A method for nondestructive evaluation of dielectric properties of insulating oil and related device

Abstract

The application discloses a kind of insulating oil dielectric performance nondestructive evaluation method and related device, it is related to electric power equipment insulation detection and evaluation field, the method includes obtaining the insulating oil standard sample of different dielectric loss factor and dielectric loss factor value;Using transmission terahertz time-domain spectroscopy system, the insulating oil standard sample is tested, and reference signal and sample signal through standard sample are obtained;The reference signal and sample signal through standard sample are preprocessed, and based on terahertz time-domain spectroscopy conversion formula, the terahertz absorption coefficient frequency spectrum of each insulating oil standard sample is obtained;For each insulating oil standard sample, the absorption coefficient integral value of insulating oil standard sample terahertz absorption coefficient frequency spectrum in full band is extracted, and the quantitative fitting relationship of absorption coefficient integral value and dielectric loss factor value is established;According to the absorption coefficient integral value of the insulating oil sample to be measured, based on quantitative fitting relationship, the dielectric loss factor value of the insulating oil sample to be measured is calculated.The application can realize insulating oil dielectric performance nondestructive evaluation.

Description

Technical Field

[0001] This application relates to the field of insulation testing and evaluation of power equipment, and in particular to a non-destructive evaluation method and related apparatus for the dielectric properties of insulating oil. Background Technology

[0002] Oil-immersed power equipment operates under complex conditions involving electrical, thermal, and mechanical stresses, inevitably leading to physicochemical degradation of the internal insulating oil. This results in a significant increase in system failure risk over time. As a key intrinsic indicator for assessing insulation health, the dielectric properties of the insulating oil directly reflect the operational risk of the equipment. According to DL / T 596-2021, oil-filled equipment must undergo periodic (1-3 years) testing and evaluation of its dielectric loss factor (tanδ). Physically, the active power loss caused by AC voltage is dielectric loss, and its factor tanδ is determined solely by the material's inherent properties, independent of geometric dimensions, and primarily affected by temperature, frequency, and voltage fluctuations. However, existing dielectric loss testing technologies still face numerous bottlenecks in practical applications. While the traditional bridge method is classic, it is highly susceptible to environmental electromagnetic interference, and its operation is cumbersome and lacks automation. Furthermore, laboratory evaluation is not only time-consuming, but samples are also prone to performance changes during storage and transportation, weakening the reliability of the test results. Summary of the Invention

[0003] The purpose of this application is to provide a non-destructive evaluation method and related apparatus for the dielectric properties of insulating oil, which uses a terahertz time-domain spectroscopy system to test the insulating oil and achieves non-destructive evaluation of the dielectric properties of the insulating oil based on the integral value of the terahertz absorption spectrum.

[0004] To achieve the above objectives, this application provides the following solution: Firstly, this application provides a non-destructive evaluation method for the dielectric properties of insulating oil, including: Obtain insulating oil standard samples with different dielectric loss factors and the dielectric loss factor values ​​of each insulating oil standard sample; The insulating oil standard sample was tested using a transmission terahertz time-domain spectroscopy system to obtain the reference signal and the sample signal transmitted through the standard sample; The reference signal and the sample signal transmitted through the standard sample are preprocessed, and the terahertz absorption coefficient spectrum of each insulating oil standard sample is obtained based on the terahertz time-domain spectral conversion formula. For each insulating oil standard sample, the integral value of the terahertz absorption coefficient spectrum of the insulating oil standard sample in the whole frequency band is extracted, and a quantitative fitting relationship between the integral value of the absorption coefficient and the dielectric loss factor is established. Based on the integral value of the absorption coefficient of the insulating oil sample to be tested, and based on the quantitative fitting relationship, the dielectric loss factor of the insulating oil sample to be tested is calculated.

[0005] Optionally, the formula for calculating the integral value of the absorption coefficient in step S3 is: .

[0006] In the formula, α is the absorption coefficient. For frequency.

[0007] Optionally, the preprocessing specifically includes: The terahertz time-domain spectrum is obtained by comparing the sample signal with the reference signal; The terahertz time-domain spectrum is processed to extract the main peak, and the portion outside the main peak is set to zero; Noise interference is removed by mean filtering.

[0008] Optionally, the terahertz time-domain spectral conversion formula is: ; ; ; ; In the formula, n For refractive index, k Extinction coefficient, α The absorption coefficient is... d For sample thickness, c At the speed of light, E ( t () represents a terahertz time-domain signal. exp iwt This represents the complex exponential factor in the Fourier transform, used to convert a time-domain signal into a frequency-domain signal. i The imaginary unit, w E is the angular frequency; A( is the frequency domain complex electric field signal after Fourier transform;) () represents the frequency domain amplitude spectrum; The frequency domain phase spectrum; and These are the phase spectra of the sample signal and the reference signal, respectively; n( ) represents the sample at angular frequency The refractive index below; and These are the amplitude spectra of the sample signal and the reference signal, respectively. The extinction coefficient is used to describe the sample's ability to attenuate terahertz waves. is the absorption coefficient, used to characterize the strength of a sample's absorption of terahertz waves.

[0009] Optionally, the dielectric loss factor of the insulating oil standard sample ranges from 0.005 to 0.2; the insulating oil standard sample is prepared by gradient accelerated thermal aging or taken from field transformer insulating oils of different operating years from the same manufacturer.

[0010] Optionally, the quantitative fitting relationship is determined based on a fitting curve established by the integral value of the absorption coefficient of the insulating oil and the value of the dielectric loss factor.

[0011] Secondly, this application provides a non-destructive evaluation system for the dielectric properties of insulating oil, used to implement the aforementioned non-destructive evaluation method for the dielectric properties of insulating oil, including: The data acquisition module is used to acquire insulating oil standard samples with different dielectric loss factors and the dielectric loss factor values ​​of each insulating oil standard sample. The testing module is used to test insulating oil standards using a transmission terahertz time-domain spectroscopy system to obtain a reference signal and a sample signal transmitted through the standard. The data processing and conversion module is used to preprocess the reference signal and the sample signal transmitted through the standard sample, and obtain the terahertz absorption coefficient spectrum of each insulating oil standard sample based on the terahertz time-domain spectral conversion formula. The fitting module is used to extract the integral value of the terahertz absorption coefficient spectrum of each insulating oil standard sample across the entire frequency band, and to establish a quantitative fitting relationship between the integral value of the absorption coefficient and the dielectric loss factor. The evaluation module is used to calculate the dielectric loss factor of the insulating oil sample under test based on the integral value of the absorption coefficient of the sample and the quantitative fitting relationship.

[0012] Thirdly, this application provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the non-destructive evaluation method for the dielectric properties of insulating oil as described in any one of the above.

[0013] Fourthly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the non-destructive evaluation method for the dielectric properties of insulating oil as described above.

[0014] Fifthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the non-destructive evaluation method for the dielectric properties of insulating oil as described above.

[0015] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a non-destructive evaluation method and related apparatus for the dielectric properties of insulating oil. By establishing a quantitative fitting relationship between the integral value of the absorption coefficient and the value of the dielectric loss factor, it solves the problem that terahertz spectral parameters cannot directly correspond to the dielectric performance indicators of insulating oil, realizes accurate and rapid evaluation of the dielectric properties of insulating oil, and the whole process does not require destructive treatment of the sample, avoids performance changes during sample transportation and storage, and improves the authenticity and reliability of the evaluation results. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is an application environment diagram of a non-destructive evaluation method for the dielectric properties of insulating oil according to an embodiment of this application; Figure 2 A flowchart illustrating a non-destructive evaluation method for the dielectric properties of insulating oil provided in an embodiment of this application; Figure 3 A flowchart for non-destructive evaluation of the dielectric properties of insulating oil provided in an embodiment of this application; Figure 4 A system block diagram of a transmission terahertz time-domain spectroscopy testing platform provided in an embodiment of this application; Figure 5 A time-domain spectrum provided in an embodiment of this application; Figure 6 An absorption spectrum provided for one embodiment of this application; Figure 7 A schematic diagram of the fitting curve provided in one embodiment of this application; Figure 8 This is a schematic diagram of the functional modules of a non-destructive evaluation device for the dielectric properties of insulating oil, provided in another embodiment of this application.

[0018] Figure 9 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Terahertz time-domain spectroscopy (THz-TDS) technology has shown great application potential in the field of aging detection of oil-paper insulation. The energy level of terahertz waves closely matches the vibrational energy level of polar molecules, resulting in a spectrum rich in material "fingerprint" information. Key aging products of oil-paper insulation degradation, such as acids, furfural, and moisture, are all polar molecules and are the root cause of increased dielectric loss. Compared to infrared or Raman spectroscopy, terahertz waves have excellent penetration into non-polar substances such as insulating oil, effectively avoiding the masking effect of oil matrix signals on aging characteristic information, thereby obtaining detection data with a high signal-to-noise ratio.

[0021] The purpose of this application is to provide a non-destructive evaluation method and related apparatus for the dielectric properties of insulating oil, which uses a terahertz time-domain spectroscopy system to test the insulating oil and achieves non-destructive evaluation of the dielectric properties of the insulating oil based on the integral value of the terahertz absorption spectrum.

[0022] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] The non-destructive evaluation method for the dielectric properties of insulating oil provided in this application embodiment can be applied to, for example... Figure 1In the application environment shown, terminal 102 communicates with server 104 via a network. A data storage system can store the data that server 104 needs to process. The data storage system can be set up independently, integrated into server 104, or placed in the cloud or on another server. Terminal 102 can send insulating oil standard samples with different dielectric loss factors and their dielectric loss factor values ​​to server 104. After receiving the insulating oil standard samples with different dielectric loss factors and their dielectric loss factor values, server 104 uses a transmission terahertz time-domain spectroscopy system to test the insulating oil standard samples, obtaining a reference signal and a sample signal transmitted through the standard samples. The reference signal and the sample signal transmitted through the standard samples are preprocessed, and the terahertz absorption coefficient spectrum of each insulating oil standard sample is obtained based on the terahertz time-domain spectral conversion formula. For each insulating oil standard sample, the integral value of the absorption coefficient spectrum of the insulating oil standard sample in the whole frequency band is extracted, and a quantitative fitting relationship between the integral value of the absorption coefficient and the dielectric loss factor value is established. Based on the integral value of the absorption coefficient of the insulating oil sample to be tested and the quantitative fitting relationship, the dielectric loss factor value of the insulating oil sample to be tested is calculated. Server 104 can feed back the dielectric loss factor of the obtained insulating oil sample to terminal 102. Furthermore, in some embodiments, the non-destructive evaluation method for the dielectric properties of insulating oil can also be implemented independently by server 104 or terminal 102. For example, terminal 102 can directly perform non-destructive evaluation of the dielectric properties of insulating oil standard samples with different dielectric loss factors and their dielectric loss factor values. Alternatively, server 104 can obtain insulating oil standard samples with different dielectric loss factors and their dielectric loss factor values ​​from the data storage system, and perform non-destructive evaluation of the dielectric properties of insulating oil based on these values.

[0024] The terminal 102 can be, but is not limited to, various desktop computers, laptops, smartphones, tablets, IoT devices, and portable wearable devices. IoT devices can include smart speakers, smart TVs, smart air conditioners, and smart in-vehicle devices. Portable wearable devices can include smartwatches, smart bracelets, and head-mounted devices. The server 104 can be implemented using a standalone server or a server cluster composed of multiple servers, or it can be a cloud server.

[0025] In one exemplary embodiment, such as Figure 2 As shown, a non-destructive evaluation method for the dielectric properties of insulating oil is provided. This method is executed by computer equipment, specifically by a terminal or server alone, or by both a terminal and a server. In this embodiment, the method is applied to... Figure 1 Taking server 104 as an example, the explanation includes the following steps 201 to 205. Wherein: Step 201: Obtain insulating oil standard samples with different dielectric loss factors and the dielectric loss factor values ​​of each insulating oil standard sample; Step 202: Use a transmission terahertz time-domain spectroscopy system to test the insulating oil standard sample and obtain the reference signal and the sample signal transmitted through the standard sample. Step 203: Preprocess the reference signal and the sample signal transmitted through the standard sample, and obtain the terahertz absorption coefficient spectrum of each insulating oil standard sample based on the terahertz time-domain spectral conversion formula. Step 204: For each insulating oil standard sample, extract the integral value of the terahertz absorption coefficient spectrum of the insulating oil standard sample in the whole frequency band, and establish a quantitative fitting relationship between the integral value of the absorption coefficient and the dielectric loss factor. Step 205: Based on the integral value of the absorption coefficient of the insulating oil sample to be tested, and based on the quantitative fitting relationship, calculate the dielectric loss factor of the insulating oil sample to be tested.

[0026] In one exemplary embodiment, when performing steps 201-205, the specific steps may be as follows: like Figure 3 As shown, the process for non-destructive evaluation of the dielectric properties of insulating oil using terahertz technology is as follows: 1) Prepare deteriorated insulating oil samples, i.e., prepare insulating oil standard samples with different dielectric loss factors: Because different types of insulating oils (mineral oil, vegetable oil, and synthetic esters, etc.) exhibit different dielectric loss characteristics after degradation, standard samples should be prepared separately for each type of insulating oil to accurately assess the dielectric loss of the sample under test. Insulating oils of different qualities can be prepared using gradient accelerated thermal aging, or insulating oils from field transformers of different operating years from the same manufacturer can be used as standard samples. The dielectric loss range of the standard samples should cover at least 0.005~0.2.

[0027] 2) Measure the dielectric loss factor of the insulating oil standard sample. The dielectric loss factor of the insulating oil standard sample was measured in accordance with GB / T5654-2007.

[0028] Specifically, using an insulating oil dielectric loss and volume resistivity tester, the dielectric loss factor of each insulating oil standard sample was measured under standard temperature conditions. The average value of multiple measurements was taken as the final dielectric loss factor value of the standard sample, thus completing the calibration of the basic parameters of the standard sample and providing accurate label data for establishing a quantitative fitting relationship in the future.

[0029] 3) Construct a transmission terahertz time-domain spectroscopy system: Specifically, the main components of the transmission-type terahertz time-domain spectroscopy testing system (platform) include: a femtosecond laser, a beam splitter, a time delay line, a reflector, a THz wave transmitter, a THz wave detector, a parabolic mirror, a lock-in amplifier, and a PC control terminal. Its system connection diagram is shown below. Figure 4 As shown. The main functions of each part are as follows: Femtosecond lasers are used to generate ultrashort pulses of femtosecond laser light (pulse widths typically between tens and hundreds of femtoseconds); beam splitters are used to split the femtosecond laser into two beams, one for exciting terahertz waves (pump light) and the other for detection (probe light); the pump light is transmitted to a photoconductive antenna, passes through a terahertz emitter, and is used to excite terahertz waves; the probe light is transmitted to a time delay control system, passes through a reflector, and then reaches a terahertz detector; a time delay line is used to adjust the optical path of the probe light, thereby controlling the relative time delay between the probe light and the terahertz wave in the detector, achieving time-resolved measurements; parabolic mirrors are used to collimate and focus the terahertz waves, enabling them to concentrate and effectively illuminate the sample or be transmitted to the detector; and a THz wave generator is used to emit terahertz waves. THz wave detectors are used to detect terahertz waves after passing through a sample. They convert terahertz signals into easily measurable electrical signals through electro-optic or photoconductive effects. Computers are used for data acquisition and processing, recording the time-domain signals of terahertz pulses, obtaining frequency-domain information through Fourier transform, and analyzing the terahertz spectrum of insulating oil standards.

[0030] In this process, a femtosecond laser generates two mutually perpendicular femtosecond pulsed laser beams using a beam splitter. These beams are then split into a pump beam and a probe beam. The terahertz pulse generated by the pump beam illuminating the terahertz generator is reflected by a specular surface and penetrates the insulating oil sample under test. The probe beam, after passing through a time delay line, along with the terahertz pulse that has penetrated the sample and undergone specular reflection, is then directed onto a terahertz detector. The two detected electrical signals are converted from digital to analog and transmitted digitized to a computer. The computer then analyzes and processes the data to obtain information about the internal composition of the test sample.

[0031] 4) Measure the terahertz spectrum of the insulating oil standard sample and extract its terahertz characteristics: Take 3.3 ml of the oil sample to be tested into the sample cell. The sample cell is a polystyrene cuvette, which has low absorption and a constant refractive index in the terahertz band, resulting in minimal interference with the measurement. Place the sample cell in the center of the optical path of the transmission portable terahertz spectrometer probe. Start the terahertz spectrometer host, start the laser software, and set the two-phase currents to 999 mA and 990 mA, respectively. Start the terahertz data acquisition software, set the acquisition range to -5 to 3, and control the laboratory temperature to approximately 25 degrees Celsius and the humidity to below 6%. Place the blank polystyrene cuvette in the center of the probe optical path, allowing the terahertz wave to penetrate the sample cell parallel to the ground. Set the averaging to 512 times, measure the reference signal, and set it as the reference signal. Remove the blank cuvette, and then place the sample cell containing the oil sample in the same position, again setting it to 512 times. Wait for the measurement to complete, and save the sample signal and reference signal. Compare the sample signal and reference signal to obtain the terahertz time-domain spectrum. The main peak of the obtained terahertz time-domain spectrum is taken, and the parts other than the main peak are set to zero. Then, the noise interference is removed by mean filtering. The preprocessed terahertz time-domain spectrum is converted into the terahertz absorption coefficient spectrum according to formulas (1) to (4).

[0032] (1).

[0033] (2).

[0034] (3).

[0035] (4).

[0036] In the formula, n For refractive index, k Extinction coefficient, α The absorption coefficient is... d For sample thickness, c At the speed of light, E ( t () represents a terahertz time-domain signal. exp iwt This represents the complex exponential factor in the Fourier transform, used to convert a time-domain signal into a frequency-domain signal. i The imaginary unit, w E is the angular frequency; A( is the frequency domain complex electric field signal after Fourier transform;) () represents the frequency domain amplitude spectrum; The frequency domain phase spectrum; and These are the phase spectra of the sample signal and the reference signal, respectively; n( ) represents the sample at angular frequency The refractive index below; and These are the amplitude spectra of the sample signal and the reference signal, respectively. The extinction coefficient is used to describe the sample's ability to attenuate terahertz waves. is the absorption coefficient, used to characterize the strength of a sample's absorption of terahertz waves.

[0037] Terahertz time-domain spectra of insulating oil standards with different dielectric properties, such as Figure 5 As shown, the terahertz absorption spectra of insulating oil standards with different dielectric properties are as follows: Figure 6 As shown.

[0038] Depend on Figure 6 It can be seen that the absorption coefficient increases with the increase of dielectric loss in the insulating oil standard sample. The integral value Sa of the absorption coefficient across the entire frequency band is extracted and calculated using the following formula: (5).

[0039] 5) Establish a quantitative fitting relationship between the integral value of the absorption coefficient and the value of the dielectric loss factor: A fitting curve is established based on the integral value of the standard sample absorption coefficient and the dielectric loss factor, as shown below. Figure 7 As shown, the formula for the fitted curve is: (6).

[0040] 6) Non-destructive evaluation of the dielectric properties of insulating oil: The accuracy of the evaluation method in this application was verified by selecting new and aged oil samples as insulating oil samples. Terahertz tests were performed on the two oil samples to obtain time-domain spectra, absorption spectra were calculated, and the integral value of the absorption spectrum was extracted according to formula (5). The dielectric loss of the oil samples was calculated according to formula (6), and the results are shown in Table 1.

[0041] Table 1 Evaluation Results

[0042] In one exemplary embodiment, such as Figure 8 As shown, a non-destructive evaluation system for the dielectric properties of insulating oil is provided, used to implement the aforementioned non-destructive evaluation method for the dielectric properties of insulating oil, characterized in that it includes: The data acquisition module 801 is used to acquire insulating oil standard samples with different dielectric loss factors and the dielectric loss factor values ​​of each insulating oil standard sample. Test module 802 is used to test insulating oil standard samples using a transmission terahertz time-domain spectroscopy system to obtain reference signals and sample signals transmitted through the standard samples; The data processing and conversion module 803 is used to preprocess the reference signal and the sample signal transmitted through the standard sample, and obtain the terahertz absorption coefficient spectrum of each insulating oil standard sample based on the terahertz time-domain spectral conversion formula. The fitting module 804 is used to extract the integral value of the terahertz absorption coefficient spectrum of each insulating oil standard sample in the whole frequency band, and to establish a quantitative fitting relationship between the integral value of the absorption coefficient and the dielectric loss factor. Evaluation module 805 is used to calculate the dielectric loss factor of the insulating oil sample under test based on the integral value of the absorption coefficient of the insulating oil sample under test and the quantitative fitting relationship.

[0043] In one exemplary embodiment, a computer device is provided, which may be a server or a terminal, and its internal structure diagram may be as follows. Figure 9 As shown, the computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs in the non-volatile storage media. The database stores the dielectric loss factor values ​​of the insulating oil samples to be tested. The I / O interfaces are used for information exchange between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a non-destructive evaluation method for the dielectric properties of insulating oil.

[0044] Figure 9 The structures shown are merely block diagrams of some structures related to the present application and do not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than shown in the figures, or combine certain components, or have different component arrangements. In an exemplary embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0045] In one exemplary embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0046] In one exemplary embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0047] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of related data must comply with relevant regulations and be authorized by the owner of the corresponding device.

[0048] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0049] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A non-destructive evaluation method for the dielectric properties of insulating oil, characterized in that, include: Obtain insulating oil standard samples with different dielectric loss factors and the dielectric loss factor values ​​of each insulating oil standard sample; The insulating oil standard sample was tested using a transmission terahertz time-domain spectroscopy system to obtain the reference signal and the sample signal transmitted through the standard sample; The reference signal and the sample signal transmitted through the standard sample are preprocessed, and the terahertz absorption coefficient spectrum of each insulating oil standard sample is obtained based on the terahertz time-domain spectral conversion formula. For each insulating oil standard sample, the integral value of the terahertz absorption coefficient spectrum of the insulating oil standard sample in the whole frequency band is extracted, and a quantitative fitting relationship between the integral value of the absorption coefficient and the dielectric loss factor is established. Based on the integral value of the absorption coefficient of the insulating oil sample to be tested, and based on the quantitative fitting relationship, the dielectric loss factor of the insulating oil sample to be tested is calculated.

2. The non-destructive evaluation method for the dielectric properties of insulating oil according to claim 1, characterized in that, The formula for calculating the integral value of the absorption coefficient in step S3 is as follows: 。 In the formula, α is the absorption coefficient. For frequency.

3. The non-destructive evaluation method for the dielectric properties of insulating oil according to claim 1, characterized in that, The preprocessing specifically includes: The terahertz time-domain spectrum is obtained by comparing the sample signal with the reference signal; The terahertz time-domain spectrum is processed to extract the main peak, and the portion outside the main peak is set to zero; Noise interference is removed by mean filtering.

4. The non-destructive evaluation method for the dielectric properties of insulating oil according to claim 1, characterized in that, The terahertz time-domain spectral conversion formula is as follows: ； ； ； ； In the formula, n For refractive index, k Extinction coefficient, α The absorption coefficient is... d For sample thickness, c At the speed of light, E ( t () represents a terahertz time-domain signal. exp iwt This represents the complex exponential factor in the Fourier transform, used to convert a time-domain signal into a frequency-domain signal. i The imaginary unit, w E is the angular frequency; A( is the frequency domain complex electric field signal after Fourier transform;) () represents the frequency domain amplitude spectrum; The frequency domain phase spectrum; and These are the phase spectra of the sample signal and the reference signal, respectively; n( ) represents the sample at angular frequency The refractive index below; and These are the amplitude spectra of the sample signal and the reference signal, respectively. The extinction coefficient is used to describe the sample's ability to attenuate terahertz waves. is the absorption coefficient, used to characterize the strength of a sample's absorption of terahertz waves.

5. The non-destructive evaluation method for the dielectric properties of insulating oil according to claim 1, characterized in that, The dielectric loss factor of the insulating oil standard sample ranges from 0.005 to 0.2; the insulating oil standard sample is prepared by gradient accelerated thermal aging or taken from insulating oil of field transformers with different operating years from the same manufacturer.

6. The non-destructive evaluation method for the dielectric properties of insulating oil according to claim 1, characterized in that, The quantitative fitting relationship is determined based on the fitting curve established by the integral value of the absorption coefficient of the insulating oil and the value of the dielectric loss factor.

7. A non-destructive evaluation system for the dielectric properties of insulating oil, used to implement the non-destructive evaluation method for the dielectric properties of insulating oil as described in claim 1, characterized in that, include: The data acquisition module is used to acquire insulating oil standard samples with different dielectric loss factors and the dielectric loss factor values ​​of each insulating oil standard sample. The testing module is used to test insulating oil standards using a transmission terahertz time-domain spectroscopy system to obtain a reference signal and a sample signal transmitted through the standard. The data processing and conversion module is used to preprocess the reference signal and the sample signal transmitted through the standard sample, and obtain the terahertz absorption coefficient spectrum of each insulating oil standard sample based on the terahertz time-domain spectral conversion formula. The fitting module is used to extract the integral value of the terahertz absorption coefficient spectrum of each insulating oil standard sample across the entire frequency band, and to establish a quantitative fitting relationship between the integral value of the absorption coefficient and the dielectric loss factor. The evaluation module is used to calculate the dielectric loss factor of the insulating oil sample under test based on the integral value of the absorption coefficient of the sample and the quantitative fitting relationship.

8. A computer device, comprising: A memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that the processor executes the computer program to implement a non-destructive evaluation method for the dielectric properties of insulating oil according to any one of claims 1-6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements a non-destructive evaluation method for the dielectric properties of insulating oil according to any one of claims 1-6.

10. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements a non-destructive evaluation method for the dielectric properties of insulating oil according to any one of claims 1-6.

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