A partial discharge detection device and method with built-in optical fiber composite structure

Abstract

This invention discloses a partial discharge detection device and method with an embedded optical fiber composite structure. The partial discharge detection device includes a reflector disk disposed within a gas-insulated metal-enclosed switch, with the parabolic surface of the reflector disk facing the high-voltage conductor region within the gas-insulated metal-enclosed switch. An optical fiber disk is disposed on the focal plane of the parabolic surface, with the normal of the optical fiber disk parallel to the axis of symmetry of the parabolic surface. An optical fiber interference demodulation device has a sensing arm connection end and an optical fiber connector, with the sensing arm connection end connected to the optical fiber disk via the optical fiber connector. This invention utilizes the physical energy-focusing effect of parabolic reflection to amplify the originally diffuse weak sound pressure at the focal plane and compress it onto the optical fiber disk on the focal plane, thereby converting it into a phase change of the interference light with the optical fiber disk as the sensing arm. The phase-changed interference light is demodulated, and based on the demodulation result, accurate detection of weak partial discharge signals in GIS can be conveniently achieved.

Description

Technical Field

[0001] This invention relates to the field of electronic and electrical technology, and in particular to a partial discharge detection device and method with an embedded optical fiber composite structure. Background Technology

[0002] Gas-insulated metal-enclosed switchgear (GIS) is a core hub device in modern high-voltage power grids, and its internal insulation condition directly affects the safety of the grid. However, during the production, installation, and long-term operation of GIS, conductive impurities such as metal particles are inevitably generated or introduced. These particles can vibrate under a high electric field, triggering partial discharges. Continuous discharges gradually degrade the insulation performance inside the GIS, potentially leading to catastrophic insulation breakdown accidents. Therefore, effective monitoring of partial discharge signals inside the GIS is a critical maintenance task for preventing such accidents.

[0003] Currently, GIS discharge detection primarily relies on PZT sensors, which convert mechanical vibration into a voltage signal output. As an electronic component, PZT sensors suffer from limited signal-to-noise ratio in environments with strong electromagnetic interference, such as substations, where the weak electrical signal output is easily drowned out by environmental noise. Fiber optic sensors, being inherently insulated and completely immune to electromagnetic interference, overcome the shortcomings of PZT sensors. However, their large probe size and thickness prevent them from being housed within the compact cavities of GIS systems, necessitating external detection. External detection systems exhibit extremely poor ability to effectively capture early, weak partial discharge signals, resulting in a severe bottleneck in overall detection sensitivity. Summary of the Invention

[0004] The technical problem to be solved by this invention is: how to conveniently and accurately detect weak partial discharge signals in GIS.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A partial discharge detection device with an integrated optical fiber composite structure, applied to gas-insulated metal-enclosed switches, includes: A reflector is disposed inside the gas-insulated metal-enclosed switch, with the parabolic surface of the reflector facing the high-voltage conductor area inside the gas-insulated metal-enclosed switch; An optical fiber disk is disposed on the focal plane of the parabola, and the normal of the optical fiber disk is parallel to the axis of symmetry of the parabola. The fiber optic interferometric demodulation device has a sensor arm connection end and a fiber optic connector, wherein the sensor arm connection end is connected to the fiber optic disk through the fiber optic connector.

[0006] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is as follows: A partial discharge detection method with an embedded optical fiber composite structure, applied to the aforementioned partial discharge detection device with an embedded optical fiber composite structure, includes the following steps: Real-time monitoring to check whether the phase of the interference light, which uses an optical fiber disk as a sensing arm, changes; If so, it indicates that a partial discharge has occurred inside the gas-insulated metal-enclosed switch; The interference light with a phase change is demodulated, and the partial discharge situation inside the gas-insulated metal-sealed switch is obtained based on the demodulation result. If not, then re-monitor and reassess.

[0007] The beneficial effects of this invention are as follows: It provides a partial discharge detection device and method with an embedded optical fiber composite structure. A reflector and an optical fiber disk are arranged inside a gas-insulated metal-enclosed switch. The parabolic surface of the reflector faces the high-voltage conductor region inside the gas-insulated metal-enclosed switch, while the optical fiber disk is positioned at the focal plane of the parabolic surface. When partial discharge occurs inside the gas-insulated metal-enclosed switch, the physical energy-focusing effect of the parabolic reflection amplifies the originally diffuse weak sound pressure at the focal plane and compresses the optical fiber disk on the focal plane, thereby converting it into a phase change of interference light with the optical fiber disk as a sensing arm. The phase-changed interference light is demodulated, and the partial discharge situation inside the gas-insulated metal-enclosed switch is analyzed based on the demodulation result. This invention enables the acoustic energy, which is too weak to be detected due to distance attenuation, to be re-concentrated in physical space, thus overcoming the signal loss problem caused by gas attenuation. Simultaneously, the sound wave no longer needs to cross the physical boundary between gas and solid to directly act on the optical fiber, overcoming the disadvantage of low sensitivity caused by impedance mismatch, and conveniently achieving accurate detection of weak partial discharge signals in GIS. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the installation of a partial discharge detection device with a built-in optical fiber composite structure on a GIS according to the present invention; Figure 2 This is a schematic diagram of the fiber optic disk of a partial discharge detection device with a built-in fiber optic composite structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the reflector of a partial discharge detection device with a built-in optical fiber composite structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the system connection of the fiber optic interferometry demodulation device of a partial discharge detection device with a built-in fiber optic composite structure according to an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the steps of a partial discharge detection method with an embedded optical fiber composite structure according to an embodiment of the present invention.

[0009] Label Explanation: 101. Reflector disk; 102. Fiber optic disk; 103. Fiber optic interferometry demodulation device; 1031, Fiber optic connector; 1032, Reference arm; 1033, Laser; 1034, First coupler; 1035, Second coupler; 1036, Photodetector; 1037, Phase demodulation module; 1038, Isolator; 300. Gas-insulated metal-enclosed switch; 301. Cover plate; 400. Oscilloscope. Detailed Implementation

[0010] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0011] This invention is applicable to monitoring partial discharge within a gas-insulated metal-enclosed switch 300. During the production, installation, and long-term operation of the gas-insulated metal-enclosed switch 300, conductive impurities such as metal particles are inevitably generated or introduced. These particles will bounce under a high electric field, triggering partial discharge. Continuous discharge will gradually degrade the insulation performance inside the gas-insulated metal-enclosed switch 300, potentially leading to a catastrophic insulation breakdown accident.

[0012] To address this, current methods for detecting discharge in gas-insulated, metal-enclosed switches (300) primarily rely on PZT sensors. However, the weak electrical signals output by PZT sensors are easily masked by environmental noise. Fiber optic sensors, being inherently insulated and completely immune to electromagnetic interference, overcome the shortcomings of PZT sensors. However, their probes are bulky and thick, making them unsuitable for the compact internal cavity of the gas-insulated, metal-enclosed switch (300), necessitating external detection. External detection systems, however, have extremely poor ability to effectively capture early, weak partial discharge signals.

[0013] Therefore, in order to solve at least the above-mentioned problems, refer to Figures 1 to 4 This invention proposes a partial discharge detection device with a built-in optical fiber composite structure, applied to a gas-insulated metal-enclosed switch 300, comprising: A reflector 101 is disposed inside the gas-insulated metal-enclosed switch 300, with the parabolic surface of the reflector 101 facing the high-voltage conductor area inside the gas-insulated metal-enclosed switch 300. The fiber optic disk 102 is positioned on the focal plane of the parabola, and the normal of the fiber optic disk 102 is parallel to the axis of symmetry of the parabola. The fiber optic interferometric demodulation device 103 has a sensor arm connection end and a fiber optic connector 1031. The sensor arm connection end is connected to the fiber optic disk 102 through the fiber optic connector 1031.

[0014] like Figure 3As shown, the reflector 101 is generally dish-shaped or mesh-shaped, and its inner surface is precisely machined into a parabolic shape, with the parabolic opening facing the high-voltage conductor region inside the gas-insulated metal-enclosed switch 300. Traditional single-point piezoelectric probes, due to their limited sensing area, cannot fully absorb the energy of the focal spot and therefore cannot capture the weak acoustic signals generated after partial discharge. To address this, the present invention uses an optical fiber disk 102 and a reflector 101 in conjunction to construct a collaborative working mechanism of acoustic parabolic convergence and optical spatial integration, as detailed below: According to acoustic theory, the reflection coefficient R0 of ultrasound at the interface between different media depends on the characteristic acoustic impedance of the two media, and its expression is:

[0015] in, These represent the density of the first medium and the velocity of the ultrasound wave in the first medium, respectively. The characteristic acoustic impedance of the first type of medium is represented as follows: These represent the density of the second medium and the velocity of the ultrasound wave in the second medium, respectively. This is represented as the characteristic acoustic impedance of the second type of medium.

[0016] Therefore, at the interface between the SF6 gas inside the gas-insulated metal-enclosed switch 300 and the metal reflector 101, the acoustic impedance of the metal (such as aluminum alloy or stainless steel) is much greater than that of the SF6 gas, which makes the reflection coefficient R0 at the interface close to 1 (i.e., approximately 100% reflection). This invention cleverly transforms the interface reflection barrier of external detection into the energy reflection advantage of internal detection. By using the reflector 101 as an acoustic hard boundary, it intercepts the partial discharge ultrasonic spherical waves that originally diverged in all directions and reflects and converges them towards the focal point of the disc.

[0017] Furthermore, to achieve optimal sound wave focusing, the geometry of the reflector 101 follows a parabolic equation:

[0018] In the formula, 'a' is the focal length (i.e., the distance from the vertex of the parabola to the focal point F). Meanwhile, to maximize the acoustic energy collection cross-sectional area, the opening radius 'r' of the reflector 101 and its depth 'h' satisfy the following geometric relationship model:

[0019] Where p=2a is twice the focal length. When the ultrasonic waves (approximately plane waves or large-radius spherical waves) generated by partial discharge enter the parabolic surface of the reflector, all parallel or nearly parallel sound beams will be reflected and converge to the focal point F and its vicinity. Theoretically, the maximum geometric sound pressure gain Γgmax brought about by parabolic reflection is proportional to the opening size of reflector 101 and the wavelength λ of the sound wave, and can be expressed as:

[0020] Through the parabolic surface, the weak ultrasonic energy that would otherwise be severely attenuated in SF6 gas due to molecular collisions and thermal conduction is forcibly concentrated in physical space, resulting in a significant increase in sound pressure level in the focal region and its reflection path by tens or even hundreds of times.

[0021] The fiber optic disk 102 includes a support member and a single-mode fiber. The support member is disposed on a parabolic surface, with its support surface corresponding to the focal plane of the parabolic surface, and the normal of the support surface being parallel to the axis of symmetry of the parabolic surface. The single-mode fiber is arranged in a horizontal spiral disk shape on the support surface of the support member and is connected to the fiber optic connector 1031.

[0022] like Figure 1 and Figure 2 As shown, the single-mode fiber is tightly coiled from the center outwards on the support surface of the support member, forming a spiral structure resembling a mosquito coil. The center point of the entire single-mode fiber is on the axis of symmetry of the parabolic surface of the reflector disk 101, meaning the entire surface of the fiber disk 102 faces the parabolic surface. The support member can be a lightweight planar skeleton, such as an extremely thin resin cross, positioned at the focal plane of the parabolic surface of the reflector disk 101. Alternatively, the support member can be a ring-shaped thin film, etc.

[0023] The diameter of the fiber optic disk 102 is designed to cover the "acoustic focal spot" formed by the parabolic focusing energy. When the focused high-intensity ultrasonic wave strikes the fiber optic disk 102, the dense spiral arrangement of the optical fibers causes microscopic deformation of the entire disk, resulting in a phase shift of the transmitted light wave inside the fiber. Therefore, by demodulating the phase-changed interference light, and based on the demodulation results, the partial discharge within the gas-insulated metal-enclosed switch 300 can be analyzed, facilitating the accurate detection of weak partial discharge signals from the gas-insulated metal-enclosed switch 300.

[0024] In some embodiments, to achieve internal integration without altering the core high-voltage structure within the gas-insulated metal-enclosed switch 300, the reflector 101 is directly mounted on the inner side of the cover plate 301 of the gas-insulated metal-enclosed switch 300 via bolt fastening or epoxy casting. The fiber optic connector 1031 passes through the cover plate 301, and a seal is provided between the fiber optic connector 1031 and the cover plate 301. One end of the fiber optic disc 102 extends to the outside via the fiber optic connector 1031. This design achieves internal energy focusing while perfectly ensuring the airtightness of the gas-insulated metal-enclosed switch 300 using the existing cover plate 301. The fiber optic connector 1031 can be either a pressure-sealed flange connector or a bolt-type fiber optic connector 1031. When using a bolt-type fiber optic connector 1031, the connector 1031 includes a sealing plug. Using an epoxy resin vacuum casting process, the portion of the fiber optic disc 102 near the end used to connect to the fiber optic interferometry demodulation device 103 is seamlessly embedded and cured inside the metal bolt plug. The sealing element can be a sealing ring, etc. During installation, multiple O-rings are threaded together and tightly fixed to the pre-drilled holes in the cover plate 301, ensuring that while extracting the optical signal, the extremely high airtightness and insulation safety requirements of the gas-insulated metal-enclosed switch 300 are maintained.

[0025] In some embodiments, such as Figure 4 As shown, the fiber optic interferometric demodulation device 103 is composed of a Mach-Zehnder (MZ) fiber optic interferometric demodulation optical path, including a sensing arm, an isolator 1038, a reference arm 1032, a laser 1033, a first coupler 1034, a second coupler 1035, a photodetector 1036, and a phase demodulation module 1037. The fiber optic disk 102 serves as the sensing arm; the laser 1033 is an ultra-narrow linewidth laser. Laser 1033 is connected to the input of first coupler 1034 via isolator 1038. The two outputs of first coupler 1034 are connected to reference arm 1032 and fiber disk 102, respectively. Fiber disk 102 and reference arm 1032 are connected to the input of second coupler 1035, respectively. The output of second coupler 1035 is connected to photodetector 1036. Photodetector 1036 is connected to phase demodulation module 1037. The processing result of fiber optic interferometry demodulation device 103 can be viewed using oscilloscope 400.

[0026] In use, the fiber optic interferometry demodulation device 103 is installed inside the external control box of the gas-insulated metal-enclosed switch 300. The fiber optic disk 102 serves as the sensing arm; a section of fiber optic cable in a constant state is installed inside the external control box as the reference arm 1032. The light emitted by the laser 1033 is split into two beams by the first coupler 1034, which enter the sensing arm and the reference arm 1032 respectively. When a partial discharge occurs inside the gas-insulated metal-enclosed switch 300, the acoustic wave is focused by the reflector 101 and squeezes the fiber optic disk 102 on the focal plane, causing a huge phase shift in the sensing arm. The two beams of light interfere at the second coupler 1035.

[0027] Furthermore, both the reflector 101 and the fiber optic disk 102 of this invention are passive, non-conductive, purely physical / optical devices. The optical fiber itself is made of quartz, which has excellent insulation properties. When placed inside the gas-insulated metal-enclosed switch 300 cavity, it is not only completely immune to strong electromagnetic interference at the substation site, but also does not introduce any electrical short circuit or tip discharge risk, ensuring the absolute safety of the gas-insulated metal-enclosed switch 300 itself.

[0028] Reference Figure 4 and Figure 5 Another embodiment of the present invention provides a partial discharge detection method 200 with an embedded optical fiber composite structure, applied to the aforementioned partial discharge detection device 100 with an embedded optical fiber composite structure, comprising the following steps: In step 202, the phase of the interference light using the fiber optic disk 102 as the sensing arm is monitored in real time to see if it changes.

[0029] In this embodiment, combined with Figure 4 As shown, the two beams of light from the laser 1033 are transmitted to the fiber disk 102 and the reference arm 1032 respectively via the first coupler 1034; the beams transmitted through the fiber disk 102 and the beams transmitted through the reference arm 1032 are controlled to interfere with each other at the second coupler 1035 to obtain interference light.

[0030] If yes in step 204, it indicates that a partial discharge has occurred inside the gas-insulated metal-sealed switch 300. The acoustic signal of the partial discharge is reflected by the reflector 101 and acts on the fiber optic disk 102, causing a change in the size of the fiber optic disk 102, which in turn causes a phase change in the interference light.

[0031] Based on the total length of the fiber disk 102 and the spatial integration of the acoustic field at the focal plane of the reflector disk 101 along the fiber path of the fiber disk 102, the total phase modulation of the interfering light is obtained, as shown below:

[0032] In the formula, n is the refractive index of the fiber core; λ LLet λ be the laser wavelength, ξ be the equivalent acousto-optic response coefficient of the optical fiber material, and P(l) be the transient high-intensity sound pressure distributed at the l-th segment of the optical fiber on the focal plane. Thus, in the aforementioned partial discharge detection device 100, by winding the optical fiber into a disc shape, an effective arrangement of tens or even hundreds of meters of optical fiber is achieved. The more turns the optical fiber has, the longer the effective integration length L, the greater the cumulative shift of the optical phase, and the greater the phase change.

[0033] When a partial discharge occurs inside the gas-insulated metal-enclosed switch 300, the sound wave is focused by the metal disk and squeezes the fiber disk 102 on the focal plane, causing a huge phase shift in the sensing arm; the two beams interfere at the output coupler, and the AC component U of the output interference light signal can be expressed as:

[0034] In the formula, U0 is the amplitude of the AC component of the interference optical signal; f0 is the frequency shift amount of the acousto-optic modulator; This represents the change in the phase of the interferometric light caused by variations in the length, refractive index, and diameter of the sensing fiber. Let t represent the initial phase of the interference optical signal, and t represent the time variable.

[0035] For acoustic emission detection, the changes in the refractive index and diameter of the sensing fiber are usually small, and the phase change of the interference light is mainly caused by the change in the length of the fiber disk 102. It can be represented as:

[0036] in, This indicates the change in the length of the fiber optic disk 102; This indicates the wavelength of the laser.

[0037] In step 206, the interference light with a phase change is demodulated. Based on the demodulation result, the partial discharge situation inside the gas-insulated metal-sealed switch 300 is analyzed. If not, the monitoring and judgment are repeated.

[0038] As can be seen from equation (7), when the acoustic signal generated by the partial discharge inside the gas-insulated metal-enclosed switch 300 acts on the sensing optical fiber, causing a change in ΔL, it will lead to a change. The internal discharge condition of the gas-insulated metal-enclosed switch 300 can be reflected by demodulating the phase of the interference optical signal.

[0039] Combination Figure 4 As shown, demodulating the interference light with a phase change specifically involves controlling the photodetector 1036 to convert the interference light with a phase change into an electrical signal, and using the phase demodulation module 1037 to demodulate the electrical signal.

[0040] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A partial discharge detection device with a built-in optical fiber composite structure, applied to gas-insulated metal-enclosed switches, characterized in that, include: A reflector is disposed inside the gas-insulated metal-enclosed switch, with the parabolic surface of the reflector facing the high-voltage conductor area inside the gas-insulated metal-enclosed switch; An optical fiber disk is disposed on the focal plane of the parabola, and the normal of the optical fiber disk is parallel to the axis of symmetry of the parabola. The fiber optic interferometric demodulation device has a sensor arm connection end and a fiber optic connector, wherein the sensor arm connection end is connected to the fiber optic disk through the fiber optic connector.

2. The partial discharge detection device with an embedded optical fiber composite structure according to claim 1, characterized in that, The fiber optic disk includes: A support member is disposed on the parabolic surface, wherein the support surface of the support member corresponds to the focal plane of the parabolic surface, and the normal of the support surface is parallel to the axis of symmetry of the parabolic surface. A single-mode optical fiber is arranged in a horizontal spiral disk on the support surface of the support member, and the single-mode optical fiber is connected to the optical fiber connector.

3. The partial discharge detection device with an embedded optical fiber composite structure according to claim 1, characterized in that, The reflector is disposed on the inward-facing side of the cover plate of the gas-insulated metal-sealed switch; The fiber optic connector passes through the cover plate, and a sealing element is provided between the fiber optic connector and the cover plate.

4. The partial discharge detection device with an embedded optical fiber composite structure according to claim 3, characterized in that, The fiber optic connector includes a sealing plug; The portion of the optical fiber disk near the end used to connect the optical fiber interference demodulation device is seamlessly embedded in the sealing plug body, and the sealing plug body is assembled onto the reserved hole of the cover plate through the sealing element.

5. The partial discharge detection device with an embedded optical fiber composite structure according to claim 1, characterized in that, The fiber optic interferometric demodulation device includes a reference arm, a laser, a first coupler, a second coupler, a photodetector, and a phase demodulation module. The laser is connected to the input of the first coupler, the two outputs of the first coupler are connected to the reference arm and the fiber optic disk, respectively, the fiber optic disk and the reference arm are connected to the input of the second coupler, the output of the second coupler is connected to the photodetector, and the photodetector is connected to the phase demodulation module.

6. The partial discharge detection device with an embedded optical fiber composite structure according to claim 2, characterized in that, The support component is a lightweight planar skeleton.

7. A method for detecting partial discharge using a built-in optical fiber composite structure, applied to a partial discharge detection device with a built-in optical fiber composite structure as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Real-time monitoring to check whether the phase of the interference light, which uses an optical fiber disk as a sensing arm, changes; If so, it indicates that a partial discharge has occurred inside the gas-insulated metal-enclosed switch; The interference light whose phase has changed is demodulated, and the partial discharge situation inside the gas-insulated metal-sealed switch is obtained based on the demodulation result. If not, the monitoring and judgment are repeated.

8. The partial discharge detection method with an embedded optical fiber composite structure according to claim 7, characterized in that, The real-time monitoring of whether the phase of the interference light, which uses an optical fiber disk as a sensing arm, changes includes: The two beams controlling the laser are transmitted to the fiber optic disk and the reference arm respectively via the first coupler; The interference light is obtained by controlling the interference between the light beam transmitted through the fiber optic disk and the light beam transmitted through the reference arm at the second coupler.

9. The partial discharge detection method with an embedded optical fiber composite structure according to claim 7, characterized in that, The demodulation of the interference light whose phase has changed specifically involves: The photodetector is controlled to convert the phase-changed interference light into an electrical signal, and the electrical signal is demodulated.

10. The partial discharge detection method with an embedded optical fiber composite structure according to claim 7, characterized in that, Also includes: The total phase modulation amount of the interference light is obtained based on the total length of the optical fiber disk and the spatial integration of the acoustic field of the focal plane of the reflector disk along the optical fiber path of the optical fiber disk.

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