METHOD FOR DETERMINING AN OPERATING STATE FOR AN ELECTRICAL OPERATING EQUIPMENT WITH A SWITCHING ELEMENT

Description

[0001] The invention relates to a method and an arrangement for determining an operating state for an electrical device with a switching element. background

[0002] The expansion and renewal of the power grid are central to a new energy infrastructure to ensure future energy security. Power grids face a number of challenges, including being able to respond effectively to fluctuating power generation from wind and solar energy. In addition to optimal system control through intelligent metering systems and intelligent load management, careful monitoring of the electrical equipment in high-voltage, medium-voltage, and low-voltage grids is also essential for utility companies.

[0003] Systems for monitoring all types of electrical equipment are already in use at many points in the power grid. Nevertheless, there are numerous requirements that conventional approaches cannot yet meet. In particular, comprehensive monitoring is not yet possible.

[0004] Electrical equipment such as circuit breakers contains numerous mechanical components that are subjected to stress with each switching operation. Depending on the number of switching operations, this leads to moderate to high wear on the components. Shock absorbers and buffers, for example, are subject to particularly high levels of stress. If a component fails or is modified, this can lead to the circuit breaker no longer switching or even being destroyed. This can result in significant economic costs, particularly if large-scale systems need to be supplied but cannot continue to operate due to the failure of a circuit breaker.

[0005] Consequently, many electrical equipment items must be regularly inspected by maintenance personnel. This allows the operating status of the electrical equipment and the condition of its components to be identified as problematic in a timely manner, and the equipment or component can be replaced if necessary. However, inspections by maintenance personnel result in substantial costs. To inspect the circuit breakers of wind turbines, for example, a maintenance technician must not only perform the necessary examinations but also visit the wind turbine, which can be particularly costly and time-consuming, especially in offshore applications.

[0006] It would therefore be advantageous if electrical equipment such as circuit breakers could be automatically monitored and the results continuously transmitted to a control center. This would prevent a costly inspection by a maintenance technician from being triggered until the automatic monitoring system indicates the presence of a problem or adverse changes in essential properties.

[0007] Document US 4 980 844 A discloses a method and apparatus for diagnosing the mechanical condition of a machine. The method according to the invention comprises the following steps: acquiring reference vibration characteristics of a machine in the time domain; creating a reference signature from the reference vibration characteristics; storing the reference signature; acquiring test vibration characteristics of the same machine in the time domain; creating a test signature from the test vibration characteristics; automatically calculating a measured distance between at least one point on the reference signature and at least one corresponding point on the test signature; automatically comparing the measured distance with a threshold value to determine whether the machine is operating normally or abnormally; and providing a signal if the comparison indicates abnormal operation.A device for implementing the method according to the invention is also disclosed.

[0008] Document US 2017 / 045481 A1 discloses a component monitoring system structured to monitor the characteristics of the components of the circuit breaker assembly. The component monitoring system includes a recording assembly, a number of vibration sensor assemblies, a comparison assembly, and an output assembly. The recording assembly contains selected nominal data for a selected circuit breaker component. The vibration sensor assembly is structured to measure a number of actual component characteristics for a substantial portion of the circuit breaker assembly and transmit actual output data of the component characteristics.The comparison arrangement is structured to receive an electronic signal from the recording arrangement and the sensor arrangements, compare the output data of the actual component characteristic curve of each sensor arrangement with the selected nominal data, and provide an indication signal indicating whether the output data of the sensor arrangement are acceptable compared to the selected nominal data. The output arrangement comprises a communication arrangement and an output device.

[0009] Embodiments of methods and systems for identifying a physical event using a vibration signature are disclosed in document US 2012 / 197546 A1. One aspect of the method includes forming one or more identified vibration signatures, each associated with a respective known physical event. The method further includes receiving a vibration signature associated with an actual physical event and identifying the actual physical event by comparing the vibration signature to the one or more identified vibration signatures, each associated with a respective known physical event.

[0010] Document US 2015 / 233792 A1 relates to methods for efficient and reliable fault diagnosis in components of mechanical systems. According to one aspect, a multi-scale envelope spectrogram is used to diagnose or detect defects in a moving component of a mechanical system. According to another aspect, a logical control model using a classification of features associated with single or multi-sensor data is used to diagnose defects in components of mechanical systems. Summary

[0011] The object of the invention is to provide a method and an arrangement for determining an operating state for an electrical device with a switching element, so that an automatic, continuous and reliable monitoring of the electrical device with a switching element can take place.

[0012] To achieve this, a method and an arrangement for determining an operating state for an electrical device with a switching element according to independent claims 1 and 14 are provided. Further embodiments are the subject of dependent subclaims.

[0013] According to one aspect, a method for determining an operating state for an electrical device with a switching element is provided. In the method, measurement signals for an electrical device with a switching element are detected by means of a sensor device having a fiber optic sensor. The measurement signals for the electrical device comprise at least one type of measurement signal from the following group: vibration signals and sound signals. Furthermore, the measurement signals are processed by means of an evaluation device. The processing comprises an analog-to-digital conversion of the measurement signals. Furthermore, an operating state for the electrical device is determined from a group of different operating states by means of the evaluation device. For this purpose, the digital measurement signals are compared with comparison signals, each of which is assigned to at least one of the different operating states.

[0014] According to a further aspect, an arrangement is provided comprising an electrical device having a switching element, a sensor device, and an evaluation device. The sensor device comprises a fiber optic sensor and is configured to detect measurement signals for the electrical device, wherein the measurement signals for the electrical device comprise at least one type of measurement signal from the following group: vibration signals and sound signals. The evaluation device is configured to process the measurement signals, wherein the processing comprises an analog-to-digital conversion of the measurement signals into digital measurement signals.The evaluation device is also designed to determine an operating state for the electrical equipment from a group of different operating states, wherein the digital measurement signals are compared with comparison signals which are each assigned to at least one of the different operating states.

[0015] Vibrations, as defined in the disclosure, are mechanical oscillations of bodies or materials. This includes periodic oscillations, but also aperiodic signals such as strains or shocks. Furthermore, the sensor can be configured to detect other physical measured variables and measurement signals.

[0016] The measurement signals can include both vibration signals and sound signals.

[0017] The measurement signals can be acquired using multiple sensors. For analog-to-digital conversion, one analog-to-digital converter can be used in multiplexed mode or several analog-to-digital converters can be used in parallel mode. The measurement signals from different sensors can be correlated with each other.

[0018] It can be provided that the sensors detect measurement signals in different frequency bands. The frequency bands can overlap or be separate from each other. Furthermore, it can be provided that the frequency bands of different sensors can be combined to increase the detectable frequency bandwidth.

[0019] The electrical device can have a drive mechanism. The drive mechanism can be arranged within a housing. At least one sensor can be arranged inside, outside, and / or on the housing of the drive mechanism. It can be provided that at least one control signal, for example, a motor-starting control signal, is detected and processed as a measurement signal.

[0020] It may be provided that at least one measurement signal is sent digitally to the evaluation device without analog-to-digital conversion. It may be provided that at least one analog measurement signal is amplified by an amplifier before the analog-to-digital conversion.

[0021] The measurement signals are recorded using a fiber optic sensor. In particular, vibration signals can be recorded using a fiber optic vibration sensor. Fiber optic sensors can enable non-wired transmission of the measurement signal and can therefore be particularly suitable for use in high-voltage equipment. Fiber optic sensors can, for example, be attached to high-voltage switch poles and thereby provide meaningful measurement signals from the switch pole. Provision can also be made for the measurement signals to be further recorded using at least one non-fiber optic sensor, for example, a piezo microphone, a piezoelectric ultrasonic sensor, a non-fiber optic vibration sensor, a condenser microphone, or a structure-borne sound sensor.

[0022] The sound signals can comprise at least one type of sound signal from the group of infrasound signals, audible sound signals, and ultrasonic signals. Sound signals within the meaning of the disclosure include pressure and density fluctuations in a medium. The medium can be either a body (structure-borne sound) or air (airborne sound).

[0023] If the measurement signals are recorded using several sensors, in particular an intrasonic frequency band and an ultrasonic frequency band can be recorded in parallel and processed in combination using a vibration sensor or an ultrasonic sensor.

[0024] The sound and vibration signals can be caused by mechanical components of the electrical equipment, such as motors, springs, shafts, shock absorbers, buffers, or by human actions. Furthermore, sound and vibration signals can be caused by electromagnetic excitations and / or external sources, such as running machines near the electrical equipment.

[0025] The operating state of an electrical device can be determined in a switchgear. Alternatively or additionally, the operating state of the electrical device can also be determined outside the switchgear. The electrical device can be provided with more than one switching element. The at least one switching element can comprise one or more of the following elements: circuit breaker, load-break switch, fuse switch-disconnector, high-voltage high-performance fuse, low-voltage high-performance fuse, earthing switch, short-circuit current limiter, recloser, and / or contactor.

[0026] The operating state can be determined for an electrical device that carries high voltage. High voltages within the meaning of the invention are electrical voltages above 1 kV. In particular, it can be provided that the electrical device carries high voltages of 3 kV, 6 kV, 10 kV, 15 kV, 20 kV, 30 kV, 60 kW, 110 kV, 220 kV, 380 kV, 500 kV, 700 kV, or 1150 kV. High voltages above 220 kV are also referred to as extra-high voltages. The operating state can also be determined for an electrical device that carries low voltage. In particular, it can be provided that the electrical device carries low voltages of up to a maximum of 1 kV.

[0027] The measurement signals can be preprocessed during processing, increasing the signal-to-noise ratio. Preprocessing can be digital and / or analog. Analog preprocessing methods include filters such as low-pass, high-pass, band-pass, or anti-aliasing filters. Digital preprocessing methods include filters such as notch filters, wavelet analysis, discrete Fourier transform, fast Fourier transform, and short-time Fourier transform. If multiple sensors are used, none, one, or several of the methods can be applied to each of the measurement signals. The measurement signals can be preprocessed using an anti-aliasing filter.

[0028] If multiple sensors are used, the signal-to-noise ratio can be further increased by correlating and / or averaging the measurement signals from different sensors. This can be done using cross-channel digital signal preprocessing.

[0029] In one embodiment, channel separation methods can be applied to the measurement signals. This allows, for example, vibration signals and sound signals within the same measurement signal to be separated and assigned to different sources. This can substantially simplify the determination of the operating state of the electrical equipment.

[0030] When determining the operating state, at least one state characteristic characterizing the operating state of the electrical equipment can be determined from the digital measurement signals.

[0031] It can be provided that the operating state is characterized by a single state characteristic, by a plurality of state characteristics, or by a combination of a plurality of state characteristics. If the measurement signals are recorded using multiple sensors, at least one state characteristic can be a position of a vibration signal source or sound signal source, which is determined using runtime effects. At least one state characteristic can also be the measurement signal and / or the comparison signal itself. It can be provided that at least one state characteristic is determined by transforming at least one measurement signal so that, if possible, only such data remains that reliably enable the operating state of the electrical equipment to be determined. State characteristics can be determined from individual measurement signals and / or by combining different measurement signals.

[0032] At least one state characteristic can be determined using at least one member of the group of Fourier transform, short-time Fourier transform, wavelet transform, template matching, and envelope. In particular, a spectrogram can be generated using a short-time Fourier transform. A spectrogram can also be generated using a wavelet transform. The determination of the at least one state characteristic can be performed in one or more steps.

[0033] The operating state of the electrical equipment can be determined by classifying at least one state characteristic using at least one classification method. Comparing the digital measurement signals with reference signals comprises the classification of the operating state.

[0034] It can also be provided that the comparison of the digital measurement signals with reference signals consists exclusively in the classification of the operating state. The classification method is a machine classification method.

[0035] Classification methods such as artificial neural networks, fuzzy logic, or decision trees can be used. The classification of the operating state can be performed in one or more stages.

[0036] The classification can be carried out by analyzing at least one condition characteristic by assigning comparable measurement signals to specific causes and / or groupings of comparable measurement signals.

[0037] The operating state can be characterized by at least one of the following states: a defect or functionality of a component of the electrical equipment, a short circuit within the electrical equipment, a maintenance and / or cleaning requirement of the electrical equipment or a component of the electrical equipment, a wear condition and / or degree of wear of a component, for example a contact, component-specific conditions such as the status of a spring component (attracted / relaxed, normal / abnormal frequency spectrum), a storage drive, a stop damper or latches, a movement status and / or rotational speed of a rotating component, for example a switch shaft or a drive shaft, a position of a contact of a switch pole (open / closed), a speed of opening and / or closing of a contact, a temporal sequence and / or a temporal interval between the opening and / or closing of several contacts,a successful completion of a switching operation, for example a successful switching of magnetic components, for example a closing magnet or a breaking magnet, a drive energy for a motor winding mechanism, for example in a spring-loaded drive, with respect to a threshold value, an energy conversion of a drive, for example a spring drive, a degree of interaction of mechanical components such that a switching function is provided.

[0038] It may be provided that the classification method is trained using the comparison signals before the method is executed. Additionally or alternatively, it may also be provided that the classification method is trained during operation.

[0039] A temporal evolution of the operating state of the electrical equipment and / or of the at least one state characteristic can be determined. The temporal evolution of the operating state can be designed as a set of different operating states, each assigned to a point in time. A comparison of operating states at different points in time can be used to increase the reliability of determining the operating state.

[0040] The determination of at least one state characteristic and the operating state can be implemented in hardware and / or software. One or more processors from the CPU, microprocessor, embedded system, digital signal processor, or GPU groups can be used. One or more configurable logic components from the CPLD (Complex Programmable Logic Device), FPGA (Field Programmable Gate Array), Gate Array, or Standard Cell Array groups can be used. Fully custom chips can be used.

[0041] An analysis of the specific operating state with an analysis result can be provided. The operating state can be assigned to a new state of the electrical equipment or a wear state of the electrical equipment.

[0042] Provision can be made for at least one result to be forwarded to an output device. The result can comprise the specific operating state and / or the analysis result of the analysis of the specific operating state. The output device can be connected to the evaluation device locally or via a network. The result can be forwarded continuously. Provision can also be made for multiple results from the arrangement and / or results from multiple arrangements to be combined in the output device. Continuous monitoring of results by maintenance personnel can be provided. The forwarding can take place, for example, via a network. In the event of spontaneously occurring problems, maintenance personnel can thus take suitable measures so that electrical equipment no longer needs to be taken out of service or does not need to be taken out of service at all.Furthermore, routine inspections of the electrical equipment can be eliminated, or the maintenance intervals can be extended. This avoids the need for removal, decommissioning, and / or intervention in the control system of the electrical equipment. This can lead to substantial cost savings.

[0043] The measurement data and / or at least one result can be stored on a physical data carrier.

[0044] The output device can comprise one or more output devices. This can be a display or a loudspeaker, for example. Provision can be made to prepare at least one result for output. At least one result can be output in at least one of the following forms: tabular form, graphs, diagrams, a list of probabilities, and signal tones. A binary or ternary representation of at least one result can be used. The representation of at least one result can be color-coded, for example, red / green (binary) or as a traffic light (ternary). The color green can signal a non-critical operating state, the color yellow a pre-critical operating state, and the color red a critical operating state.

[0045] The output of at least one result can include an instruction for maintenance personnel. For example, a critical operating condition can be associated with an instruction for immediate maintenance and / or a pre-critical operating condition can be associated with an instruction for timely maintenance.

[0046] The evaluation device can be connected to an input device, such as a keyboard. The connection can be established locally and / or via a network. Using the input device, for example, the determination of the operating state can be configured and / or the output of at least one result can be adjusted.

[0047] The evaluation device can be arranged inside and / or outside the electrical equipment.

[0048] In connection with the arrangement, the embodiments described above in connection with the method for determining the operating state for an electrical device with a switching element can be provided accordingly. Description of implementation examples

[0049] Further embodiments are explained in more detail below with reference to the figures of a drawing. Herein: Fig. 1 shows a schematic representation of an arrangement for determining the operating state of a circuit breaker; Fig. 2 shows a schematic representation of the method for determining the operating state of the circuit breaker; Fig. 3 shows a schematic representation of a spectrogram based on measurement signals from the circuit breaker; Fig. 4 shows a schematic representation of a spectrogram based on measurement signals from the circuit breaker, in which a total switching angle was changed via a shock absorber of the circuit breaker; Fig. 5 shows a schematic representation of a spectrogram based on measurement signals from the circuit breaker, in which a shock absorber with a modified damping characteristic was used; Fig. 6 shows a schematic representation of a spectrogram based on measurement signals from acoustic sensors attached to switch poles during a switch-on operation of the circuit breaker with an increased switching stroke at the switch poles of approximately 13 mm;Fig. 7: a further schematic representation of a spectrogram based on measurement signals from acoustic sensors attached to switch poles during a circuit breaker closing operation with a reduced switching stroke of approximately 10 mm; Fig. 8: a schematic representation of a spectral frequency distribution over time, determined on the basis of a wavelet analysis, during a closing operation with an increased switching stroke of the circuit breaker; Fig. 9: a further schematic representation of a spectral frequency distribution over time, determined on the basis of a wavelet analysis, during a closing operation.

[0050] Fig. 1shows a schematic representation of an arrangement for determining the operating state of the circuit breaker 10. Such a circuit breaker 10 is typically used with a closed housing in a switchgear and comprises mechanical components such as a motor, springs, shafts, shock absorbers, and buffers. When the circuit breaker 10 is in operation, the mechanical components cause vibrations and / or acoustic signals that are emitted into the entire surrounding area. Further vibrations or acoustic signals are generated by mains voltage (for example, 50 Hz hum or 100 Hz hum or hum of other mains frequencies) or by external sources such as running machines near the circuit breaker 10.

[0051] An experienced maintenance technician can determine the operating state of circuit breaker 10 solely based on the noise generated when the springs are tensioned and when a switching operation is triggered. This method enables, in particular, automated determination and analysis of the operating state. Furthermore, other operating states can be determined in addition to those processes perceptible by human hearing.

[0052] Sensors 11a, 11b, 11c are arranged in or near the circuit breaker 10 for this purpose. Sensors 11a, 11b, 11c are each capable of recording vibrations, structure-borne sound, or airborne sound and operate according to a suitable physical principle. Piezo microphones, condenser microphones, structure-borne sound sensors, fiber-optic sound sensors, or fiber-optic vibration sensors can be used as sensors 11a, 11b, 11c, for example. Analog measurement signals 12a, 12b, 12c from sensors 11a, 11b, 11c subsequently undergo analog preprocessing 13, in which the analog measurement signals 12a, 12b, 12c are amplified if necessary and / or pass through an anti-aliasing filter.

[0053] Subsequently, an analog-to-digital conversion 14 of the analog measurement signals 12a, 12b, 12c takes place, whereby a single analog-to-digital converter can be used in a multiplexing process or several analog-to-digital converters can be used in a parallel process. The digitized measurement signals are then processed in an evaluation device 15 by one or more processors (for example, a CPU, a microprocessor, an embedded system, a digital signal processor, or another special processor), by one or more programmable logic components (for example, a complex programmable logic device, CPLD, or a field programmable gate array, FPGA), or by a fully custom chip. An operating state of the circuit breaker 10 is then determined, a result is generated, and output in an output device 16 and / or routed to a network 17. The output device 16 comprises, for example, an LED or a display.

[0054] For interaction with the evaluation device 15, an input device 18, such as a keyboard, is provided, which is connected to the evaluation device 15 locally or via a network. This allows a maintenance technician to retrieve details of the measurements and / or the operating status.

[0055] In principle, a single sensor is sufficient for the process. However, the number of installed vibration and sound sensors 11a, 11b, 11c influences the quality of the condition assessment. Thus, by using multiple sensors 11a, 11b, 11c, the signal-to-noise ratio with which the measurement signals 12a, 12b, 12c are recorded can in principle be improved. Furthermore, the frequency bandwidth with which the vibration signals and / or sound signals 12a, 12b, 12c are recorded can be increased by combining the frequency bands of different sensors 11a, 11b, 11c. By combining the vibration and ultrasonic sensors 11a, 11b, 11c, the infrasound emitted by vibrations can be recorded in parallel with the ultrasound with moderate effort.

[0056] The use of multiple sensors 11a, 11b, 11c further enables the localization of sources responsible for the vibration and / or sound signals using time-of-flight measurements. This is important because the location of a vibration and / or sound event also allows the cause of the respective event to be identified. If a vibration and / or sound event can be localized during a switch-on process, for example, near a buffer responsible for the switch-on process, the sound is likely to have been generated by the shaft striking the buffer. By using the measurement signals 12a, 12b, 12c not only to assess the functionality of the circuit breaker 10 as a whole, but also to assess the functionality of the buffer, the reliability of the operating state analysis can be improved and made more precise.

[0057] The assignment of the cause of vibration signals and / or sound signals 12a, 12b, 12c can be improved by considering control signals that trigger actions on the circuit breaker 10. For example, if springs are tensioned using a motor, the motor must be supplied with power. A motor signal 12d obtained by tapping a motor-starting control signal and / or a measurement on a power supply line of the motor (for example, using additional sensors that operate non-mechanically) can be used by the evaluation device 15 to attribute the resulting vibrations and sound emissions to the motor or another component involved.

[0058] Fig. 2shows a schematic representation of the method for determining the operating state of the circuit breaker 10. After the analog-to-digital conversion 14 of the measurement signals 12a, 12b, 12c by means of the analog-to-digital converters 21a, 21b, 21c, the generated digital signals are algorithmically processed as explained below. In principle, fewer or more than three input channels are possible. This is Fig. 3 represented by dots between elements 21b and 21c through 24a and 24c. In specific implementations, variations of the algorithms and the order in which the algorithms are executed are possible. The algorithms can be implemented in hardware and / or software.

[0059] Following the analog-to-digital conversion 14, a first processing step involves digital preprocessing 22a, 22b, 22c of the digital signals. In this processing step, the measurement data from each individual sensor 11a, 11b, 11c is processed separately. This processing step is optional, but particularly advantageous if the measurement signals 12a, 12b, 12c are interspersed with interference signals (noise) that are irrelevant to the operating state analysis. In the vicinity of the circuit breaker 10, highly noisy measurement signals 12a, 12b, 12c will generally occur. To improve the signal-to-noise ratio of the measurement signals 12a, 12b, 12c, noise reduction methods such as low-pass filters, notch filters, or wavelets are suitable.

[0060] If multiple sensors are used, the digital signals can be correlated. In a second processing step, cross-channel digital signal preprocessing 23a, 23b, 23c takes place. This enables a further improvement in the signal-to-noise ratio. Furthermore, using channel separation methods, the vibration and sound signals 12a, 12b, 12c caused by different signal sources at the circuit breaker 10 can be separated and assigned to different sources. For example, if a switching operation is triggered and vibrations are caused simultaneously by a spring and a buffer, two separate signals can be calculated by utilizing runtime effects, one of which can be assigned exclusively to the spring and the other exclusively to the buffer. Separating the individual signals considerably simplifies the operating state analysis of the circuit breaker 10.

[0061] In a third processing step, the preprocessed signals are categorized. The goal of this processing step is to transform the preprocessed signals in such a way that, if possible, only those state characteristics remain that reliably enable an assessment of the operating state of the circuit breaker 10. To determine the state characteristics, the signals from different channels can be combined, 24a, or obtained from a single channel, 24c. Signal processing methods such as (short-time) Fourier transformation, wavelet transformation, and / or template matching can be used in this processing step. In simple cases, it may be sufficient to determine the state characteristics directly by evaluating the preprocessed signals, for example, by determining the envelope curves of the respective signals.

[0062] In a fourth processing step, the previously determined state characteristics are analyzed in a first classification unit 25 so that comparable measurement signals 12a, 12b, 12c are assigned to specific causes by grouping the measurement signals 12a, 12b, 12c. This processing step is necessary because different measurements never generate the same measurement data. On the one hand, the operating state of the circuit breaker 10 changes with each switching operation (because, for example, a spring loses its tensile force over time or breaks, or the operating voltage varies); on the other hand, the method presented here is intended to be used on different circuit breakers, which may differ in terms of the vibration and noise emissions they generate. The installation and location of the circuit breaker 10 also significantly alter its frequency response.Algorithms such as artificial neural networks, fuzzy logic, deep learning, machine-based learning, or decision trees can be used as classification methods. By classifying the vibration or sound events in the first classification unit 25, the operating state of the circuit breaker 10 can be analyzed and statements about the operating state can be made.

[0063] In a fifth processing step, temporal information 26 is used to increase the reliability of determining the operating state. For this purpose, a second classification unit 27 exploits the fact that the operating state of the circuit breaker 10 changes in small steps over time.

[0064] In a sixth processing step, results, including, for example, the operating state of the circuit breaker 10 and / or an analysis result of an analysis of the operating state, undergo a result processing 28.

[0065] If the motor signal 12d is initially present in analog form, it is subjected to an analog-to-digital conversion 29. Subsequently, the motor signal 12d can be included and processed during the execution of the second to sixth processing steps.

[0066] The results can be sent directly to a user via network 17. However, since the system's internal representation of the results is poorly suited for user interpretation, it is particularly useful for maintenance personnel to translate the results into an easily understandable format. Thus, the input data and results can be visualized in tabular form, as graphs or diagrams, by listing probabilities, and presented via output device 16. Maintenance personnel can retrieve details of the measurements and / or the operating status using input device 18.

[0067] For a quick operating status analysis, a binary or ternary representation as a traffic light would also be useful. Green indicates that circuit breaker 10 does not currently require maintenance. Yellow indicates that circuit breaker 10 may continue to operate but should be serviced promptly because there have been changes in the behavior of circuit breaker 10 that have led to a deviation from the original state. Red indicates that circuit breaker 10 may no longer be operated safely.

[0068] Not all to Fig. 2The steps described must be implemented in every implementation. For example, the cross-channel digital signal preprocessing 23a, 23b, 23c can be omitted. In another software-implemented implementation, several processing steps can also be processed together (for example, the first classification unit 25 and the second classification unit 27). It is also possible to modify the order in which the described steps are executed or to omit individual processing steps.

[0069] This method makes it possible to automatically monitor the mechanics of circuit breakers 10 and assess their operating status. In the event of spontaneously occurring problems, this prevents the circuit breaker 10 from having to be taken out of service for extended periods (for example, because a defect leads to the destruction of the circuit breaker 10) or from having to be taken out of service altogether (for example, in the event of damage that allows the circuit breaker to continue operating for a short time).

[0070] Since appropriately equipped circuit breakers 10 are continuously monitored, routine inspections can either be eliminated entirely or maintenance intervals can be extended compared to conventional circuit breakers 10. This allows for cost savings. Existing circuit breakers 10 can be retrofitted with a diagnostic system for permanent operating status analysis. Performing the operating status analysis of circuit breakers 10 does not require removal or decommissioning. Normal maintenance on circuit breakers 10 requires their removal or at least decommissioning and intervention in the control system of circuit breaker 10. This is not necessary if the method described here is used.

[0071] The method enables the use of a simple and cost-effective embedded system as well as suitable, cost-effective, conventional sensors 11a, 11b, 11c. The production of a correspondingly equipped circuit breaker 10 is therefore hardly more expensive than that of a conventional circuit breaker. At the same time, however, significant added value is achieved. In particular, remote maintenance and monitoring are possible, thus offering significant savings potential in terms of maintenance and repair costs, since the condition of the circuit breaker 10 can be continuously monitored.

[0072] The electronics and sensors can be mounted in circuit breakers in a way that avoids the need to modify safety-critical components. Contact with low-, medium-, or high-voltage components is also not required. When using fiber optic sensors, contact with medium- and high-voltage components is possible, for example. Furthermore, the technology can be retrofitted without great effort.

[0073] Fig. 3 shows a schematic representation of a spectrogram determined by means of a short-time Fourier transformation based on measurement signals during a switching-off process of a circuit breaker 10, which were recorded with a fiber-optic microphone. Here, a quotient of power and frequency Plf against term t and frequency f Higher values ​​of Plf are dark colored. Fig. 4shows a schematic representation of a spectrogram based on measurement signals during a switching-off process of the circuit breaker 10, wherein the angle of rotation of the switching shaft of the circuit breaker 10 was changed during the measurements. Fig. 5 shows a schematic representation of a spectrogram based on measurement signals during the opening process of the circuit breaker 10, using a shock absorber with a modified damping characteristic. The areas within the dashed lines 31, 41, 51 in the Fig. 3 to 5show how the individual modifications are reflected in the acoustic emissions and thus in the spectrogram. The dotted lines 32, 42, 52 delimit a range of maximum amplitudes of the respective frequency. A change in the respective amplitude of a frequency component is significant for a specific condition at the circuit breaker. The time of occurrence of a specific frequency component as well as the amplitude in Fig. 5 Represented by the intensity of the blackening, it is suitable as a classification feature. The dashed lines 31, 41, and 51 each show an area that is relevant and suitable for determining the condition of the circuit breaker and contains features to be classified.

[0074] Fig. 6shows a schematic representation of a spectrogram based on measurement signals from acoustic sensors attached to switch poles during a closing operation of a circuit breaker 10 with an increased switching stroke at the switch poles of approximately 13 mm. A pulse 61 from a closing coil is followed in time by a pulse 62 at the closing time (contact making) and then by a pulse 63 at the latching time. In particular, the triggering of a closing magnet can be assigned to pulse 61 and the latching of a switch shaft to pulse 63. A change in the switching stroke, for example, towards a larger stroke, means that the closing of the circuit breaker 10 takes longer. This applies analogously to the contact closure. In the spectrogram according to Fig. 6 the corresponding points in time are clearly identifiable.

[0075] In a similar way, the tripping of a tripping solenoid and the processes occurring during opening can be represented and analyzed. Changes in the switching stroke also have a significant impact on the mechanical, electrical, and physical behavior of the circuit breaker 10 during opening. Extended opening times with simultaneous current flow are associated with increased wear on the switch contacts. Changes in switching times during contact making are also associated with this and can be determined in the same way. The switching speeds and switching times of a circuit breaker 10 are fundamental for the successful opening and closing of the circuit breaker 10. For this reason, there are separate standards for switching equipment in the field of electrical engineering standards, in which the functions of circuit breakers must be demonstrated in tests.

[0076] Fig. 7shows a further schematic representation of a spectrogram based on measurement signals from acoustic sensors attached to switch poles during a closing operation of the circuit breaker 10 with a reduced switching stroke of approximately 10 mm. A pulse 71 from the closing coil is followed by a pulse 72 at the closing time and then by a pulse 73 at the latching time. In particular, Fig. 7the change in the temporal resolution of the spectrogram with a reduced switching stroke from 13 mm to 10 mm. If a closing spring in the circuit breaker 10 is set in motion by the triggering of a closing mechanism in accordance with the impulse of the closing coil, contact elements in one switch pole first meet. Subsequently, a mechanical latching takes place such that the switch remains closed. With different switching strokes, both the time until the contact elements meet and the time until the mechanical latch on the circuit breaker 10 engages change. All these times as well as the changes due to the different strokes can be determined from the Fig. 6 and 7 be determined by suitable comparison. The pulse 72 at the switch-on time in Fig. 7 with a smaller stroke compared to the pulse 62 at the time of switching on in Fig. 6a higher excitation. This is because the closing spring, due to its shorter travel distance, has a higher stored energy, which is released when the mechanism latches.

[0077] Fig. 8 and 9 each show a spectral frequency distribution over time, determined on the basis of a wavelet analysis, during a switch-on process with different settings of the switching stroke of the circuit breaker 10. Areas of medium amplitude are colored dark, areas of low and high amplitude are colored light. Fig. 8 The switching stroke was increased during the corresponding switching process and the Fig. 9 The switching stroke of one pole is increased, maintained or reduced in the corresponding switching operation.

[0078] In Fig. 8An upper white spot 81 can be seen. Spot 81 is created when the three contact elements meet simultaneously, thus causing a high overall mechanical excitation. However, if the individual contact elements meet at different times due to different switching strokes in the individual poles, the frequency and intensity distributions are as shown in Fig. 9 with spots 91, 92, and 93. Here, three individual white spots 91, 92, and 93 with a small extent are visible. At the same time, the distances between the spots 91, 92, and 93 in the x-direction reveal the temporal relationship between the contacting of the individual switch poles. From the representation in Fig. 9 The switching times of the individual switch poles can thus be determined.

[0079] If data on the new condition of the circuit breaker 10 is determined as reference data (corresponding to an acoustic vibration fingerprint of the circuit breaker 10), the data can serve as a basis for determining contact wear. If contact wear occurs on a breaker pole, the switching times of the circuit breaker 10 change. The contact elements close at a different time than in the original state. At the same time, by comparing the individual switching times for each breaker pole, the wear of each individual switching pole can be determined from the different switching times. This allows the switching time of each individual switch pole to be measured, which allows statements to be made about the wear of the contacts of the breaker poles, the mechanics, or switching speeds, and thus about the mechanical function of the drive system and the triggering of closing and opening coils.This display also shows whether circuit breaker 10 has switched at all and / or whether the switching times or movement sequences of circuit breaker 10 have changed. This is particularly important because a non-switching circuit breaker must be replaced in its function by other circuit breakers in operation.

[0080] Data such as the Fig. 3 to 9enable, for example, statements regarding the opening of a contact of a switch pole; the speed of a contact closing; the sequence of contacts closing; a time delay between individual contact points; the wear status and / or degree of wear of a contact; the speed of a rotary movement of a switching shaft; the success of an on and / or off switching process; the drive energy for a motor winding in a spring-loaded drive; the question of whether a spring is wound or relaxed and / or whether an unrecorded, abnormal frequency spectrum is present; the triggering process of a closing magnet; the release process of pawls; the switching success of a breaking magnet; the loosening of a drive shaft, the engagement of latches, the functionality of a storage drive, the magnitude of rotary movements of the switching shaft; the reaching of an end position of the switching shaft;a change in a characteristic and / or a need to replace a stop damper; an energy consumption of a spring operating system in the circuit breaker; or a question as to whether all mechanical parts are functioning together in such a way that a switching function is ensured.

[0081] Using the findings presented, it is possible to determine the operating state of a circuit breaker 10 using one or more conventional and fiber optic sensors 11a, 11b, 11c and a computer-aided system. Fiber optic sensors 11a, 11b, 11c are preferable, as they can also be mounted on high-voltage breaker poles and thus obtain meaningful measurement data on the state of each individual breaker pole at the source.

[0082] Attaching them to the housing of a drive mechanism of circuit breaker 10 also allows for information about the current condition of circuit breaker 10, whether a mechanism of circuit breaker 10 is operating properly, or whether changes are occurring, for example, due to resinous greases, that lead to a change in switching times. The application of fiber optic sensors is not limited to a single circuit breaker type or variant. Likewise, there are no restrictions regarding the voltage level or the switching capacity of circuit breaker 10.

[0083] The application of the described method has the significant advantage that simply attaching the sensors 11a, 11b, 11c to the circuit breaker 10 enables an operating state analysis and continuous monitoring. Unlike previous analyses on circuit breakers, this eliminates the need to intervene in the circuit breaker 10. Furthermore, the circuit breaker 10 does not need to be shut down, and no intervention in the control system of the circuit breaker 10 is necessary. This eliminates long downtimes of the circuit breaker 10 during which it is unavailable.

[0084] The features disclosed in the above description and the drawings may be important for the realization of the various embodiments both individually and in any combination.

Claims

1. A method for determining an operating state for an item of electrical equipment with a switch element, comprising: - capturing measurement signals (12a, 12b, 12c) for an item of electrical equipment with a switch element by means of a sensor device which has a sensor, wherein the measurement signals (12a, 12b, 12c) for the item of electrical equipment comprise at least one type of measurement signal (12a, 12b, 12c) from the following group: vibration signals and sound signals; - processing the measurement signals (12a, 12b, 12c) by means of an evaluation device (15), wherein the processing comprises an analogue-digital conversion (14) of the measurement signals (12a, 12b, 12c) into digital measurement signals; and - determining an operating state for the item of electrical equipment from a group of different operating states by means of the evaluation device (15), wherein the digital measurement signals are compared with comparison signals which are assigned in each case to at least one of the different operating states, wherein the comparison of the digital measurement signals with the comparison signals comprises a machine classification of the operating state, characterised in that the measurement signals (12a, 12b, 12c) are captured by means of a fibre-optic sensor (11a, 11b, 11c).

2. The method according to Claim 1, characterised in that the measurement signals (12a, 12b, 12c) comprise both vibration signals and sound signals.

3. The method according to Claim 1 or 2, characterised in that the measurement signals (12a, 12b, 12c) are captured by means of a plurality of sensors (11a, 11b, 11c).

4. The method according to at least one of the preceding claims, characterised in that the sound signals (12a, 12b, 12c) comprise at least one type of sound signal (12a, 12b, 12c) from the following group: infrasound signals, audible sound signals and ultrasound signals.

5. The method according to at least one of the preceding claims, characterised in that - the operating state for an item of electrical equipment is determined inside and / or outside a switchgear; and / or - the operating state is determined for an item of electrical equipment which carries high voltage or low voltage.

6. The method according to at least one of the preceding claims, characterised in that the measurement signals (12a, 12b, 12c) are pre-processed during the processing, wherein the signal-noise ratio is increased for the measurement signals (12a, 12b, 12c).

7. The method according to Claim 6, characterised in that the measurement signals (12a, 12b, 12c) are pre-processed in an analogue manner by means of at least one of the group including low-pass filter, high-pass filter, band-pass filter and anti-aliasing filter.

8. The method according to Claim 6 or 7, characterised in that the measurement signals (12a, 12b, 12c) are pre-processed in a digital manner by means of at least one of the group including notch filter, wavelet analysis, discrete Fourier transform, fast Fourier transform and short-time Fourier transform.

9. The method according to at least one of the preceding claims, characterised in that during the determination of the operating state at least one state characteristic which characterises the operating state of the item of electrical equipment is determined from the digital measurement signals.

10. The method according to Claim 9, characterised in that the at least one state characteristic is determined by means of at least one member of the group including Fourier transform, short-time Fourier transform, wavelet transform, template matching, spectrogram and envelope curve.

11. The method according to Claim 9 or 10, characterised in that the operating state of the item of electrical equipment is determined by classification of at least one state characteristic by means of at least one machine classification method.

12. The method according to Claim 11, characterised in that the machine classification method is trained by means of the comparison signals before the implementation of the method and / or during operation.

13. The method according to at least one of Claims 9 to 12, characterised in that a time development of the operating state of the item of electrical equipment and / or the at least one state characteristic is determined.

14. An arrangement comprising: - an item of electrical equipment which has a switch element; - a sensor device which has a sensor and is configured to capture measurement signals (12a, 12b, 12c) for the item of electrical equipment, wherein the measurement signals (12a, 12b, 12c) for the item of electrical equipment comprise at least one type of measurement signal (12a, 12b, 12c) from the following group: vibration signals and sound signals; and - an evaluation device (15) which is configured - to process the measurement signals (12a, 12b, 12c), wherein the processing comprises an analogue-digital conversion (14) of the measurement signals (12a, 12b, 12c) into digital measurement signals; and - to determine an operating state for the item of electrical equipment from a group of different operating states, wherein the digital measurement signals are compared with comparison signals which in each case are assigned to at least one of the different operating states, wherein the comparison of the digital measurement signals with the comparison signals comprises a machine classification of the operating state, characterised in that the sensor is a fibre-optic sensor (11a, 11b, 11c).