Discharge optical signal coupling device

Abstract

The invention discloses a discharge optical signal coupling device, which is characterized in that quartz is adopted as a main material of the discharge optical signal coupling device (i.e., a light guide), and optical radiation in different angle ranges is directionally collected by designing a light guide structure. The light guide structure adopts a circular uniform section-light cone combined structure design and is composed of a uniform section part and a light cone part, the uniform section part is a light guide with the same interface radius, and the light cone part is a light guide with the section radius linearly changing in the axial direction. According to the invention, the time sequence information, intensity information and spectral information of the partial discharge optical signal can be collected, and the azimuth information of the partial discharge optical signal can be effectively collected, so that technical support is provided for traceability positioning of partial discharge in GIS equipment and improvement of the partial discharge detection level; the method is crucial for improving the reliability and safety of a power system, preventing equipment faults and ensuring stable operation of a power grid.

Description

Technical Field

[0001] The present invention belongs to the field of partial discharge detection of power equipment, and particularly relates to a discharge optical signal coupling device and its structural design method. Background Art

[0002] The voltage level of GIS equipment is relatively high, and it is very sensitive to defects such as metal tips and burrs inside the gas chamber. Therefore, considering the influence of the strong electric field on the working stability of secondary equipment and the influence of secondary equipment on the internal electric field distribution of GIS, optoelectronic sensor devices cannot be directly installed inside the GIS gas chamber. In order to detect the partial discharge optical signal inside the gas chamber, an optical signal coupling device made of dielectric material must be used to lead the light out of the device for optoelectronic conversion to meet the electromagnetic compatibility requirements. The common structures of GIS equipment include linear, T-shaped, and L-shaped, and their structures are characterized by being long and narrow. Therefore, when using optical detection methods, there are high requirements for the detection field of view angle and coupling efficiency of the optical coupling device. In the field of imaging optics, the field of view angle of traditional imaging lens modules can exceed 180 degrees, that is, ultra-wide-angle lenses, which provides new possibilities for expanding the detection range of optical signals. However, the detection methods based on such imaging principles are not applicable to the detection and positioning of weak partial discharge light, and their structures are complex, consisting of multiple lenses. The inside of the lens group cannot bear a large pressure, and the GIS equipment is filled with sulfur hexafluoride gas at 5 times atmospheric pressure. Therefore, such devices are difficult to install in GIS equipment.

[0003] In the field of optical detection of partial discharge, the most commonly used discharge optical signal coupling device is a cylindrical quartz light guide. Due to the high light transmittance, good dielectric compatibility of the cylindrical quartz light guide, and the fact that at a certain detection angle, the optical signal can undergo total internal reflection at the quartz-gas interface inside the light guide, the cylindrical quartz light guide can be effectively applied to partial discharge light pulse detection and spectral detection systems. However, this application method can only obtain the timing information, intensity information, and spectral information of the partial discharge optical signal, and does not include the azimuth information of the optical signal. In order to realize the traceability and positioning of partial discharge inside the GIS equipment, it is also necessary to obtain the light radiation intensity information in different directions. Summary of the Invention

[0005] Based on the above analysis, the present invention proposes a discharge optical signal coupling device. Considering that the geometric shape of the light guide will affect the optical path and light field distribution caused by optical processes such as refraction and reflection, a combined structure of an equal cross-section light guide and a light cone is proposed. The present invention can not only collect the timing information, intensity information and spectral information of the partial discharge optical signal, but also effectively collect the azimuth information of the partial discharge optical signal, providing technical support for realizing the traceability and positioning of internal partial discharges in GIS equipment and improving the level of partial discharge detection, which is crucial for improving the reliability and safety of the power system, preventing equipment failures and ensuring the stable operation of the power grid.

[0006] The present invention provides the following technical solutions:

[0007] A discharge optical signal coupling device, the structure design of the device adopts a circular equal cross-section - light cone combined structure design.

[0008] Preferably, the device uses quartz as the main material.

[0009] A discharge optical signal coupling device (i.e., light guide) uses quartz as the main material, and realizes the directional collection of light radiation in different angular ranges by designing the light guide structure. The structure design of the device adopts a circular equal cross-section - light cone combined structure design.

[0010] Preferably, the circular equal cross-section - light cone combined structure design consists of an equal cross-section part and a light cone part.

[0011] Preferably, the equal cross-section part is a light guide with the same interface radius.

[0012] Preferably, the light cone part is a light guide whose cross-sectional radius changes linearly along the axis.

[0013] Preferably, the upper end face of the light cone part is larger and the lower end face is smaller.

[0014] Preferably, the size of the upper end face of the light cone part is the same as that of the equal cross-section part.

[0015] Preferably, the size of the lower end face of the light cone part depends on the optoelectronic device used.

[0016] Preferably, the optoelectronic device is a silicon photomultiplier tube.

[0017] Preferably, the device is mainly used for collecting partial discharge optical signals of GIS equipment.

[0018] Preferably, the field of view angle obtained by using the circular equal cross-section - light cone combined structure design is 156.2°, and the coupling efficiency is 0.0116.

[0019] Further, for the field of view angle: for the optical fiber array, the optical radiation flux coupled to the optical fiber is tested at different light source angles. When the radiation flux decays to less than 30% of the maximum value as the angle increases, it is considered that the effective detection ability of the optical signal is lost at this time, and the field of view angle of the entire optical fiber array is obtained accordingly.

[0020] Further, for the coupling efficiency: on the premise that the area of the detection end of the optical fiber is the same, considering all the optical signals at all angles within the field of view angle comprehensively, the average value of the coupled optical radiation flux at different light source angles is calculated, and the ratio of this average value to the total radiation flux emitted by the light source is used as an index of the optical fiber coupling efficiency.

[0021] Advantages of the present invention:

[0022] The circular equal-cross-section - optical cone combined structure design of the present invention can not only collect the timing information, intensity information and spectral information of the partial discharge optical signal, but also effectively collect the azimuth information of the partial discharge optical signal, providing technical support for realizing the traceability and positioning of internal partial discharges in GIS equipment and improving the partial discharge detection level. It can be understood that:

[0023] The equal-cross-section part maintains the transmission stability of the optical signal and reduces the optical loss during the refraction / reflection process;

[0024] The optical cone part is equivalent to guiding the optical signals with different incident angles to be directionally focused on the optoelectronic device (such as a silicon photomultiplier) through the cross-section gradient, realizing the directional control of the optical path; the incident angles of the optical signals in different directions are distinguished through the geometric characteristics of the optical cone, providing spatial dimension data for positioning;

[0025] If the equal-cross-section part is an optical fiber with the same interface radius and the optical cone part is an optical fiber with the cross-section radius changing linearly along the axis, it means that the present invention realizes the spatial vector analysis of the innovative discharge light source through the directional control of the incident angle by the optical cone structure and the field of view angle coverage of the multi-optical fiber array, supporting the positioning requirements;

[0026] The size of the lower end face of the optical cone part depends on the optoelectronic device used, which means that the size of the lower end face of the optical cone part matches the detection end face of the optoelectronic device such as a silicon photomultiplier. The benefit brought by this is that the optical signals incident at a wide angle are focused on the small-area photosensitive surface of the optoelectronic device such as a silicon photomultiplier through the optical cone, improving the signal conversion efficiency, which is obviously beneficial to using the high-gain characteristics of the optoelectronic device such as a silicon photomultiplier to amplify the weak optical pulse signal of the partial discharge;

[0027] The field of view angle is 156.2°, covering multi-directional light radiation within the long and narrow structure of the GIS device; the coupling efficiency of 0.0116 means enhanced weak light detection ability; the performance parameters of both mean that through the optimization of the field of view angle coverage and coupling efficiency, combined with the azimuth data fusion of multiple light guides, the present invention realizes excellent traceability and positioning ability of the discharge light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0029] Figure 1 In one embodiment of the present invention, it is a schematic diagram of the propagation process of light rays within the light cone.

[0030] Figure 2 In one embodiment of the present invention, it is a schematic diagram of the propagation process of mirror image light rays in the image space of the light cone.

[0031] Figure 3 In one embodiment of the present invention, it is a schematic diagram of the conditions for light rays to reach the small end face.

[0032] Figure 4 In one embodiment of the present invention, it is a schematic diagram of the conditions for light rays incident from the upper edge to reach the small end face.

[0033] Figure 5 In one embodiment of the present invention, it is a schematic diagram of the conditions for light rays incident from the lower edge to reach the small end face.

[0034] Figure 6 In one embodiment of the present invention, it is a schematic diagram of the equal cross-section - light cone combined structure.

[0035] Figure 7 In one embodiment of the present invention, it is a three-dimensional structure diagram of the equal cross-section - light cone combined structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the specific embodiments of the present invention in detail in combination with the embodiments of the specification. To further describe the present invention, the following will be combined with the attached Figures 1 to 7 Further explanation will be made thereto.

[0037] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways than those specifically described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0038] Secondly, as used herein, an "embodiment" or "embodiments" refers to a particular feature, structure, or characteristic that may be included in at least one implementation of the present invention. The appearances of "in one embodiment" in various places in this specification are not all referring to the same embodiment, nor are they separate or alternative embodiments that exclude each other.

[0039] The present invention discloses a discharge optical signal coupling device (i.e., an optical waveguide) that uses quartz as the main material and realizes the directional collection of light radiation within different angular ranges by designing the structure of the optical waveguide. The structural design of the device adopts a circular cross-section - optical cone combined structure design.

[0040] In one embodiment, the present invention discloses a discharge optical signal coupling device:

[0041] The structure of the discharge optical signal coupling device is a combined structure of an equal cross-section optical waveguide and an optical cone.

[0042] The optical cone is also known as a tapered optical fiber. The optical cone is a commonly used coupling structure in fiber optics, referring to an optical waveguide whose cross-sectional radius changes linearly along the axial direction. Since the areas of the two end faces of the optical cone are not equal, a larger equivalent receiving area can be obtained at the small end face of the optical cone, thereby indirectly increasing the coupling efficiency of optoelectronic devices. The transmission process of light in the optical cone is as Figure 1 shown:

[0043] Let the cone angle of the optical cone be δ. During the transmission process, the reflection angle φ of the light at the dielectric interface n gradually decreases as the number of reflections n increases. This law can be described by the mathematical relationship:

[0044] (1)

[0045] where θ is the apex angle of the optical cone;

[0046] Suppose there is light incident from a certain medium with a refractive index of n 0 to an external medium with a refractive index of n 1 , and the incident angle is φ 0 . Then, according to the law of refraction, we have:

[0047] ,

[0048] Then,

[0049] ,

[0050] Substituting into Equation (1) gives:

[0051] (2)

[0052] This shows that when light enters from the large end face of the light cone, due to the continuous decrease of the reflection angle, the condition of total internal reflection may not be satisfied, so the numerical aperture of the incident light on the large end face of the light cone is limited. To analyze the condition for the light to exit from the small end face of the light cone, the image space corresponding to each reflection on the side is drawn. According to the law of reflection, the mirror image light travels along a straight line between each image space. Taking the light incident on the center of the end face as an example, the reflection path of the light and the path of the mirror image light are as Figure 2 shown.

[0053] From Figure 3 it can be seen that a necessary condition for the light to reach the small end face of the light cone is that there is an intersection between the mirror image light and the circle with point B as the center and BE as the radius. Otherwise, after enough reflections, the light will return to the large end face of the light cone.

[0054] In addition, to ensure that there is no energy loss when the light is reflected on the side of the light cone and total internal reflection occurs each time, it is also necessary to satisfy:

[0055] (3)

[0056] In the formula: α i —— The incident angle corresponding to the i-th reflection / rad; n 1 —— The refractive index of the external medium; n 2 —— The refractive index of the light cone material.

[0057] Since the incident angles of each reflection inside the light cone decrease in turn, only the incident angle α m of the last time needs to satisfy the total internal reflection condition. First, analyze the light incident on the center of the large end face of the light cone. Let the radius of the small end face, the radius of the large end face, and the length of the light cone be a 1 , a 2 , l, and the cone angle of the light cone be δ. In △EFB:

[0058] (4)

[0059] In △ABC, according to the sine theorem:

[0060] (5)

[0061] Let the refractive indices of the external medium and the optical waveguide material be n 1 and n 2, the total internal reflection condition on the side is as follows:

[0062] (6)

[0063] As Figure 4 shown, when the light enters from the upper side edge of the large end face of the light cone:

[0064] In △DBC, according to the sine theorem, we can get:

[0065] (7)

[0066] According to the total internal reflection condition, we can get:

[0067] (8)

[0068] As Figure 5 shown, when the light enters from the lower side edge of the large end face of the light cone:

[0069] In △GBC, according to the sine theorem:

[0070] (9)

[0071] According to the total internal reflection condition, we can get:

[0072] (10)

[0073] Since , thus by combining the above three equations, we can get:

[0074] (11)

[0075] The above formula shows that when the angle θ between the light entering the light cone from the large end face and the principal optical axis is less than the critical value, it can reach the small end face through total internal reflection without loss. When it exceeds this critical value, the coupling efficiency of the light cone will gradually decrease as the incident angle increases.

[0076] It should be noted that when the light is incident from a high refractive index medium to the interface of a low refractive index medium and the incident angle is greater than the critical angle, total internal reflection will occur. The value of the critical angle θ c is the critical value, which is obtained from the following formula:

[0077] ,

[0078] where n 高 , n 低 are the refractive indices of the high refractive index medium and the low refractive index medium respectively.

[0079] In another embodiment, the circular equal cross-section - light cone combined structure design consists of two parts: an equal cross-section part and a light cone part.

[0080] For the above embodiments, the technical effect of the constant cross-section part is to directionally collect the light radiation within different angular ranges.

[0081] In another embodiment,

[0082] The constant cross-section part is an optical waveguide with the same interface radius.

[0083] In another embodiment,

[0084] The upper end surface of the light cone part is larger, and the lower end surface is smaller.

[0085] In another embodiment,

[0086] The size of the upper end surface of the light cone part is the same as that of the constant cross-section part.

[0087] In another embodiment,

[0088] The size of the lower end surface of the light cone part depends on the optoelectronic device used.

[0089] In another embodiment,

[0090] The optoelectronic device is a silicon photomultiplier tube.

[0091] In another embodiment,

[0092] The device is used for collecting the partial discharge optical signals of GIS equipment.

[0093] In another embodiment, based on the light cone structure, the optical waveguide array disclosed by the present invention is as Figure 6 shown:

[0094] The relationship between the optical radiation flux coupled to the optical waveguide array and the light source angle is measured using a simulation model. The results show that the field of view angle of the optical waveguide array is 156.2°, and the coupling efficiency is 0.0116.

[0095] Furthermore, for the field of view angle: for the optical waveguide array, the optical radiation flux coupled to the optical waveguide is tested at different light source angles. When the radiation flux decays to less than 30% of the maximum value as the angle increases, it is considered that the effective detection ability of the optical signal is lost at this time, and the angle value when it decays to 30% of the maximum value is used as the field of view angle of the entire optical waveguide array.

[0096] Furthermore, for the coupling efficiency: on the premise that the detection end area of the optical waveguide is the same, considering the optical signals at all angles within the field of view angle, the average value of the coupled optical radiation flux at different light source angles is calculated, and the ratio of this average value to the total radiation flux emitted by the light source is used as the coupling efficiency of the optical waveguide.

[0097] The above general description of the invention involved in the present invention and the description of its specific embodiments should not be construed as limiting the technical solution of the invention. Those skilled in the art can, based on the content disclosed in the present invention, add, subtract, or combine the disclosed technical features in the above general description or / and specific embodiments (including examples) without violating the constituent elements of the involved invention, thereby forming other technical solutions within the protection scope of the present invention.

Claims

1. A discharge optical signal coupling device, characterized in that: The structural design of the device adopts a circular equal-section-light cone combined structural design.

2. The discharge light signal coupling device according to claim 1, characterized in that: Preferably, the device uses quartz as the main material.

3. The discharge optical signal coupling device according to claim 1, characterized in that: The circular equal-section-light cone combined structure design consists of two parts: an equal-section part and a light cone part.

4. The discharge light signal coupling device according to claim 3, characterized in that: The equal cross-section parts are light guides with the same interface radius.

5. The discharge light signal coupling device according to claim 3, characterized in that: The light cone portion is a light guide whose cross-sectional radius changes linearly along the axial direction.

6. The discharge light signal coupling device according to claim 3, characterized in that: The upper end surface of the light cone portion is larger, and the lower end surface is smaller.

7. The discharge light signal coupling device according to claim 6, characterized in that: The upper end surface of the light cone portion is the same size as that of the equal-section portion.

8. The discharge light signal coupling device according to claim 6, characterized in that: The size of the lower end surface of the light cone portion depends on the optoelectronic device used.

9. The discharge light signal coupling device according to claim 8, characterized in that: The photoelectric device is a silicon photomultiplier tube.

10. The discharge optical signal coupling device according to claim 1, characterized in that: The device is used for collecting local discharge optical signals of GIS equipment.

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