In situ monitoring of dynamically mechanically stressed supply and / or control lines

Abstract

A device is used to monitor an electrical line in order to predict failure, wear and / or aging of the electrical line. The electrical line has a first and a second end. The electrical line is configured and laid out to connect a useful signal source to a consumer. The device has a measurement evaluation unit connected between the useful signal source and the first end of the electrical line. The device further has a first filter connected between the useful signal source and the measurement evaluation unit. The first filter is configured and designed to block a measurement signal to the useful signal source and to allow a useful signal to pass through to the consumer. The useful signal source is configured and designed to send the useful signal through the first filter, the measurement evaluation unit and through the electrical line to the consumer.The measurement evaluation unit is configured and designed to add a measurement signal to the useful signal, to receive and evaluate at least part of a measurement signal reflected in the electrical line, and to output a measure of a probability of occurrence of a failure, wear and / or aging of the electrical line.

Description

background

[0001] This article presents a device and method for in-situ monitoring of dynamically mechanically stressed connecting and / or control lines. Features and properties of the device and method are defined in the claims; however, the description and figures also reveal characteristics of the device and method, as well as their various aspects and interrelationships.

[0002] Efficient maintenance is becoming increasingly important for maintaining the operation of electrically operated systems and machines. For electrical cables and wires, the two main approaches to maintenance are reactive maintenance, i.e., replacing cables / wires or connectors, etc., in the event of damage, and preventive maintenance. Preventive maintenance involves performing maintenance and replacing wear parts at predetermined intervals. Predictive maintenance involves collecting and evaluating key data from systems and machines during ongoing operation. To optimize costs and operational reliability, maintenance must be performed neither too early (resulting in high costs) nor too late (resulting in system and machine failure).

[0003] In industrial electrical systems and machines, the electrical cables that connect a signal or energy source to a signal sink or load are sometimes subject to extremely strong environmental influences. In moving and force-guided applications, such as in a cable chain, cables are subjected to considerable bending and flexing loads. In robotic applications, torsional forces also act. Within wind turbines, torsional and tensile forces (determined by the cable's own weight) act on the cables.

[0004] Therefore, there is a need to predict unplanned degradations or failures of dynamically mechanically stressed lines in order to prevent a possible failure. State of the art

[0005] DE 10 2021 000 284 A1 discloses a system and method for monitoring a line connected to a frequency converter-fed electrical machine. The associated frequency converter is used to adjust the speed of the electrical machine using rectangular pulses. These rectangular pulses change when the electrical line shows signs of degradation. Based on these changes in the rectangular pulses provided by the frequency converter, a measure of the probability of failure can be determined.

[0006] According to DE 1 038 140, a core of a cable with absorbent insulation material is surrounded by an impregnating substance, in this case paraffin. When the temperature changes, the dielectric constant changes. This allows the temperature and fault location to be determined by measuring the propagation time against a reference conductor. This requires a cable design that differs significantly from current cables, which also poses significant challenges for certification (e.g., fire safety). The arrangement described here has an evaluation device installed at both cable ends.

[0007] A time-domain reflectometer (TDR) is a device used to analyze an electrical line for impedance changes in order to identify associated anomalies based on those impedance changes. A TDR injects a pulse of electrical energy into an electrical line. When the electrical pulse encounters a local impedance change along the length of the electrical line, a portion of the pulse's energy is reflected back to the time-domain reflectometer. By evaluating, for example, the amplitude and polarity of the reflected wave, a measure of the impedance change can be determined. Additionally, by measuring the pulse's travel time, the location of the impedance change can also be determined. Typical anomalies that can cause an impedance change include, but are not limited to, connectors, splices, damage, neutral corrosion, broken conductors, etc.

[0008] US 2015 016 0283 A1 concerns a time-domain reflectometer to be used in situ, which is to be operated without having to take the electrical line out of operation.

[0009] For connection or control cables, two approaches have essentially been established: Firstly, a measurement with an additional sensor element in the cable, in the form of an expanded wire that breaks in the event of overload, or a temperature / humidity sensor (see also DE 20 2017 102 410 U1, DE 10 2013 227 051 B4, DE 10 2018 204 171 A1). Secondly, the wires are disconnected during system downtimes and semi-automated measurement of resistance, TDR, capacitance, and breakdown voltage strength (see also EP 3 199 960 A1).

[0010] DE 10 2020 111 743 A1 relates to an integrated circuit and a method for monitoring a switching transistor and a motor system. For this purpose, a monitoring circuit is used, which is arranged on a monolithic integrated circuit and monitors an output signal of a first switching transistor for a first output edge transition at a monitoring terminal. A time measuring circuit on the integrated circuit serves to measure a first time delay between a first input edge transition of a first control signal and the first output edge transition. The first control signal is configured to cause a state change of the first switching transistor.An analysis circuit arranged on the integrated circuit is arranged to compare the measured first time delay with a first predetermined threshold value to form a first comparison result and to indicate a first error condition based on the first comparison result.

[0011] DE 2018 127 444 discloses a method in which aging parameters are determined via the surface roughness of the copper conductor.

[0012] DE 20 2021 106 364 U1 describes a monitoring system for monitoring the condition of a cable guided through a cable guide device, in particular an energy guide chain. The monitoring system comprises a movable cable guide device for guiding a cable between a first connection point and a second connection point movable relative thereto, having at least one movable section and at least one cable, which is guided through the cable guide device with a cable section to be monitored. Furthermore, this monitoring system comprises a monitoring device with a first module and a second module, each of which is provided on either side of the cable section to be monitored.The monitoring system is characterized in that the modules are designed to cooperate in order to determine at least one electrical transmission property of the line section in relation to a predetermined radio frequency (HF) signal during operation, and the first module comprises an HF generator which is coupled to the line to be monitored in order to couple or bring a predetermined HF signal to the line section as a test signal, which signal is preferably independent of the intended use of the line to be monitored; and the second module has an HF receiver which is coupled to the line to be monitored in order to decouple or receive the HF signal from the line section and is set up to evaluate properties of the received HF signal in order to determine at least one value relating to the transmission quality over the line section, in particular with regard to the received signal strength orsignal attenuation.

[0013] DE 196 50 974 A1 discloses a method for detecting the condition of an electrical line comprising several steps. A first electrical pulse is fed into the line at a first end, a resulting first echo signal from the line is detected at the first end, a second electrical pulse is fed into the first end of the line, a second resulting echo signal is detected, and the two echo signals are compared.

[0014] If there is a deviation and / or a match between the two echo signals, a corresponding alarm signal is generated.

[0015] DE 10 2016 116 719 A1 discloses a device for locating a fault on a conductor of an electrical network having at least one phase conductor and at least one counter conductor. This device comprises a device for coupling at least one test pulse into the conductor and a device for coupling echo pulses reflected at the fault from the conductor, as well as a steering device for coupling the pulses at least preferably in the forward direction to the fault. The device is characterized in that the coupling and decoupling devices are designed to be inductively coupled, and in that the steering device is designed as a capacitor arranged backward from the coupling devices between the conductor and the counter conductor.

[0016] DE 101 12 844 A1, US 6,657,437 B1, EP 2 157 438 A1, DE 10 2010 000249 A1, DE 10 2005 055429 A1, DE 10 2018 204 173 A1, DE 10 2018 204 171 A1, DE 10 2018 204 177 A1, and DE 10 2018 204 174 A1 concern further technological background.

[0017] What is needed is a cost-effective, universal variant that continuously monitors the electrical line during operation of a consumer without the need for additional sensor lines, thus ensuring high system availability. Proposed solution

[0018] To solve this problem, the devices or methods with features or steps of the independent claims are proposed.

[0019] A device is used for the (continuous / time-continuous) monitoring of an electrical line in order to predict failure, wear and / or aging of the electrical line. The electrical line has a first and a second end. The electrical line is configured and laid to connect a useful signal source to a consumer. The device has a measurement evaluation unit connected between the useful signal source and the first end of the electrical line. The device further has a first filter connected between the useful signal source and the measurement evaluation unit. The first filter is configured and designed to block a measurement signal to the useful signal source, in particular at least partially, and to allow a useful signal to pass to the consumer.The useful signal source is configured and designed to send the useful signal through the first filter, the measurement evaluation unit, and through the electrical line to the consumer. The measurement evaluation unit is configured and designed to add a measurement signal to the useful signal, in particular in a potential-free manner, to receive and evaluate at least part of a measurement signal reflected in the electrical line, and to output a measure of the probability of failure, wear, and / or aging of the electrical line. The useful signal source can be configured as an energy signal source. The consumer can be configured as a sink.

[0020] The measured signal may have a measured signal level / peak / amplitude value that is (significantly) reduced compared to the effective value of the desired signal. The measured signal level / peak / amplitude value may correspond to between 1% and 15%, in particular 2%, 4%, 6%, 8%, 10%, 12%, or 14%, of the effective value of the desired signal.

[0021] One advantage is that the line to be monitored does not need to be disconnected for monitoring and no additional sensor line needs to be inserted / attached to the existing line.

[0022] The measurement evaluation unit can be set up and designed to add a measurement signal to the useful signal, in particular potential-free, or to impress it on the useful signal.

[0023] The device can further comprise an interface connected between the second end of the electrical line and the consumer, wherein the interface is configured and designed to reflect the measurement signal (at least in part) back to the consumer, to the line, in particular to the measuring unit, and to allow the useful signal to pass to the consumer. The interface can be designed as a second filter or at least comprise this second filter. The interface can be designed as a passive element, in particular as a toroidal core. In other words, the interface can be designed as a passive element that operates without an additional power supply.

[0024] An advantage of this design variant is that the measurement signal added to the useful signal remains within the line to be monitored and is only applied at the points relevant for monitoring. The defined reflection points of the first filter and the interface / second filter ensure that the measurement signal is not influenced by changes in the electrical line, thus reducing the measurement influences caused by unwanted effects. This reduces the probability of false detections and is lower than in designs with additional measurement / sensor wires.

[0025] The first and / or second filter can be designed as a common-mode choke or as a toroidal core, particularly as an iron, ferrite, or nanocrystalline toroidal core. Compared to ferrite designs, nanocrystalline material has the advantage that its higher relative permeability allows for the same functionality while requiring less space / weight. Furthermore, the material offers advantages in terms of mechanical robustness, temperature resistance, and magnetic saturation behavior compared to ferrite designs.

[0026] The first and / or the second filter may have an inductance in a range of 15 µH to 25 µH, in particular 19 µH, 20 µH, or 21 µH.

[0027] The measurement evaluation unit can comprise a measurement signal unit configured and designed to add the measurement signal to the useful signal. The measurement signal unit can be configured and designed to add a measurement signal to the useful signal or to impress it onto the useful signal.

[0028] The measurement evaluation unit can further comprise a detection unit and an evaluation stage. The detection unit can be configured and designed to detect at least a portion of a reflected measurement signal (in the electrical line), in particular amplitude values of the at least a portion of the reflected measurement signal. The detection unit can be configured and designed to send the at least a portion of the reflected measurement signal, in particular in digitized form, to the evaluation stage. The detection of the at least a portion of the reflected measurement signal can be detected / sampled by the detection unit at time intervals of less than 50 ns, in particular (including the limits) between 1 ns and 10 ns and / or 2 ns, 6 ns, or 8 ns.

[0029] In other words, for detecting at least a portion of the reflected measurement signal by the detection unit, a temporal resolution of at most 50 ns, in particular (including the limits) between 1 ns and 10 ns and / or 2 ns, 6 ns, or 8 ns, can be provided in order to thereby enable rapid sampling of the reflected signal.

[0030] The detection unit can be configured and designed to receive / detect a number of parts (N reflection profiles or samples) of the reflected measurement signal (in the electrical line), in particular amplitude values of the number of parts of the reflected measurement signal, in particular within a time window to be determined. The time window / sampling time can be (including the limits) between 5 ms and 10 s, in particular approximately 3 s.

[0031] The detection unit can be configured and designed to send the number of parts of the reflected measurement signal, in particular in digitalized form, to the evaluation stage.

[0032] The evaluation stage can be set up and designed to receive the at least one part of the reflected measurement signal and / or the number of parts of the reflected measurement signal and / or to process the at least one part and / or the number of parts of the reflected measurement signal, in particular to process it by means of image processing, and to store it.

[0033] In other words, the corresponding received measurement signals can be preprocessed so that the reflection profiles they contain have the same axis / data scaling for subsequent processing.

[0034] The evaluation stage can be set up and designed to determine a reflection profile from the processed at least one part of the reflected measurement signal and / or to determine an averaged and / or a reconstructed reflection profile from the processed number of parts of the reflected measurement signal.

[0035] A reconstructed reflection profile can be the result of a reflection profile reconstruction, where the reconstruction can be based on at least one component of a principal component analysis of the number of components of the reflected measurement signal. In other words, unwanted signal components can be filtered out of the number of components of the reflected measurement signal using multivariate statistical methods, and a (single) reflection profile can be reconstructed from the filtered data.

[0036] The evaluation stage can be set up and designed to determine and output a type and / or location of a line fault, in particular insulation, wire connection and / or copper faults, based on the reflection profile, the averaged reflection profile and / or the reconstructed reflection profile, in particular based on its course(s), in particular to output whether there is a spatially uniform deterioration of the electrical line or a local defect.

[0037] This has the advantage that possible fluctuations in the reflection profiles caused by, for example, external unwanted electromagnetic influences (EMC) or simultaneous switching operations / changes in the useful signal can be compensated or reduced.

[0038] The evaluation stage can further be configured and designed to determine and store a processed initial reflection profile in a first operating phase of the electrical line. The evaluation stage can be configured and designed to determine and store at least one processed, a processed averaged, and / or a processed reconstructed reflection profile in a second operating phase of the electrical line. The evaluation stage can be configured and designed to determine an integral over the squared difference between the reflection profile during the second operating phase and the initial reflection profile over a length of the electrical line.

[0039] The integral can be calculated as follows: f(TDR)=∫0l(raged(t)−rorigin(l))2dl

[0040] Where r aged is the reflection profile from the second operating phase and r originthe initial reflection profile from the first operating phase.

[0041] The result of the integral can serve as a measure of the probability of failure, wear, and / or aging of the electrical cable. The initial reflection profile can serve as a baseline measure for a cable's status, e.g., a cable status of 100% indicates that the cable is OK and / or that no failure is expected.

[0042] The evaluation stage can be set up and designed to send the measure of the probability of occurrence as an analog value or digitized analog value to a higher-level control unit / process unit, wherein the digital analog value is sent protocol-based (e.g. PROFINET), in particular wired, or radio-based.

[0043] The useful signal can be a continuous voltage signal, in particular a direct voltage or a continuous low-frequency alternating voltage signal. The continuous (low-frequency alternating) voltage signal can be a sinusoidal 50 Hz, 230 V alternating voltage signal (3x 400 V, 50 Hz or for the USA: 110 V, 60 Hz or 3x 480 V, 60 Hz). The measured signal can have a maximum voltage / voltage peak of less than 40 V, in particular approximately 1, 4, 6, 8, 10, or 15 V.

[0044] The useful signal can be embodied as a discontinuous / stepped signal, in particular as a discontinuous / stepped control signal. The evaluation stage can be synchronized with the measurement signal unit. The evaluation stage can further be configured and designed to disregard / ignore the reflected measurement signal if its amplitude values coincide with a switching instant, in particular with a switching instant from 0 V to 24 V / 24 V to 0 V or 0 V to 48 V / 48 V to 0 V or 0 V to 230 V / 230 V to 0 V, of the discontinuous / stepped signal.

[0045] The electrical cable can be designed as a power, connection, control, or charging cable. The electrical cable can undergo dynamic / dynamic-mechanical movement, in particular torsional, bending, and / or flexion. The electrical cable can (preferably) have PE, PP, or PTFE-insulated conductors. The described device and method can also be used with PVC-insulated conductors, with limitations regarding the accuracy and the maximum installation length of the cable to be monitored.

[0046] The measurement signal unit can have a measurement signal source and a coupling circuit, in particular a capacitive one. The measurement signal source can be designed as a pulse signal source, in particular a low-impedance one. The pulse signal source can be configured and designed to generate a plurality of pulses, in particular a plurality of rectangular or sawtooth measurement pulses. The pulse signal source can be configured and designed to send the plurality of pulses to the coupling circuit. The coupling circuit can be configured and designed to receive the plurality of pulses and to add / add them to the useful signal present in the electrical line, in particular in a potential-free manner.

[0047] The electrical line can have at least two wires and a protective conductor. The at least two wires can be routed / wound through / around a first and / or second filter. Alternatively, two first and / or two second filters can be provided for each wire. The protective conductor can be routed / wound through / around another filter of the same design as the first or second filter. The detection unit can be configured and designed to detect the reflected measurement signal in relation to the protective conductor.

[0048] The electrical line can be designed as a multi-core electrical line. The measurement evaluation unit can have a switching matrix unit, which can be configured and designed to provide a first connection between the measurement signal unit and a core / core pair, and between the one core / core pair and the detection unit. Thus, the measurement signal from the measurement signal unit can be added to a useful signal present in a core / core pair, and a reflected measurement signal on the one core / core pair can be detected by the detection unit. The switching matrix unit can further be configured and designed to disconnect the first connection and provide a further connection between the measurement signal unit and a further core / core pair, and between the one further core / core pair and the detection unit.Thus, the measurement signal from the measurement signal unit can be added to a useful signal present in the further wire / wire pair and a reflected measurement signal on the further wire / wire pair can be detected by the detection unit.

[0049] The electrical line can be configured as a multi-core electrical line, and the measurement evaluation unit can be configured and designed to add a measurement signal to the useful signal on free cores of the multi-core electrical line, and to receive and evaluate at least part of a measurement signal reflected in the electrical line. Free cores are defined as cores that are free of any wiring or are only partially wired.

[0050] A method for (continuous / time-continuous) monitoring of an electrical line to predict failure, wear and / or aging of the electrical line comprises the steps: - Laying the electrical cable to connect a useful signal source to a consumer and to supply the consumer with a useful signal provided by the useful signal source; - Generating and adding / adding a measuring signal to the useful signal present in the electrical line; - detecting at least a reflected part of the measurement signal; - evaluating at least one reflected part of the measurement signal; and - Output of a measure of the probability of occurrence of failure, wear and / or aging of the electrical cable.

[0051] The method may further comprise the step(s): - determining and storing a processed initial reflection profile in a first operating phase of the electrical line; and / or - determining and storing at least one processed, a processed averaged and / or a processed reconstructed reflection profile in a second operating phase.

[0052] Further features, properties, advantages, and advantages of the devices and methods can be found in the following description in conjunction with the drawings. Possible modifications will become clear to a person skilled in the art from the following description, which refers to the accompanying drawings. The figures show embodiments of the devices discussed here. Short description of the characters

[0053] Here we show: Fig. 1 a schematic representation of the device for monitoring an electrical line; Fig. 2 a schematic representation of the evaluation stage and the data processing steps; Fig. 3 a schematic representation of the coupling unit and the first / second filter; and Fig. 4 a schematic representation of the coupling unit and the first / second filter. Detailed description of the characters

[0054] Fig. 1 shows a schematic representation of the device 100 for monitoring a line L. The line L connects a useful signal source NQ to a consumer V. The useful signal source NQ is set up and designed to supply the consumer V with a useful signal NQS. The device 100 further comprises: a first filter 32, a second filter 34 and a measurement evaluation unit 10. The measurement evaluation unit 10 is connected between the useful signal source NQ and a first end LA of the line L. The first filter 32 is connected between the measurement evaluation unit 10 and the useful signal source NQS. The second filter 34 is connected between a second end LB of the line L and the consumer V.

[0055] In this case, the useful signal NQS is a 230 V AC voltage, illustrated in the diagram, which shows the signal curve immediately after the useful signal source NQ and before the first filter 32. A measurement signal 40 is added to this useful signal NQS. The measurement signal 40 is provided by a measurement signal unit 12. In this case, the measurement signal 40 is a square-wave pulse voltage signal. This measurement signal 40 is illustrated in the diagram, which shows the already superimposed signal curve immediately at the measurement signal source 18.

[0056] The measurement signal 40 is added to the useful signal NQS via a coupling circuit 20. This results in the useful signal NQS having the measurement signal 40. This can be seen in the diagram, which shows the combined measurement signal 40 and useful signal NQS immediately after the measurement evaluation unit 10 and before the first end LA of the line L. The representation of the measurement signal 40 on the useful signal NQS is exaggerated in the diagram for illustrative purposes and does not reflect the actual amplitude ratios of the measurement signal 40 and the useful signal NQS. The measurement signal has a maximum voltage peak of 10 V, with a pulse repetition rate of 5 ms. The pulse duration is a few µs. The edge steepness here is less than 15 ns.

[0057] The useful signal NQS, which includes the measurement signal 40, can supply the load V with voltage because the second filter 34 filters out the measurement signal 40. If the line L is blocked or defective, information about the wear or defect is imprinted on the measurement signal 40.

[0058] A detection unit 14, which is integrated into the measurement evaluation unit 10, receives a number of the reflected measurement signals 42, 42a, 42b, 42c continuously at intervals; in the example, approximately 5 ms. The amplitude values of the number of reflected measurement signals 42, 42a, 42b, 42c are sampled, digitized, and sent to an evaluation stage 16. In other words, the reflected measurement signals 42, 42a, 42b, 42c are to be understood as discrete reflection profiles that are processed and evaluated continuously.

[0059] In the evaluation stage 16, the reflected measurement signals 42, 42a, 42b, 42c are preprocessed. This can involve averaging several reflected measurement signals, with the averaging relating to discrete and temporally / spatially assignable sections of the line ( Fig. 2, diagram D2, T2). The number of parts is superimposed to average them and determine an averaged reflection profile. Based on the course of the averaged reflection profile T2, information about the location and type of a fault in line L can be determined and output via S1. In the variant shown, S1 is a programmable alarm output (potential-free contact or switched 24 V), which is set as soon as a failure / wear is indicated.

[0060] Alternatively, the detection unit 14 can capture a portion of the reflected measurement signal 42 and send it to preprocessing. During preprocessing, one portion is, for example, noise-reduced and a reflection profile is determined. Based on the course of one reflection profile, information about the location and type of a fault in line L can be determined and output via the programmed alarm output.

[0061] The Fig. 2 shows a schematic representation of the evaluation stage 16 and the data processing steps 22, 24, 26 before and within the evaluation stage 16 for the temporal monitoring of the line L. In a first operating phase OP1 at time T0, the detection unit 14 detects part of a reflected measurement signal 42 and sends it to the evaluation stage 16. The reflection profile determined by the evaluation stage 16 at time T0 (e.g., at the beginning of commissioning of the electrical line L) can be used as an initial reflection profile and indicates that the electrical line L is 100% intact, the cable status KS(T0) is 100%. Since no further reflection profile has been determined at time T0, the result of the integral 24 is 0. The initial reflection profile is stored in the evaluation stage 16 for later use.

[0062] In a second operating phase OP2, the detection unit 14 detects another portion of a reflected measurement signal 42a and sends it to the evaluation stage 16. In a preprocessing step, another reflection profile is determined and superimposed on the previously saved initial reflection profile. This can be seen in diagram D1, which illustrates the data between the preprocessing 22 and the integral 24. The superimposed reflection profiles are fed to the integral 24, and the resulting result IE(T2) is stored 26. Since the initial reflection profile differs from the additional reflection profile due to wear on the line L, the result of the integral IE is different from zero at time T2. This indicates that an imminent failure of the electrical line L is to be expected. The cable status KS(T2) is different from 100%.

[0063] The cable status can be assigned limit values and display the status of the electrical cable L to be monitored, for example, via colored LEDs on the device 100, in particular on the measurement evaluation unit 10. Between 100% and 80%, a corresponding LED could switch to green, between less than 80% and 60% to yellow, and less than 60% to red. Yellow means that the electrical cable L is intact but must be replaced promptly. Red indicates that the electrical cable L has reached the end of its service life and must be replaced immediately. Alternatively, the cable status can be displayed on a button / display area via output S1.

[0064] The Fig. Figure 3 shows a schematic representation of a variant of an embodiment of the device 100 with the components relevant for the potential-free coupling and decoupling of the measurement signal 40 to the useful signal NQS. The detection unit 14 and the evaluation stage 16 are not shown for reasons of clarity, but would be attached separately to the wires of the electrical line L.

[0065] In the Fig. 3, the electrical line L is designed as a two-wire line. The useful signal source NQ is connected to a consumer V via the two-wire electrical line L. In addition, Fig. 3 shows a first filter 32 and a second filter 34. The first filter 32 is connected between the useful signal source NQ and a first end LA of the electrical line L. The second filter 34 is connected between a second end LB of the electrical line L and the load V. The first and second filters 32, 34 are each designed as two toroidal cores L100, L101 and L201, L200. Each wire is guided through a toroidal core. Each toroidal core has an inductance of 20 µH. A measurement signal unit 12, which has a measurement signal source 18 and a coupling circuit 20, is connected between the first end LA of the electrical line L and the first filter 32. The coupling circuit 20 has two capacitors C51, C52 and a resistor R27. The capacitors C51, C52 have a capacitance of 50 nF and the resistor R27 has a resistance of 50 ohms.For the capacitances C51, C52, values from 10 nF to 100 nF are suitable, in particular 20 nF, 40 nF, 60 nF, and / or 80 nF.

[0066] Alternatively, a signal transformer (BALUN) or a current transformer, particularly a Rogowski coil, can be used for the potential-free coupling and decoupling of the measurement signal 40. These variants allow galvanic isolation of the measurement signal 40 and the useful signal NQS. The measurement signal source 18 provides a pulse measurement signal with a maximum amplitude of 10 V, a pulse width of 2 µs, and a pulse repetition rate of 5 ms. The useful signal source NQ provides a sinusoidal voltage with a frequency of 50 Hz and a voltage amplitude of 325 V.

[0067] The measurement signal 40 from the measurement signal source 18 is added to the useful signal NQS via the coupling circuit 20. The second filter 34 provides a defined reflection point at which the measurement signal 40 is reflected. The first filter 32 prevents the measurement signal 40 from propagating to the useful signal source NQ. The detection unit 14 and the evaluation stage 16 are not shown for reasons of clarity. However, the detection unit 14 would be attached separately to the wires of the electrical line L. Capacitors would be connected between the detection unit 14 and the electrical line L, the capacitances of which would be equal to the capacitances C51, C52 used for coupling.

[0068] The Fig. Figure 4 shows a schematic representation of a variant of an embodiment of the device 100 with the components relevant for the potential-free coupling and decoupling of the measurement signal 40 to the useful signal NQS. The evaluation stage 16 in the measurement evaluation unit 10 is not shown for reasons of clarity.

[0069] In Fig. 4, the electrical line L is designed as a two-wire line. The useful signal source NQ is connected to a consumer V via the two-wire electrical line L. In addition, Fig. 4 shows a first filter 32 and a second filter 34. The first filter 32 is connected between the useful signal source NQ and a first end LA of the electrical line L. The second filter 34 is connected between a second end LB of the electrical line L and the load V. The first and second filters 32, 34 are each designed as two toroidal cores L100, L101 and L201, L200. Each wire is guided through a toroidal core. Each toroidal core has an inductance of 20 µH. A measurement evaluation unit 10, which has a measurement signal source 18 and a coupling circuit 20, is connected between the first end LA of the electrical line L and the first filter 32. The coupling circuit 20 has two capacitors C51, C52 and a resistor R27. The capacitors C51, C52 have a capacitance of 50 nF and the resistor R27 has a resistance of 50 ohms.For the capacitances C51, C52, values from 10 nF to 100 nF are suitable, in particular 20 nF, 40 nF, 60 nF, and / or 80 nF.

[0070] The measurement signal source 18 provides a pulse measurement signal with a maximum amplitude of 10 V, a pulse width of 2 µs, and a pulse repetition rate of 5 ms. The useful signal source NQ provides a sinusoidal voltage with a frequency of 50 Hz and a voltage amplitude of 325 V.

[0071] The measurement signal 40 from the measurement signal source 18 is added to the useful signal NQS via the coupling circuit 20. The second filter 34 provides a defined reflection point at which the measurement signal 40 is reflected. The first filter 32 prevents the measurement signal 40 from propagating to the useful signal source NQ.

[0072] The detection unit 14 detects the reflected measurement signal between resistor R27 and capacitance C51 as well as between measurement signal source 18 and capacitance C52. In comparison with the variant in Fig. 3 components are saved and installation space is reduced.

[0073] The variants of the device described above, their construction and operating aspects, as well as the variants of the procedure, serve only to improve understanding of the structure, mode of operation, and properties; they do not limit the disclosure to the exemplary embodiments. The figures are partly schematic. Key properties and effects are sometimes shown significantly enlarged in order to clarify the functions, operating principles, technical designs, and features. Each mode of operation, each principle, each technical design, and each feature disclosed in the figures or in the text can be used with all claims, each feature in the text, and in the other figures., other modes of operation, principles, technical designs and features contained in this disclosure or resulting therefrom can be freely and arbitrarily combined so that all conceivable combinations can be assigned to the described procedure. This also includes combinations between all individual embodiments in the text, i.e. in every section of the description, in the claims and also combinations between different variants in the text, in the claims and in the figures. The claims also do not limit the disclosure and thus the possible combinations of all the features shown with one another. All disclosed features are explicitly disclosed here, both individually and in combination with all other features.

Claims

[1] A device (100) for monitoring an electrical line (L) to predict failure, wear and / or aging of the electrical line, wherein - the electrical line (L) has a first and a second end (LA, LB) and the electrical line (L) is designed and laid to connect a useful signal source (NQ) to a consumer (V), the device (1) comprising - a measurement evaluation unit (10) connected between the useful signal source (NQ) and the first end of the electrical line (LA), - a first filter (32) connected between the useful signal source (NQ) and the measurement evaluation unit (10), wherein the first filter (32) is designed and constructed to block a measurement signal (40) to the useful signal source (NQ) and to allow a useful signal (NQS) to pass to the consumer, wherein the useful signal source (NQ) is arranged and designed to send the useful signal (NQS) through the first filter (32), the measurement evaluation unit (10) and through the electrical line (L) to the consumer (V), wherein the measurement evaluation unit (10) is set up and designed to add a measurement signal (40) to the useful signal (NQS), to receive and evaluate at least part of a measurement signal reflected in the electrical line, and to output (S1) a measure of a probability of occurrence of a failure, wear and / or aging of the electrical line (L). [2] The device according to one of the preceding claims, wherein the measurement signal has a measurement signal level which is reduced, in particular significantly, compared to a useful signal effective value. [3] The device according to one of the preceding claims, wherein the measuring signal level corresponds to between 1% and 15%, in particular 2%, 4%, 6%, 8%, 10%, 12% or 14%, of the useful signal effective value. [4] The device (100) according to the preceding claim, further comprising - an interface (34) connected between the second end of the electrical line (LB) and the consumer (V), wherein the interface is configured and designed to reflect the measurement signal (40) to the consumer (V) back to the line and to allow the useful signal (NQS) to pass to the consumer (V). [5] The device (100) according to any one of the preceding claims, wherein the interface (34) is designed as a second filter. [6] The device (100) according to one of the preceding claims, wherein the first (32) and / or the second filter (32) is / are designed as a common mode choke, a current compensated choke, a wired coil with / without a core or as a toroidal core, in particular as an iron, ferrite or nanocrystalline toroidal core. [7] The device (100) according to one of the preceding claims, wherein the measurement evaluation unit (10) comprises a measurement signal unit (12) which is configured and designed to add the measurement signal (40) to the useful signal (NQS). [8] The device (100) according to one of the preceding claims, wherein the measurement evaluation unit (10) comprises a detection unit (14) and an evaluation stage (16), wherein the detection unit (14) is set up and designed to - to detect at least a part of a reflected measurement signal (42), in particular amplitude values of at least a part of the reflected measurement signal, - and to send at least a part of the reflected measurement signal (42), in particular digitized, to the evaluation stage (16). [9] The device (100) according to any one of the preceding claims, wherein the detection unit (14) is configured and designed to -to receive / detect a number of parts of the reflected measurement signal (42a, 42b, 42c), in particular amplitude values of the number of parts of the reflected measurement signal, in particular within a time window to be determined, - and to send the number of parts of the reflected measurement signal (42a, 42b, 42c) to the evaluation stage (16). [10] The device (100) according to one of the preceding claims, wherein the evaluation stage (16) is set up and designed to receive the at least one part of the reflected measurement signal (42) and / or the number of parts of the reflected measurement signal (42a, 42b, 42c) and / or to process the at least one part and / or the number of parts of the reflected measurement signal (42a, 42b, 42c), in particular to process it using image processing means, and to store it. [11] The device (100) according to one of the preceding claims, wherein the evaluation stage (16) is set up and designed to determine a reflection profile from the processed at least one part of the reflected measurement signal and / or to determine an averaged and / or a reconstructed reflection profile from the processed number of parts of the reflected measurement signal (42a, 42b, 42c). [12] The device (100) according to one of the preceding claims, wherein the evaluation stage (16) is set up and designed to determine and output (S1) a type and / or location of a line fault, in particular insulation, wire connection and / or copper faults, based on the reflection profile, the averaged reflection profile and / or the reconstructed reflection profile, in particular based on its course(s), in particular to indicate whether there is a spatially uniform deterioration or a local defect in the electrical line. [13] The device (100) according to one of the preceding claims, wherein the evaluation stage is further configured and designed to - to determine and store a processed initial reflection profile in a first operating phase (OP1) of the electrical line (L), - in a second operating phase (OP2) of the electrical line, to determine and store at least one processed, one processed averaged and / or one processed reconstructed reflection profile, - and to determine an integral over the squared difference of the reflection profile during the second operating phase and the initial reflection profile over a length of the electrical line (L), whereby the result of the integral can serve as a measure of the probability of occurrence of a failure, wear and / or ageing of the electrical line (L). [14] The device (100) according to one of the preceding claims, wherein the evaluation stage (16) is set up and designed to send the measure of the probability of exit as an analog value or digitalized analog value (S1) to a higher-level control / process unit, wherein the digital analog value is sent in a protocol-based manner, in particular wired or radio-based. [15] The device (100) according to one of the preceding claims, wherein the useful signal (NQS) is designed as a continuous voltage signal, in particular as a direct voltage or continuous low-frequency alternating voltage signal. [16] The device (100) according to one of the preceding claims, wherein the useful signal (NQS) is designed as a discontinuous / stepped signal, in particular as a discontinuous / stepped control signal, wherein the evaluation stage (16) is synchronized with the measurement signal unit (12), and the evaluation stage (16) is further configured and designed to disregard the reflected measurement signal if its amplitude values coincide with a switching time of the discontinuous / stepped signal. [17] The device (100) according to one of the preceding claims, wherein the, in particular multi-core, electrical line (L) is designed as a power, connection, control or charging line and / or the electrical line undergoes a dynamic, in particular a torsional, bending and / or flexing movement. [18] The device (100) according to one of the preceding claims, wherein the measuring signal unit (12) comprises a measuring signal source (18) and a coupling circuit (20), in particular a capacitive one, wherein the measuring signal source (18) is designed as a pulse signal source, in particular a low-impedance one, and is configured and designed to generate a plurality of pulses, in particular a plurality of rectangular or sawtooth measuring pulses, to send them into the coupling circuit (20), wherein the coupling circuit (20) is configured and designed to receive the plurality of pulses and to add them to the useful signal (NQS) present in the electrical line (L). [19] The device (100) according to one of the preceding claims, wherein the electrical line (L) has at least two wires and a protective conductor, wherein the at least two wires are guided through a first and / or second filter (32, 34), the protective conductor is guided through a further filter of the same design as the first or second filter (32, 34), and the detection unit (14) is set up and designed to detect the reflected measurement signal in relation to the protective conductor. [20] The device (100) according to one of the preceding claims, wherein the electrical line (L) is designed as a multi-core electrical line, wherein the measurement evaluation unit (10) has a switching matrix unit, configured and designed to provide a first connection between the measurement signal unit (12) and one core, and between the one core and the detection unit (14), so that the measurement signal (40) from the measurement signal unit (12) is added to a useful signal present in one core and a reflected measurement signal on the one core is detected by the detection unit (14), wherein the switching matrix unit is further configured and designed to separate the first connection and to provide a further connection between the measurement signal unit (12) and a further core, and between the one further core and the detection unit (14),so that the measuring signal (40) from the measuring signal unit (12) is added to a useful signal present in the further wire and a reflected measuring signal on the one further wire is detected by the detection unit (14). [21] The device (100) according to one of the preceding claims, wherein the electrical line is designed as a multi-core electrical line and the measurement evaluation unit (10) is set up and designed to add a measurement signal (40) to the useful signal (NQS) on free wires of the multi-core electrical line, and to receive and evaluate at least part of a measurement signal reflected in the electrical line. [22] A method for monitoring an electrical line (L) to predict failure, wear and / or aging of the electrical line, the method comprising the steps of: - Laying the electrical cable (L) to connect a useful signal source (NQ) to a consumer (V) and to supply the consumer (V) with a useful signal (NQS) which is provided by the useful signal source (NQ); - generating and adding a measuring signal (40) to the useful signal (NQS) present in the electrical line (L); - detecting at least a reflected part of the measurement signal (42); - evaluating the at least one reflected part of the measurement signal (42); and - Outputting a measure of the probability of occurrence of failure, wear and / or aging of the electrical line (L). [23] The method of claim 22, comprising the step of: - determining and storing a processed initial reflection profile in a first operating phase (OP1) of the electrical line (L); and / or - Determining and storing at least one processed, one processed averaged and / or one processed reconstructed reflection profile in a second operating phase (OP2).

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