] - The exploitation phase includes an additional step of calculation by the unit of calculation of the current flowing in each section from the current source, and during the analysis phase, the calculation unit analyzes the voltage measured by the rail-ground voltage sensor and the calculated current and detects a possible degradation of the insulation between the rails and the ground by comparing on the one hand the measured voltage to a previous value of rail-ground voltage and on the other hand the calculated current to a previous value of the current flowing in the rails.

[0011] - The method comprises a deployment phase comprising at least one step initial consisting, on the one hand, of measuring for each rail-ground voltage sensor a reference value of the voltage generated by the stabilized current between the rails and the ground and, on the other hand, of calculating for each section a reference value of the current flowing in the rails from the current source.

[0012] - During the analysis step by the calculation unit, for each voltage sensor rail-ground, the comparison is made between the rail-ground voltage measured during the measurement step and the reference value of the rail-ground voltage measured during the initial measurement step, and for each section, the comparison is made between the current flowing on the section calculated during the calculation step and the reference value of the current flowing in the rails calculated during the initial calculation step.

[0013] - The railway infrastructure monitoring system comprises at least two rail-to-ground voltage sensors and at least two sections and the analysis step of the operating phase locates the location on the rails of the degradation of the insulation between the rails and the ground by identifying the section on which the current variation is the greatest, the degradation of the insulation being deemed to be located on this section.

[0014] - The railway infrastructure monitoring system comprises at least two rail-to-ground voltage sensors and at least two sections and the analysis step of the operating phase locates the location on the rails of the degradation of the insulation between the rails and the ground on the basis of a model comprising longitudinal resistances each representing the longitudinal electrical resistance of the rail on a section and transverse resistances representing the rail-to-ground insulation at the rail-to-ground voltage sensors, in which the transverse resistances are calculated from the voltage between rails and ground measured by voltage sensors, current emitted by current sources and longitudinal resistances, preferably using a matrix calculation, and in which the values ​​of transverse resistances are compared with reference values, calculated during a deployment phase of the monitoring method, to locate the location of insulation degradation.

[0015] - The operating phase is carried out in the absence of railway vehicle traffic. roviaires on the railway infrastructure and the operating phase includes an additional step, prior to the stage of emission of a stabilized current, which consists of verifying the absence of circulation of railway vehicles on the infrastructure.

[0016] - The exploitation phase includes an additional step consisting of calculating, for each section, a value of the insulation between the rails and the ground by approximating the current flowing in the rails and that the analysis step of the operating phase also analyzes this insulation value to detect possible degradation of the insulation between the rails and the ground.

[0017] - The railway infrastructure also includes additional voltage sensors for the rails arranged at each end of each section, during the measurement step of the operating phase, the ancillary sensors measure the voltage of the rails at each end of each section when a stabilized current is emitted by the current source, the operating phase includes an additional calculation step in which the calculation unit calculates, from these rail voltages, the current flowing on the rails at each end of each section of the rails, during the calculation step of the operating phase, from these currents, the calculation unit calculates a value of the insulation between the rails and the ground for each section, and during the analysis step of the operating phase, the calculation unit analyzes, for each section of the rails, the evolution of the insulation between the rails and the ground to detect a possible degradation of this insulation.

[0018] According to another aspect, the invention also relates to a railway infrastructure comprising:

[0019] - rails laid on a ground and insulated from the ground by an insulation system; - substations generating a voltage, preferably direct current, to supply a railway vehicle; and - a monitoring system comprising rail-to-ground voltage sensors and at least one computing unit.

[0020] According to the invention, this infrastructure further comprises:

[0021] - at least one stabilized current source; - possibly additional rail tension sensors; and - means of implementing the monitoring method mentioned above.

[0022] This infrastructure induces the same advantages as those mentioned above regarding the monitoring method of the invention.

[0023] The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of an embodiment of a method for monitoring the evolution of stray currents of a railway infrastructure and of a railway infrastructure monitored using this method, given solely by way of example and with reference to the appended drawings in which:

[0024] [Fig-1] [Fig.l] is a diagram of a railway infrastructure conforming to the invention; and

[0025] [Fig.2] [Fig.2] is a flowchart of the current monitoring method vagrants according to the invention.

[0026] A railway infrastructure 1 is shown schematically in [Fig.l]. This infrastructure comprises rails 2 forming a traffic lane laid on a ground 3, a contact line 4 and several substations 5. The contact line 4 is, for example, a catenary, an overhead contact line or a ground power supply taking the form of a rail dedicated to the electrical power supply.

[0027] A railway vehicle not shown, for example a train, a tram or a metro, can run on the rails 2. This vehicle is supplied with electrical energy by the substations 5, which generate a voltage, preferably a direct voltage, between the rails 2 and the contact line 4. In practice these substations are distributed along the rails 2, for example every 2 to 5 km in the case of a tram running in an urban environment and deliver a direct voltage between 600 and 3000 V, for example 1500 V, between the rails 2 and the contact line 4.

[0028] The supply current required to set the vehicle in motion is supplied to the vehicle via the contact line 4. The vehicle current is collected on the contact line, for example, by a pantograph or a pole. The return current flows from the vehicle to the substations 5 via the rails 2, which are made of electrically conductive material.

[0029] The rails 2 are laid on an insulation system 21, itself laid on the ground 3. Thus, the rails 2 are therefore normally electrically insulated from the ground 3.

[0030] The insulation system 21 nevertheless only allows for imperfect electrical insulation. Thus, the return current flowing through the rails between the vehicle and the substations creates a voltage between the rails 2 and the ground 3 and this voltage creates stray currents. These stray currents are currents that leave the rails 2 and flow between the vehicle and the substations via other uncontrolled paths, generally buried metal infrastructures, for example gas pipes. These stray currents can result in the corrosion of metal elements located near the rails 2, and therefore their deterioration.

[0031] The location and intensity of stray currents varies over time during operation of the railway infrastructure 1. This variation is, for example, caused by degradation of the materials of the rails 2 and of the insulation system 21.

[0032] For the operator of the railway infrastructure 1, it is important to know the evolution of these stray currents, and therefore to know the evolution of the insulation between the rails 2 and the ground 3.

[0033] According to the invention, this evolution is measured using a monitoring system 7.

[0034] The monitoring system 7 comprises a stabilized current source 71, rail-to-ground voltage sensors 73, a communication network 75, a local computing unit 77 and a remote computing unit 79.

[0035] The stabilized current source 71 designates in practice an adjustable source of direct current, connected to an electrical network not shown, and powered by this electrical network. This current source is described as “stabilized” because the current supplied does not depend, or depends in a non-significant manner:

[0036] - variations in the effective value and frequency of the power supplied by the electrical network which may occur during a day; - micro-cuts that may occur in the power supply provided by the electrical network; and - electrical characteristics of the railway infrastructure 1.

[0037] When no railway vehicle is running on the rails 2, the stabilized current source emits a control current which propagates in the rails. The presence of this control current generates a voltage between the rails 2 and the ground 3, called rail-ground voltage. The voltage sensors 73 make it possible to measure this rail-ground voltage. The voltage sensors are arranged along the entire length of the rails 2, for example spaced apart by a distance L of between 0.5 and 5 km, preferably equal to 1 km. In practice, the voltage sensors are preferably placed at the level of the substations 5. The rails 2 are then composed of track sections S of length L, a track section extending between two successive voltage sensors 73. Preferably, the length L is the same for all sections S. The rails further comprise an initial section S', which extends between the stabilized current source 71 and the voltage sensor 73 closest to this source.The length L' of this section S' is preferably as short as possible.

[0038] The measurements made by the voltage sensors 73 are then transmitted by the communication network 75 to the local calculation unit 77 which is, for example, a computer, then from the local unit to the remote calculation unit 79 which is, for example, a server, by remote communication means, for example via the Internet.

[0039] The rail-ground voltage measured by the sensors 73 depends mainly on three factors:

[0040] - the control current flowing in the rails 2; - the linear electrical resistance of the rails; and - insulation between the rails and the ground.

[0041] The linear electrical resistance of the rails is defined as the resistance of the rails to the passage of an electric current per unit of length, expressed in Ohm per kilometer.

[0042] Two voltage sensors, not shown, are placed on either side of the stabilized current source. These sensors make it possible to measure, by a known method, the linear electrical resistance of the rails, noted Rraiiet expressed in Ohm / km, when the current source 71 emits the control current.

[0043] The control current generated by the current source 71 being controlled and constant over time during the operation of the monitoring system and the linear electrical resistance of the rails being measured during this operation, the only factor influencing the rail-ground voltage measured by the sensors is the insulation between the rails and the ground. The measurement of this voltage and the study of the evolution of these measurements over time therefore make it possible to analyze the evolution of the insulation between the rails and the ground. Thus, in the monitoring method of the invention, the stray currents generated by the circulation of railway vehicles are not directly measured, but knowledge of the insulation between the rails and the ground makes it possible to deduce the evolution of the stray currents, which are directly caused by the rail-ground insulation defect.In other words, using a stabilized current source to generate a known and controlled current makes it possible to monitor stray currents without the need to measure them directly.

[0044] Advantageously, the monitoring system 7 further comprises additional rail tension sensors 9. Each section S and S' of the rails 2 comprises two additional sensors 9, which are arranged at the two ends of the section. In practice, the additional sensors are therefore located in the immediate vicinity of the rail-ground tension sensors 73, and each tension sensor 73 is located between two additional sensors 9. For example, the distance between the sensors 73 and the additional sensors 9 is 1 m.

[0045] These additional rail voltage sensors 9 measure the voltage of the rails 2, denoted Traib when a stabilized current is emitted by the current source 71. For this, each additional sensor comprises two measuring points placed on the rails 2 and separated by a distance D of between 10cm and 1m, preferably equal to 50cm.

[0046] For the sake of clarity of the drawing, only four additional sensors 9 are shown in [Fig.l], even if their number within the infrastructure 1 is much higher.

[0047] Thanks to the additional rail voltage sensors 9, the current flowing on the rails 2 at the level of each additional sensor, noted Craii, is calculated by the remote calculation unit 79, according to the following formula:

[0048] c _ Trail ral RrallxD

[0049] The stray current monitoring method of the invention comprises two phases: a PI deployment phase and a P2 exploitation phase.

[0050] The PI deployment phase includes the following steps:

[0051] - PI 10: installation of the railway infrastructure 1. - P130: initial measurement of the rail-to-ground voltage. This measurement allows establishing a voltage reference value Tl corresponding to the new condition of the railway infrastructure. In practice, a reference value Tl is established for each sensor 73. These measurements are taken at several points, i.e. at several sensors 73, preferably each sensor 73. In addition, a current reference value Cl and C' 1 flowing in each section S and S' of the rails 2 is calculated, from the reference voltages Tl measured by the sensors 73 located at the two ends of the section and the linear electrical resistance of the rails, according to the formulas:

[0052] Cl = 21 TT for sections S R rail x L

[0053] C'I = 41 TT for section S' ^raii x L'

[0054] where ATI is the difference between the voltages Tl measured at the two ends of the section considered.

[0055] - P190: end of PI phase

[0056] The operating phase P2 is carried out regularly during the operation of the railway infrastructure, for example once per night or according to another frequency determined by the operator, and comprises the following steps:

[0057] - P210: emission by the current source 71 of a stabilized current propagating in rails 2. This current depends on the insulation between rails 2 and ground 3, as well as on the length of rails 2 and varies, for example, from 50 to 350 amperes - P230: measurement at several points of the rail-ground voltage T2 by the sensors of voltage 73. - P250: transmission of measured data from voltage sensors 73 to the remote computing unit 79, via the local computing unit 77. - P260: calculation, by the remote calculation unit 79, of currents C2 and C'2 circulating in each section S and S' of rails 2, according to the formulas:

[0058] = ^^"2 for S sections ^rail X

[0059] ^"'2 — AT2 for section S' Rail X

[0060] where AT2 is the difference between the voltages T2 measured by the sensors 73 at the two ends of the section considered. The calculated currents C2 and C'2 are approximations of the currents actually flowing in the sections S and S'.

[0061] Equipping the railway infrastructure with several sensors 73 makes it possible, on the one hand, to make rail-ground voltage measurements more reliable in the case of very long rails, and on the other hand to locate the location on the rails 2 of any possible degradation of the insulation. At each point, the measured rail-ground voltage T2 is representative of the rail-ground insulation. Indeed, for a given current emitted by the source 71 during step P210, for example 100 amperes, and for a given section S, part of the current flows in the rails 2, for example 70 amperes, and part leaks into the ground 3, for example 30 amperes, this distribution being dependent on the rail-ground insulation of the section S. In the theoretical case of perfect rail-ground insulation, 100% of the current would flow in the rails 2 and no current would leak to the ground 3, the rail-ground voltage T2 would then be maximum.

[0062] When a degradation of the rail-ground insulation is present on a section, the rail-ground voltages T2 measured on all the sections decrease and the currents C2 and C'2 calculated on all the sections vary, this variation being greater on the section whose insulation is degraded. The more the rail-ground insulation is degraded, the greater the decrease in the voltages T2 and the greater the variation in the currents C2 and C'2.

[0063] - P270: analysis, by the remote calculation unit 79, of the data measured by the voltage sensors in step P230 and data calculated in step P260. This analysis consists, on the one hand, in comparing, for the data from each sensor 73, the measured voltages T2 during step P230 with the reference voltages T1 measured during step P130, and possibly with the measured voltages T2 during step P230 of the phases P2 previously executed and, on the other hand, in comparing the currents C2 and C'2 calculated during step P260 with the reference currents C1 and C'1 calculated during step P130, and possibly with the currents C2 and C'2 calculated during step P260 of the phases P2 previously executed. If at each measurement point, i.e. for the data from each voltage sensor, on the one hand, the measured voltage T2 is consistent with the reference voltage T1 and possibly with the voltages T2 measured during previous phases and, on the other hand, the calculated current C2 or C'2 is consistent with the reference current Cl or C'1 and possibly with the 。currents C2 or C'2 measured during previous phases, then phase P2 ends in a step P290. If too large a deviation is measured, that is to say if, at one or more measurement points corresponding to a sensor 73, the measured voltage and the calculated current change significantly over time, that is to say for example if the voltage or the current deviates by more than 15% from the reference value, the remote calculation unit detects a significant degradation of the rail-ground insulation. Step P280 is then triggered. Depending on the measurement points showing a significant change in the current flowing in the rails and their location, the degradation of the rail-ground insulation can be located along the rails 2.The selection criterion for determining whether a deviation of the measured rail-ground voltages from the reference voltages or whether a deviation of the calculated currents flowing in the rails from the reference currents are too large and constitute a fault is, for example: . • the absolute value of a difference between the current calculated at a measuring point and the reference value of the current at this measuring point is equal to at least 5% of the reference value. In this case, by "compliant" is meant that the difference C2-C1 or C'2-C' 1 is, in absolute value, less than 5% of the value Cl or C' 1; • the absolute value of a difference between the voltage at a measurement point and the voltage value T2 measured during the previous phase is equal to at least 5% of the voltage value T2 measured during the previous phase; • a change in the profile of the curve of the evolution of the voltages measured over time; or • a change in the profile of the evolution curve of the currents calculated over time. • Other selection criteria may be applied. - P280: alert from the railway infrastructure operator 1. The calculation unit remote 79 is configured to alert the operator of the railway infrastructure 1 of the degradation of the rail-ground insulation when a fault is detected. This alert can, for example, be the automatic sending of an e-mail, the display of an alert message in a control station of the infrastructure 1, or the sending of predetermined instructions.

[0064] The approximate localization of the degradation of the rail-ground insulation along the rails 2 is made possible by the use of several sensors 73. Indeed, when an insulation fault appears, the current flowing in the rails does not vary uniformly along the rails 2, and this current variation will be greater near the fault, that is to say on the section S or S' which contains the fault. Thus, the variation of the calculated currents C2 and C'2 is greater for the current C2 or C'2 of the section containing this fault than for the currents measured on the other sections, which makes it possible to identify the section containing the location on rails 2 where the degradation of the insulation is located. In practice, the section where the degradation is located is therefore the section where the calculated current C2 or C'2 varies the most.

[0065] As long as no drift is detected in step 270, the operating phase P2 is repeated over time, at a given frequency, in order to carry out permanent monitoring of the rail-ground insulation. For example, phase P2 is carried out daily, or even weekly.

[0066] Another way to locate the degradation of the rail-ground insulation during the analysis step P270 is to use a model including resistors arranged in a ladder, where longitudinal resistors, denoted "RL", represent the rail and its longitudinal electrical resistance, so that each longitudinal resistance corresponds to the resistance of the rail on a section S or S', and in which transverse resistors, denoted "RT", placed at the locations of the voltage sensors 73, represent the insulation between the rail and the ground. From the last voltage measurements, the current injected by the current source 71, and the last measurement of the rail resistance, a set of reference values ​​is calculated for the set of transverse resistances RT.

[0067] Thus, with each new joint measurement of the rail resistance, the injected current, and the rail-ground voltages, it is possible to recalculate the elements of the ladder-arranged resistance model, i.e. the longitudinal RL and transverse RT resistances. On the basis of reference values ​​calculated during the PI deployment phase of the monitoring method, the comparison of the calculated transverse resistance values ​​with the reference RT transverse resistance values ​​makes it possible, in the event of the appearance of a fault, to locate the section(s) S and S' in which a variation in the track insulation occurs.

[0068] More precisely, knowing the longitudinal resistance RL of the rails, the injected current and the rail-ground voltages, only the transverse resistances RT are unknown. These transverse resistances are then determined by a matrix calculation.

[0069] Thus, during the installation of the monitoring system, in other words during the deployment phase PI of the monitoring method, a model of electrical resistances specific to the track, and particularly dependent on the transverse resistances RT, is obtained. Then, during a measurement of the insulation of the track, if the value of the longitudinal resistances RL of the sections S or S' are substantially identical to the reference values, measured during the installation of the monitoring system), new rail-ground voltages are measured using the sensors 73, which are substantially equal to the reference rail-ground voltages if no fault is present on the sections concerned. In the case where the values ​​of the new rail-to-ground voltages differ from the reference rail-to-ground voltage values, generally by being lower than these reference values, the new RT transverse resistances are determined using a matrix calculation. The ratio of the new RT transverse resistance values ​​to the reference RT transverse resistance values ​​then makes it possible to assess the evolution of the track insulation. In particular, the further this ratio is from 1, the greater the track insulation defect.

[0070] Furthermore, in the case where the longitudinal resistances have varied, for example due to a variation in the ambient temperature, a new reference model must be determined. Based on the values ​​of the reference transverse resistances, and taking into account the new values ​​of longitudinal resistors RL, the rail-ground voltages theoretically expected at the voltage sensors 73 are determined. The measurement of the rail-ground voltages, using the sensors 73, then makes it possible to determine the transverse resistances RT, as explained above. The presence of a fault in the track insulation and the evolution of such a fault are then observed by studying the ratio of the values ​​of the determined resistances RT to the reference transverse resistances.

[0071] Phase P2 is carried out in the absence of any railway vehicle traffic on the railway infrastructure 1, in order to avoid any other source of current, for example the supply currents necessary for setting the vehicles in motion. This has the advantage of ensuring that the monitoring method only analyses the variation in the track insulation. For example, phase P2 is carried out at night.

[0072] Another embodiment of the stray current monitoring method consists in calculating, for each section S or S', the value of the insulation G between the rails 2 and the ground 3 on this section by approximating the value of the current I2 flowing in the rails and leaving this section. This calculation is carried out during an additional step P265, taking place between steps P260 and P270. It is carried out initially for the section S', then successively for each section S of the rails 2, starting with the section S adjacent to the section S'.

[0073] The formula applied is as follows:

[0074]

[0075]

[0076] cosh (ylGRraii x / ) - x sinh (^GRraii x / ) ' % x sinh (^GRratl x Z) cosh (^GRrail xl) In which: Vi and V2 are the voltages, expressed in volts, between rails 2 and ground 3 respectively at the input and output of section S or section S', measured using rail-ground voltage sensors 73 located at the ends of the section, which therefore correspond in practice to the rail-ground voltages T2. In the case of the first section S', the rail-ground voltage VI is measured at the current source 71. - Ii and I2 are the currents, expressed in amperes, flowing on rails 2 respectively at the input and output of section S or section S'. In the case of the first section S', h corresponds to the stabilized current emitted by the current source 71, which is therefore known. - Rraii is the linear electrical resistance of rails 2, in Ohm / km. - f is the length of the section on which the formula is applied expressed in kilometers, i.e. the length L for the S sections and the length L' for the S' section - G is the rail-ground insulation of the section, calculated in S / km. - cosh and sinh represent the hyperbolic cosine function and the hyperbolic sine function respectively.

[0077] This formula has two unknowns, which are the current I2 at the output of the section on which the formula is applied and the rail-ground insulation G of the section, and two equations, which allows its resolution. The current I2 calculated at the output of a section corresponding to the current L at the input of the adjacent section, it is thus possible to calculate, for each section successively, the current flowing in the rails at the output of the section and the rail-ground insulation of the section, starting with section S'.

[0078] The data calculated by this formula then make it possible to complete the analysis carried out during step P270, because they provide an estimate of the rail-ground insulation values ​​of each section of the rails 2. This additional data makes it possible to increase the reliability of the method for monitoring the evolution of stray currents and to provide more information to the operator of the railway infrastructure 1.

[0079] Another embodiment of the stray current monitoring method consists of calculating precisely, for each section S or S', the value of the insulation G' between the rails 2 and the ground 3. This calculation is carried out during an additional step P265' taking place between steps P260 and P270 using the additional voltage sensors 9, which make it possible, for the ends of each section S or S', to measure the voltage T rail and to calculate precisely the current Craii. The formula for calculating the value of the insulation G' for a section is as follows:

[0080] r'_ 1 / / - / 2' 7 “ 7 x (^ + ^2) / 2

[0081] In which:

[0082] - G' is the rail-ground insulation of the section, expressed in S / km. - 7 is the length of the section on which the formula is applied expressed in kilometers, that is to say the length L for the S sections and the length L' for the S' section. - Ui and U2 are the voltages, expressed in volts, measured by the auxiliary rail voltage sensors 9 at the two ends of section S or section S'. These voltages therefore correspond in practice to the TraU voltages. - Ii' and I2' are the currents, expressed in amperes, flowing on rails 2 at the two ends of section S or section S'. These currents therefore correspond in practice to the currents Craii.

[0083] Thus, thanks to the addition of the additional rail voltage sensors 9 on the railway infrastructure 1, the insulation G' between the rails 2 and the ground 3 can be calculated precisely for each section S and S' and its evolution controlled over time. Indeed, the data used for the calculation being measured when a stabilized and controlled current is emitted by the current source 71, the different variables which can influence the calculation of the insulation G' are controlled by the operator of the railway infrastructure. Thanks to this calculation, the monitoring method is improved:

[0084] - during step P130 of phase PI, for each section, a reference value of the rail-ground insulation G'i is calculated; - during step P230 of phase P2, for each additional sensor 9, a voltage value of rails 2 Trdii is measured; - during step P265' of phase P2, for each section, a value of the currents Crdii and the rail-ground insulation G'2 is calculated; and - during step P270, the calculation unit analyzes, for each section S and S', the evolution of the insulation G'2 over time. This analysis consists of comparing, for each section, the insulation G'2 calculated during step P230 with the reference insulation G\ calculated during step P130 and possibly with the insulations G'2 calculated during step P230 of the phases P2 previously executed. When an excessive drift of the rail-ground insulation is detected on one or more sections S or S', step P280 is triggered. For example, an excessive drift will be detected if the absolute value of a difference between G'2 and G\ is equal to at least 5% of G'i, or if the profile of the evolution curve of the rail-ground insulations calculated over time changes.

[0085] Steps P265 and P'265 being optional, since not implemented in the first embodiment of the invention, they are represented in dotted lines in [Fig.2],

[0086] In a variant of the invention not shown, phase P2 comprises an additional step P205, prior to step P210, which consists of verifying the absence of circulation of railway vehicles on the infrastructure 1, for example by carrying out a measurement of rail-ground voltage, assumed to be negligible in the absence of circulation.

[0087] In a variant of the invention not shown, the stabilized current generated in step P210 comes from several sources 71 which successively emit an identical current. For example, a stabilized current source 71 is installed every 25 to 35 km along the rails 2. The use of several sources 71 makes it possible to make the monitoring method more reliable on very long infrastructures.

[0088] In a variant of the invention not shown, phase PI does not include the initial measurement step P130 and the monitoring method is based solely on the analysis of the variation of the voltage measurements T2, carried out in step P230 of phase P2, and of the variation of the currents C2 and C'2 calculated in step P260 of phase P2, over time.

[0089] In a variant of the invention not shown, in step P230, only some of the sensors 73 carry out a measurement of the rail-ground voltage T2.

[0090] In a variant of the invention not shown, the monitoring system 7 contains a single rail-ground voltage sensor 73.

[0091] In a variant of the invention not shown, steps P260 and P270 are executed by the local calculation unit 77.

[0092] The embodiments and variations contemplated above may be combined to generate new embodiments in the invention.

Claims

Claims

1. Method for monitoring the evolution of stray currents of a railway infrastructure (1), the railway infrastructure comprising: - rails (2) laid on a ground (3) and insulated from the ground by an insulation system (21), the rails defining at least one section (S, S') of track; - substations (5) generating a voltage, preferably direct current, for supplying a railway vehicle; and - a monitoring system (7) comprising at least one rail-to-ground voltage sensor (73) and at least one computing unit (77, 79); characterized in that the railway infrastructure further comprises at least one stabilized current source (71), in that the monitoring method comprises an operating phase (P2) comprising at least the following steps: - (P210) emission of a stabilized current by each source of current (71) in at least one of the rails; - (P230) measurement of the voltage (T2) generated by the current stabilized between the rails (2) and the ground (3) by the at least one rail-ground voltage sensor (73); - (P260) calculation, by the calculation unit (77, 79), of the current (C2, C'2) circulating in each section (S, S') from the current source; - (P270) analysis by the calculation unit (77, 79) of the voltage measured by the rail-ground voltage sensor (79) and the calculated current and detection of possible degradation of the insulation between the rails (2) and the ground (3). and in that, during the analysis phase (P270), the calculation unit (77, 79) analyses the voltage measured by the rail-ground voltage sensor (79) and the calculated current and detects a possible degradation of the insulation between the rails (2) and the ground (3) by comparing on the one hand the measured voltage to a previous rail-ground voltage value (Tl, T2) and on the other hand the calculated current to a previous value of the current (Cl, C' 1, C2, C'2) flowing in the rails.

2. Monitoring method according to claim 1, characterized in that it comprises a deployment phase (PI) comprising at least one initial step (P 130) consisting, on the one hand, in measuring for each rail-ground voltage sensor (73) a reference value (Tl) of the voltage generated by the stabilized current between the rails (2) and the ground (3) and, on the other hand, in calculating for each section (S, S') a reference value (Cl, C' 1) of the current flowing in the rails from the current source.

3. Monitoring method according to claim 2, characterized in that during the analysis step (P270) by the calculation unit (77, 79): - for each rail-ground voltage sensor (73), the comparison is made between the rail-ground voltage (T2) measured during the measurement step (P230) and the reference value (T1) of the rail-ground voltage measured during the initial measurement step (P130); and - for each section (S, S'), the comparison is made between the current (C2, C'2) flowing on the section calculated during the calculation step (P260) and the reference value (Cl, C'1) of the current flowing in the rails calculated during the initial calculation step (P130).

4. Monitoring method according to any one of the preceding claims, characterized in that the monitoring system (7) of the railway infrastructure (1) comprises at least two rail-ground voltage sensors (73) and at least two sections (S, S') and in that the analysis step (P270) of the operating phase (P2) locates the location on the rails (2) of the degradation of the insulation between the rails (2) and the ground (3) by identifying the section (S, S') on which the variation in the current (C2, C'2) is the greatest, the degradation of the insulation being deemed to be located on this section.

5. Monitoring method according to any one of the preceding claims, characterized in that the monitoring system (7) of the railway infrastructure (1) comprises at least two rail-ground voltage sensors (73) and at least two sections (S, S') and in that the analysis step (P270) of the operating phase (P2) locates the location on the rails (2) of the degradation of the insulation between the rails (2) and the ground (3) on the basis of a model comprising resistances longitudinal (RL) each representing the longitudinal electrical resistance of the rail (2) over a section (S, S') and transverse resistances (RT) representing the rail-ground insulation at the rail-ground voltage sensors (73), wherein the transverse resistances are calculated from the voltage (T2) between the rails (2) and the ground (3) measured by the voltage sensors (73), the current emitted by the current sources (71) and the longitudinal resistances (RL), preferably using a matrix calculation, and wherein the values ​​of the transverse resistances are compared with reference values, calculated during a deployment phase (PI) of the monitoring method, to locate the location of the insulation degradation.

6. Monitoring method according to any one of the preceding claims, characterized in that the operating phase (P2) is carried out in the absence of circulation of railway vehicles on the railway infrastructure (1) and in that the operating phase (P2) comprises an additional step (P205), prior to the step (P210) of emission of a stabilized current, which consists of verifying the absence of circulation of railway vehicles on the infrastructure (1).

7. Monitoring method according to any one of the preceding claims, characterized in that the operating phase (P2) comprises an additional step (P265) consisting of calculating, for each section (S, S'), a value of the insulation (G) between the rails (2) and the ground (3) by approximating the current (I2) flowing in the rails (2) and in that the analysis step (P270) of the operating phase (P2) also analyses this insulation value to detect a possible degradation of the insulation between the rails (2) and the ground (3).

8. Monitoring method according to any one of claims 1 to 6, characterized in that: - the railway infrastructure (1) further comprises additional sensors (9) for the voltage of the rails (2) arranged at each end of each section (S, S'); - during the measurement step (P230) of the operating phase (P2), the additional sensors measure the voltage of the rails (TraU) at each end of each section (S, S') when a stabilized current is emitted by the current source (71); - the operating phase (P2) comprises a calculation step

9. (P265') additional in which the calculation unit (77, 79) calculates, from these rail voltages, the current (Craii) flowing on the rails at each end of each section of the rails; - during the calculation step of the operating phase, from these currents, the calculation unit (77, 79) calculates a value of the insulation (G'2) between the rails (2) and the ground (3) for each section (S, S'); and - during the analysis step (P270) of the operating phase, the calculation unit (77, 79) analyses, for each section (S, S') of the rails (2), the evolution of the insulation (G'i, G'2) between the rails and the ground to detect a possible degradation of this insulation. Railway infrastructure (1) including: - rails (2) placed on a ground (3) and insulated from the ground by an insulation system (21); - substations (5) generating a voltage, preferably direct current, for supplying a railway vehicle; and - a monitoring system (7) comprising rail-ground voltage sensors (73) and at least one computing unit (77, 79); characterized in that the monitoring system (7) of the railway infrastructure (1) further comprises: - at least one stabilized current source (71); - possibly additional rail tension sensors (9); and - means (71-79) for implementing the monitoring method of claims 1 to 8.

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