Patent Description:
A power device, in particular comprising physical components operating mechanically, more particularly a tap changer, e.g. an on-load tap changer, OLTC, exhibits a vibroacoustic signal with a unique signature belonging to the assembled power device as a whole. Such vibroacoustic signal is ideally time-invariant given constant physical conditions of said physical components and environmental conditions. A defect in any of said physical components generates a vibroacoustic signal, which deviates from the obtained vibroacoustic signal with a unique signature belonging to the power converter. Thus, conventional methods identify defects in the power device by analysing the monitoring vibroacoustic signal based on the obtained vibroacoustic signal with a unique signature. The defects in the power device affect the performance thereof, in particular mechanical inconsistencies, and can potentially cause a power outage. Thus, it is of interest to identify the malfunction in the power device before the failure of the power device. In addition, it might be of interest once a malfunction occurred to identify its cause without disassembly of the device. It is particularly interesting to identify which of the physical components causes such deviation through signal processing, so as to replace the defected components without further examination. However, the conventional approaches fail to achieve such effect due to a complex superposition of vibroacoustic signals generated by simultaneous movements of individual physical components during operation of the power device.

<CIT> discloses a sensor system which includes a sensor network comprising at least one optical fiber having one or more optical sensors. At least one of the optical sensors is arranged to sense vibration of an electrical device and to produce a time variation in light output in response to the vibration. A detector generates an electrical time domain signal in response to the time variation in light output. An analyzer acquires a snapshot frequency component signal which comprises one or more time varying signals of frequency components of the time domain signal over a data acquisition time period. The analyzer detects a condition of the electrical device based on the snapshot frequency component signal. <CIT> discloses a voltage transformer on-load tap-changer mechanical fault diagnosis method in which a vibration detection probe is adhered to a box wall of an on-load tap-changer in a surface-mounted manner and vibration signals generated in tap-changer operation processes can be captured.

Thus, there is a need to improve a method for monitoring a power device, in particular vibroacoustic monitoring of an on-load tap changer.

The present disclosure relates to a method for monitoring a power device, the method comprising: obtaining at least one frequency spectrum of at least one physical component of the power device, wherein the at least one frequency spectrum comprises at least one eigenfrequency of the at least one physical component of the power device; measuring, using at least one sensor, a vibroacoustic signal of the power device; and determining a signal contribution of the at least one physical component of the power device to the vibroacoustic signal based on the obtained at least one frequency spectrum.

According to an embodiment, the measuring a vibroacoustic signal of the power device is performed during operation of the device. In this context, during operation of the device may refer to the mechanical operation of at least one physical component of the power device, e.g. rotation or translational movement of at least one physical component. The mechanical operation may be performed by a respective motor or manually. The mechanical operation may be of the at least one physical component with the obtained at least one frequency spectrum but is not limited to. The mechanical operation may be of any other physical component of the power device.

According to an embodiment, the method further comprises transforming the measured vibroacoustic signal into frequency domain.

According to an embodiment, determining the signal contribution comprises comparing amplitudes and/or frequencies of the vibroacoustic signal with the obtained at least one frequency spectrum or with a previously measured vibroacoustic signal.

According to an embodiment, the method further comprises identifying at least one frequency component in the vibroacoustic signal which corresponds to the at least one eigenfrequency in the obtained at least one frequency spectrum.

According to an embodiment, the method further comprises identifying at least one physical component of the at least one physical component of the power device which causes a deviation in the vibroacoustic signal.

According to an embodiment, the method further comprises identifying an abnormal behaviour in the at least one physical component based on the determining of the signal contribution of the at least one physical component of the power device to the vibroacoustic signal.

According to an embodiment, the steps: measuring, using the at least one sensor, the vibroacoustic signal of the power device; and determining the signal contribution of the at least one physical component of the power device to the vibroacoustic signal based on the obtained at least one frequency spectrum; are executed when an abnormal behaviour in the power device has been detected.

According to an embodiment, the method further comprises iteratively measuring the vibroacoustic signal of the power device and determining the signal contribution of the at least one physical component of the power device to the vibroacoustic signal based on the obtained at least one frequency spectrum.

According to an embodiment, the obtained at least one frequency spectrum is obtained prior to assembly of the power device.

According to an embodiment, determining the signal contribution comprises at least one of truncating, filtering, and applying at least one transformation to the measured vibroacoustic signal.

According to an embodiment, determining the signal contribution comprises removing the identified at least one frequency component from the vibroacoustic signal.

According to an embodiment, the at least one transformation is or comprises at least one of a wavelet transformation, a Fourier transformation, a short-time Fourier transformation, a Hilbert transformation or a Wigner transformation.

According to an embodiment, the at least one sensor is or comprises any one of a vibration sensor, an accelerometer, a pressure sensor, a microphone, a hydrophone or an optical sensor. The optical sensor may be a laser doppler vibrometer.

The expression "vibroacoustic" in the context of the present disclosure may refer to any vibration signal, in particular to any vibration signal that can be measured by at least one of a vibration sensor, an accelerometer, a pressure sensor, a microphone, a hydrophone or an optical sensor.

According to an embodiment, the power device is or comprises at least one of an on-load tap changer, OLTC, a circuit breaker or a disconnector.

According to an embodiment, the at least one physical component is or comprises at least one of a tap changer housing, a diverter switch, a selector switch, at least one movable contact, or at least one vacuum interrupter.

According to an embodiment, the at least one sensor is attached or located anywhere on the exterior and/or interior of the power device. According to another embodiment, the at least one sensor is not attached to the power device. According to yet another embodiment, the at least one sensor measures an environmental condition, in particular a temperature and/or pressure. The at least one sensor may be a temperature sensor.

The present disclosure also relates to a monitoring device for monitoring a power device, the device comprising a processor configured to: obtain at least one frequency spectrum of at least one physical component of the power device, wherein the at least one frequency spectrum comprises at least one eigenfrequency of the at least one physical component of the power device; measure, using at least one sensor, a vibroacoustic signal of the power device; and determine a signal contribution of the at least one physical component of the power device to the vibroacoustic signal based on the obtained at least one frequency spectrum.

According to an embodiment, the processor is further configured to transform the measured vibroacoustic signal into frequency domain.

According to an embodiment, the processor is further configured to identify at least one frequency component in the vibroacoustic signal which corresponds to the at least one eigenfrequency in the obtained at least one frequency spectrum.

According to an embodiment, the processor is further configured to identify at least one physical component of the at least one physical component of the power device which causes a deviation in the vibroacoustic signal.

According to an embodiment, the processor is further configured to identify an abnormal behaviour in the at least one physical component based on the determining of the signal contribution of the at least one physical component of the power device to the vibroacoustic signal.

According to an embodiment, the processor is further configured to execute: measuring the vibroacoustic signal of the power device; and determining the signal contribution of the at least one physical component of the power device to the vibroacoustic signal based on the obtained at least one frequency spectrum; when an abnormal behaviour in the power device has been detected.

According to an embodiment, the processor is further configured to iteratively measure the vibroacoustic signal of the power device and determine the signal contribution of the at least one physical component of the power device to the vibroacoustic signal based on the obtained at least one frequency spectrum.

The present disclosure also relates to a system comprising a power device, at least one sensor and a monitoring device according to any one of the aforementioned preferred embodiments.

Various exemplary embodiments of the present disclosure disclosed herein are directed to providing features that will become readily apparent by reference to the following description when taken in conjunction with the accompanying drawings. In accordance with various embodiments, exemplary systems, methods, and devices are disclosed herein. It is understood, however, that these embodiments are presented by way of example and not limitation, and it will be apparent to those of ordinary skill in the art who read the present disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of the present disclosure.

In the following, exemplary embodiments of the disclosure will be described. It is noted that some aspects of any one of the described embodiments may also be found in some other embodiments unless otherwise stated or obvious. However, for increased intelligibility, each aspect will only be described in detail when first mentioned and any repeated description of the same aspect will be omitted.

<FIG> shows a flow chart of a method, according to an embodiment of the present disclosure.

In step S101, the method obtains at least one frequency spectrum of at least one physical component of the power device, wherein the at least one frequency spectrum comprises at least one eigenfrequency of the at least one physical component of the power device.

Then, in step <NUM>, the method measures, using at least one sensor, a vibroacoustic signal of the power device, in particular during operation of the power device.

In step S103, the method determines a signal contribution of the at least one physical component of the power device to the vibroacoustic signal based on the obtained at least one frequency spectrum.

<FIG>) illustrates a method of obtaining eigenfrequency spectrums, according to an embodiment of the present disclosure. A first physical component <NUM> exhibits a unique frequency characteristic with a first eigenfrequency <NUM> and the corresponding frequency spectrum <NUM> is plotted. Similarly, a second physical component <NUM> exhibits a unique frequency characteristic with a first eigenfrequency <NUM> and a second eigenfrequency <NUM> and the corresponding frequency spectrum <NUM> is plotted. In the embodiment shown in <FIG>, the frequency characteristics of the physical components <NUM> and <NUM> of a power device are obtained before the power device is assembled. It is understood by the skilled person in the art that the shapes of the first physical component <NUM> and the second physical component <NUM> are of illustrative nature and can take any shape. It is further understood by the skilled person that the frequency characteristics plotted in the frequency spectrums <NUM> and <NUM> may be in any shape, from which eigenfrequencies are derived.

<FIG>) illustrates a system comprising a device comprising a processor and a power device, according to an embodiment of the present disclosure. In particular, the system <NUM> comprises a power device, e.g. an OLTC, <NUM> which comprises the first physical component <NUM> and the second physical component <NUM>. A sensor <NUM>, which might also be part of the system <NUM>, is attached to the OLTC <NUM> and measures the vibration of the OLTC <NUM>. It is understood by the skilled person that the sensor <NUM> does not need to be attached or connected to the power device. For example, optical sensors exist in the art which can measure vibration signals from a distance. The measured vibration data, i.e. the vibroacoustic signal, <NUM> is fed to the device <NUM>. A processor <NUM> of the device <NUM> is configured to determine a signal contribution of the first physical component <NUM> and the second physical component <NUM> of the OLTC <NUM> to the vibroacoustic signal <NUM> based on the obtained frequency spectrums <NUM> and <NUM>.

According to an embodiment, the at least one sensor is attached or located anywhere on the exterior and/or interior of the power device. According to another embodiment, the at least one sensor is not attached to the power device. According to yet another embodiment, the at least one sensor measures an environmental condition, in particular a temperature and/or pressure.

According to an embodiment, the device is further configured to transform the measured vibroacoustic signal into frequency domain.

According to an embodiment, the device is further configured to identify at least one frequency component in the vibroacoustic signal which corresponds to the at least one eigenfrequency in the obtained at least one frequency spectrum.

According to an embodiment, the device is further configured to identify at least one physical component of the at least one physical component of the power device which causes a deviation in the vibroacoustic signal.

According to an embodiment, the device is further configured to identify an abnormal behaviour in the at least one physical component based on the determining of the signal contribution of the at least one physical component of the power device to the vibroacoustic signal.

According to an embodiment, the device is further configured to execute: measuring the vibroacoustic signal of the power device; and determining the signal contribution of the at least one physical component of the power device to the vibroacoustic signal based on the obtained at least one frequency spectrum; when an abnormal behaviour in the power device has been detected.

According to an embodiment, the device is further configured to iteratively measure the vibroacoustic signal of the power device during operation and determine the signal contribution of the at least one physical component of the power device to the vibroacoustic signal based on the obtained at least one frequency spectrum.

According to an embodiment, the at least one transformation is or comprises wavelet transformation or short-time Fourier transformation.

According to an embodiment, the at least one sensor is or comprises any one of a vibration sensor, an accelerometer, a pressure sensor, a microphone, a hydrophone or an optical sensor.

<FIG> illustrates a measurement result of an on-load tap changer, OLTC, according to an embodiment of the present disclosure. Particularly, the commutation time sequence <NUM> is plotted against time which represents an electrical measurement, for instance a voltage, of the OLTC during switching sequences. Similarly, the vibration signal <NUM> of the OLTC is measured using at least one sensor and is plotted against time. The commutation time sequence <NUM> comprises three steps of absolute values and the transition among the steps indicate mechanical movements of physical components inside the OLTC, which consequently results in the vibration signal <NUM>. Generally, the vibration signal <NUM> lags behind the commutation time sequence <NUM>. By processing the vibration signal <NUM>, e.g. by truncating, filtering and/or applying at least one transformation, the signal contribution of one or more physical components of the OLTC can then be determined.

A skilled person would further appreciate that any of the various illustrative logical blocks, units, processors, means, circuits, methods and functions described in connection with the aspects disclosed herein can be implemented by electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two), firmware, various forms of program or design code incorporating instructions (which can be referred to herein, for convenience, as "software" or a "software unit"), or any combination of these techniques. To clearly illustrate this interchangeability of hardware, firmware and software, various illustrative components, blocks, units, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware or software, or a combination of these techniques, depends upon the particular application and design constraints imposed on the overall device. In accordance with various embodiments, a processor, device, component, circuit, structure, machine, unit, etc. can be configured to perform one or more of the functions described herein. The term "configured to" or "configured for" as used herein with respect to a specified operation or function refers to a processor, device, component, circuit, structure, machine, unit, etc. that is physically constructed, programmed and/or arranged to perform the specified operation or function.

Furthermore, a skilled person would understand that various illustrative methods, logical blocks, units, devices, components and circuits described herein can be implemented within or performed by an integrated circuit (IC) that can include a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, or any combination thereof. The logical blocks, units, and circuits can further include antennas and/or transceivers to communicate with various components within the network or within the device.

Claim 1:
A method for monitoring a power device (<NUM>), the method comprising:
obtaining at least one frequency spectrum of at least one physical component of the power device (<NUM>), wherein the at least one frequency spectrum comprises at least one eigenfrequency of the at least one physical component of the power device (<NUM>), and wherein the obtained at least one frequency spectrum is obtained prior to assembly of the power device (<NUM>);
measuring, using at least one sensor, a vibroacoustic signal (<NUM>) of the power device (<NUM>); and
determining a signal contribution of the at least one physical component of the power device (<NUM>) to the vibroacoustic signal (<NUM>) based on the obtained at least one frequency spectrum.