Insulating oil fault characteristic gas in-situ nondestructive detection method and system

Abstract

The present invention discloses an in-situ nondestructive detection method and system for characteristic gas of insulating oil fault, which relates to the field of gas detection technology, including building a transmission terahertz time-domain spectroscopy test platform to obtain the time domain signal of a set of insulating oil samples; performing Fourier transform on the time domain signal to obtain the refractive index of each insulating oil sample; determining the absorption coefficient according to the refractive index, and determining the terahertz absorption spectrum according to the absorption coefficient; and detecting characteristic gas in the insulating oil. The in-situ nondestructive detection method for characteristic gas of insulating oil fault provided by the present invention accurately calculates the refractive index of the sample and identifies the difference in refractive index caused by different gas content. In this way, even a trace change in polar gas can be manifested in the refractive index, achieving high-sensitivity detection. By detecting the frequency amplitude of the characteristic peak, not only can the presence of CO gas be confirmed, but also the quantitative analysis of the gas content can be achieved through the positive correlation between the amplitude and the concentration.

Description

Technical Field

[0001] The present invention relates to the technical field of gas detection, and in particular to an in-situ nondestructive detection method and system for insulating oil fault characteristic gas. Background Art

[0002] Transformers are core equipment of power systems. The performance and health level of their internal oil-paper insulation systems are directly related to the safety and stability of the power grid. When an overheating fault occurs in the oil-paper insulation system, fault characteristic gases such as carbon monoxide (CO) will be generated. The generated CO will dissolve in the insulating oil and eventually form a dissolution equilibrium between the gas phase and the liquid phase. By detecting the CO concentration in the insulating oil, the state of the oil-paper insulation system can be effectively judged. At present, the widely used method for detecting the concentration of dissolved CO in insulating oil is mainly gas chromatography. This method requires sampling the insulating oil, degassing it by shaking, and injecting the degassed gas into a gas chromatograph for analysis to obtain the CO gas concentration. This method has cumbersome steps, lossy testing, and expensive equipment. At the same time, researchers have also proposed a variety of detection methods using spectral technology, such as infrared spectroscopy and Raman spectroscopy detection technology, but because the insulating oil itself also absorbs the Raman signal, the above-mentioned spectral technology still requires the insulating oil to be degassed.

[0003] Therefore, there is an urgent need to provide an in-situ, rapid, and non-destructive detection method for CO gas dissolved in insulating oil, which can realize a rapid detection method for the concentration of CO gas dissolved in insulating oil without degassing. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is: the existing gas chromatography detection method has the problems of complex operation, low detection efficiency, expensive equipment, and how to achieve rapid and non-destructive detection of dissolved gas concentration in insulating oil. "

[0006] To solve the above technical problems, the present invention provides the following technical solutions: an in-situ nondestructive detection method for characteristic gas of insulating oil fault, comprising building a transmission terahertz time-domain spectroscopy test platform to obtain the time domain signal of a set of insulating oil samples; performing Fourier transform on the time domain signal to obtain the refractive index of each insulating oil sample; determining the absorption coefficient according to the refractive index, and determining the terahertz absorption spectrum according to the absorption coefficient; and detecting the characteristic gas in the insulating oil.

[0007] As a preferred solution of the in-situ nondestructive detection method of insulating oil fault characteristic gas described in the present invention, the transmission terahertz time-domain spectroscopy test platform includes a femtosecond laser, a beam splitter, a time delay line, a reflector, a terahertz transmitter, a terahertz detector, a first parabolic mirror, a second parabolic mirror, a phase-locked amplifier and a PC control terminal.

[0008] As a preferred solution of the in-situ nondestructive detection method of insulating oil fault characteristic gas of the present invention, wherein: the construction of the transmission terahertz time-domain spectroscopy test platform includes a femtosecond laser emitted by a femtosecond laser, and obtaining mutually perpendicular pump light and detection light through the femtosecond laser;

[0009] The pump light is irradiated onto the insulating oil sample via the terahertz emitter and the first parabolic mirror, and then transmitted to the terahertz detector via the first parabolic mirror;

[0010] The detection light is transmitted to the terahertz detector via the time delay line and the reflector;

[0011] The terahertz detector converts the terahertz signal into an electrical signal through the electro-optic effect or the photoconductive effect;

[0012] The lock-in amplifier is used to amplify the electrical signal and transmit it to the PC control terminal;

[0013] The PC control terminal is used to determine the time domain signal of the terahertz pulse according to the amplified electrical signal.

[0014] As a preferred solution of the insulating oil fault characteristic gas in-situ nondestructive detection method of the present invention, wherein: the obtaining of the time domain signal of the insulating oil sample set includes preparing the insulating oil sample set before obtaining the time domain signal of the insulating oil sample set.

[0015] As a preferred solution of the in-situ nondestructive detection method of insulating oil fault characteristic gas according to the present invention, the preparation of the insulating oil sample set includes vacuum drying the insulating oil in the transformer;

[0016] Place the dried insulating oil in a glass container;

[0017] A set volume of pure characteristic gas is injected into the container, and magnetic stirring is performed for a set time, so that the characteristic gas reaches a dissolution equilibrium in the insulating oil;

[0018] The prepared insulating oil sample containing the characteristic gas is diluted by a mother liquor dilution method, and the insulating oil sample containing the characteristic gas is tested by a gas chromatograph to obtain insulating oil samples containing the characteristic gas at different concentrations.

[0019] As a preferred solution of the in-situ nondestructive detection method of insulating oil fault characteristic gas according to the present invention, wherein: the determination of the absorption coefficient according to the refractive index and the determination of the terahertz absorption spectrum according to the absorption coefficient include: Determine the absorption coefficient at frequency ω, where c is the speed of light in a vacuum and κ(ω) is the extinction coefficient at frequency ω. The extinction coefficient κ(ω) is:

[0020]

[0021] Where n(ω) is the refractive index at frequency ω, d is the thickness of the insulating oil sample, φ s (ω) is the frequency domain phase information of the frequency domain signal of the sample, φ r (ω)] is the frequency domain phase information of the reference frequency domain signal, A s (ω) is the frequency domain amplitude information of the frequency domain signal of the sample, A r (ω is the frequency domain amplitude information of the reference frequency domain signal.

[0022] As a preferred embodiment of the in-situ nondestructive detection method for characteristic gas of insulating oil fault described in the present invention, the detection of characteristic gas in insulating oil includes obtaining the corresponding terahertz absorption spectrum of the insulating oil to be tested, and realizing the detection of characteristic gas in insulating oil based on the comparison result of the absorption peak of the terahertz absorption spectrum and the characteristic peak frequency amplitude.

[0023] Another object of the present invention is to provide an in-situ nondestructive detection system for insulating oil fault characteristic gas, which can penetrate non-polar molecules (such as the main component of insulating oil) through terahertz waves, and absorb specific frequencies on polar molecules. This feature enables the presence of CO in insulating oil to be detected through its specific absorption peak, solving the problem that the existing gas chromatography detection method cannot detect quickly.

[0024] As a preferred solution of the insulating oil fault characteristic gas in-situ nondestructive detection system of the present invention, it includes: a test platform building module, a time domain signal acquisition module, a refractive index determination module, a terahertz absorption spectrum determination module, a characteristic peak frequency amplitude determination module, and a characteristic gas detection module;

[0025] The test platform building module is used to build a transmission-type terahertz time-domain spectroscopy test platform, and the transmission-type terahertz time-domain spectroscopy test platform is used to perform terahertz testing;

[0026] The time domain signal acquisition module is used to respectively acquire time domain signals of an insulating oil sample set according to a transmission terahertz time domain spectroscopy test platform, wherein the insulating oil sample set includes insulating oil samples containing characteristic gas and insulating oil samples not containing characteristic gas;

[0027] The refractive index determination module is used to perform Fourier transform on the time domain signals of the insulating oil sample set respectively to obtain the refractive index of each insulating oil sample;

[0028] The terahertz absorption spectrum determination module is used to determine the corresponding absorption coefficient according to the refractive index of each insulating oil sample, and determine the terahertz absorption spectrum of each insulating oil sample according to the absorption coefficient;

[0029] The characteristic peak frequency amplitude determination module is used to determine the characteristic peak frequency amplitude according to the terahertz absorption spectra of the insulating oil sample containing the characteristic gas and the insulating oil sample not containing the characteristic gas;

[0030] The characteristic gas detection module is used to obtain the terahertz absorption spectrum corresponding to the insulating oil to be tested, and realize the characteristic gas detection in the insulating oil according to the comparison result of the absorption peak of the terahertz absorption spectrum and the characteristic peak frequency amplitude.

[0031] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement a step of an in-situ nondestructive detection method of insulating oil fault characteristic gas.

[0032] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of an in-situ nondestructive detection method for insulating oil fault characteristic gas.

[0033] Beneficial effects of the present invention: The in-situ nondestructive detection method for characteristic gas of insulating oil fault provided by the present invention accurately calculates the refractive index of the sample and identifies the difference in refractive index caused by different gas content. In this way, even a trace change in polar gas can be manifested in the refractive index, achieving high-sensitivity detection. By detecting the frequency amplitude of the characteristic peak, not only can the presence of CO gas be confirmed, but also the quantitative analysis of the gas content can be achieved through the positive correlation between amplitude and concentration. The present invention achieves better results in terms of accuracy and nondestructive detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0035] Figure 1 An overall flow chart of an in-situ nondestructive detection method for insulating oil fault characteristic gas provided in the first embodiment of the present invention.

[0036] Figure 2 A schematic structural diagram of a transmission terahertz time-domain spectroscopy testing platform for an in-situ nondestructive testing method for insulating oil fault characteristic gas provided in the first embodiment of the present invention.

[0037] Figure 3 A schematic diagram of the time domain spectrum of a terahertz pulse passing through blank oil in an in-situ nondestructive detection method for insulating oil fault characteristic gas provided by the first embodiment of the present invention.

[0038] Figure 4 A schematic diagram of the absorption spectra of insulating oils containing CO gas at different concentrations according to an in-situ nondestructive detection method for insulating oil fault characteristic gas provided in the first embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0040] Example 1, reference Figure 1-Figure 4 , which is an embodiment of the present invention, provides an in-situ nondestructive detection method for insulating oil fault characteristic gas, comprising:

[0041] S1: Build a transmission terahertz time-domain spectroscopy test platform to obtain the time domain signal of the insulating oil sample set.

[0042] Furthermore, the transmission terahertz time-domain spectroscopy test platform includes a femtosecond laser, a beam splitter, a time delay line, a reflector, a terahertz transmitter, a terahertz detector, a first parabolic mirror, a second parabolic mirror, a phase-locked amplifier, and a PC control terminal.

[0043] The construction of a transmission terahertz time-domain spectroscopy test platform includes the femtosecond laser emitted by the femtosecond laser to obtain mutually perpendicular pump light for exciting terahertz waves and detection light for detection. The pulse width of the femtosecond laser is usually between tens and hundreds of femtoseconds.

[0044] The pump light is irradiated onto the insulating oil sample via the terahertz emitter and the first parabolic mirror, and then transmitted to the terahertz detector via the first parabolic mirror.

[0045] The detection light is transmitted to the terahertz detector through the time delay line and reflector. The time delay line is used to adjust the optical path of the detection light, thereby controlling the relative time delay between the detection light and the terahertz wave in the detector and realizing time-resolved measurement.

[0046] Terahertz detectors convert terahertz signals into electrical signals through the electro-optic effect or the photoconductive effect.

[0047] The lock-in amplifier is used to amplify the electrical signal and transmit it to the PC control terminal.

[0048] The PC control terminal is used to determine the time domain signal of the terahertz pulse according to the amplified electrical signal.

[0049] The femtosecond laser generates two mutually perpendicular femtosecond pulse lasers under the action of the beam splitter. The laser beam is divided into pump light and probe light by the beam splitter. The terahertz pulse generated by the pump light of the terahertz generator is reflected by the mirror and penetrates the insulating oil sample. After the probe light passes through the time delay line, it is shot to the terahertz detector together with the terahertz pulse that has penetrated the sample and reflected by the mirror. The two detected electrical signals are converted from digital to analog and transmitted to the computer in digital form. The internal material information of the test sample is obtained through computer data analysis and processing.

[0050] The first parabolic mirror and the second parabolic mirror are used to collimate and focus the terahertz wave, so that the terahertz wave is concentrated and can be effectively irradiated on the insulating oil sample, or transmitted to the detector.

[0051] It should be noted that the frequency range of terahertz waves is 0.1 to 10 THz, and the wavelength is electromagnetic radiation in the band of 30m to 3mm. Terahertz waves can pass through non-polar molecules without loss, but will produce absorption when passing through polar molecules. Specific polar molecules will produce absorption peaks of specific frequencies. The main components of insulating oil are non-polar molecules, while CO gas is a polar molecule. Under the action of terahertz waves, it will produce absorption peaks of specific frequencies. Therefore, terahertz technology is used to detect the concentration of dissolved CO in oil.

[0052] S2: Perform Fourier transform on the time domain signal to obtain the refractive index of each insulating oil sample. Determine the absorption coefficient based on the refractive index, and determine the terahertz absorption spectrum based on the absorption coefficient.

[0053] Furthermore, obtaining the time domain signal of the insulating oil sample set includes preparing the insulating oil sample set before obtaining the time domain signal of the insulating oil sample set.

[0054] The insulating oil sample set includes: insulating oil samples containing characteristic gas and insulating oil samples not containing characteristic gas. In this embodiment, CO gas is selected as the characteristic gas.

[0055] It should be noted that the preparation of the insulating oil sample set includes vacuum drying the insulating oil in the transformer, placing the transformer in a vacuum drying oven at 90°C for vacuum drying to remove the influence of moisture on the terahertz test results.

[0056] Place the dried insulating oil in a glass container.

[0057] A set volume of pure characteristic gas is injected into the container and magnetically stirred for a set time to allow the characteristic gas to reach a dissolution equilibrium in the insulating oil. The set volume is usually 30 ml and the set time is usually 3 hours.

[0058] The prepared insulating oil samples containing characteristic gases were diluted by the mother liquor dilution method, and the insulating oil samples containing characteristic gases were tested by gas chromatograph to obtain insulating oil samples containing characteristic gases of different concentrations. The concentration of dissolved CO in insulating oil samples with different dilution degrees was detected by gas chromatograph. The final prepared CO concentrations were: 0ppm, 114ppm, and 886ppm, and the sample numbers were AC.

[0059] from Figure 3 It can be seen that compared with the terahertz signal without the sample to be tested, after the terahertz pulse passes through the blank oil, the signal amplitude is only slightly attenuated, and there is an obvious phase delay. This is because the main components of the blank mineral insulating oil are large molecular hydrocarbons with a small dipole moment, and no hydrogen bonds are formed within or between molecules, which reduces the absorption rate of the mineral insulating oil to the terahertz wave, and the main peak of the terahertz pulse passing through the insulating oil sample is less attenuated. At the same time, because the refractive index of the insulating oil is greater than that of the air, the transmission speed of the electromagnetic wave in the insulating oil is reduced, resulting in a significant delay in the terahertz signal passing through the blank oil.

[0060] For homogeneous media, the refractive index can be calculated using the transmitted terahertz time domain signal:

[0061]

[0062] Where Δt is the time difference between the peak of the sample signal and the peak of the reference signal, d is the thickness of the sample, c is the speed of light, and n is s is the refractive index of the sample. Figure 3 It can be seen that the terahertz pulse passing through the sample has a time delay of 15.73ps. The thickness of the insulating oil sample is 10mm, and the refractive index of the insulating oil is calculated to be 1.47, which is consistent with the actual refractive index of Karamay 25# insulating oil.

[0063] It should also be noted that in the terahertz frequency band, mineral insulating oil does not have a strong absorption signal, so terahertz technology can be directly used for in-situ detection of polar substances in mineral insulating oil. At the same time, the time domain signal of terahertz waves has a good dynamic range, and the changes of trace substances in the oil are also easy to capture. The time domain signal obtained by the terahertz time domain spectrometer is Fourier transformed, and the measured terahertz time domain electric field can be converted into frequency domain form:

[0064]

[0065] Among them, ω is the angular frequency, E(ω) is the terahertz frequency domain electric field, E(t) is the terahertz time domain electric field, A(ω) is the frequency domain amplitude, and φ(ω) is the frequency domain phase.

[0066] Furthermore, the absorption coefficient is determined according to the refractive index, and the terahertz absorption spectrum is determined according to the absorption coefficient, including Determine the absorption coefficient at frequency ω, where c is the speed of light in a vacuum and κ(ω) is the extinction coefficient at frequency ω. The extinction coefficient κ(ω) is:

[0067]

[0068] Where n(ω) is the refractive index at frequency ω, d is the thickness of the insulating oil sample, φ s (ω) is the frequency domain phase information of the frequency domain signal of the sample, φ r (ω)] is the frequency domain phase information of the reference frequency domain signal, A s (ω) is the frequency domain amplitude information of the frequency domain signal of the sample, A r (ω is the frequency domain amplitude information of the reference frequency domain signal.

[0069] S3: Detect characteristic gases in insulating oil.

[0070] Furthermore, Figure 4 is the terahertz absorption spectra of gas insulating oil samples containing different concentrations of CO, such as Figure 4 It can be seen that there is a difference in the amplitude of the terahertz absorption spectrum of the insulating oil samples with and without CO gas, and the terahertz absorption spectrum has characteristic peaks near 1.83THz, 2.1THz and 2.25THz. At 1.83THz, the characteristic peak amplitude has a positive correlation with the gas concentration, and the characteristic peak has no offset, so 1.83THz is used as the absorption characteristic peak of CO gas in the insulating oil. Therefore, the absorption coefficient after the terahertz wave penetrates the insulating oil sample can detect whether the insulating oil sample contains CO gas, thereby realizing the in-situ non-destructive detection of the characteristic gas of the insulating oil fault.

[0071] It should be noted that the corresponding terahertz absorption spectrum of the insulating oil to be tested is obtained, and the characteristic gas detection in the insulating oil is achieved based on the comparison result of the absorption peak and the characteristic peak frequency amplitude of the terahertz absorption spectrum.

[0072] Example 2, an embodiment of the present invention, provides an in-situ nondestructive detection method for insulating oil fault characteristic gas. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0073] First, in order to verify the feasibility and superiority of an in-situ nondestructive detection method for fault characteristic gas in insulating oil, a transmission terahertz time-domain spectroscopy test platform was built. The platform includes a femtosecond laser, a beam splitter, a time delay line, a reflector, a terahertz transmitter, a terahertz detector, the first and second parabolic mirrors, a phase-locked amplifier and a PC control terminal. The platform is built to detect the absorption characteristics of CO gas of different concentrations in insulating oil through high-sensitivity terahertz time-domain spectroscopy technology, so as to achieve rapid nondestructive detection of fault gas dissolved in insulating oil.

[0074] First, prepare the experimental sample set. Select typical insulating oil samples and perform vacuum drying (temperature set at 90 ℃ , for 4 hours) to remove moisture from the sample and prevent moisture from interfering with the terahertz signal. The dried insulating oil was then divided into clean glass containers. Different volumes of pure CO gas were injected into the container and magnetically stirred to ensure that the gas reached a solubility equilibrium in the oil. Finally, three groups of samples were prepared, containing CO gas concentrations of 0ppm, 150ppm, and 600ppm, respectively. The CO concentration of the sample was preliminarily verified by gas chromatography to ensure that the concentration of the sample met expectations.

[0075] The prepared samples are placed in the terahertz test platform for testing. The femtosecond laser generates two mutually perpendicular femtosecond laser pulses, which are divided into pump light and probe light by a beam splitter. The pump light is used to excite the terahertz emitter to generate terahertz pulses, which pass through the insulating oil sample and are focused by a parabolic mirror and transmitted to the terahertz detector. The probe light is transmitted to the terahertz detector through a time delay line and a reflector. The terahertz detector converts the signal into an electrical signal, which is then transmitted to the PC for analysis through a phase-locked amplifier.

[0076] On the PC side, the extracted time domain signal is Fourier transformed to obtain frequency domain information, and then the refractive index and absorption coefficient of each sample are calculated. The terahertz absorption spectrum of the sample is constructed through the absorption coefficient to facilitate the observation of the characteristic peaks of samples with different CO concentrations. At 1.83THz, the higher the CO gas concentration, the greater the amplitude of its absorption peak, indicating that the concentration of CO gas and the amplitude of the absorption peak are positively correlated.

[0077] Table 1 Experimental data comparison table

[0078]

[0079] It can be seen from the experimental data that when CO gas of different concentrations is dissolved in insulating oil, its absorption peak amplitude at specific terahertz frequencies (1.83THz and 2.10THz) shows significant differences. In samples without CO (samples A and D), the absorption peak amplitude of the terahertz absorption spectrum is low (0.05 and 0.06), indicating that the characteristic absorption peak of CO is not detected at these frequencies. In samples containing CO (samples B, C, E and F), the absorption peak amplitude is significantly increased (0.18 to 0.78), and the absorption peak amplitude at 1.83THz and 2.10THz frequencies is positively correlated with the CO concentration. This relationship shows the feasibility of quantitative detection of CO gas concentration.

[0080] Experimental data show that this method uses the sensitive absorption characteristics of terahertz waves to polar molecules such as CO, and can accurately distinguish different concentrations of CO gas through non-destructive detection. Compared with traditional gas chromatography, the detection method of the present invention does not require destructive treatment of samples and directly measures the CO concentration in oil. This advantage significantly improves the efficiency and accuracy of detection, reduces the time of sample preparation and cumbersome operation steps. In addition, in the blank sample without CO added, the amplitude of the detected terahertz absorption peak is low, indicating the high sensitivity and low detection limit of this method.

[0081] Example 3, an embodiment of the present invention provides an in-situ nondestructive detection system for characteristic gas of insulating oil fault, including a test platform building module, a time domain signal acquisition module, a refractive index determination module, a terahertz absorption spectrum determination module, a characteristic peak frequency amplitude determination module, and a characteristic gas detection module.

[0082] Among them, the test platform construction module is used to build a transmission terahertz time-domain spectroscopy test platform, and the transmission terahertz time-domain spectroscopy test platform is used to perform terahertz testing. The time domain signal acquisition module is used to obtain the time domain signals of the insulating oil sample set according to the transmission terahertz time-domain spectroscopy test platform, and the insulating oil sample set includes insulating oil samples containing characteristic gases and insulating oil samples without characteristic gases. The refractive index determination module is used to perform Fourier transform on the time domain signals of the insulating oil sample set to obtain the refractive index of each insulating oil sample. The terahertz absorption spectrum determination module is used to determine the corresponding absorption coefficient according to the refractive index of each insulating oil sample, and determine the terahertz absorption spectrum of each insulating oil sample according to the absorption coefficient. The characteristic peak frequency amplitude determination module is used to determine the characteristic peak frequency amplitude according to the terahertz absorption spectrum of the insulating oil sample containing characteristic gas and the insulating oil sample without characteristic gas. The characteristic gas detection module is used to obtain the corresponding terahertz absorption spectrum of the insulating oil to be tested, and realize the detection of characteristic gas in the insulating oil according to the comparison result of the absorption peak of the terahertz absorption spectrum and the characteristic peak frequency amplitude.

[0083] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0084] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0085] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering, or processing in another suitable manner as necessary, and then stored in a computer memory.

[0086] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc. It should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limited. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

[0087] 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 preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An in-situ nondestructive detection method for insulating oil fault characteristic gas, characterized in that: include: Build a transmission terahertz time-domain spectroscopy test platform to obtain the time-domain signal of the insulating oil sample set; Performing Fourier transformation on the time domain signal to obtain the refractive index of each insulating oil sample; determining the absorption coefficient according to the refractive index, and determining the terahertz absorption spectrum according to the absorption coefficient; Detect characteristic gases in insulating oil.

2. The in-situ nondestructive testing method for insulating oil fault characteristic gas according to claim 1, characterized in that: The transmission type terahertz time domain spectroscopy test platform comprises a femtosecond laser, a beam splitter, a time delay line, a reflector, a terahertz transmitter, a terahertz detector, a first parabolic mirror, a second parabolic mirror, a phase-locked amplifier and a PC control terminal.

3. The in-situ nondestructive testing method for insulating oil fault characteristic gas according to claim 2, characterized in that: The construction of the transmission terahertz time-domain spectroscopy testing platform includes obtaining mutually perpendicular pump light and detection light from a femtosecond laser emitted by a femtosecond laser; The pump light is irradiated onto the insulating oil sample via the terahertz emitter and the first parabolic mirror, and then transmitted to the terahertz detector via the first parabolic mirror; The detection light is transmitted to the terahertz detector via the time delay line and the reflector; The terahertz detector converts the terahertz signal into an electrical signal through the electro-optic effect or the photoconductive effect; The lock-in amplifier is used to amplify the electrical signal and transmit it to the PC control terminal; The PC control terminal is used to determine the time domain signal of the terahertz pulse according to the amplified electrical signal.

4. The in-situ nondestructive testing method for insulating oil fault characteristic gas according to claim 3, characterized in that: The obtaining of the time domain signal of the insulating oil sample set includes preparing the insulating oil sample set before obtaining the time domain signal of the insulating oil sample set.

5. The in-situ nondestructive testing method for insulating oil fault characteristic gas according to claim 4, characterized in that: The preparing of the insulating oil sample set includes vacuum drying the insulating oil in the transformer; Place the dried insulating oil in a glass container; A set volume of pure characteristic gas is injected into the container, and magnetic stirring is performed for a set time, so that the characteristic gas reaches a dissolution equilibrium in the insulating oil; The prepared insulating oil sample containing the characteristic gas is diluted by a mother liquor dilution method, and the insulating oil sample containing the characteristic gas is tested by a gas chromatograph to obtain insulating oil samples containing the characteristic gas at different concentrations.

6. The in-situ nondestructive testing method for insulating oil fault characteristic gas according to claim 5, characterized in that: Determining the absorption coefficient according to the refractive index and determining the terahertz absorption spectrum according to the absorption coefficient includes: Determine the absorption coefficient at frequency ω, where c is the speed of light in a vacuum and κ(ω) is the extinction coefficient at frequency ω. The extinction coefficient κ(ω) is: Where n(ω) is the refractive index at frequency ω, d is the thickness of the insulating oil sample, φ s (ω) is the frequency domain phase information of the frequency domain signal of the sample, φ r (ω)] is the frequency domain phase information of the reference frequency domain signal, A s (ω) is the frequency domain amplitude information of the frequency domain signal of the sample, A r (ω is the frequency domain amplitude information of the reference frequency domain signal.

7. The in-situ nondestructive testing method for insulating oil fault characteristic gas according to claim 6, characterized in that: The detection of characteristic gas in insulating oil includes obtaining a terahertz absorption spectrum corresponding to the insulating oil to be tested, and realizing the detection of characteristic gas in insulating oil according to a comparison result of an absorption peak of the terahertz absorption spectrum and a characteristic peak frequency amplitude.

8. A system using the insulating oil fault characteristic gas in-situ nondestructive testing method according to any one of claims 1 to 7, characterized in that: It includes a test platform building module, a time domain signal acquisition module, a refractive index determination module, a terahertz absorption spectrum determination module, a characteristic peak frequency amplitude determination module, and a characteristic gas detection module; The test platform building module is used to build a transmission-type terahertz time-domain spectroscopy test platform, and the transmission-type terahertz time-domain spectroscopy test platform is used to perform terahertz testing; The time domain signal acquisition module is used to respectively acquire the time domain signals of the insulating oil sample set according to the transmission terahertz time domain spectroscopy test platform, wherein the insulating oil sample set includes insulating oil samples containing characteristic gas and insulating oil samples not containing characteristic gas; The refractive index determination module is used to perform Fourier transform on the time domain signals of the insulating oil sample set respectively to obtain the refractive index of each insulating oil sample; The terahertz absorption spectrum determination module is used to determine the corresponding absorption coefficient according to the refractive index of each insulating oil sample, and determine the terahertz absorption spectrum of each insulating oil sample according to the absorption coefficient; The characteristic peak frequency amplitude determination module is used to determine the characteristic peak frequency amplitude according to the terahertz absorption spectra of the insulating oil sample containing the characteristic gas and the insulating oil sample not containing the characteristic gas; The characteristic gas detection module is used to obtain the terahertz absorption spectrum corresponding to the insulating oil to be tested, and realize the characteristic gas detection in the insulating oil according to the comparison result of the absorption peak of the terahertz absorption spectrum and the characteristic peak frequency amplitude.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the in-situ nondestructive detection method of insulating oil fault characteristic gas according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the in-situ nondestructive detection method of insulating oil fault characteristic gas according to any one of claims 1 to 7 are implemented.

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