Gis built-in installation structure and measurement method of fiber-optic current sensor

Abstract

GIS built-in installation structure and measurement method of optical fiber current sensor, the device includes a built-in GIS basin insulator triangular plate mounting base, and a number of consistent polarization maintaining fiber ring and signal transmission unit. The method comprises: 1) using external light source to generate light signal; 2) using polarizer to convert light signal into linearly polarized light; 3) transmitting linearly polarized light through signal transmission unit to polarization maintaining fiber ring, conductor flow in GIS device generates annular magnetic field, polarization maintaining fiber ring under the action of magneto-optic effect makes Faraday rotation of light signal, and the light signal after Faraday rotation is obtained; 4) using coupling analyzer to convert the light signal after Faraday rotation from polarization state change to light intensity change, and the light intensity signal is obtained; 5) using photoelectric detector to convert light intensity signal into electric signal, and the real-time current value of GIS device internal conductor is obtained, and displayed through current data display. The application realizes efficient and reliable integration of sensor and GIS device.

Description

Technical Field

[0001] This invention relates to the field of power equipment sensing and measurement technology, specifically to a GIS-embedded installation structure and measurement method for fiber optic current sensors. Background Technology

[0002] Current monitoring in gas-insulated switchgear (GIS) is a core component ensuring the safe and stable operation of power systems. Traditional electromagnetic current transformers, due to inherent defects such as magnetic saturation, ferroresonance, and small dynamic range, can no longer meet the high-precision and high-reliability requirements of modern power systems for current monitoring. Fiber optic current sensors, with their advantages of strong anti-electromagnetic interference capability, large dynamic range, excellent insulation performance, and compact size, have become an ideal alternative for GIS current monitoring.

[0003] However, existing fiber optic current sensors face key technical bottlenecks in their integration and installation design with GIS equipment, particularly in their compatibility with the core component of GIS—the basin-type insulator.

[0004] 1. Unreasonable installation structure: Most solutions adopt external installation, which requires additional installation interfaces to be opened in the GIS housing. This not only compromises the overall sealing of the equipment and increases the risk of SF6 gas leakage, but also makes it susceptible to interference from the external electromagnetic environment. A few built-in solutions simply attach the sensor components to the surface of the basin insulator without achieving integrated fusion. This results in components being prone to loosening, a high risk of gap leakage, and occupies extra space inside the GIS.

[0005] 2. Insufficient insulation and stability: In some built-in solutions, the sensor base and the basin insulator are connected with epoxy resins of different materials or non-homologous materials. Gaps are prone to appear at the joint surface, causing local electric field distortion and increasing the risk of insulation failure. At the same time, the fiber optic selection is not optimized for the "built-in base" scenario, and ordinary optical fibers are mostly used. The polarization state is easily interfered with during optical signal transmission, resulting in poor sensing stability. Summary of the Invention

[0006] The purpose of this invention is to provide a GIS-embedded installation structure and measurement method for an optical fiber current sensor.

[0007] The technical means adopted to achieve the technical objective of this invention are as follows: the GIS built-in installation structure of the fiber optic current sensor includes a triangular plate mounting base built into the GIS basin insulator, and a number of identical polarization-maintaining fiber optic rings and signal transmission units.

[0008] The triangular plate mounting base has several polarization-maintaining fiber ring mounting slots on its surface, which are the same number as the polarization-maintaining fiber rings, and a conductor mounting hole is provided at the center of the polarization-maintaining fiber ring mounting slot.

[0009] The position of the conductor mounting hole corresponds to the position of the conductor reserved hole on the GIS basin insulator.

[0010] The number of conductor mounting holes corresponds to the number of conductors inside the GIS equipment.

[0011] One side of the polarization-maintaining fiber ring mounting slot is provided with a fiber lead-out channel, which extends to the corner of the triangular plate mounting base.

[0012] The corner of the triangular plate mounting base is provided with a flange connection channel.

[0013] The triangular plate mounting base is fixed together with the GIS basin insulator.

[0014] The conductors inside the GIS equipment pass through the conductor pre-drilled holes of the GIS basin insulator and the conductor mounting holes of the triangular plate mounting base.

[0015] The polarization-maintaining fiber is wound around the polarization-maintaining fiber ring mounting slot, and the central axis of the polarization-maintaining fiber ring is collinear with the conductor axis inside the GIS equipment.

[0016] The signal transmission unit is installed in the optical fiber lead-out channel, with one end of the signal transmission unit connected to the polarization-maintaining optical fiber ring and the other end connected to external devices through a flange connection channel.

[0017] When using the structure for measurement, the optical signal generated by the external device is transmitted to the polarization-maintaining fiber ring through the signal transmission unit. When the conductor inside the GIS device flows, it generates a ring magnetic field. Under the action of magneto-optical effect, the polarization-maintaining fiber ring causes the optical signal to undergo Faraday rotation. The optical signal after Faraday rotation is transmitted to the external device through the signal transmission unit, and finally the real-time current value of the conductor inside the GIS device is obtained.

[0018] Furthermore, the material used for the triangular plate mounting base includes epoxy resin.

[0019] Furthermore, the triangular plate mounting base is fixed to the GIS pot-type insulator through a secondary casting process.

[0020] The secondary casting process uses epoxy resin as the casting material.

[0021] The triangular plate mounting base is provided with a drainage hole for secondary pouring, and the drainage hole is located inside the optical fiber outlet channel.

[0022] Furthermore, the signal transmission unit includes a special armored optical fiber.

[0023] The special armored optical fiber comprises a three-layer structure, consisting of an inner core optical fiber, a glass fiber reinforced plastic armor layer, and a polytetrafluoroethylene outer sheath, from the inside out.

[0024] The inner optical fiber is used to transmit optical signals.

[0025] The glass fiber reinforced plastic armor layer is used to provide mechanical protection and avoid electromagnetic interference.

[0026] The polytetrafluoroethylene outer sheath is used to adapt to the internal environment of GIS equipment.

[0027] The method of connecting special armored optical fiber with polarization-maintaining optical fiber ring is to use fusion welding to connect the inner core optical fiber and the polarization-maintaining optical fiber ring together.

[0028] Furthermore, the polarization-maintaining fiber ring mounting groove is also provided with a fiber positioning boss.

[0029] The optical fiber lead-out channel is equipped with an annular anti-slip groove.

[0030] Furthermore, the polarization-maintaining fiber ring is made of polarization-maintaining fiber containing erbium.

[0031] The outer diameter of the polarization-maintaining fiber ring is adapted to the inner diameter of the polarization-maintaining fiber ring mounting slot.

[0032] Furthermore, the mounting structure is sealed by applying silicone rubber sealant.

[0033] Furthermore, the mounting structure also includes a fixing block.

[0034] The fixing block is used to fix the polarization-maintaining fiber ring.

[0035] The fixing block is made of epoxy resin.

[0036] Furthermore, the external devices include an external light source, a polarizer, a coupled analyzer, a photodetector, and a current data display.

[0037] The external light source is used to generate light signals.

[0038] The polarizer is used to convert optical signals into linearly polarized light.

[0039] Linearly polarized light is transmitted to the polarization-maintaining fiber ring through the signal transmission unit.

[0040] The coupled analyzer is used to convert the change in polarization state of the light signal after Faraday rotation into a change in light intensity, thereby obtaining a light intensity signal.

[0041] The photodetector is used to convert light intensity signals into electrical signals to obtain the real-time current value of the conductors inside the GIS equipment.

[0042] The current data display is used to show the real-time current value of the conductors inside the GIS equipment.

[0043] A method for measurement using the above structure includes the following steps:

[0044] 1) Use an external light source to generate light signals.

[0045] 2) Use a polarizer to convert the optical signal into linearly polarized light.

[0046] 3) The linearly polarized light is transmitted to the polarization-maintaining fiber ring through the signal transmission unit. When the conductor inside the GIS equipment flows, a ring magnetic field is generated. Under the action of magneto-optical effect, the polarization-maintaining fiber ring causes the optical signal to undergo Faraday rotation, resulting in an optical signal that has undergone Faraday rotation.

[0047] 4) The light signal that has undergone Faraday rotation is transmitted to the coupled analyzer through the signal transmission unit, and the coupled analyzer is used to convert the change in polarization state of the light signal that has undergone Faraday rotation into a change in light intensity, so as to obtain the light intensity signal.

[0048] 5) Use a photodetector to convert light intensity signals into electrical signals to obtain the real-time current value of the conductors inside the GIS equipment, and display it through a current data display.

[0049] The technical effects of this invention are undeniable. The installation structure of this invention, in which an epoxy resin triangular plate is completely integrated into a GIS basin-type insulator, combined with high-performance polarization-maintaining optical fiber, overcomes the bottlenecks of existing technologies from three dimensions: structural integration, material homogeneity, and optical fiber compatibility, achieving efficient and reliable integration of sensors and GIS equipment. This invention has the following significant beneficial effects:

[0050] 1. High degree of structural integration and excellent sealing: The epoxy resin triangular plate base is completely embedded in the GIS pot-type insulator. Through a secondary casting process, it is fused with the same epoxy resin as the insulator body, resulting in no splicing gaps and completely eliminating the "extra interfaces" or "fitting gaps" caused by traditional installation methods. Gas leak risk, leak rate It meets the sealing performance requirements of GB / T 11022-2020 for GIS; at the same time, the integrated structure prevents the base from loosening and improves long-term operational stability.

[0051] 2. Reliable insulation performance, suitable for high-voltage environments. The epoxy resin triangular plate base and the pot-type insulator use the same EPGC201 epoxy resin, with a bonding strength of ≥15MPa and an overall volume resistivity of ≥15MPa. With a 1-minute power frequency withstand voltage ≥100kV and a lightning impulse withstand voltage ≥250kV, it can withstand the internal high-voltage environment of 110kV-500kV GIS equipment, avoid insulation faults caused by local electric field distortion, and comply with the requirements of GB / T 22389-2018 for the insulation performance of high-voltage equipment.

[0052] 3. Strong sensing stability and adaptability to complex working conditions: The fiber ring adopts a high extinction ratio (≥25dB) polarization-maintaining fiber ring, and the fiber ring is built into the basin-type insulator along with the epoxy resin triangular plate, which is in a stable internal environment, effectively reducing the interference of external vibration and temperature fluctuation on the polarization state of the optical signal. At the same time, the glass fiber reinforced plastic (FRP) armor layer of the special armored fiber avoids the electromagnetic interference of metals, ensuring that the optical signal transmission loss is ≤0.1dB, thus ensuring the stability and accuracy of the sensing data.

[0053] 4. Excellent engineering adaptability; no additional modifications are needed to the internal space of the 110kV-500kV GIS basin insulator, which is designed to fit the dimensions and structure of the epoxy resin triangular plate base. No modifications are required to the existing GIS shell or other components, and it can be directly integrated into new GIS equipment or used for upgrading old equipment. The installation process is seamlessly integrated with the basin insulator production process, without the need for additional complex procedures, and it is suitable for large-scale engineering applications. Attached Figure Description

[0054] Figure 1 This is a front view of the overall assembly of the mounting structure of the present invention;

[0055] Figure 2 This is a schematic diagram of the overall assembly back of the mounting structure of the present invention;

[0056] Figure 3 The figures provided are detailed diagrams of the present invention.

[0057] Figure 4 This is a schematic diagram of the I-structure of the test system;

[0058] Figure 5 This is a schematic diagram of the test system II structure;

[0059] In the diagram: 1. GIS basin insulator; 2. Triangular plate mounting base; 3. Drain hole; 4. Conductor mounting hole; 5. Polarization-maintaining fiber ring embedding groove; 6. Flange connection channel; 7. Fiber optic lead-out channel; 8. External light source; 9. Polarizer; 10. Polarization-maintaining fiber ring; 11. Coupler analyzer; 12. Photodetector; 13. Current data display; 14. Conductor reserved hole. Detailed Implementation

[0060] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0061] Example 1:

[0062] See Figures 1 to 5 The GIS-embedded installation structure of the fiber optic current sensor includes a triangular plate mounting base 2 built into the GIS basin insulator 1, as well as a number of identical polarization-maintaining fiber optic rings 10 and signal transmission units.

[0063] The triangular plate mounting base 2 has a number of polarization-maintaining fiber ring embedding slots 5, which are the same number as the polarization-maintaining fiber rings 10, and a conductor mounting hole 4 is provided at the center of the polarization-maintaining fiber ring embedding slot 5.

[0064] The conductor mounting hole 4 corresponds to the position of the conductor reserved hole 14 on the GIS basin insulator 1.

[0065] The number of conductor mounting holes 4 is consistent with the number of conductors inside the GIS equipment.

[0066] The polarization-maintaining fiber ring mounting slot 5 has a fiber optic lead-out channel 7 on one side, and the fiber optic lead-out channel 7 extends to the corner of the triangular plate mounting base 2.

[0067] The corner of the triangular plate mounting base 2 is provided with a flange connection channel 6.

[0068] The triangular plate mounting base 2 is fixed together with the GIS basin insulator 1.

[0069] The conductors inside the GIS equipment pass through the conductor reserved hole 14 of the GIS basin insulator 1 and the conductor mounting hole 4 of the triangular plate mounting base 2.

[0070] The polarization-maintaining fiber ring 10 is wound inside the polarization-maintaining fiber ring mounting groove 5, and the central axis of the polarization-maintaining fiber ring 10 is collinear with the conductor axis inside the GIS equipment.

[0071] The signal transmission unit is installed in the optical fiber lead-out channel 7, and one end of the signal transmission unit is connected to the polarization-maintaining optical fiber ring 10, while the other end is connected to external devices through the flange connection channel 6.

[0072] When using the structure for measurement, the optical signal generated by the external device is transmitted to the polarization-maintaining fiber ring 10 through the signal transmission unit. When the conductor inside the GIS device flows, a ring magnetic field is generated. Under the action of magneto-optical effect, the polarization-maintaining fiber ring 10 causes the optical signal to undergo Faraday rotation. The optical signal after Faraday rotation is transmitted to the external device through the signal transmission unit, and finally the real-time current value of the conductor inside the GIS device is obtained.

[0073] Example 2:

[0074] The GIS built-in installation structure of the fiber optic current sensor is described in Example 1. Furthermore, the material used for the triangular plate mounting base 2 includes epoxy resin.

[0075] Example 3:

[0076] The GIS built-in installation structure of the fiber optic current sensor is described in any one of Embodiments 1 and 2. Furthermore, the triangular plate mounting base 2 is fixed to the GIS basin insulator 1 through a secondary casting process.

[0077] The secondary casting process uses epoxy resin as the casting material.

[0078] The triangular plate mounting base 2 is provided with a drainage hole 3 for secondary pouring, and the drainage hole 3 is located in the optical fiber lead-out channel 7.

[0079] Example 4:

[0080] The GIS built-in installation structure of the fiber optic current sensor, the main technical contents of which are described in any one of Embodiments 1 to 3, further wherein the signal transmission unit includes a special armored optical fiber.

[0081] The special armored optical fiber comprises a three-layer structure, consisting of an inner core optical fiber, a glass fiber reinforced plastic armor layer, and a polytetrafluoroethylene outer sheath, from the inside out.

[0082] The inner optical fiber is used to transmit optical signals.

[0083] The glass fiber reinforced plastic armor layer is used to provide mechanical protection and avoid electromagnetic interference.

[0084] The polytetrafluoroethylene outer sheath is used to adapt to the internal environment of GIS equipment.

[0085] The method of connecting the special armored optical fiber to the polarization-maintaining optical fiber ring 10 is to use fusion welding to connect the inner core optical fiber to the polarization-maintaining optical fiber ring 10.

[0086] Example 5:

[0087] The GIS built-in installation structure of the fiber optic current sensor is described in any one of embodiments 1 to 4. Furthermore, the polarization-maintaining fiber ring mounting groove 5 is also provided with a fiber positioning boss.

[0088] The optical fiber lead-out channel 7 is provided with an annular anti-slip groove.

[0089] Example 6:

[0090] The GIS built-in installation structure of the fiber optic current sensor is described in any one of embodiments 1 to 5. Furthermore, the polarization-maintaining fiber ring 10 is made of polarization-maintaining fiber containing erbium.

[0091] The outer diameter of the polarization-maintaining fiber ring 10 is adapted to the inner diameter of the polarization-maintaining fiber ring mounting groove 5.

[0092] Example 7:

[0093] The GIS built-in installation structure for the fiber optic current sensor, the main technical contents of which are described in any one of Embodiments 1 to 6, further wherein the installation structure is sealed by applying silicone rubber sealant.

[0094] Example 8:

[0095] The GIS built-in installation structure for the fiber optic current sensor mainly includes any one of embodiments 1 to 7. Furthermore, the installation structure also includes a fixing block.

[0096] The fixing block is used to fix the polarization-maintaining fiber ring 10.

[0097] The fixing block is made of epoxy resin.

[0098] Example 9:

[0099] The GIS built-in installation structure of the fiber optic current sensor is described in any one of embodiments 1 to 8. Further, the external devices include an external light source 8, a polarizer 9, a coupling analyzer 11, a photodetector 12, and a current data display 13.

[0100] The external light source 8 is used to generate light signals.

[0101] The polarizer 9 is used to convert optical signals into linearly polarized light.

[0102] Linearly polarized light is transmitted to polarization-maintaining fiber ring 10 through signal transmission unit.

[0103] The coupled analyzer 11 is used to convert the light signal that has undergone Faraday rotation from a change in polarization state to a change in light intensity, thereby obtaining a light intensity signal.

[0104] The photodetector 12 is used to convert light intensity signals into electrical signals to obtain the real-time current value of the conductor inside the GIS equipment.

[0105] The current data display 13 is used to display the real-time current value of the conductors inside the GIS equipment.

[0106] Example 10:

[0107] A method for measuring the structure described in any one of embodiments 1 to 9 includes the following steps:

[0108] 1) Use an external light source to generate light signals.

[0109] 2) Use a polarizer to convert the optical signal into linearly polarized light.

[0110] 3) The linearly polarized light is transmitted to the polarization-maintaining fiber ring through the signal transmission unit. When the conductor inside the GIS equipment flows, a ring magnetic field is generated. Under the action of magneto-optical effect, the polarization-maintaining fiber ring causes the optical signal to undergo Faraday rotation, resulting in an optical signal that has undergone Faraday rotation.

[0111] 4) The light signal that has undergone Faraday rotation is transmitted to the coupled analyzer through the signal transmission unit, and the coupled analyzer is used to convert the change in polarization state of the light signal that has undergone Faraday rotation into a change in light intensity, so as to obtain the light intensity signal.

[0112] 5) Use a photodetector to convert light intensity signals into electrical signals to obtain the real-time current value of the conductors inside the GIS equipment, and display it through a current data display.

[0113] Example 11:

[0114] See Figures 1 to 5 The GIS-embedded installation structure and measurement method of fiber optic current sensors, the main technical contents of which include:

[0115] An embedded installation structure for a fiber optic current sensor in a GIS includes an epoxy resin triangular mounting base, a polarization-maintaining fiber ring, and a signal lead-out unit. The epoxy resin triangular mounting base is an isosceles triangular insulating component with a side length of 478 mm and a thickness of 30 mm. It is molded from high-temperature resistant epoxy resin and has an annular polarization-maintaining fiber ring embedding groove and multiple axial fiber lead-out holes on its surface. It is integrally formed with the epoxy resin layer of the GIS basin insulator body through a secondary casting process. The polarization-maintaining fiber is wound around the polarization-maintaining fiber ring embedding groove, and its central axis is collinear with the axis of the internal conductor of the GIS. The signal lead-out unit includes multiple special armored optical fibers. One end of each special armored optical fiber is connected to the polarization-maintaining fiber ring, and the other end extends through the fiber lead-out hole to the outside of the GIS, connecting with polarizers, couplers, and other components located outside the GIS.

[0116] The epoxy resin triangular plate mounting base is molded from EPGC201 high-temperature resistant epoxy resin, with 30%-40% quartz powder filler added. After molding, it is integrally embedded into the prefabricated cavity of the GIS basin insulator. It is then fused with the basin insulator body using the same EPGC201 epoxy resin through a secondary casting process. After curing, the bonding strength between the epoxy resin triangular plate base and the basin insulator is ≥15MPa, and the overall structural volume resistivity is... The fiber optic cable withstand voltage is ≥100kV for 1 minute and ≥250kV for lightning impulse withstand voltage. The polarization-maintaining fiber ring has an inner diameter of 83mm, a depth of 5mm, and a width of 25mm. The groove is equipped with a 1mm deep fiber positioning boss. Each fiber lead-out hole has a diameter of 3mm and three annular anti-slip grooves on the inner wall. The lead-out hole is precisely aligned with the reserved channel of the basin-type insulator to ensure that the special armored fiber is passed out without offset.

[0117] The polarization-maintaining fiber ring is made of erbium-doped polarization-maintaining fiber with 80-120 turns, a fiber diameter of 1.0-1.5mm, an extinction ratio ≥25dB, and polarization crosstalk ≤-20dB / km. The outer diameter of the polarization-maintaining fiber ring is precisely matched with the inner diameter of the polarization-maintaining fiber ring mounting slot. The whole ring is built into the basin-type insulator along with the epoxy resin triangular plate base. The two ends of the polarization-maintaining fiber ring are firmly fixed to the epoxy resin triangular plate base by epoxy resin fixing blocks to prevent displacement caused by vibration.

[0118] The special armored optical fiber comprises an inner optical fiber, a glass fiber reinforced plastic (FRP) armor layer, and a polytetrafluoroethylene (PTFE) outer sheath. The inner optical fiber and the polarization-maintaining fiber ring are fused together, with a welding loss ≤0.1dB. The FRP armor layer thickness is 0.5-0.8mm, and the PTFE outer sheath thickness is 0.3-0.5mm. The special armored optical fiber exits through the lead-out hole of the epoxy resin triangular plate base built into the basin insulator, with a bending radius ≥40mm, a temperature resistance range of -40℃ to 130℃, and an insulation resistance of [missing information]. .

[0119] A fiber optic current sensor GIS built-in measurement method based on the above installation structure includes the following steps: (1) Fusion of epoxy resin triangular plate base and secondary casting: embedding the epoxy resin triangular plate mounting base into the prefabricated cavity of the GIS basin insulator, and using the secondary casting process to integrally form the epoxy resin base and the epoxy resin layer of the basin insulator body, so that the epoxy resin triangular plate is completely built into the basin insulator; (2) Assembly of polarization-maintaining fiber ring: winding and fixing the polarization-maintaining fiber ring in the polarization-maintaining fiber ring mounting groove of the epoxy resin triangular plate base, and connecting the polarization-maintaining fiber ring to the polarizer and coupler outside the GIS through special armored fiber; (3) Signal acquisition: the 1550nm laser outside the GIS emits linearly polarized light, which is transmitted to the polarization-maintaining fiber ring built into the basin insulator through the polarizer and special armored fiber; When current flows through the internal conductor, a ring magnetic field is generated. Under the action of magneto-optical effect, the polarization-maintaining fiber ring causes the linearly polarized light to undergo Faraday rotation. The rotation angle is proportional to the conductor current. (4) Signal processing and output: The linearly polarized light after Faraday rotation is transmitted to the coupler, analyzer and photodetector outside the GIS through a special armored fiber. After being converted into an electrical signal, it is differentially amplified and filtered, and finally outputs the real-time current value of the internal conductor of the GIS.

[0120] Example 12:

[0121] See Figures 1 to 5 The GIS-embedded installation structure and measurement method of fiber optic current sensors, the main technical contents of which include:

[0122] (a) GIS-embedded installation structure for fiber optic current sensors

[0123] This installation structure is based on the "integration of fiber optic current sensing epoxy resin triangular plate and basin insulator", and specifically includes the following three parts, which work together to achieve structural stability, reliable insulation, and accurate sensing:

[0124] 1. Epoxy resin triangular plate mounting base built into GIS pot-type insulator

[0125] As the core carrier of the entire sensor, the design and installation of the epoxy resin triangular plate base directly determine the degree of structural integration. Its specific characteristics are as follows:

[0126] Material and molding: EPGC201 high-temperature resistant epoxy resin is used for molding, with 30%-40% quartz powder filler added to improve structural strength and ensure insulation performance; the molding process parameters are 120℃, 15MPa, and pressure holding for 30min to ensure that the base is dense and free of air bubbles.

[0127] Dimensions and Structure: Designed as an isosceles triangular insulating component with a side length of 478mm and a thickness of 30mm, it is suitable for the internal space of 110kV-500kV GIS basin insulators. The surface has an annular polarization-maintaining fiber ring embedding groove (inner diameter 83mm, depth 5mm, width 25mm), with a 1mm deep fiber positioning boss inside the groove, for precise fixation of the polarization-maintaining fiber ring and to prevent winding deviation. At the same time, three axial fiber lead-out holes (diameter 3mm) are opened, and three annular anti-slip grooves (groove width 2mm, groove depth 0.5mm, groove spacing 10mm) are machined on the inner wall of the holes to prevent the special armored fiber from shifting during the lead-out process.

[0128] Built-in fusion method: During the production stage of GIS basin insulators, a cavity that perfectly matches the epoxy resin triangular plate base is pre-designed in the insulator mold (the cavity size is 0.5mm larger than the epoxy resin triangular plate base, leaving a casting gap). After the molded epoxy resin triangular plate base is precisely embedded into the cavity, a second casting is performed using EPGC201 epoxy resin of the same origin as the basin insulator body, so that the epoxy resin triangular plate base and the basin insulator body are completely fused together to form an integrated structure without splicing gaps. The casting process is carried out in a vacuum environment to avoid residual air bubbles affecting the bonding strength.

[0129] 2. The polarization-maintaining fiber optic ring is embedded in the basin-type insulator along with the epoxy resin triangular plate base.

[0130] The polarization-maintaining fiber optic loop is the core component for current sensing, and its performance and installation method directly affect the sensing accuracy. Specific characteristics are as follows:

[0131] Fiber selection: Erbium-doped single-mode polarization-maintaining fiber with a diameter of 1.0-1.5mm, an extinction ratio ≥25dB, and polarization crosstalk ≤-20dB / km is used to ensure the stability of the polarization state of the optical signal during transmission and reduce the impact of external interference on the signal; the erbium doping concentration is 500ppm, which can improve the absorption efficiency of the fiber for 1550nm laser and enhance the sensitivity of magneto-optical effect.

[0132] Winding and Fixing: The number of turns is adjusted according to the GIS voltage level: 80 turns for 110kV, 100 turns for 220kV, and 120 turns for 500kV. A dedicated fiber winding machine is used during winding, controlling the winding tension to 5-8N to ensure the fiber is tightly fitted to the positioning bosses in the mounting slot, without overlap or crossing. Both ends of the polarization-maintaining fiber ring (10mm from the slot opening) are fixed with epoxy resin fixing blocks (10mm long, 8mm wide, 15mm high). The fixing blocks are made of EPGC201 epoxy resin, the same type as the epoxy resin triangular base, and cured at room temperature for 24 hours to ensure a firm connection between the polarization-maintaining fiber ring and the base. Vibration testing: frequency 10-500Hz, acceleration... There was no subsequent displacement.

[0133] Signal extraction unit

[0134] Used to enable optical signal transmission between polarization-maintaining fiber optic rings and external components of GIS, while ensuring the sealing performance of basin-type insulators, with the following specific features:

[0135] Special armored fiber structure: includes inner fiber core, glass fiber reinforced plastic (FRP) armor layer, and polytetrafluoroethylene (PTFE) outer sheath; the FRP armor layer is 0.5-0.8mm thick, providing mechanical protection and avoiding electromagnetic interference from metal armor; the PTFE outer sheath is 0.3-0.5mm thick, with a temperature range of -40℃ to 130℃, and has excellent chemical stability, making it suitable for GIS internal environments.

[0136] Connection and Lead-out: The inner core fiber and the polarization-maintaining fiber ring are welded by arc fusion welding with a welding current of 8-10mA and a welding time of 1-2s, with a welding loss ≤0.1dB. The special armored fiber emerges from the lead-out hole of the epoxy resin triangular plate base and then extends to the outside of the GIS through the pre-set fiber exit channel of the basin insulator. During the lead-out process, the fiber bending radius is controlled to be ≥40mm to avoid excessive bending leading to optical signal loss. Silicone rubber sealant is applied to the fiber exit position outside the basin insulator, and after curing, a sealed structure is formed to prevent… Gas leak.

[0137] (II) Key performance parameters of the installation structure

[0138] Experimental verification shows that the core performance parameters of this installation structure are as follows, and fully meet the operational requirements of GIS equipment:

[0139] Structural strength: The bonding strength between the epoxy resin triangular plate base and the pot insulator is ≥15MPa (tested by a tensile testing machine, peel rate 5mm / min).

[0140] Insulation performance: Overall structural volume resistivity 1min power frequency withstand voltage ≥100kV, lightning impulse withstand voltage ≥250kV;

[0141] Sealing performance: Gas leakage rate ;

[0142] Fiber performance: Polarization-maintaining fiber ring extinction ratio ≥25dB, special armored fiber welding loss ≤0.1dB, insulation resistance... .

[0143] (III) GIS Built-in Measurement Method for Fiber Optic Current Sensor

[0144] This measurement method relies on the aforementioned installation structure of "epoxy resin triangular plate embedded in basin-type insulator" and uses the magneto-optical effect (Faraday effect) to acquire and process current signals. The specific steps are as follows:

[0145] 1. The epoxy resin triangular plate base is integrated with the secondary casting.

[0146] An epoxy resin triangular plate cavity is pre-set in the GIS basin insulator production mold. The epoxy resin triangular plate base, which has been molded and aged (held at 80℃ for 24 hours), is precisely embedded into the cavity. The position is fixed by positioning pins to ensure that the lead-out hole of the epoxy resin triangular plate is coaxial with the optical fiber exit channel pre-set in the basin insulator (coaxiality error ≤0.1mm).

[0147] EPGC201 type epoxy resin, which is of the same origin as the pot insulator body, is injected into the mold. The casting is completed in an environment with a vacuum degree ≤-0.09MPa. Then, it is placed in a constant temperature oven and cured according to the process of "holding at 85℃ for 5 hours → naturally cooling to room temperature" to make the epoxy resin triangular plate base completely fused with the pot insulator.

[0148] After curing and demolding, the integrated structure is subjected to ultrasonic testing (probe frequency 2.5MHz, scanning speed 5mm / s) to ensure that the bonding layer is free of defects such as bubbles and cracks, and at the same time, the appearance is checked for missing materials and deformation.

[0149] 2. Polarization-maintaining fiber ring assembly and optical path construction

[0150] The polarization-maintaining fiber ring is wound in the mounting groove of the polarization-maintaining fiber ring in the epoxy resin triangular plate base using a special fiber winding machine. During the winding process, the tension (5-8N) and the number of turns (80-120 turns) are monitored in real time. After the winding is completed, the two ends of the polarization-maintaining fiber ring are fixed by epoxy resin fixing blocks.

[0151] Three special armored optical fibers were selected, and the outer sheaths and FRP armor layers at both ends were stripped to expose the inner core optical fibers. These fibers were then arc-welded to both ends of the polarization-maintaining fiber ring. After welding, the loss was tested with an optical power meter to ensure that it was ≤0.1dB.

[0152] Special armored optical fibers are sequentially passed through the epoxy resin triangular plate lead-out holes and the basin-type insulator exit channels to extend to the outside of the GIS. Sealant is applied and cured at the exit points. At the same time, external components (1550nm laser, polarizer, coupler, analyzer, photodetector, and signal processing module) are connected in the optical path sequence to form a complete measurement optical path.

[0153] 3. Signal Acquisition

[0154] Turn on the 1550nm laser outside the GIS, adjust the output power to 10mW, the laser is converted into linearly polarized light by the polarizer, and then transmitted to the polarization-maintaining fiber ring built into the basin insulator through special armored fiber.

[0155] When current flows through the conductor inside the GIS, a ring magnetic field is generated around the conductor (the magnetic field strength is proportional to the current magnitude). The polarization-maintaining fiber ring is in this magnetic field, and the linearly polarized light undergoes a Faraday rotation in the fiber. The rotation angle θ satisfies θ=V×N×I (where V is the Verdet constant, N is the number of fiber turns, and I is the conductor current), that is, the rotation angle is proportional to the current magnitude.

[0156] 4. Signal Processing and Output

[0157] The linearly polarized light after undergoing Faraday rotation is transmitted through a special armored optical fiber to a coupler outside the GIS. The coupler distributes the optical signal to the analyzer, which converts the polarization state change into a light intensity change.

[0158] The photodetector converts the light intensity signal into an electrical signal, which is then processed by the signal processing module (differential amplification and low-pass filtering).

[0159] The processed electrical signal is directly output as the real-time current value of the internal conductor of the GIS. Experimental verification shows that it fully meets the real-time requirements of current monitoring of GIS equipment.

[0160] Example 13:

[0161] See Figures 1 to 5 The GIS-embedded installation structure and measurement method of fiber optic current sensors, the main technical contents of which include:

[0162] (a) Implementation of installation structure

[0163] 1. Prefabricated epoxy resin triangular plate mounting base

[0164] Mold preparation: Make an isosceles triangular mold body (side length 478mm, thickness 30mm), and polish the inner wall of the mold to a roughness Ra≤0.8μm to avoid the mold sticking to the surface after the base is formed;

[0165] Raw material mixing: Weigh the raw materials at a mass ratio of 6:4 (EPGC201 type epoxy resin: quartz powder filler). The quartz powder is pre-dried at 120℃ for 2 hours to remove moisture. Put the raw materials into a high-speed mixer and stir at 500r / min for 15 minutes to ensure uniform mixing and no particle agglomeration.

[0166] Compression molding: The mixed raw materials are injected into the mold, and after the mold is closed, it is placed in a hydraulic molding machine. The temperature is set to 120℃ and the pressure is 15MPa. The pressure is held for 30 minutes. After the pressure is held, the mold is removed to obtain the epoxy resin triangular plate base blank.

[0167] Machining: The blank is machined using a CNC milling machine. First, the polarization-maintaining fiber ring embedding groove (inner diameter 83mm, depth 5mm, width 25mm) is milled. Then, a fiber positioning boss with a depth of 1mm is milled at the bottom of the groove. Subsequently, three fiber lead-out holes with a diameter of 3mm are drilled. The inner wall of the holes is machined with three annular anti-slip grooves (groove width 2mm, groove depth 0.5mm, groove spacing 10mm) using a lathe.

[0168] Aging treatment: Place the processed base in a constant temperature oven and keep it at 80℃ for 24 hours. Allow it to cool naturally to room temperature to eliminate internal stress generated during molding and processing, and ensure dimensional stability (the flatness error of the base after treatment is ≤0.1mm).

[0169] 2. Prefabrication of GIS basin-type insulators and embedding of epoxy resin triangular plates

[0170] Insulator mold design: Fabricate a 220kV GIS basin insulator mold. The mold has a pre-set cavity that matches the epoxy resin triangular plate base (cavity dimensions: side length 478.5mm, thickness 30.5mm, with a 0.5mm casting gap). The center of the cavity is aligned with the center of the insulator to ensure that the lead-out hole of the epoxy resin triangular plate is coaxial with the pre-set optical fiber exit channel of the insulator.

[0171] Epoxy resin triangular plate positioning: Place the aged epoxy resin triangular plate base into the mold cavity, and use 3 positioning pins (8mm in diameter) to fix the position of the epoxy resin triangular plate. The positioning pins cooperate with the pre-set positioning holes of the epoxy resin triangular plate to ensure that the gap between the epoxy resin triangular plate and the cavity wall is ≤0.1mm.

[0172] Insulator raw material casting: Inject EPGC201 type epoxy resin (of the same origin as epoxy resin triangular plate base) into the mold. The injection amount should be enough to completely cover the epoxy resin triangular plate base and fill the mold cavity. During the injection process, a vibrating table (vibration frequency 50Hz) is used to assist in degassing and reduce air bubbles in the raw material.

[0173] Vacuum treatment: Place the mold into a vacuum tank, close the tank door, and evacuate to a vacuum level of ≤-0.09MPa. Maintain this for 10 minutes to further remove air bubbles from the raw materials and prevent air bubble defects in the bonding layer.

[0174] 3. Secondary pouring, fusion, and curing

[0175] Curing process: Place the vacuum-treated mold into a constant temperature oven and control the temperature according to the following curve: room temperature → increase the temperature to 85℃ at 5℃ / min → keep it at the temperature for 5 hours → cool naturally to room temperature (cooling rate ≤2℃ / min).

[0176] Demolding and appearance inspection: Demold after cooling to room temperature, observe the appearance of the basin insulator and the built-in epoxy resin triangular plate. The surface should be free of missing material, cracks, and bubbles, and there should be no obvious dividing line between the epoxy resin triangular plate and the insulator.

[0177] Performance testing: The bonding layer was tested using an ultrasonic flaw detector (probe frequency 2.5MHz), with the scanning range covering the entire bonding surface to ensure there were no internal defects; at the same time, the bonding strength of the bonding layer was tested using a tensile testing machine, with 3 test points selected, and the peel strength of each point was ≥15MPa.

[0178] 4. Polarization-maintaining fiber ring assembly

[0179] Fiber selection and cutting: Select erbium-doped single-mode polarization-maintaining fiber (diameter 1.2mm, extinction ratio 28dB, polarization crosstalk -22dB / km). Calculate the fiber length based on 100 turns (circumference of each turn is about 0.91m, total length is about 91m). Cut the fiber and remove 10mm of coating from both ends.

[0180] Polarization-maintaining fiber winding: Fix the epoxy resin triangular plate base on the special fiber winding machine, align the winding head of the fiber winding machine with the mounting groove, set the winding tension to 6N, start the fiber winding machine to wind 100 turns, and ensure that the fiber is tightly attached to the positioning boss during the winding process, without overlap or crossing.

[0181] Fixing the polarization-maintaining fiber ring: Place epoxy resin fixing blocks at both ends of the polarization-maintaining fiber ring (10mm from the groove opening). The fixing blocks are pre-processed into a shape that matches the groove (10mm long, 8mm wide, and 15mm high). Inject EPGC201 epoxy resin into the gap between the fixing blocks, the fiber, and the mounting groove, and cure at room temperature for 24 hours.

[0182] Verification of fixing effect: After curing, vibration tests were performed on the polarization-maintaining fiber ring (frequency 10-500Hz, acceleration). The test lasted 30 minutes. After the test, the polarization-maintaining fiber ring was observed under a microscope to show no displacement or loosening.

[0183] 5. Special armored fiber optic connection and lead-out

[0184] Preparation of special armored optical fiber: Select special armored optical fiber (the inner core fiber is the same as the polarization-maintaining fiber, the FRP armor layer thickness is 0.6mm, and the PTFE outer sheath thickness is 0.4mm), cut 3 optical fibers with a length of 2m, and strip the outer sheath (100mm) and FRP armor layer (10mm) at both ends to expose the inner core fiber.

[0185] Fusion welding: The inner core fiber was welded to both ends of the polarization-maintaining fiber ring using an arc fusion welding machine. The welding current was set to 9mA and the welding time was 1.5s. After welding, the welding loss was detected by an optical power meter. The losses of the three weld points were 0.08dB, 0.07dB and 0.09dB, respectively, all ≤0.1dB.

[0186] Fiber optic lead-out and sealing: The welded special armored optical fiber is sequentially passed through the lead-out hole of the epoxy resin triangular plate and the lead-out channel of the basin insulator. During the lead-out process, the bending radius of the optical fiber is controlled to be 45mm. Silicone rubber sealant (model: HT-870) is applied to the optical fiber lead-out position outside the insulator. The sealant layer is 5mm thick and is cured at room temperature for 48 hours.

[0187] Sealing performance test: Place the insulator into the sealing test chamber and fill it with... The gas pressure was increased to 0.6 MPa, and the leakage rate at the penetration point was detected using a helium mass spectrometer leak detector. The detection results were as follows: It meets the sealing requirements.

[0188] 6. Overall performance testing

[0189] Insulation performance testing: A power frequency withstand voltage tester was used to perform a 1-minute power frequency withstand voltage test on the insulator and the built-in epoxy resin triangular plate. The test voltage was 100kV, and the test lasted for 1 minute. No breakdown or flashover was observed. A high-resistivity meter was used to measure the overall volume resistivity. Under conditions of 25℃ and 50% RH, the resistivity was [value missing]. ;

[0190] Fiber optic performance testing: The extinction ratio of the polarization-maintaining fiber ring was measured using a polarization analyzer, and the result was 27 dB, ≥25 dB; the insulation resistance of the special armored fiber was measured using an insulation resistance meter, and the result was... .

[0191] (II) Implementation of Measurement Methods

[0192] 1. External component connection and optical path debugging

[0193] Component selection and connection: Select a 1550nm laser (output power 10mW, linewidth ≤10kHz), polarizer (polarization extinction ratio ≥40dB), coupler (splitting ratio 1:1), analyzer (matched to the polarizer), photodetector (responsivity 0.9A / W, bandwidth 100MHz), and signal processing module (including differential amplifier and low-pass filter); connect them in the following order: "laser → polarizer → special armored fiber → coupler → analyzer → photodetector → signal processing module → current data output terminal", ensuring that all interfaces are securely connected and without looseness;

[0194] Optical path adjustment: Turn on the laser and adjust the polarization direction of the polarizer and analyzer to make the initial electrical signal intensity output by the photodetector reach its maximum value (at which point the optical path is in its optimal working state); record the initial signal value as 0.5V as the reference for subsequent current measurement.

[0195] 2. Current Measurement and Verification

[0196] Simulated current flow test: Connect the GIS basin insulator equipped with sensors to the simulation test platform, and pass different currents (100A, 500A, 1000A) into the conductor inside the GIS, with each current value stabilizing for 30 seconds;

[0197] Signal acquisition and processing: Under different current conditions, the current values ​​output by the signal processing module are recorded, and a standard current transformer (accuracy class 0.05) is used as a reference to compare the measurement results;

[0198] Response time test: A step current signal (from 0A to 2000A, rise time ≤1μs) was generated using a function generator. The input current signal and the sensor output signal were simultaneously acquired using an oscilloscope. The response time was measured to be 45μs, ≤50μs.

[0199] Stability test: The sensor was continuously operated at 2000A current for 24 hours, and the measurement value was recorded once per hour. The fluctuation range of the measurement value was ≤±0.1%, which indicates that the sensor has good stability.

[0200] This invention achieves deep integration of sensors and GIS equipment through the innovative design of "epoxy resin triangular plates fully embedded in GIS basin insulators," solving the core defects of existing technologies. At the same time, through optimization of material homogeneity and fiber optic compatibility, it ensures structural strength, insulation performance, and sensing stability. Experimental verification shows that it fully meets the operating requirements of 110kV-500kV GIS equipment, demonstrating significant technological innovation value and promising engineering application prospects.

Claims

1. A GIS-embedded installation structure for fiber optic current sensors, characterized in that, Includes a triangular plate mounting base (2) built into the GIS basin insulator (1), and several polarization-maintaining fiber optic rings (10) and signal transmission units of equal number; The triangular plate mounting base (2) has a number of polarization-maintaining fiber ring mounting slots (5) that are the same number as the number of polarization-maintaining fiber rings (10), and a conductor mounting hole (4) is provided at the center of the polarization-maintaining fiber ring mounting slot (5). The position of the conductor mounting hole (4) corresponds to the position of the conductor reserved hole (14) on the GIS basin insulator (1); The number of conductor mounting holes (4) is consistent with the number of conductors inside the GIS equipment; The polarization-maintaining fiber ring mounting slot (5) has a fiber lead-out channel (7) on one side, and the fiber lead-out channel (7) extends to the corner of the triangular plate mounting base (2). The corner of the triangular plate mounting base (2) is provided with a flange connection channel (6). The triangular plate mounting base (2) is fixed together with the GIS basin insulator (1); The conductor inside the GIS equipment passes through the conductor reserved hole (14) of the GIS basin insulator (1) and the conductor mounting hole (4) of the triangular plate mounting base (2). The polarization-maintaining fiber ring (10) is wound in the polarization-maintaining fiber ring mounting groove (5), and the central axis of the polarization-maintaining fiber ring (10) is collinear with the conductor axis inside the GIS equipment. The signal transmission unit is installed in the optical fiber lead-out channel (7), and one end of the signal transmission unit is connected to the polarization-maintaining optical fiber ring (10), while the other end is connected to external devices through the flange connection channel (6). When the structure is used for measurement, the optical signal generated by the external device is transmitted to the polarization-maintaining fiber ring (10) through the signal transmission unit. When the conductor inside the GIS device flows, a ring magnetic field is generated. Under the action of magneto-optical effect, the polarization-maintaining fiber ring (10) causes the optical signal to undergo Faraday rotation. The optical signal after Faraday rotation is transmitted to the external device through the signal transmission unit, and finally the real-time current value of the conductor inside the GIS device is obtained.

2. The GIS-embedded installation structure for the fiber optic current sensor according to claim 1, characterized in that, The triangular plate mounting base (2) is made of epoxy resin.

3. The GIS-embedded installation structure for the fiber optic current sensor according to claim 1, characterized in that, The triangular plate mounting base (2) is fixed together with the GIS pot insulator (1) through a secondary casting process; The secondary casting process uses epoxy resin as the casting material. The triangular plate mounting base (2) is provided with a drainage hole (3) for secondary casting, and the drainage hole (3) is located in the optical fiber lead-out channel (7).

4. The GIS-embedded installation structure for the fiber optic current sensor according to claim 1, characterized in that, The signal transmission unit includes a special armored optical fiber; The special armored optical fiber comprises a three-layer structure, consisting of an inner core optical fiber, a glass fiber reinforced plastic armor layer, and a polytetrafluoroethylene outer sheath, from the inside out. The inner optical fiber is used to transmit optical signals; The glass fiber reinforced plastic armor layer is used to provide mechanical protection and avoid electromagnetic interference; The polytetrafluoroethylene outer sheath is used to adapt to the internal environment of the GIS equipment; The method of connecting the special armored optical fiber to the polarization-maintaining optical fiber ring (10) is to use fusion welding to connect the inner core optical fiber to the polarization-maintaining optical fiber ring (10).

5. The GIS-embedded installation structure for the fiber optic current sensor according to claim 1, characterized in that, The polarization-maintaining fiber ring mounting groove (5) is also provided with a fiber positioning boss; The optical fiber lead-out channel (7) is provided with an annular anti-slip groove.

6. The GIS-embedded installation structure of the fiber optic current sensor according to claim 1, characterized in that, The polarization-maintaining fiber ring (10) is made of polarization-maintaining fiber containing erbium. The outer diameter of the polarization-maintaining fiber ring (10) is adapted to the inner diameter of the polarization-maintaining fiber ring mounting groove (5).

7. The GIS-embedded installation structure for the fiber optic current sensor according to claim 1, characterized in that, The mounting structure is sealed by applying silicone rubber sealant.

8. The GIS-embedded installation structure of the fiber optic current sensor according to claim 1, characterized in that, The mounting structure also includes a fixing block; The fixing block is used to fix the polarization-maintaining fiber ring (10); The fixing block is made of epoxy resin.

9. The GIS-embedded installation structure of the fiber optic current sensor according to claim 1, characterized in that, The external devices include an external light source (8), a polarizer (9), a coupling analyzer (11), a photodetector (12), and a current data display (13). The external light source (8) is used to generate light signals; The polarizer (9) is used to convert optical signals into linearly polarized light; Linearly polarized light is transmitted to the polarization-maintaining fiber ring (10) through the signal transmission unit. The coupled analyzer (11) is used to convert the light signal that has undergone Faraday rotation from a change in polarization state to a change in light intensity, thereby obtaining a light intensity signal; The photodetector (12) is used to convert light intensity signals into electrical signals to obtain the real-time current value of the conductor inside the GIS equipment; The current data display (13) is used to display the real-time current value of the conductor inside the GIS equipment.

10. A method for measurement using the structure described in any one of claims 1-9, characterized in that, Includes the following steps: 1) Generating light signals using an external light source; 2) Use a polarizer to convert the optical signal into linearly polarized light; 3) The linearly polarized light is transmitted to the polarization-maintaining fiber ring through the signal transmission unit. When the conductor inside the GIS equipment flows, a ring magnetic field is generated. Under the action of magneto-optical effect, the polarization-maintaining fiber ring causes the optical signal to undergo Faraday rotation, and the optical signal after Faraday rotation is obtained. 4) The optical signal that has undergone Faraday rotation is transmitted to the coupled analyzer through the signal transmission unit, and the coupled analyzer is used to convert the change in polarization state of the optical signal that has undergone Faraday rotation into a change in light intensity, so as to obtain the light intensity signal. 5) Use a photodetector to convert light intensity signals into electrical signals to obtain the real-time current value of the conductors inside the GIS equipment, and display it through a current data display.

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