A transformer oil fluorescence excitation source and optimal excitation wavelength selection method

Abstract

The application discloses a transformer oil fluorescence excitation source and an optimal excitation wavelength selection method, belongs to the technical field of transformer fault diagnosis, and solves the problems of large volume and weight, high cost and inconvenient use of existing devices. The application selects the excitation wavelength of a monochromatic LED excitation light source by comparing the main peak intensity and the dispersion degree of sample characteristics under different excitation wavelengths, and the excitation wavelength is the excitation wavelength of the monochromatic LED excitation light source. The monochromatic LED excitation light source emits monochromatic excitation light, the excitation light is converged on the optical fiber head through a converging lens, the optical fiber head collects the excitation light and conducts the excitation light out through an optical fiber interface for exciting transformer oil to generate fluorescence. The device is simple in structure, directly uses a fluorescence spectrometer for excitation compared with the prior art, greatly reduces the volume and weight of the device, is convenient to use, and has a long service life and low cost.

Description

Technical Field

[0001] This invention belongs to the field of transformer fault diagnosis technology, and relates to a transformer oil fluorescence excitation source and a method for selecting the optimal excitation wavelength. Background Technology

[0002] Transformers are the core of energy conversion in the process of power generation and distribution. They are numerous and have a wide impact. Their operating status directly affects the safe and reliable operation of the power system. Once a transformer has an accident, it will not only damage expensive electrical equipment (the price of a single transformer can be as high as 50 million yuan), but also cause large-scale power outages, and even cause casualties, environmental pollution, and huge economic and social losses. Therefore, monitoring the operating status of transformers has become particularly important.

[0003] Transformer oil refers to a type of insulating oil used in oil-filled electrical equipment such as transformers, reactors, instrument transformers, bushings, and oil switches, serving as insulation, cooling, and arc-extinguishing agents. Transformer oil is a fractionation product of petroleum, and its main components are alkanes, cycloalkanes, aromatic unsaturated hydrocarbons, and non-hydrocarbon compounds. Transformer oil can fluoresce under ultraviolet or X-ray irradiation. Fluorescence refers to a photoluminescence phenomenon. When a substance at room temperature is irradiated with incident light of a certain wavelength (usually ultraviolet or X-rays), it absorbs the light energy, enters an excited state, and immediately de-excites, emitting outgoing light with a wavelength longer than the incident light (usually in the visible light range); and once the incident light stops, the luminescence disappears immediately. This property of outgoing light is called fluorescence.

[0004] Fluorescent detection technology (FMS) for transformer operation status analyzes changes in the optical signal of transformer oil through a fluorescence detection device, thereby achieving the purpose of monitoring the transformer. For example, the Chinese invention patent document "An Online Fluorescent Detection Device for Transformer Oil" with a publication date of July 13, 2021 and publication number CN113109682A discloses an online fluorescent detection device for transformer oil that has the characteristics of high sensitivity, short analysis time, no interference from the surrounding magnetic and electric fields, good stability and reproducibility, and can meet the online fault detection needs of transformer operation status.

[0005] When using a fluorescence detection device, a fluorescence excitation source needs to be designed to generate monochromatic light of a specific wavelength to excite the transformer oil. Current technology directly uses a fluorescence spectrometer for excitation. The excitation source of the fluorescence spectrometer uses a xenon lamp in conjunction with an excitation monochromator, which can generate many different wavelengths of monochromatic light for users to choose from. However, the xenon lamp and excitation monochromator used as the excitation source are large and heavy, which is inconvenient to carry due to limited on-site operating space. Furthermore, fluorescence spectrometers are expensive. The national standard for transformer oil, GB2536-90, classifies transformer oil into three grades based on its pour point: 10... # 25 # and 45 # Transformer oils have fluorescence characteristic values ​​distributed in the 350nm to 500nm band, so only one monochromatic light is needed to detect transformer faults, without the need for monochromatic light of multiple wavelengths. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to design a transformer oil fluorescence excitation source with an optimal excitation wavelength, so as to solve the problems of large size and weight, high cost and inconvenience of use of existing devices.

[0007] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0008] A transformer oil fluorescence excitation source includes: a fluorescence excitation dark chamber (120), a monochromatic optimal wavelength LED excitation source (121), a converging lens (123), and an optical fiber head (125); the monochromatic optimal wavelength LED excitation source (121), the converging lens (123), and the optical fiber head (125) are all fixedly disposed inside the fluorescence excitation dark chamber (120), the converging lens (123) is disposed between the monochromatic optimal wavelength LED excitation source (121) and the optical fiber head (125), and the center lines of the monochromatic optimal wavelength LED excitation source (121), the converging lens (123), and the optical fiber interface (126) are on a straight line; The method for selecting the excitation wavelength of the monochromatic optimal wavelength LED excitation source (121) is as follows: Three-dimensional fluorescence spectral data of different types of transformer oil are collected. Based on the distribution range of fluorescence characteristic values ​​of the transformer oil fluorescence spectrum, the optimal excitation wavelength range is determined. The peak intensity of the sample characteristics under different excitation wavelengths is compared using the excitation wavelength as the abscissa and the peak intensity as the ordinate. The dispersion of the sample characteristics under different excitation wavelengths is compared using the excitation wavelength as the abscissa and the coefficient of variation as the ordinate. The excitation wavelength that maximizes both the peak intensity and the coefficient of variation is selected as the excitation wavelength of the monochromatic optimal wavelength LED excitation source (121). The formula for calculating the coefficient of variation is as follows: Among them, c vδ is the coefficient of variation, μ is the standard deviation, and μ is the mean. The larger the coefficient of variation, the greater the dispersion.

[0009] This invention compares the peak intensity and dispersion of sample characteristics under different excitation wavelengths, and selects the excitation wavelength that maximizes both the peak intensity and the coefficient of variation as the excitation wavelength of the monochromatic optimal wavelength LED excitation source (121). The monochromatic optimal wavelength LED excitation source (121) emits monochromatic excitation light, which is focused onto the fiber optic head (125) by the converging lens (123). The fiber optic head (125) collects the excitation light and transmits it through the fiber optic interface (126) to excite the transformer oil to generate fluorescence. The device structure of this invention is simple. Compared with the prior art, which directly uses a fluorescence spectrometer for excitation, it greatly reduces the size and weight of the device and is easy to use. The device uses a monochromatic LED excitation source with long life and low cost.

[0010] Furthermore, it also includes: an optical fiber interface (126), which is fixedly installed on the side wall outside the fluorescence excitation dark chamber (120), and the optical fiber head (125) is connected to the optical fiber interface (126).

[0011] Furthermore, it also includes: an excitation light source mounting bracket (122), which is fixedly mounted on the bottom plate inside the fluorescence excitation dark chamber (120), and the monochromatic optimal wavelength LED excitation light source (121) is mounted on the excitation light source mounting bracket (122).

[0012] Furthermore, it also includes: a lens mounting bracket (124), which is fixedly mounted on the bottom plate inside the fluorescence excitation dark chamber (120), and the converging lens (123) is embedded in the lens mounting bracket (124).

[0013] Furthermore, the optical fiber interface (126) adopts the ST-SC standard optical fiber interface.

[0014] The advantages of this invention are:

[0015] This invention compares the peak intensity and dispersion of sample characteristics under different excitation wavelengths, and selects the excitation wavelength that maximizes both the peak intensity and the coefficient of variation as the excitation wavelength of the monochromatic optimal wavelength LED excitation source (121). The monochromatic optimal wavelength LED excitation source (121) emits monochromatic excitation light, which is focused onto the fiber optic head (125) by the converging lens (123). The fiber optic head (125) collects the excitation light and transmits it through the fiber optic interface (126) to excite the transformer oil to generate fluorescence. The device structure of this invention is simple. Compared with the prior art, which directly uses a fluorescence spectrometer for excitation, it greatly reduces the size and weight of the device and is easy to use. The device uses a monochromatic LED excitation source with long life and low cost. Attached Figure Description

[0016] Figure 1 This is a first three-dimensional view of the transformer oil fluorescence excitation source according to an embodiment of the present invention;

[0017] Figure 2 This is a second three-dimensional view of the transformer oil fluorescence excitation source according to an embodiment of the present invention;

[0018] Figure 3 This is a top view of the transformer oil fluorescence excitation source according to an embodiment of the present invention;

[0019] Figure 4 This is a flowchart of the optimal excitation wavelength selection method for the transformer oil fluorescence excitation source according to an embodiment of the present invention;

[0020] Figure 5 This is a fluorescence spectrum scanned at the excitation wavelength of a fresh oil sample;

[0021] Figure 6 This is a graph showing the relationship between the main peak intensity and different excitation wavelengths when determining the optimal excitation wavelength for Karamay oil according to an embodiment of the present invention.

[0022] Figure 7 This is a graph showing the relationship between the coefficient of variation and different excitation wavelengths when determining the optimal excitation wavelength for Karamay oil according to an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0025] Example 1

[0026] like Figures 1 to 3 As shown, the transformer oil fluorescence excitation source of this embodiment includes: a fluorescence excitation dark chamber (120), a monochromatic optimal wavelength LED excitation light source (121), an excitation light source mounting bracket (122), a converging lens (123), a lens mounting bracket (124), an optical fiber head (125), and an optical fiber interface (126); the excitation light source mounting bracket (122) is fixedly installed at the left end of the bottom plate inside the fluorescence excitation dark chamber (120), and the monochromatic optimal wavelength LED excitation light source (121) is installed on the excitation light source mounting bracket (122); the lens mounting bracket (124) is fixedly installed on the bottom plate inside the fluorescence excitation dark chamber (120). The converging lens (123) is embedded in the lens mounting bracket (124) and positioned in the middle of the fluorescence excitation dark chamber (120). The fiber optic head (125) is fixedly installed on the right side wall inside the fluorescence excitation dark chamber (120), and the fiber optic interface (126) is fixedly installed on the right side wall outside the fluorescence excitation dark chamber (120). The fiber optic head (125) and the fiber optic interface (126) are connected in a cooperative manner. The center lines of the monochromatic optimal wavelength LED excitation light source (121), the converging lens (123), and the fiber optic interface (126) are on a straight line.

[0027] The inner wall of the fluorescence excitation darkroom (120) is coated with a light-absorbing coating to prevent external ambient light from entering and to eliminate the influence of multiple internal reflections. The monochromatic optimal wavelength LED excitation source (121) emits monochromatic ultraviolet light to excite the transformer oil. The converging lens (123) is a convex lens used to converge the monochromatic ultraviolet light emitted by the monochromatic optimal wavelength LED excitation source (121) onto the fiber optic head (125). The fiber optic head (125) is used to collect the monochromatic ultraviolet light emitted by the monochromatic optimal wavelength LED excitation source (121). The fiber optic interface (126) is an ST-SC standard fiber optic interface used to export the monochromatic ultraviolet light emitted by the monochromatic optimal wavelength LED excitation source (121).

[0028] The workflow of a fluorescence excitation source:

[0029] The monochromatic optimal wavelength LED excitation source (121) emits monochromatic excitation light, which is focused onto the fiber optic head (125) by the converging lens (123). The fiber optic head (125) collects the excitation light and transmits it through the fiber optic interface (126) to excite the transformer oil to produce fluorescence.

[0030] like Figure 4 As shown, the method for selecting the optimal excitation wavelength of the monochromatic optimal wavelength LED excitation light source (121) is as follows:

[0031] First, three-dimensional fluorescence spectral data of different types of transformer oil were collected, such as... Figure 5 As shown, scanning the fluorescence spectrum of the new oil sample at the excitation wavelength reveals that the fluorescence characteristic values ​​of the transformer oil fluorescence spectrum are distributed in the 350nm to 500nm band. Within this range, the fluorescence spectrum can most significantly show the characteristics of the sample, that is, the characteristic peaks are clearly distinguishable and regular. The excitation wavelength range is 270nm to 310nm.

[0032] Secondly, using excitation wavelength as the x-axis and peak intensity as the y-axis, the peak intensity of sample features under different excitation wavelengths is compared. Then, using excitation wavelength as the x-axis and coefficient of variation as the y-axis, the dispersion of sample features under different excitation wavelengths is compared. The formula for calculating the coefficient of variation is as follows: Among them, c v denoted as coefficient of variation, δ as standard deviation, and μ as mean. A larger coefficient of variation indicates a greater degree of dispersion.

[0033] The optimal excitation wavelength should maximize both peak intensity and coefficient of variation.

[0034] like Figure 6 and Figure 7 As shown, a three-dimensional fluorescence spectroscopy analysis experiment was conducted on Karamay oil. The excitation wavelengths were selected from 270 nm to 310 nm. The peak intensity and coefficient of variation were compared. It was found that both were the largest at an excitation wavelength of 270 nm. Therefore, the optimal excitation wavelength is 270 nm.

[0035] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A transformer oil fluorescence excitation source, characterized in that, include: The fluorescent excitation dark chamber (120), the monochromatic optimal wavelength LED excitation source (121), the converging lens (123), and the fiber optic head (125) are all fixedly installed inside the fluorescent excitation dark chamber (120). The converging lens (123) is positioned between the monochromatic optimal wavelength LED excitation source (121) and the fiber optic head (125). The center lines of the monochromatic optimal wavelength LED excitation source (121), the converging lens (123), and the fiber optic interface (126) are on a straight line. The method for selecting the optimal excitation wavelength of the monochromatic optimal wavelength LED excitation source (121) is as follows: collect three-dimensional fluorescence spectral data of different types of transformer oil, and determine the optimal excitation wavelength range according to the distribution range of fluorescence characteristic values ​​of the transformer oil fluorescence spectrum; compare the main peak intensity of the sample characteristics under different excitation wavelengths with the excitation wavelength as the abscissa and the main peak intensity as the ordinate. Using the excitation wavelength as the abscissa and the coefficient of variation as the ordinate, the dispersion of sample characteristics under different excitation wavelengths is compared; the excitation wavelength that maximizes both the main peak intensity and the coefficient of variation is selected as the optimal wavelength for the monochromatic LED excitation light source (121); the formula for calculating the coefficient of variation is as follows: Among them, c v δ is the coefficient of variation, μ is the standard deviation, and μ is the mean. The larger the coefficient of variation, the greater the dispersion.

2. The transformer oil fluorescence excitation source according to claim 1, characterized in that, Also includes: The fiber optic interface (126) is fixedly installed on the side wall outside the fluorescence excitation dark chamber (120), and the fiber optic head (125) is connected to the fiber optic interface (126).

3. The transformer oil fluorescence excitation source according to claim 2, characterized in that, Also includes: An excitation light source mounting bracket (122) is fixedly mounted on the bottom plate inside the fluorescence excitation dark chamber (120), and the monochromatic optimal wavelength LED excitation light source (121) is mounted on the excitation light source mounting bracket (122).

4. The transformer oil fluorescence excitation source according to claim 3, characterized in that, Also includes: The lens mounting bracket (124) is fixedly mounted on the bottom plate inside the fluorescence excitation dark chamber (120), and the converging lens (123) is embedded in the lens mounting bracket (124).

5. The transformer oil fluorescence excitation source according to claim 4, characterized in that, The fiber optic interface (126) adopts the ST-SC standard fiber optic interface.

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