Partial discharge monitoring sensor for high-voltage power equipment based on surface acoustic wave and its application

Abstract

The present invention discloses a surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment and its application, comprising a piezoelectric substrate on which a first interdigital electrode, a third interdigital electrode, a fourth interdigital electrode, and a fifth interdigital electrode are provided. The first interdigital electrode is connected to a transceiver antenna, and the fifth interdigital electrode is connected to a partial discharge antenna. The first interdigital electrode and the fifth interdigital electrode are spaced apart and arranged in perpendicular directions, and the third interdigital electrode and the fourth interdigital electrode are symmetrically arranged on both sides of the fifth interdigital electrode. The present application realizes wireless detection and wireless transmission of partial discharge of high-voltage power equipment without providing power to the sensor. The sensor of the present application can be used for temperature and partial discharge monitoring of high-voltage power equipment such as current contactors with large currents. It is safe and reliable, and solves the problem in the prior art that partial discharge sensors are difficult to use reliably in harsh environments such as high temperature and difficult power supply environments, and pose safety risks.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrical fault testing devices, and in particular relates to a surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment and its application. Background Art

[0002] Continuous partial discharge in the insulation system of power equipment can cause localized temperature rises in electrical components or joints. This continued temperature rise can also cause degradation of the insulation material, exacerbating partial discharge within the equipment, shortening the service life of the equipment and even causing electrical accidents. Therefore, monitoring partial discharge in power equipment is necessary.

[0003] Currently, surface acoustic waves (SAWs) have become widely used for temperature measurement in power equipment. Due to their passive and wireless nature, SAWs can be used in environments with high temperatures and high electromagnetic interference. On the other hand, partial discharge (PD) sensors, such as UHF and HFCT pulse current methods, are susceptible to electromagnetic interference, requiring multiple algorithms for backend processing. Furthermore, since PD sensor front-ends typically require wired power supply, data acquisition, and transmission, their application is limited to high-temperature environments with limited power supply. Summary of the Invention

[0004] The purpose of the present invention is to provide a surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment and its application, so as to solve or improve the problem in the prior art that partial discharge sensors are difficult to use reliably in harsh environments such as high temperature and difficult power supply environment, and pose safety hazards.

[0005] Specific technical solution of the present invention: The present invention provides a local discharge monitoring sensor for high-voltage power equipment based on surface acoustic waves, including a piezoelectric substrate, on which a first interdigital electrode, a third interdigital electrode, a fourth interdigital electrode and a fifth interdigital electrode are provided, the first interdigital electrode is connected to a transceiver antenna, the fifth interdigital electrode is connected to a local discharge antenna, the first interdigital electrode and the fifth interdigital electrode are arranged at intervals and in perpendicular directions, the third interdigital electrode and the fourth interdigital electrode are respectively connected to the fifth interdigital electrode, and are symmetrically arranged on both sides of the fifth interdigital electrode, the angle between the third interdigital electrode and the fifth interdigital electrode is an acute angle, and the angle between the fourth interdigital electrode and the fifth interdigital electrode is also an acute angle.

[0006] The known working principle of existing surface acoustic wave wireless sensors is to sense electrical signals at the interdigitated electrodes, and then generate surface acoustic waves through the piezoelectric effect of the interdigitated electrodes and the piezoelectric substrate that supports the interdigitated electrodes. After the surface acoustic wave propagates on the piezoelectric substrate, it senses various temperature and gas changes, which will change the speed of sound. The reflected sound speed forms an acoustic-to-electric conversion on the interdigitated electrodes again, and then an electrical signal with frequency and phase changes is reflected from the interdigitated electrodes. The present application achieves specific requirements such as resonant frequency and reflected surface acoustic wave transmission time by setting different numbers and different arrangements of interdigitated electrodes. Among them, the fifth interdigitated electrode connected to the partial discharge antenna is perpendicular to the propagation direction of the interdigitated electrode connected to the transceiver antenna, which can reduce interference signals. The symmetrical arrangement of the third and fourth interdigitated electrodes has a filtering effect and further enhances the transmission of partial discharge signals.

[0007] Preferably, the piezoelectric substrate is further provided with a second interdigital electrode, positioned between the first interdigital electrode and the third or fourth interdigital electrode, and arranged parallel to the first interdigital electrode. The provision of the second interdigital electrode enables the sensor to simultaneously measure the temperature of high-voltage power equipment (i.e., the sensor can simultaneously measure temperature and partial discharge). Furthermore, the second interdigital signal can serve as a reference point for surface acoustic wave propagation, facilitating better interception of the partial discharge signal in the time domain.

[0008] Preferably, the third interdigital electrodes and the fourth interdigital electrodes are provided in one or more groups, and the third interdigital electrodes, the fourth interdigital electrodes and the fifth interdigital electrodes are connected to form a closed loop, such as a triangle or a polygon.

[0009] Preferably, the device further includes a micro short-circuiting ring shield, wherein the third interdigital electrode, the fourth interdigital electrode, and the fifth interdigital electrode are respectively disposed within the micro short-circuiting ring shield, and the micro short-circuiting ring shield has a shield opening for the partial discharge antenna to pass through. The micro short-circuiting ring shield can shield other signal interference and enhance the partial discharge signal.

[0010] Preferably, the partial discharge antenna is an inductor not higher than 100uH; the inductor is a hollow three-dimensional coil or a PCB planar coil.

[0011] Preferably, the fifth number of interdigital electrode pairs P5>3×P 34 , P 34 is the number of electrode pairs of the third interdigital electrode or the fourth interdigital electrode. 34 The logarithms are different, which makes it easier to couple partial discharge signals with more frequencies.

[0012] Preferably, the rated wavelength of the fifth interdigital electrode λ5<0.5×λ 34 , where λ 34is the minimum of the rated wavelengths of the third and fourth interdigital electrodes. Electrode rated wavelength λ = v / f. v is the propagation velocity of sound through the piezoelectric substrate, and f is the frequency of the electrical signal between the interdigital electrodes.

[0013] Preferably, the first interdigital electrode, the second interdigital electrode, the third interdigital electrode and the fourth interdigital electrode all have the same frequency f, and the highest induction frequency f5 of the fifth interdigital electrode is greater than 2×f.

[0014] Another technical solution of the present application: a partial discharge monitoring system for power equipment, comprising:

[0015] A sensor employing the aforementioned surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment. The sensor senses partial discharge based on interdigitated electrodes, utilizes the interdigitated electrodes and a piezoelectric substrate to perform electroacoustic conversion from an electrical signal to a surface acoustic wave signal, and then transmits an electrical signal containing partial discharge of the high-voltage power equipment based on the surface acoustic wave signal-to-electrical signal conversion. Simultaneously, the sensor receives electromagnetic wave signals emitted by a reader and reflects the electrical signal through electroacoustic conversion and acoustic-to-electrical conversion.

[0016] The reader receives the transmitted electrical signal of the surface acoustic wave sensor of the sensor and processes and outputs the intensity and frequency value of the partial discharge when measuring the partial discharge signal;

[0017] When measuring temperature without partial discharge signal, the electromagnetic wave signal required for the sensor to work is emitted, and the reflected electric signal of the sensor is received and the output temperature value is converted based on the time difference intercepted on the time domain waveform of the electric signal.

[0018] Another technical solution of the present application is a method for monitoring partial discharge of power equipment, which uses the above-mentioned surface acoustic wave-based partial discharge monitoring sensor and reader for monitoring, and specifically includes the following steps:

[0019] A-Partial Discharge Measurement

[0020] Step A1: The partial discharge antenna of the sensor senses a pulse electrical signal from the power equipment, and the equivalent capacitance of the fifth interdigital electrode couples to the electrical signal, generating a surface acoustic wave on the piezoelectric substrate. The surface acoustic wave is filtered and amplified by the third and fourth interdigital electrodes and then transmitted to the second interdigital electrode. The surface acoustic wave signal is then converted to an electrical signal at the first interdigital electrode, and the electrical signal containing the partial discharge of the high-voltage power equipment is transmitted via the transceiver antenna.

[0021] Step A2: The reader receives the electrical signal from the sensor, filters out the frequency of the radio electromagnetic wave signal received by the sensor, obtains the signal and then performs amplitude or spectrum conversion to obtain the intensity and frequency value of the partial discharge;

[0022] B-Temperature Measurement

[0023] Step B1: the reader transmits a high-frequency electromagnetic wave signal to the sensor;

[0024] Step B2: After receiving the high-frequency electrical signal, the first interdigital electrode of the sensor completes the electroacoustic conversion of the electrical signal into a surface acoustic wave signal. The surface acoustic wave signal propagates to the second interdigital electrode and is reflected back to the first interdigital electrode, and the reflection time is recorded as t12; the surface acoustic wave signal propagates to the third interdigital electrode and is reflected back to the first interdigital electrode, and the reflection time is recorded as t13; the surface acoustic wave signal propagates to the fourth interdigital electrode and is reflected back to the first interdigital electrode, and the reflection time is recorded as t14; the surface acoustic wave signal propagates to the fifth interdigital electrode and is reflected back to the first interdigital electrode, and the reflection time is recorded as t15;

[0025] Step B3: Calculate the temperature value of the monitored electrical equipment through at least one of the reflection times t12, t13, t14, and t15; calculate the temperature value of the monitored electrical equipment based on the reflection times t12, t13, t14, and t15, and use a table lookup of a standard value sequence corresponding to the reflection time of data obtained in a standard temperature experimental environment to obtain a corresponding temperature value; when multiple temperature values ​​are obtained using multiple reflection times t12, t13, t14, and t15, use the average value of the multiple temperatures as the average temperature of the device under test, or use t15 as the temperature of the partial discharge monitoring point and t12 as the temperature adjacent to the monitoring point.

[0026] The beneficial effects of the present invention are:

[0027] 1. The sensor of this application fully utilizes the wireless, passive, and high-temperature resistant characteristics of surface acoustic waves to achieve wireless detection and transmission of partial discharge in high-voltage power equipment, without requiring a power supply. This sensor can be used for temperature and partial discharge monitoring in high-voltage power equipment, such as high-current contactors. It is safe and reliable, resolving the problem of existing partial discharge sensors being difficult to use reliably in harsh environments such as high temperatures and difficult power supply environments. Furthermore, its power-free operation eliminates numerous safety concerns, such as the personal safety issues associated with discharge voltage introduced by traditional cables.

[0028] 2. The sensor of the present application achieves specific requirements such as resonant frequency and reflected surface acoustic wave transmission time by setting different numbers of interdigitated electrodes with different arrangements. It can be used for partial discharge detection of electrical equipment and has strong anti-interference ability. Among them, the propagation direction of the fifth interdigitated electrode connected to the partial discharge antenna is perpendicular to the propagation direction of the interdigitated electrode connected to the transceiver antenna, which can reduce interference signals. The third interdigitated electrode and the fourth interdigitated electrode are connected to the fifth motor and are symmetrically arranged, which have a filtering effect and enhance the transmission of partial discharge signals. The third interdigitated electrode, the fourth interdigitated electrode and the fifth interdigitated electrode are connected to form a closed loop and are arranged in a miniature short-circuit ring shielding cover, which can shield other signal interference and further enhance the partial discharge signal.

[0029] 3. The sensor of the present application sets a second interdigital signal between the first interdigital signal and the fifth interdigital signal, so that the sensor can be used to measure the temperature of high-voltage power equipment at the same time (that is, the sensor can measure temperature and partial discharge at the same time). At the same time, the second interdigital signal can also be used as a reference point for the propagation of surface acoustic waves, which facilitates better interception of partial discharge signals in the time domain signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 2. It is a schematic structural diagram of a partial discharge monitoring sensor for high-voltage power equipment based on surface acoustic waves according to the present invention;

[0031] Figure 2 This sensor is used to measure the time domain signal wave received by the partial discharge of high-voltage power equipment.

[0032] Figure 3 yes Figure 2 The time domain signal is further analyzed and processed into the signal wave.

[0033] Description of the main figures: 1. First interdigital electrode; 2. Second interdigital electrode; 3. Third interdigital electrode; 4. Fourth interdigital electrode; 5. Fifth interdigital electrode; 6. Piezoelectric substrate; 7. Transceiver antenna; 8. Partial discharge antenna; 9. Micro short-circuit ring shielding cover. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0036] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0037] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items. Example

[0038] In order to solve or improve the problem that existing partial discharge sensors are difficult to use reliably and have safety hazards in harsh environments such as high temperature, difficult power supply environment, and high voltage coupling that endangers personal safety, the following is proposed: Figure 1The illustrated surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment includes a piezoelectric substrate 6, on which are disposed a first interdigital electrode 1, a second interdigital electrode 2, a third interdigital electrode 3, a fourth interdigital electrode 4, and a fifth interdigital electrode 5. The first interdigital electrode 1 is connected to a transceiver antenna 7, and the fifth interdigital electrode 5 is connected to a partial discharge antenna 8. The first interdigital electrode 1 and the fifth interdigital electrode 5 are spaced apart and arranged perpendicularly, which improves the sensor's anti-interference performance. The third interdigital electrode 3 and the fourth interdigital electrode 4 are respectively connected to the fifth interdigital electrode 5 and are symmetrically arranged on either side of the fifth interdigital electrode 5. The angle between the third interdigital electrode 3 and the fifth interdigital electrode 5 is acute, and the angle between the fourth interdigital electrode 4 and the fifth interdigital electrode 5 is also acute. In this embodiment, the third interdigital electrode 3, the fourth interdigital electrode 4, and the fifth interdigital electrode 5 form an isosceles triangle, with the vertex of the isosceles triangle pointing toward the second interdigital electrode 2. The third interdigitated electrode 3 and the fourth interdigitated electrode 4 are symmetrically arranged, have a filtering effect, and further enhance the transmission of the partial discharge signal. The second interdigitated electrode 2 is arranged parallel to the first interdigitated electrode 1, and the distance between the second interdigitated electrode 2 and the isosceles triangle electrode is equal to the distance between the second interdigitated electrode 2 and the first interdigitated electrode 1. After the partial discharge antenna 8 senses the high-frequency signal, the signal directly reaches the second interdigitated electrode 2, is then converted into an acoustic wave signal and reaches the first interdigitated electrode 1, and is then coupled out through the transceiver antenna 7. On the other hand, the acoustic wave signal formed by the partial discharge pulse signal sensed by the second interdigitated electrode 2 also reaches the fifth interdigitated electrode 5. When the ambient temperature changes, the fifth interdigitated electrode 5 serves as a good reference for the delay of the acoustic signal. At the same time, the fifth interdigitated electrode 5 can effectively absorb the reflection problem between the second interdigitated electrode 2 and the partial discharge probe, releasing some of the reflected energy. That is, the provision of the second interdigital electrode 2 enables the sensor to be used simultaneously to measure the temperature of high-voltage power equipment (i.e., the sensor can measure temperature and partial discharge simultaneously). At the same time, the second interdigital signal can also be used as a reference point for the propagation of surface acoustic waves, facilitating better interception of partial discharge signals in the time domain signal.

[0039] The device further includes a micro short-circuiting ring shield 9, within which the third interdigital electrode 3, the fourth interdigital electrode 4, and the fifth interdigital electrode 5 are respectively disposed. The micro short-circuiting ring shield 9 has an opening through which the partial discharge antenna 8 passes. The micro short-circuiting ring shield 9 can shield other signal interference and further enhance the partial discharge signal.

[0040] Furthermore, the number of fifth interdigital electrodes 5 pairs P5>3×P 34 , P 34 is the number of electrode pairs of the third interdigital electrode 3 and the fourth interdigital electrode 4. The rated wavelength λ5 of the fifth interdigital electrode 5 is <0.5×λ 34 ,λ 34is the minimum of the rated wavelengths of the third and fourth interdigital electrodes 3 and 4. Rated wavelength λ = v / f, where v is the propagation velocity of sound through the piezoelectric substrate 6 and f is the frequency of the electrical signal between the interdigital electrodes. For the fifth interdigital electrode 5f5, the first, second, third, and fourth interdigital electrodes 1, 2, 3, and 4 all have the same frequency f. Assuming the width and spacing of the fifth interdigital electrode 5 are a5 and b5, then λ5 = 2 × (a5 + b5), resulting in a maximum induced frequency f5 of the fifth interdigital electrode 5 greater than 2 × f.

[0041] Furthermore, the partial discharge antenna 8 is an inductor with a resistance not higher than 100uH; the inductor is a hollow three-dimensional coil or a PCB planar coil.

[0042] This sensor works as follows:

[0043] (1) Receiving end pure receiving signal mode: The PD antenna 8 senses the pulse electrical signal of the power equipment, and forms an LC series resonant network with the PD antenna 8L through the equivalent capacitance C of the fifth interdigital electrode 5. The C in the series resonant network is the fifth interdigital electrode 5. Under the action of the PD signal pulse, the equivalent capacitance of the fifth interdigital electrode 5 couples to the electrical signal, generating a surface acoustic wave on the piezoelectric substrate 6. The surface acoustic wave forms a filtering effect through the third interdigital electrode 3 and the fourth interdigital electrode 4. Since the rated wavelength λ34 of the third interdigital electrode 3 and the fourth interdigital electrode 4 is different from the rated wavelength λ5 of the fifth interdigital electrode 5, dual-frequency filtering of the PD signal can be achieved by optimizing and adjusting the λ3 of the third interdigital electrode 3 and the λ4 of the fourth interdigital electrode 4.

[0044] (2) The transceiver antenna 7 receives the electromagnetic pulse signal, which stimulates the first interdigitated electrode 1 to generate a surface acoustic wave. The surface acoustic wave generates a surface acoustic wave along the second interdigitated electrode 2, the third interdigitated electrode 3, and the fourth interdigitated electrode 4, and the reflected acoustic wave signal is obtained in sequence, and the reflected electrical signals t12, t13, t14, and t15 at different times are induced on the first interdigitated electrode 1. At this time, except that t15 is affected by the pulse discharge signal sensed by the partial discharge antenna 8, t12, t13, and t14 are mainly affected by the ambient temperature and humidity. Therefore, by observing the received pulse signal with a network analyzer and analyzing the S11 value, multiple time domain pulse signals t12, t13, t14, and t15 can be obtained. The signal from t12 to t15 is intercepted from the time domain signal and mixed, and the frequency of the wireless electromagnetic wave signal received by the surface acoustic wave sensor is filtered out. The obtained signal is then converted by amplitude or spectrum to obtain the partial discharge intensity and frequency value.

[0045] (3) The entire sensor is placed in a temperature-controlled box under laboratory conditions to obtain the t12 and t15 time points at different temperatures as reference values.

[0046] Place the PD antenna 8 in a heater in a temperature-controlled box. The heater temperature T2 is higher than the temperature of the temperature-controlled box T1. At least two high-temperature points with a temperature greater than T2 are set near the PD antenna 8 but not in contact with the antenna. During the PD monitoring process of methods (1) and (2) above, the values ​​of t12 and t15 are measured simultaneously. The relationship between |T2-T1| and the absolute value of Δt = |t12-t15| is analyzed to establish a mathematical fitting model.

[0047] In field applications, the field temperature is obtained as T1 based on the t12 value, and the temperature T2 of the partial discharge point is obtained based on the t15 time value.

[0048] The time difference Δt between t12 and t15 is calculated, and T1 and the time difference Δt are substituted into the mathematical fitting model to obtain the maximum temperature value of the device near the detection point of the partial discharge antenna 8. In other embodiments, when multiple reflection times t12, t13, t14, and t15 are used to obtain multiple temperature values, the average of the multiple temperatures is used as the average temperature of the device under test.

[0049] like Figure 2 As shown, the signal sensed in the t15 period is a pulse signal with a high frequency, which appears as a jittery, unstable, and poorly repeatable signal.

[0050] When the corresponding method (2) is adopted, the test end reflects the signal in sequence, and the above-mentioned time domain signal can be obtained. If it is transmitted multiple times, a continuous partial discharge signal can be obtained. On the contrary, if method (1) is adopted, that is, the test end does not transmit the signal but only receives it, then the above graph is highly repetitive in the time domain, except that the intensity and frequency of the repeated partial discharge signal may be different each time, which is consistent with the unstable characteristics of partial discharge. Of course, when the surface acoustic wave signal is triggered by the partial discharge signal, since the resonance frequency of the partial discharge signal and the multiple finger electrodes of the surface acoustic wave may be quite different, for example, the partial discharge signal is 300M-400MHz, and the resonance frequency of the first and second finger electrodes 2 is 200MHz, then the sound wave generated by the finger electrodes excited by the partial discharge signal on the piezoelectric substrate 6 may be weak, resulting in the intensity at position t15 being higher than that at positions t12, t13, and t14. At the same time, Figure 1 In the continuous time domain signal of 1.5 cycles, a relatively obvious partial discharge signal can be observed. The partial discharge signal can be intercepted by time period and amplitude measurement and spectrum analysis can be performed to further analyze the partial discharge characteristics. The time domain signal wave after further processing is as follows Figure 2As shown, the horizontal axis is: t0 is the pulse electrical signal of the first interdigital electrode 1, which serves as the starting point. T12 is the electrical signal converted from the reflected surface acoustic wave signal of the signal reaching the second interdigital electrode 2 and then reaching the first interdigital electrode 1; T13 is the electrical signal converted from the surface acoustic wave signal reflected from the third interdigital electrode and then reaching the first interdigital electrode 1; T14 is the electrical signal converted from the surface acoustic wave signal reflected from the fourth interdigital electrode and then reaching the first interdigital electrode 1; T15 is the electrical signal converted from the surface acoustic wave signal reflected from the fifth interdigital electrode 5 and then reaching the first interdigital electrode 1, and the electrical signal converted from the partial discharge signal sensed by the fifth interdigital electrode 5 and then propagated to the first interdigital electrode 1; the vertical axis is the electrical signal intensity, typically in units of mV, uV, dBuV, or dBmV.

[0051] At the same time, when the temperature at the sensor location is high, the times t12, t13, and t14 will all change. Based on this, the temperature value can be analyzed to explain whether the cause of the partial discharge signal is related to temperature.

[0052] Because temperature measurement can be performed using multiple reflection times, high temperature measurement accuracy can be achieved. Furthermore, the temperature at the PD measurement point and the temperature at the surface acoustic wave center can be resolved. The temperature difference between the two, or the temporal variation of the temperature difference, can be used to infer the temperature change rate and trend of the monitored device. Therefore, multiple reflection times provide supporting data for in-depth exploration of the temperature characteristics of the device under test. The relevant mathematical algorithms are not described here.

[0053] In addition to measuring temperature, the second interdigitated electrode 2 designed in this patent can also be used as a reference point for the propagation of surface acoustic waves, thereby facilitating better interception of partial discharge signals in the time domain signal.

[0054] This patent solves the problem of wireless passive monitoring of partial discharge signals. By using isolated transmission, it solves a series of problems caused by the integration of traditional partial discharge antenna 8 and electronic circuit signal conditioning, such as low reliability and introduction of high voltage.

[0055] The problem of temperature difference caused by different contact point positions during temperature measurement, which produces different temperature change gradient relationships at different positions on the surface acoustic wave substrate, is simultaneously solved. Therefore, the highest temperature value nearby can be further obtained to achieve more accurate fault warning.

[0056] The partial discharge detection method in this application is fundamentally different from the conventional approach of directly adding a pure antenna at the partial discharge detection location:

[0057] 1. Existing pure partial discharge pulses passing through antennas can experience significant differences in reflected power at various frequencies, resulting in low receiver sensitivity. Using this patented method, the partial discharge signal generates an electrical signal to trigger the surface acoustic wave sensor. Furthermore, since the propagation speed of surface acoustic waves is much lower than that of electromagnetic waves, the characteristics of the partial discharge signal are effectively modulated onto the slow-speed surface acoustic wave substrate in the form of acoustic wave energy. This is then converted back through the interdigitated electrodes and transmitted. This delay allows for better visualization of the dynamic characteristics of the partial discharge signal. If interference is present during the partial discharge signal's jitter cycle, the slow speed of the surface acoustic wave means that by the time the surface acoustic wave signal is converted into an electrical signal, the original interference signal has long disappeared. Furthermore, because the reflected signal is ultimately transmitted within a certain bandwidth centered around the resonant frequency of the surface acoustic wave interdigitated electrodes, effective frequency selection is achieved. If wider-band partial discharge detection is required, multiple surface acoustic wave sensors can be deployed to detect different partial discharge spectrum bandwidths. Therefore, this solution offers a higher signal-to-noise ratio and greater resolvability than traditional pure antenna methods.

[0058] 2. This application can also detect partial discharges by means of reflected signals from the receiving end. By triggering the surface acoustic wave operation through non-contact orderly signal transmission, orderly segmented monitoring and interception of partial discharge data can be achieved, avoiding the problems of aliasing and difficulty in decomposing continuous signals.

[0059] In summary, the sensor described in this application can be used safely and reliably to monitor the temperature and partial discharge of high-voltage electrical equipment, such as high-current contactors. This solves the existing problem of partial discharge sensors being difficult to use reliably in harsh environments such as high temperatures and difficult power supply conditions, posing safety risks. The corresponding partial discharge detection method described in this application offers a higher signal-to-noise ratio and greater resolvability than traditional antenna-only methods.

[0060] In the embodiments provided in the present application, it should be understood that the division of units is merely a logical function division, and there may be other division methods in actual implementation, for example, multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored, etc.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment, comprising a piezoelectric substrate, characterized in that: The piezoelectric substrate is provided with a first interdigital electrode, a third interdigital electrode, a fourth interdigital electrode and a fifth interdigital electrode, the first interdigital electrode is connected to a transceiver antenna, the fifth interdigital electrode is connected to a local discharge antenna, the first interdigital electrode and the fifth interdigital electrode are arranged at intervals and in perpendicular directions, the third interdigital electrode and the fourth interdigital electrode are respectively connected to the fifth interdigital electrode and are symmetrically arranged on both sides of the fifth interdigital electrode, the angle between the third interdigital electrode and the fifth interdigital electrode is an acute angle, and the angle between the fourth interdigital electrode and the fifth interdigital electrode is also an acute angle.

2. The surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment according to claim 1, characterized in that: A second interdigital electrode is further provided on the piezoelectric substrate. The second interdigital electrode is provided between the first interdigital electrode and the third or fourth interdigital electrode, and the second interdigital electrode is provided parallel to the first interdigital electrode.

3. The surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment according to claim 1, characterized in that: It also includes a micro short-circuit ring shielding cover, in which the third interdigital electrode, the fourth interdigital electrode and the fifth interdigital electrode are respectively arranged. The micro short-circuit ring shielding cover is provided with a cover opening for the partial discharge antenna to pass through.

4. The surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment according to claim 1, characterized in that: The partial discharge antenna is an inductor with an inductance not higher than 100uH; the inductor is a hollow three-dimensional coil or a PCB planar coil.

5. The surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment according to claim 1, characterized in that: The fifth number of interdigital electrode pairs P 5>3 ×P 34 , P 34 is the number of electrode pairs of the third interdigital electrode or the fourth interdigital electrode.

6. The surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment according to claim 2, characterized in that: The rated wavelength of the fifth interdigital electrode λ5<0.5×λ 34 , where λ 34 is the minimum value of both the rated wavelengths of the third and fourth interdigital electrodes.

7. The surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment according to claim 6, characterized in that: The first interdigital electrode, the second interdigital electrode, the third interdigital electrode and the fourth interdigital electrode all have the same frequency f, and the highest induction frequency f5 of the fifth interdigital electrode is greater than 2×f.

8. A partial discharge monitoring system for power equipment, characterized in that: include: A sensor, wherein the sensor adopts the surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment according to any one of claims 1 to 7, wherein the sensor senses partial discharge based on interdigital electrodes, utilizes the interdigital electrodes and a piezoelectric substrate to complete electroacoustic conversion of an electrical signal to a surface acoustic wave signal, and then transmits an electrical signal containing partial discharge of the high-voltage power equipment based on the surface acoustic wave signal-to-electrical signal conversion; simultaneously, the sensor receives an electromagnetic wave signal emitted by a reader and reflects the electrical signal through electroacoustic conversion and acoustic-to-electric conversion; The reader receives the transmitted electrical signal of the surface acoustic wave sensor of the sensor and processes and outputs the intensity and frequency value of the partial discharge when measuring the partial discharge signal; When measuring temperature without partial discharge signal, the electromagnetic wave signal required for the sensor to work is emitted, and the reflected electric signal of the sensor is received and the output temperature value is converted based on the time difference intercepted on the time domain waveform of the electric signal.

9. A method for monitoring partial discharge of power equipment, characterized in that: The method of using the surface acoustic wave-based partial discharge monitoring sensor for high-voltage power equipment and the reader for monitoring according to claim 2 specifically includes the following steps: A-Partial Discharge Measurement Step A1: The partial discharge antenna of the sensor senses a pulse electrical signal from the power equipment, and the equivalent capacitance of the fifth interdigital electrode couples to the electrical signal, generating a surface acoustic wave on the piezoelectric substrate. The surface acoustic wave is filtered and amplified by the third and fourth interdigital electrodes and then transmitted to the second interdigital electrode. The surface acoustic wave signal is then converted to an electrical signal at the first interdigital electrode, and the electrical signal containing the partial discharge of the high-voltage power equipment is transmitted via the transceiver antenna. Step A2: The reader receives the electrical signal from the sensor, filters out the frequency of the radio electromagnetic wave signal received by the sensor, obtains the signal and then performs amplitude or spectrum conversion to obtain the intensity and frequency value of the partial discharge; B-Temperature Measurement Step B1: the reader transmits a high-frequency electromagnetic wave signal to the sensor; Step B2: After receiving the high-frequency electrical signal, the first interdigital electrode of the sensor completes the electroacoustic conversion of the electrical signal into a surface acoustic wave signal. The surface acoustic wave signal propagates to the second interdigital electrode and is reflected back to the first interdigital electrode, and the reflection time is recorded as t12; the surface acoustic wave signal propagates to the third interdigital electrode and is reflected back to the first interdigital electrode, and the reflection time is recorded as t13; the surface acoustic wave signal propagates to the fourth interdigital electrode and is reflected back to the first interdigital electrode, and the reflection time is recorded as t14; the surface acoustic wave signal propagates to the fifth interdigital electrode and is reflected back to the first interdigital electrode, and the reflection time is recorded as t15; Step B3: Calculate the temperature value of the monitored electrical equipment through at least one of the reflection times t12, t13, t14, and t15; calculate the temperature value of the monitored electrical equipment based on the reflection times t12, t13, t14, and t15, and use a table lookup of a standard value sequence corresponding to the reflection time of data obtained in a standard temperature experimental environment to obtain a corresponding temperature value; when multiple temperature values ​​are obtained using multiple reflection times t12, t13, t14, and t15, use the average value of the multiple temperatures as the average temperature of the device under test, or use t15 as the temperature of the partial discharge monitoring point and t12 as the temperature adjacent to the monitoring point.

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