Patent ID: 12196784

Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.

DETAILED DESCRIPTION OF THE INVENTION

Advantages of embodiments of the present disclosure include a method and system for measuring a state of an electrical conductor in an individual component or the state of an associated system with a non-invasive sensor. The method and system allow calculation of the state to use frequency-selective current detection to sense asset health, imminent asset failures, or actual asset failures, including catastrophic events (such as faults). In field applications, sensor assemblies may be located near current carrying conductors (CCC) or electrical conductors and will respond to frequency composition of current without touching the CCC or being a part of the circuit. Conditions and/or the state that may be determined includes slowly increasing ground fault current, frequencies (indicative of degradation or arc faults), instantaneous excessive harmonic(s) composition (indicative of many abnormal behavior) and other parasitic faults (such as ground or line-to-line faults).

FIG.1shows a sensor assembly100according to an embodiment of the present disclosure. Sensor assembly100includes a magnetostrictive resonator sensor101and a signal detector103arranged and disposed to measure a frequency profile from the magnetostrictive resonator sensor101. When magnetostrictive resonator sensor101is in sufficiently close proximity to an AC electrical conductor (i.e., an electrical conductor carrying alternating current (AC)), the alternating magnetic field generated by the alternating current creates a frequency profile of alternating intensities of the magnetic field. Magnetoelastic resonator101generates an AC magnetic response signal when subjected to an externally applied alternating (AC) magnetic interrogation signal.FIG.1shows an embodiment where sensor assembly100includes an interrogator105arranged and disposed to interrogate magnetostrictive resonator sensor101with an interrogation signal at an interrogation frequency.

Magnetostrictive resonator sensor101includes a resonating structure107and may include a planar film. Alternatively, the resonating structure107may include one or more resonating structures107(e.g., resonator portions). Resonating structure107have a geometry and are formed from a material that respond to an applied magnetic field. The resonating structure107can be a planar film with any useful geometry (e.g., including one or more resonator portions or, alternatively, including a planar, non-patterned layer). InFIG.1, the resonating portion107is a rectangular prism. In the embodiment wherein the resonating portion107is a rectangular prism, the prism includes a length (L) and magnetic bias angle β determines its resonance frequency. When activated by an externally applied AC magnetic field, the resonating structure107vibrates mechanically due to the Joule effect (i.e., the material strain induced by an applied magnetic field known as magnetostriction). Resonating structure107continues to vibrate, generating its own AC magnetic response signal detectable by the same external loop antenna. Suitable magnetostrictive resonator sensors101may be fabricated utilizing any suitable technique. For example, the magnetostrictive resonator sensor101may be fabricated according to U.S. Pat. No. 10,260,969, issued Apr. 16, 2019, entitled “Microfabricated Magnetostrictive Resonator”, which is incorporated by reference in its entirety.

In the embodiment shown inFIG.1, the magnetostrictive resonator sensor101includes a resonating structure107(e.g., a CoxFeyfilm) located on top of a base structure109(e.g., silicon base) or between two base structures109, thereby forming a composite. The film can be deposited directly on a surface of the base structure109. Alternatively, the film can be embedded within a matrix (e.g., an epoxy or polymer matrix), which in turn is in contact with at least a portion of the surface of the base structure109. Thus, the magnetostrictive resonator sensor101includes, at least, a magnetostrictive material (e.g., a CoxFeyfilm) as resonating structure107and a base structure109. The magnetostrictive resonator sensor101may have any useful form, such as a stack, a laminate structure, a monolithic structure, etc.

Furthermore, the resonating structure107may include a plurality of resonating portions or resonators. The presence of multiple resonators of varying lengths and magnetic bias angles result in a multi-frequency signal that becomes the resonator's identity. That is, a plurality of resonating structures107may be utilized to monitor multiple frequencies, which have distinct responsive frequencies in response to exposure to AC magnetic field either from an electrical conductor203or from an interrogator105. For instance, microfabricated arrays can include a plurality of magnetoelastic longitudinal mode resonators. In some embodiments, each resonating structure107includes a suspended magnetostrictive CoxFeystructure (e.g., resonator portion(s)) deposited and patterned by electrodeposition. In other embodiments, the resonating structure107is integrated with a permanent biasing magnet to achieve the optimal magnetoelastic operating point.

The resonating structure107of magnetostrictive resonator sensor101may be formed from any useful magnetostrictive material, e.g., having a saturation magnetostriction λsatmore than about 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 125 ppm, 150 ppm, 175 ppm, 200 ppm, 225 ppm, 250 ppm, 275 ppm, or more. Exemplary magnetostrictive materials include CoFe alloys (e.g., Co1-xFexalloys, where 0.1≤x≤0.9, such as Co0.66Fe0.34, Co0.7Fe0.3, Co0.8Fe0.2, or CoxFeyalloys, as described herein); FeGa alloys (e.g., Fe1-xGaxalloys, where 0<x≤0.35, 0.04<x<0.35, or 0.04<x<0.27, such as in Galfenol); FeGaAl alloys (e.g., Fe(20-y)at % Gayat % Al, where 0<y≤15; and Fe— (27.5−y) at. % Gayat % Al, where 0≤y≤14); FeAl alloys (e.g., Fe1-xAlx, where 0<X≤0.35, such as in Alfenol); FeSiB alloys (e.g., alloys having 85-95 wt. % Fe, 5-10 wt. % Si, and 1-5 wt. % B, such as Metglas®. 2605SA1 and 2605HB1M having λsatof about 27 ppm, available from Metglas®., Inc., Conway, S.C.); FeCrSiB alloys (e.g., alloys having 85-95 wt. % Fe, 1-5 wt. % Cr, 1-5 wt. % Si, and 1-5 wt. % B, such as Metglas®. 2605S3A having λsatof about 20 ppm, available from Metglas®., Inc.); NiFeMoB alloys (e.g., alloys having 40-50 wt. % Ni, 40-50 wt. % Fe, 5-10 wt. % Mo, and 1-5 wt. % B, such as Metglas®. 2826 MB having λsatof about 12 ppm, available from Metglas®., Inc.); FeSiBC alloys (e.g., alloys having about 81 wt. % Fe, about 3.5 wt. % Si, about 13.5 wt. % B, and about 2 wt. % C, such as Metglas®. 2605SC (Fe81Si3.5B13.5C2)); FeSeBC alloys; SmFe2-based alloys (e.g., SmxDy1-xFey, where 0.14<x<0.9 and 1.9<y≤2, such as Sm0.86Dy0.14Fe2in Samfenol-D; or SmxEr1-xFey, where 0.14<x<0.9 and 1.9<y≤2, such as in Samfenol-E); FeRh alloys (e.g., such as that described in Ibarra M R et al., “Giant volume magnetostriction in the FeRh alloy,” Phys. Rev. B 1994 August; 50 (6): 4196-9); DyFe2-based alloys (e.g., (Dy0.33Fe0.67)1-xBx, where 0≤x≤0.1); TbFe2-based alloys (e.g., TbxDy1-xFey, where 0.27<x<0.3 and 1.9<y≤2, such as Tb0.3Dy0.7Fe1.92in Terfenol-D®. having λsatof about 1000-2000 ppm), as well as other NiFeCo-based alloys (e.g., a FeNiCoTi-based alloys, such as Fe31.9Ni9.8Co4.1Ti, where subscripts refer to atomic %, as described in Kakeshita T et al., “Magnetic field-induced martensitic transformation and giant magnetostrictions in Fe—Ni—Co—Ti and ordered Fe3Pt shape memory alloys,” Mater. Trans. JIM 2000; 41 (8): 882-7). In particular embodiments, the magnetostrictive material is any alloy having λsatof about 10 to about 275 ppm or more than about 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 125 ppm, 150 ppm, 175 ppm, 200 ppm, 225 ppm, 250 ppm, 275 ppm, or more.

Base structure109of magnetostrictive resonator sensor101may be any suitable material for supporting the resonating structure107, while permitting mechanical oscillations with limited dampening. In other embodiments, the base structure109includes an interface (e.g., a post) configured to attach to the resonator portion(s) and to allow vibration of the resonator portion(s). Exemplary materials for the base structure109include a polymer (e.g., polystyrene), a metal (e.g., Si), or glass, optionally including one or more damping layers (e.g., an electrostatic coating, a polymer coating, and/or a coating that includes one or more particles or fibers). In other embodiments, the base structure109can include a seeding layer (e.g., a copper layer) to assist in electrodeposition of the magnetostrictive material.

The magnetostrictive resonator sensor101may include one or more coatings. Such coatings can be useful for altering the physical properties of the magnetostrictive resonator sensor101.

Magnetostrictive resonator sensor101includes a magnetoelastic material, as described above, that respond to externally applied magnetic fields. Exposure of the resonating structure107to a time-varying, externally applied magnetic signal (e.g., an AC magnetic frequency profile from an electrical conductor or an AC magnetic interrogation signal from an interrogator105) results in Joule magnetostriction, λ=ΔL/L (i.e., a physical deformation characterized by change in length ΔL, where λsatis the value λ at saturation). In addition, this exposure generates longitudinal vibrations, which in turn produces elastic waves that emit a magnetic response signal (e.g., an AC magnetic response signal). The emitted response signal can be detected in any useful way, e.g., by magnetic, acoustic, and/or optical systems. Conversely, exposure to an external mechanical stress or strain results in a change in magnetostriction, termed the Villari effect. Thus, a pristine surface and a structurally flawed surface exhibit different magnetostriction, λ, when exposed to an applied magnetic field.

As discussed above, sensor assembly100as shown inFIG.1, includes a magnetostrictive resonator sensor101and a signal detector103arranged and disposed to measure a frequency profile from the magnetostrictive resonator sensor101. When magnetostrictive resonator sensor101is in sufficiently close proximity to an AC electrical conductor203(i.e., an electrical conductor203carrying alternating current (AC)), the alternating magnetic field generated by the alternating current creates a frequency profile of alternating intensities of the magnetic field. Magnetoelastic resonator sensor101generates an AC magnetic response signal when subjected to an externally applied alternating (AC) magnetic interrogation signal.FIG.1shows an embodiment where sensor assembly100includes an interrogator105arranged and disposed to interrogate magnetostrictive resonator sensor101with an interrogation signal at an interrogation frequency. Magnetostrictive resonator sensor101can be interrogated by any useful technique, e.g., by using the interrogator105. Interrogator105may include, but is not limited to an external loop antenna that generates an AC magnetic field, which causes the resonating structure107to vibrate mechanically due to the Joule effect (i.e., the material strain induced by an applied magnetic field known as magnetostriction). Upon removal of the interrogation signal, the resonating structure107may continue to vibrate, thereby generating its own AC magnetic response signal that is detectable by signal detector103. Suitable devices for use as the signal detector103may include, but are not limited to a receiving loop antenna, the same transmitting antenna switched to a receiving circuit, or any detector described herein.

Signal detector103may include any useful components to provide and/or detect signals (e.g., interrogation signals and/or response signals). Exemplary components for signal detector103may include, but is not limited to, an excitation circuit configured to provide one or more interrogation signals (e.g., including one or more of a frequency domain sine wave generator, a time domain pulse generator, an AC excitation circuit (e.g., including an input from a direct digital synthesis component, a potentiometer, and/or one or more amplifiers)), and/or a DC excitation circuit (e.g., including a voltage source, a potentiometer, an inductor, and/or one or more amplifiers); an excitation coil to provide a magnetic interrogation signal (e.g., one or more of Helmholtz coils, pick-up coils, solenoid coils, AC coils, and/or DC coils, which can optionally also serve as the sensing coil); a bias coil to provide a rotating bias field (e.g., one or more of Helmholtz coils); one or more electronic switches (e.g., for use in combination with one coil capable of both providing an interrogation signal and receiving a response signal, where the electronic switch isolates excitation and receiving circuits); a permanent biasing magnet to achieve the optimal λsatoperating point; a power supply (e.g., a supply to provide current to one or more coils); a multimeter; a laser emitter to detect magnetostriction of the resonator (e.g., a light-emitting diode or a laser that is aligned to reflect off of a surface of the resonator); a detector to detect one or more response signals (e.g., a microphone to detect an acoustic response signal, a sensing coil to detect a magnetic response signal (e.g., any coil described herein optionally in combination with a multiplexer), and/or a phototransistor to detect an optical response signal (e.g., optionally in combination with one or more mirrors, beam splitters, coarse sensors, fine sensors, piezoelectric translators, locked-in amplifiers, oscillators, and/or phase shifters); and/or a receiving circuit configured to process one or more response signals (e.g., including one or more of a microcontroller (e.g., to control any components described herein, such as one or more excitation circuits and one or more detectors), a multichannel analog-to-digital converter (ADC), a frequency domain lock in amplifier, a time domain digital oscilloscope, a network impedance analyzer, a phase detection circuit (e.g., including a comparator, an XOR gate, an ADC, and/or a filter), and/or an amplitude detection circuit (e.g., including on amplifier, an RMS-DC converter, and/or an ADC)).

WhileFIG.1shows interrogator105and signal detector103as separate devices, in one embodiment, the interrogator105and signal detector103may be incorporated into a unitary device.

Interrogation and response signals, such as those provided and detected by signal detector103and interrogator105, may be provided and detected in any useful format. In some embodiments, the magnetostrictive resonator sensor101relies on a time-domain measurement technique, where the interrogation signal is a sinusoidal magnetic field impulse (e.g., using an excitation coil) and the response signal is a time-domain response that can be analyzed in any useful way. For example, the signal detector103is configured to determine the resonance frequency by converting the response to a frequency spectrum and then identifying the peak in that spectrum (e.g., with a Fast Fourier Transform algorithm or with statistical fitting by a Poisson process) or by counting the number of oscillations for a given period (e.g., with frequency counting). In other embodiments, the magnetostrictive resonator sensor101relies on a frequency-domain measurement technique, where the interrogation signal is a fixed-frequency, steady state signal, and the response signal is detected by sweeping a frequency range and by determining the frequency that provides the maximum amplitude signal. In yet another embodiment, the signal detector103relies on an impedance de-tuning method, where the resonator tag interacts with an inductive solenoid, and the response signal is the change in impedance of the solenoid measured as a function of frequency (e.g., by using a network impedance analyzer).

FIG.2shows a fault monitoring system200according to an embodiment of the present disclosure. Fault monitoring system200includes a fault detector201in electrical communication with sensor assembly100via signal lines202. While signal lines202may include physical lines, the signals may also be sent wirelessly. Fault detector201is configured to receive the frequency profile from the magnetostrictive resonator sensor101. The sensor assembly100is arranged and disposed to provide the magnetostrictive resonator sensor101in sufficiently close proximity to the electrical conductor203to permit a magnetostriction effect between the electrical conductor203and the magnetostrictive resonator sensor101. The magnetostriction effect, as utilized herein, is mechanical vibration of the resonating structure107of the magnetostrictive resonator sensor101induced due to the Joule effect in response to AC magnetic fields, such as from either an electrical conductor203or from an interrogator105. Determination of a fault condition or other state of the electrical conductor203may also provide a location within the fault monitoring system200by sensing the state and providing the location of the measured state. Such fault locations can be reported to the fault detector201, where the fault monitoring system200may be monitored and appropriate action may be taken in response to the measured state. WhileFIG.2shows a fault monitoring system200with sensor assemblies100arranged in sufficiently close proximity to the electrical conductor203to permit a magnetostriction effect between the electrical conductor203and the magnetostrictive resonator sensor101, the fault monitoring system200may also be utilized to determine the state of associated systems to electrical conductor203. Associated systems, as utilized herein, are electrical systems that utilize electrical conductors203and may include, but are not limited to power loads, such as electrical motors or heaters, power transmission, and/or power generation, such as photovoltaic generation.

Fault detector201may include a data processing system300that is capable of analyzing frequency profiles and determining a state of an electrical conductor203and/or an associated system.FIG.3shows an illustration of a data processing system300as depicted in accordance with an illustrative embodiment. Data processing system300inFIG.3is an example of a data processing system300that may be used to implement the illustrative embodiments. In this illustrative example, data processing system300includes communications fabric301, which provides communications between processor unit303, memory305, persistent storage307, communications unit309, input/output (I/O) unit311, and display313.

Processor unit303may be a number of processors, a multi-processor core, or some other type of processor, depending on the particular implementation. A number, as used herein with reference to an item, means one or more items. Further, processor unit303may be implemented using a number of heterogeneous processor systems in which a main processor is present with secondary processors on a single chip. As another illustrative example, processor unit303may be a symmetric multi-processor system containing multiple processors of the same type.

Memory305and persistent storage307are examples of storage devices315. A storage device315is any piece of hardware that is capable of storing information, such as, for example, without limitation, data, program code317in functional form, and/or other suitable information either on a temporary basis and/or a permanent basis. Storage devices315may also be referred to as computer readable storage devices in these examples. Memory305, in these examples, may be, for example, a random access memory305or any other suitable volatile or non-volatile storage device315. Persistent storage307may take various forms, depending on the particular implementation.

For example, persistent storage307may contain one or more components or devices. For example, persistent storage307may be a hard drive, a flash memory, a rewritable optical disk, a rewritable magnetic tape, or some combination of the above. The media used by persistent storage307also may be removable. For example, a removable hard drive may be used for persistent storage307.

Communications unit309, in these examples, provides for communications with other data processing systems300or devices. In these examples, communications unit309is a network interface card. Communications unit309may provide communications through the use of either or both physical and wireless communications links.

Input/output (I/O) unit311allows for input and output of data with other devices that may be connected to data processing system300. For example, input/output (I/O) unit311may provide a connection for user input through a keyboard, a mouse, and/or some other suitable input device. Further, input/output (I/O) unit311may send output to a printer. Display313provides a mechanism to display information to a user.

Instructions for the operating system, applications, and/or programs may be located in storage devices315, which are in communication with processor unit303through communications fabric301. In these illustrative examples, the instructions are in a functional form on persistent storage307. These instructions may be loaded into memory305for execution by processor unit303. The processes of the different embodiments may be performed by processor unit303using computer implemented instructions, which may be located in a memory, such as memory305.

These instructions are referred to as program code317, computer usable program code, or computer readable program code that may be read and executed by a processor in processor unit303. The program code317in the different embodiments may be embodied on different physical or computer readable storage media319, such as memory305or persistent storage307.

Program code317is located in a functional form on computer readable storage media319that is selectively removable and may be loaded onto or transferred to data processing system300for execution by processor unit303. Program code317and computer readable storage media319form computer program product323in these examples. In one example, computer readable storage media319may be computer readable storage media319or computer readable signal media321. Computer readable storage media319may include, for example, an optical or magnetic disk that is inserted or placed into a drive or other device that is part of persistent storage307for transfer onto a storage device315, such as a hard drive, that is part of persistent storage307. Computer readable storage media319also may take the form of a persistent storage307, such as a hard drive, a thumb drive, or a flash memory, that is connected to data processing system300. In some instances, computer readable storage media319may not be removable from data processing system300.

Alternatively, program code317may be transferred to data processing system300using computer readable signal media321. Computer readable signal media321may be, for example, a propagated data signal containing program code317. For example, computer readable signal media321may be an electromagnetic signal, an optical signal, and/or any other suitable type of signal. These signals may be transmitted over communications links, such as wireless communications links, optical fiber cable, coaxial cable, a wire, and/or any other suitable type of communications link. In other words, the communications link and/or the connection may be physical or wireless in the illustrative examples.

In some illustrative embodiments, program code317may be downloaded over a network to persistent storage307from another device or data processing system300through computer readable signal media321for use within data processing system300. For instance, program code317stored in a computer readable storage medium319in a server data processing system300may be downloaded over a network from the server to data processing system300. The data processing system300providing program code317may be a server computer, a client computer, or some other device capable of storing and transmitting program code317.

The different components illustrated for data processing system300are not meant to provide architectural limitations to the manner in which different embodiments may be implemented. The different illustrative embodiments may be implemented in a data processing system300including components in addition to or in place of those illustrated for data processing system300. Other components shown inFIG.3can be varied from the illustrative examples shown. The different embodiments may be implemented using any hardware device or system capable of running program code317. As one example, the data processing system300may include organic components integrated with inorganic components and/or may be comprised entirely of organic components excluding a human being. For example, a storage device315may be comprised of an organic semiconductor.

In another illustrative example, processor unit303may take the form of a hardware unit that has circuits that are manufactured or configured for a particular use. This type of hardware may perform operations without needing program code317to be loaded into a memory305from a storage device315to be configured to perform the operations.

For example, when processor unit303takes the form of a hardware unit, processor unit303may be a circuit system, an application specific integrated circuit (ASIC), a programmable logic device, or some other suitable type of hardware configured to perform a number of operations. With a programmable logic device, the device is configured to perform the number of operations. The device may be reconfigured at a later time or may be permanently configured to perform the number of operations. Examples of programmable logic devices include, for example, a programmable logic array, programmable array logic, a field programmable logic array, a field programmable gate array, and other suitable hardware devices. With this type of implementation, program code317may be omitted because the processes for the different embodiments are implemented in a hardware unit.

In still another illustrative example, processor unit303may be implemented using a combination of processors found in computers and hardware units. Processor unit303may have a number of hardware units and a number of processors that are configured to run program code317. With this depicted example, some of the processes may be implemented in the number of hardware units, while other processes may be implemented in the number of processors.

The different illustrative embodiments can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment containing both hardware and software elements. Some embodiments are implemented in software, which includes but is not limited to forms such as, for example, firmware, resident software, and microcode.

Furthermore, the different embodiments can take the form of a computer program product323accessible from a computer usable or computer readable medium providing program code317for use by or in connection with a computer or any device or system that executes instructions. For the purposes of this disclosure, a computer usable or computer readable medium can generally be any tangible apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.

The computer usable or computer readable medium can be, for example, without limitation an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, or a propagation medium. Non-limiting examples of a computer readable medium include a semiconductor or solid-state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and an optical disk. Optical disks may include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W), and DVD.

Further, a computer usable or computer readable medium may contain or store a computer readable or computer usable program code317such that when the computer readable or computer usable program code317is executed on a computer, the execution of this computer readable or computer usable program code317causes the computer to transmit another computer readable or computer usable program code317over a communications link. This communications link may use a medium that is, for example, without limitation, physical or wireless.

A data processing system300suitable for storing and/or executing computer readable or computer usable program code317will include one or more processors coupled directly or indirectly to memory305elements through a communications fabric, such as a system bus. The memory305elements may include local memory employed during actual execution of the program code317, bulk storage, and cache memories which provide temporary storage of at least some computer readable or computer usable program code317to reduce the number of times code may be retrieved from bulk storage during execution of the code.

Input/output or I/O311devices can be coupled to the system either directly or through intervening I/O controllers. These devices may include, for example, without limitation, keyboards, touch screen displays, and pointing devices. Different communications adapters may also be coupled to the system to enable the data processing system300to become coupled to other data processing systems300or remote printers or storage devices315through intervening private or public networks. Non-limiting examples of modems and network adapters are just a few of the currently available types of communications adapters.

FIG.4shows a method400for determining a state of an electrical conductor203or an associated system according to an embodiment of the present disclosure. Method400includes providing a sensor assembly100including a magnetostrictive resonator sensor101and a signal detector103(step401). The providing may include placing the Magnetostrictive resonator sensor101in close proximity to an electrical conductor203, which has a state to be determined. A first frequency profile of the electrical conductor203is obtained from the magnetostrictive resonator sensor101(step403). A second frequency profile of the electrical conductor203is obtained from the magnetostrictive resonator sensor101(step405). The first frequency profile and the second frequency profile are transmitted via a wired or wireless connection to a fault detector201(step407). A state of the electrical conductor203or an associated system is determined with the fault detector201in response to the first frequency profile and the second frequency profile (step409). The sensor assembly100is arranged and disposed to provide the magnetostrictive resonator sensor101in sufficiently close proximity to the electrical conductor203to permit a magnetostriction effect between the electrical conductor203and the magnetostrictive resonator sensor101(see for exampleFIGS.1and2). In another embodiment according to the present disclosure, method400includes interrogating the magnetostrictive resonator sensor101with an interrogator105at an interrogation frequency, wherein the first frequency profile and the second frequency profile from the magnetostrictive resonator sensor101are in response to the interrogation frequency.

To determine the state of the electrical conductor203and/or an associated system with the fault detector201, the first frequency profile and the second frequency profile are analyzed using fault monitoring system200, as shown and described with respect toFIGS.2and3. In one embodiment, the analysis and calculation is performed using a computer system, as shown and described with respect toFIG.3.

The determination of the state of the electrical conductor203and/or an associated system may include, for example, asset health, or asset failures, including catastrophic events (such as faults). For example, the state of the electrical conductor203or associated system is determined from the first frequency profile and the second frequency profile may include a condition, such as slow leakage currents (indicative of slow degradation), frequencies (indicative of arc faults), instantaneous excessive harmonic(s) composition (indicative of many abnormal behavior) or other parasitic faults (such as ground or line-to-line faults).

In other embodiments, the state determined is a current of the electrical conductor203. In order to calculate the current, a sensor assembly101according to the present invention is brought into close proximity to the electrical conductor203. The sensor assembly101includes a resonating structure107with a characteristic resonance frequency (fo) and resonance response with some full width at half max (FWHM). For example, Δf, FWHM and fomay depend upon the specific material of the resonating structure107. The applied magnetic field causes a shift in this resonance frequency (Δf) depending on if the magnetic field is parallel or anti-parallel. Since current flow in a conductor causes a magnetic field, measurement of the sensor frequency response is indicative of current flow in the conductor. An alternating current (AC) will cause the resonance frequency to dither around the nominal (no current) resonance frequency. The extent of this dithering (from positive Δf to negative Δf) is related to the magnitude of the AC current.

In one embodiment, in step409shown inFIG.4, a plurality of specific frequencies are monitored. While a full frequency spectrum sweep of frequencies may be utilized, it is desirable to only be able to characterize a single or a few frequencies and recreate the behavior of the entire frequency response. A current magnitude is measured by the shift in peak frequency. The resolution of the sensor is a function of the Q-factor, where Q=fr/Δf where Δf is the full width at half maximum (FWHM). For example, the current intensity can be determined by the shape of the frequency response. The shape of the frequency response may be at least partially determined by the FWHM. From this, the intensity of the current can be determined.
I=g(f)
where I is the expected intensity and f is a given frequency.

With a single specific frequency that is monitored, the current magnitude can be determined at the monitored frequent. With this current magnitude, fo+Δf can be calculated. fo+Δf represents how far the curve has dithered or shifted, which is directly related to the magnitude of the magnetic field. Since the frequency response in most embodiments is symmetric around fo+Δf, two solutions are determined depending if you're on the leading or trailing edge of the envelope. Accordingly, in one embodiment, multiple frequencies are monitored as a given instance in time in another embodiment, the response of monitored frequency can be measured in time.

The resolution of the current magnitude is related to the number of frequencies monitored. While not wishing to be bound by theory or explanation, it is believed that the entire envelope can be recreated with only two measured frequencies or a single frequency measured over time. In order to recreate the envelope, the shape of the envelop would be assumed to be static and that there are perfect or near perfect measurement capabilities (e.g., no noise). In these embodiments, monitoring multiple frequency can relax the static and measurement assumptions to a certain degree. That is, increasing the number of monitored frequencies not only increases the resolution, but also the confidence of the back calculation.

In another embodiment, in step409shown inFIG.4, a time series reading for a monitored frequency for a given current may be determined. For example, the time series reading for a specific frequency at a specific frequency can be determined utilizing the response shape and the FWHM of the frequency profile. Current can be determined by taking the measured frequency response and comparing to all known frequency responses (i.e., in the second frequency profile). This embodiment can give a value for the current that minimizes error between expected and measured, which reduces the number of monitored frequencies required to determine the current.

FIG.5shows an exemplary frequency profile, wherein the frequency response (i.e., the intensity in dB) shows a frequency response around a zero current point fo.corresponding to a particular magnetostrictive resonator sensor101. When monitoring an alternating current in an electrical conductor203, the frequency peak dithers so that the peak varies between f1and f2. In order to monitor the electrical conductor203, the magnetostrictive resonator sensor101is configured (e.g., by interrogation by interrogator105or by configuration of resonating structure107) to monitor frequency intensities at each of fA, fB, fC, fD, and fE. While this embodiment shows five distinct frequencies being monitored, the invention is not so limited, and any suitable number of frequencies may be monitored. In one embodiment, the number of frequencies monitored corresponds to a computation infrastructure that collects and analyzes the information in a predetermined measurement time. For example, a suitable measurement time is at least ten times the resonant frequency.

FIG.6shows a first frequency profile utilizing the monitored frequency intensities as shown inFIG.5. The frequency signal inFIG.6represents a response to a current:
i=I0·sin(ωt)
In the embodiment shown inFIG.6, frequency responses are obtained at frequency fA, fB, fC, fD, and fE. In this embodiment, the frequencies correspond to frequency responses from interrogation frequencies corresponding to each of frequencies fA, fB, fC, fD, and fE. The intensity peaks are illustrated at each of the frequencies fA, fB, fC, fD, and fE. As shown inFIG.6, the f0peak601is the peak at the fundamental frequency f0. In addition, f1peak603and the f2peak605are shown along the frequency responses. The signal response repeats at a frequency of the line signal from the electrical conductor203. If the dither of the frequency peak is greater than the full width at half maximum (FWHM), then there will be dead time in the frequency profile. Accordingly, the signals further from the fundamental frequency (e.g., fB, >fC, >fD, >fE) have greater dead time in the frequency profile.FIG.6shows the increased dead time as the monitored frequencies move from fAto fBto fCto fDto fE. The lack of presence of a signal at fEprovides an outer limit to the dither of the frequency peak and provides the ability to calculate or estimate the current from the peak shape/FWHM or Δf/A (Hz/A).

FIG.7shows a first frequency profile utilizing the monitored frequency intensities as shown inFIG.5. The frequency signal inFIG.7represents a response to a current:
i=I1·sin(ωt) whereI1<<I0
As inFIG.6, the intensity peaks are illustrated at each of the frequencies fA, fB, fC, fD, and fE. As shown inFIG.7, the f0peak601is the peak at the fundamental frequency f0. f1peak603and the f2peak605are shown along the frequency responses. The signals further from the fundamental frequency (e.g., fB, >fC, >fD, >fE) have greater dead time in the frequency profile.FIG.7shows the increased dead time as the monitored frequencies move from fAto fBto fCto fDto fE. The lack of presence of a signal at fDprovides an outer limit to the dither of the frequency peak and provides the ability to calculate or estimate the current from the peak shape/FWHM. These frequency profiles are indicative of levels of current amplitudes.

FIG.8illustrates a current profile801of an electrical conductor203including a transient condition803according to an embodiment of the present disclosure. The transient condition803may result from any number of properties or conditions of the electrical conductor203, such as, but not limited to a surge or fault condition.FIG.9, illustrates a second frequency profile for an operational state including a transient condition803, such as the transient condition803shown inFIG.8. In one embodiment,FIG.9shows the response profile according to a second frequency profile. In this embodiment, the second frequency profile is compared to a first frequency profile, such asFIG.6, and differences determine a state of the conductor or the associated system.

FIG.10shows the magnetic field response of a magnetostrictive resonator sensor101to an electrical conductor203. As shown and described above with respect toFIG.1,FIG.10includes a sensor assembly100according to an embodiment of the present disclosure. Sensor assembly100includes a magnetostrictive resonator sensor101, a signal detector103and an interrogator105. In addition, magnetostrictive resonator sensor101includes a resonating structure107. In order to provide the first and second profiles, the frequency response may be calculated as the magnetomechanical resonance induced by drive coil AC field1001, HDrive, as shown inFIG.10.

Resonance frequency determined primarily by resonator length, L, DC bias field, HB, and electrical conductor magnetic field1003is generated by current carrying wire, HI(t). Presence of bias field turns the sensor assembly100“on” and provides maximum signal amplitude at that field. The resonance frequency may be calculated according to the following equation:

fr=12⁢L[ρE0+9⁢λs2⁢ρ⁡((❘"\[LeftBracketingBar]"HB+HI(t)❘"\[RightBracketingBar]"⁢cos⁡(β)))2Js⁢HA3]-1
where L is the resonator length, ρ is the density of the resonator structure107, HBis the DC bias field, HI(t) is the magnetic field generated by the electrical conductor203, β is the magnetic bias angle of resonator structure107, λS2is the magnetostriction coefficient of the material of resonator structure107, E0is the elastic modulus of the resonator structure107, Jsis the magnetization of the resonator structure107, and HAis the alternating bias field. The presence of HI(t) superimposed with HBcausing shifts in both frequency and amplitude due to nonlinear behavior in Young's modulus. The first frequency profile may be taken at a first point in time or may be set according to historical or stored values and the second frequency profile may be taken at a second point of time.

In another embodiment, a DC system may be monitored utilizing a sensor assembly100according to the present disclosure. In this embodiment, for example an electrical conductor203carrying current from a photovoltaic (PV) panel, may include a sensor assembly100mounted to provide the magnetostrictive resonator sensor101in sufficiently close proximity to the electrical conductor203to permit a magnetostriction effect between the electrical conductor203and the magnetostrictive resonator sensor101. A first frequency profile is measured at a plurality of monitored frequencies and a second frequency profile at the plurality of monitored frequencies is measured and compared to the first frequency profile to provide current detection.FIG.11Ashows a coil output for the signal detector103of frequency vs. coil output in dB andFIG.11Bshows the magnetostrictive resonator sensor characterization for DC amps vs. frequency. The current detection results in amplitude and frequency shift and the frequency shifts semi-linearly until saturation.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.