Ultrahigh voltage through-wall bushing epoxy impregnated paper core body model surface potential measurement system and method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2023-11-22
- Publication Date
- 2026-07-21
Smart Images
Figure CN117471196B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of DC power transmission technology, specifically relating to a surface potential measurement system and method for epoxy-impregnated paper core model of ultra-high voltage through-wall bushing. Background Technology
[0002] Ultra-high voltage direct current (UHVDC) wall bushings are core equipment in DC transmission projects, serving as the sole DC output channel in the transmission hall. There are two main types of wall bushings: one uses pure SF6 gas as the internal insulation medium, and the other uses a composite insulation structure of epoxy-impregnated paper and SF6 gas. The composite insulation structure provides higher mechanical strength, avoiding the deflection issues common in gas-insulated bushings due to insufficient support, gravity, and thermal deformation. Furthermore, the composite insulation structure, with its hundreds of metal plates within the epoxy-impregnated paper core, offers greater flexibility in adjusting the internal electric field. Therefore, it is widely used in DC transmission projects.
[0003] In recent years, UHVDC bushing failures have occurred frequently, and the causes of some failures remain unclear. To ensure the stable operation of UHV projects, it is essential to study these bushing failures, identify their root causes, and find corresponding solutions.
[0004] Under prolonged DC voltage conditions, ultra-high voltage direct current (UHVDC) bushings accumulate surface charge on their core under a normal electric field. This surface charge accumulation exacerbates the non-uniformity of the electric field on the core surface. Combined with conductor heating, a temperature gradient exists in the radial direction of the bushing core, affecting the conductivity of the insulation material and further intensifying the non-uniformity of the electric field inside the bushing. The accumulation of localized charge on the core surface can ultimately lead to surface flashover within the bushing core. Therefore, understanding the process of charge accumulation on the surface of composite insulated bushing cores is crucial for exploring the mechanism of surface flashover and maintaining the normal operation of composite insulated bushings. Summary of the Invention
[0005] To address the problems existing in the prior art, the present invention aims to provide a surface potential measurement system and method for epoxy-impregnated paper core models of ultra-high voltage through-wall bushings. The present invention can simulate the surface potential of the bushing core under actual operating conditions. By analyzing the surface potential, the accumulation and dissipation process of surface charge can be understood, which is of great significance for exploring the mechanism of surface flashover of the bushing core and maintaining the normal operation of composite insulated through-wall bushings.
[0006] The technical solution adopted in this invention is as follows:
[0007] A surface potential measurement system for an epoxy-impregnated paper core model of an ultra-high voltage (UHV) through-wall bushing includes a sealed cavity, a high-voltage insulating bushing, a grounding assembly, a turntable, a telescopic mechanism, a main inflation / deflation pipe assembly, an electrostatic probe, and a flange. The flange can be fitted onto the outside of the epoxy-impregnated paper core model and contact the grounding tap of the model. The high-voltage insulating bushing is installed on top of the sealed cavity and penetrates the cavity; the connection between the high-voltage insulating bushing and the sealed cavity is insulated and sealed. One end of the grounding assembly is fixedly connected to the sealed cavity, and the other end can contact the outer surface of the flange. The lower end of the conductor of the pressure insulating sleeve is connected to a rotating connection mechanism that can be rotatably connected to the upper end of the epoxy impregnated paper core model guide rod. The rotating connection mechanism is a conductor. The turntable is installed in the sealed cavity and located below the high-voltage insulating sleeve. An insulating support is installed on the upper part of the turntable that can be connected to the lower end of the epoxy impregnated paper core model guide rod. The electrostatic probe is set in the sealed cavity. The electrostatic probe is insulatedly installed at the movable end of the telescopic mechanism. The fixed end of the telescopic mechanism is connected to the sealed cavity. The telescopic direction of the telescopic mechanism is parallel to the rotation axis of the turntable. The inflation / deflation manifold assembly is connected to the sealed cavity.
[0008] Preferably, the end of the grounding component that is in contact with the flange is provided with an elastic device, on which a rolling pulley is installed. The rolling pulley can contact the flange surface, and the elastic device can keep the surface of the rolling pulley in contact with the flange surface. The rolling pulley is a conductor and is electrically connected to the sealing cavity.
[0009] Preferably, the rotating connection mechanism adopts a rotating tip, which is a conductor. The upper end of the rotating tip is fixedly connected to the conductor inside the high-voltage insulating sleeve 2, and the lower end of the rotating tip can be detachably electrically connected to the upper end of the epoxy impregnated paper core model guide rod.
[0010] Preferably, the surface potential measurement system for epoxy impregnated paper core model of ultra-high voltage through-wall bushing of the present invention further includes a turntable drive mechanism for driving the turntable to rotate. The turntable drive mechanism includes a rotary transmission component, a rotary motion servo motor, a rotary motion servo motor mounting base, and a reducer. The rotary transmission component is installed at the bottom of the sealed cavity and penetrates the sealed cavity. The rotary transmission component is rotatably connected to and sealed with the sealed cavity. The rotary motion servo motor mounting base is installed outside the sealed cavity. The rotary motion servo motor is installed on the rotary motion servo motor mounting base. The output shaft of the rotary motion servo motor is connected to the input end of the rotary transmission component through the reducer. The output end of the rotary transmission component is connected to the turntable.
[0011] Preferably, both the turntable and the rotary transmission assembly are conductors, the turntable, the rotary transmission assembly and the sealed cavity are at the same potential, and the diameter of the turntable is the same as the outer diameter of the epoxy impregnated paper core model.
[0012] Preferably, the electrostatic probe is perpendicular to and coplanar with the axis of rotation of the turntable.
[0013] Preferably, the inflation / deflation manifold assembly includes an inflation valve, a vacuum valve, and a tee. One end of the tee is connected to the inner cavity of the sealed chamber, and the inflation valve and vacuum valve are respectively installed at the other two ends of the tee.
[0014] Preferably, the sealed cavity is provided with a sight glass observation window.
[0015] Preferably, a pressure gauge is provided on the sealed cavity for detecting the pressure inside the sealed cavity.
[0016] This invention also provides a method for measuring the surface potential of an epoxy-impregnated paper core model of an ultra-high voltage through-wall bushing. This method uses the surface potential measurement system for the epoxy-impregnated paper core model of an ultra-high voltage through-wall bushing as described above, and includes the following steps:
[0017] Installation process: First, fit a flange over the epoxy-impregnated paper core model to be tested, ensuring the flange contacts the grounding tap of the model. After the flange and model are in place, connect the upper end of the guide rod to the rotating connection mechanism, and fix the lower end of the guide rod to the upper end of the insulating support, ensuring the axis of the epoxy-impregnated paper core model is coaxial with the turntable's axis. Then, bring the grounding component into contact with the outer surface of the flange. After the epoxy-impregnated paper core model is installed, adjust the electrostatic probe to maintain a preset distance from the model. Finally, ground the sealed cavity and the lower end of the insulating support.
[0018] Inflation and deflation process: After the installation process is completed, the sealed cavity is sealed, and the inner cavity of the sealed cavity is evacuated through the inflation and deflation manifold assembly. When the vacuum degree in the sealed cavity reaches the preset value, the inflation and deflation manifold assembly is switched to stop evacuating the vacuum, and then insulating gas is filled into the sealed cavity. When the insulating gas in the sealed cavity reaches the preset pressure, the inflation and deflation manifold assembly is switched to stop filling the insulating gas.
[0019] Voltage measurement process: Before applying voltage, the position of the electrostatic probe is adjusted by the telescopic mechanism, and the voltage of the electrostatic probe is calibrated to 0. After the voltage calibration is completed, the preset voltage is applied to the epoxy impregnated paper core model through the high-voltage insulating sleeve, and then the surface potential of the epoxy impregnated paper core model is measured.
[0020] The process of measuring the surface potential of an epoxy-impregnated paper core model includes the following steps:
[0021] Step 1: Drive the electrostatic probe through the telescopic mechanism to move the electrostatic probe from the lower end of the epoxy impregnated paper core model to the flange. The electrostatic probe stops moving and measures the surface potential of the epoxy impregnated paper core model during the movement. Then, drive the epoxy impregnated paper core model to rotate by a preset angle through the turntable, and then the turntable stops.
[0022] Step 2: Drive the electrostatic probe through the telescopic mechanism to return the electrostatic probe to the lower end of the epoxy impregnated paper core model. The electrostatic probe stops moving. During the movement, the electrostatic probe measures the surface potential of the epoxy impregnated paper core model. Then, drive the epoxy impregnated paper core model to rotate by a preset angle through the turntable.
[0023] Step 3: Repeat steps 1 to 2 until the turntable rotates at least one revolution to complete the measurement of the surface potential of the epoxy impregnated paper core model.
[0024] Compared with the prior art, the present invention has the following technical effects:
[0025] In the surface potential measurement system of the epoxy impregnated paper core model for ultra-high voltage through-wall bushings of this invention, a turntable is used to drive the epoxy impregnated paper core model to be measured to rotate around its axis by a preset angle. The lower end of the conductor of the high-voltage insulating bushing is connected to a rotating connection mechanism that can rotatably connect to the upper end of the guide rod of the epoxy impregnated paper core model. This rotating connection mechanism ensures that the epoxy impregnated paper core model maintains electrical connection with the conductor of the high-voltage insulating bushing while rotating, ensuring that the high-voltage insulating bushing applies a preset voltage to the guide rod of the epoxy impregnated paper core model. An insulating support post is used to isolate the guide rod of the epoxy impregnated paper core model from the ground potential, while also supporting the epoxy impregnated paper core model. During normal operation of the epoxy impregnated paper core model, the epoxy impregnated paper core... A voltage is applied to the guide rod at the center of the model. The last electrode plate inside the epoxy impregnated paper core model needs to be grounded through a grounding tap. To ensure that the last electrode plate is always grounded during the rotation of the epoxy impregnated paper core model, this invention uses a flange to encase the epoxy impregnated paper core model, with the flange in contact with the grounding tap of the epoxy impregnated paper core model. Simultaneously, a grounding component is in contact with the outer surface of the flange. This ensures that the grounding tap maintains electrical contact with the grounding component during the rotation of the epoxy impregnated paper core model, ultimately achieving constant grounding of the last electrode plate. A telescopic mechanism drives the electrostatic probe to move axially along the epoxy impregnated paper core model. Combined with the intermittent rotation of the turntable at a preset angle, the electrostatic probe can measure the surface potential of the entire epoxy impregnated paper core model. After obtaining the surface potential of the entire epoxy impregnated paper core model, the accumulation and dissipation process of surface charge can be understood by analyzing the potential distribution. This is of great significance for exploring the mechanism of surface flashover of the bushing core and maintaining the normal operation of composite insulated through-wall bushings. Attached Figure Description
[0026] Figure 1 This is a schematic front view of the surface potential measurement system for an epoxy-impregnated paper core model of an ultra-high voltage through-wall bushing according to an embodiment of the present invention.
[0027] Figure 2This is a schematic side view of the surface potential measurement system for an epoxy-impregnated paper core model of an ultra-high voltage through-wall bushing according to an embodiment of the present invention.
[0028] In the diagram: 1. Sealed cavity; 2. High-voltage insulating bushing; 3. Grounding assembly; 4. Insulating support; 5. Main inflation / deflation manifold assembly; 6. Rotary transmission assembly; 7. Moving bracket; 8. Turntable; 9. Linear motion servo motor mounting base; 10. Rotary motion servo motor mounting base; 11. Probe clamp; 12. Rotating center; 13. Planetary reducer; 14. Rotary motion servo motor; 15. Linear motion servo motor; 16. Pressure gauge; 17. Adjustable needle valve; 8. SF6 inflation valve; 19. Quick-connect air hose connector; 20. Pressure gauge connector; 21. Vacuum bellows; 22. Oil-gas separator; 23. Rotary vane vacuum pump; 24. Control box; 25. Industrial computer; 26. Display screen; 27. Vacuum fiber optic connector; 28. Sight glass observation window; 29. Probe wiring flange; 30. Vacuum valve; 31. Cavity door / window; 32. Fastening bolts; 33. Epoxy impregnated paper core model; 34. Flange; 35. Electrostatic probe. Detailed Implementation
[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0030] like Figure 1 and Figure 2 As shown, the surface potential measurement system for the epoxy impregnated paper core model of the ultra-high voltage through-wall bushing of the present invention includes a sealed cavity 1, a high-voltage insulating sleeve 2, a grounding assembly 3, a turntable 8, a telescopic mechanism, a gas filling and discharging main pipe assembly 5, an electrostatic probe 34, and a flange 34. The flange 34 can be sleeved on the outside of the epoxy impregnated paper core model 33 and contact the grounding tap of the epoxy impregnated paper core model 33, ensuring that the flange 34 is electrically connected to the grounding tap and that there is no relative sliding between the flange 34 and the epoxy impregnated paper core model 33. The high-voltage insulating sleeve 2 is installed on the top of the sealed cavity 1 and penetrates the sealed cavity 1. The connection between the high-voltage insulating sleeve 2 and the sealed cavity 1 is insulated and sealed. One end of the grounding assembly 3 is fixedly connected to the sealed cavity 1. The other end of the grounding component 3 can contact the outer surface of the flange 34. The lower end of the conductor of the high-voltage insulating sleeve 2 is connected to a rotating connection mechanism that can be rotatably connected to the upper end of the guide rod of the epoxy impregnated paper core model 33. The rotating connection mechanism is a conductor. The turntable 8 is installed in the sealed cavity 1 and located below the high-voltage insulating sleeve 2. An insulating support 4 that can be connected to the lower end of the guide rod of the epoxy impregnated paper core model 33 is installed on the upper part of the turntable 8. The electrostatic probe 35 is set in the sealed cavity 1. The electrostatic probe 35 is insulatedly installed at the movable end of the telescopic mechanism. The fixed end of the telescopic mechanism is connected to the sealed cavity 1. The telescopic direction of the telescopic mechanism is parallel to the rotation axis of the turntable 8. The inflation / deflation manifold assembly 5 is connected to the sealed cavity 1.
[0031] The process of measuring the surface potential of the epoxy impregnated paper core model 33 to be tested using the UHV through-wall bushing epoxy impregnated paper core model surface potential measurement system of the present invention includes:
[0032] Installation process: First, fit a flange 34 over the epoxy impregnated paper core model 33 to be tested, ensuring the flange 34 contacts the grounding tap of the epoxy impregnated paper core model 33. After the flange 34 is attached to the epoxy impregnated paper core model 33, connect the upper end of the guide rod of the epoxy impregnated paper core model 33 to the rotating connection mechanism, and fix the lower end of the guide rod of the epoxy impregnated paper core model 33 to the upper end of the insulating support 4, ensuring the axis of the epoxy impregnated paper core model 33 is coaxial with the axis of rotation of the turntable 8. Then, make the grounding component 3 contact the outer surface of the flange 34. After the epoxy impregnated paper core model 33 is installed, adjust the electrostatic probe 35 to maintain a preset distance from the epoxy impregnated paper core model 33. Finally, ground the lower ends of the sealed cavity 1 and the insulating support 4.
[0033] Gas filling and venting process: After the installation process is completed, the sealing cavity 1 is sealed, and the inner cavity of the sealing cavity 1 is evacuated through the gas filling and venting manifold assembly 5. When the vacuum degree in the sealing cavity 1 reaches the preset value, the gas filling and venting manifold assembly 5 is switched to stop evacuation, and then insulating gas is filled into the sealing cavity 1. When the insulating gas in the sealing cavity 1 reaches the preset pressure, the gas filling and venting manifold assembly 5 is switched to stop filling the insulating gas.
[0034] Voltage measurement process: Before applying voltage, the position of the electrostatic probe 35 is adjusted by the telescopic mechanism, and the voltage of the electrostatic probe 35 is calibrated to 0. After the voltage calibration is completed, a preset voltage is applied to the epoxy impregnated paper core model 33 through the high-voltage insulating sleeve 2, and then the surface potential of the epoxy impregnated paper core model 33 is measured.
[0035] The process of measuring the surface potential of epoxy-impregnated paper core model 33 includes the following steps:
[0036] Step 1: Drive the electrostatic probe 35 through the telescopic mechanism to move the electrostatic probe 35 from the lower end of the epoxy impregnated paper core model 33 to the flange 34. The electrostatic probe 35 stops moving. During the movement, the electrostatic probe 35 measures the surface potential of the epoxy impregnated paper core model 33. Then, drive the epoxy impregnated paper core model 33 to rotate by a preset angle through the turntable 8. After that, the turntable 8 stops.
[0037] Step 2: Drive the electrostatic probe 35 through the telescopic mechanism to return the electrostatic probe 35 to the lower end of the epoxy impregnated paper core model 33, and stop the movement of the electrostatic probe 35. During the movement, the electrostatic probe 35 measures the surface potential of the epoxy impregnated paper core model 33; then drive the epoxy impregnated paper core model 33 to rotate by a preset angle through the turntable 8.
[0038] Step 3: Repeat steps 1 to 2 until turntable 8 rotates at least one revolution to complete the measurement of the surface potential of epoxy impregnated paper core model 33.
[0039] In a preferred embodiment of the present invention, both the turntable 8 and the rotary transmission component 6 are conductors. The turntable 8, the rotary transmission component 6, and the sealed cavity 1 are at the same potential. Thus, grounding of the lower end of the insulating support 4 can be achieved by grounding the turntable 8. When performing voltage calibration on the electrostatic probe 35, the position of the electrostatic probe 35 can be adjusted to one side of the turntable 8 by means of the telescopic mechanism. The diameter of the turntable 8 is the same as the outer diameter of the epoxy impregnated paper core model 33. Thus, by adjusting the distance between the electrostatic probe 35 and the turntable 8, the distance between the electrostatic probe 35 and the surface of the epoxy impregnated paper core model 33 can be ensured to meet the requirements for measuring the surface potential of the epoxy impregnated paper core model 33.
[0040] As a preferred embodiment of the present invention, the electrostatic probe 35 is perpendicular to and coplanar with the rotation axis of the turntable 8, which ensures that the detection end of the electrostatic probe 35 remains perpendicular to the surface of the epoxy impregnated paper core model 33 when measuring the surface potential of the epoxy impregnated paper core model 33.
[0041] Example
[0042] like Figure 1 As shown, the surface potential measurement system of the epoxy impregnated paper core model of the ultra-high voltage through-wall bushing in this embodiment mainly includes: a high voltage insulating bushing 2 containing a conductor, a rotary servo motor 14, a linear motion servo motor 15, a sealed cavity 1, a control box 24, a rotary vane vacuum pump 23, a pressure gauge 16, and a gas filling and discharging main pipe assembly 5.
[0043] The sealed cavity 1 is fixed to the movable bracket 7 by bolts, which facilitates the movement of the device.
[0044] The high-voltage insulating sleeve 2 has excellent insulation properties. Passing through the sealed cavity 1, it transmits the high voltage generated by the high-voltage power supply to the interior of the sealed cavity 1, while ensuring that the conductor of the high-voltage insulating sleeve 2 is isolated from the grounded sealed cavity 1, preventing conductor-to-ground discharge. The high-voltage insulating sleeve 2 can be connected to an external high-voltage power supply, which includes one positive and one negative power supply, enabling surface charge accumulation experiments on the epoxy-impregnated paper core model 33 under different voltage polarities. The high-voltage power supply is connected to the rotating tip 12 inside the sealed cavity 1 through the high-voltage insulating sleeve 2 containing conductors. The rotating tip 12 is a metal conductor that transmits high voltage to the central guide rod of the epoxy-impregnated paper core model 33, while also allowing relative rotation between the epoxy-impregnated paper core model 33 and the conductor of the high-voltage insulating sleeve 2.
[0045] The sealed cavity 1 contains a rotating tip 12, an epoxy-impregnated paper core model 33 to be tested, a grounding assembly 3 with rolling pulleys, an insulating support 4, and a turntable 8. The outer shell of the sealed cavity 1 contains a main gas filling / discharging pipe assembly 5, a pressure gauge 16, and a sight glass observation window 28. Before the experiment, the epoxy-impregnated paper core model 33 is first installed inside the sealed cavity 1. The bottom of the guide rod of the epoxy-impregnated paper core model 33 is threaded to the upper end of the insulating support 4, and the top of the guide rod is fixed to the lower end of the rotating tip 12 with a set screw. The connected epoxy-impregnated paper core model 33 is then inserted into the sealed cavity 1. First, the head of the rotating tip 12 is bolted to the conductor of the high-voltage insulating sleeve 2, and then the insulating support 4 is bolted to the turntable 8 at the bottom of the sealed cavity 1. The entire sealed cavity 1 is made of stainless steel and is grounded. Flange 34 is connected to the sealed cavity 1 via grounding assembly 3 to achieve grounding. Grounding assembly 3 contains a compression spring, which ensures a reliable ground connection between the rolling pulley and the surface of flange 34, guaranteeing safety during the experiment. This single grounding assembly 3 connection to flange 34 also simplifies the complexity of installing the epoxy impregnated paper core model 33.
[0046] After the epoxy impregnated paper core model 33 is installed, close the cavity door 31 on the sealed cavity 1 and tighten it with the fastening bolts 32. Open the vacuum valve 30 of the main charging / discharging pipe assembly 5, close the SF6 charging valve 18, and start the rotary vane vacuum pump 23 to extract the air inside the sealed cavity 1 through the vacuum bellows 21. The gas extracted through the vacuum bellows 21 and the vacuum pump oil can be separated by the oil-gas separator 22. The filtered vacuum pump oil is recycled through the oil return pipe, and the discharged gas is oil-free, achieving a pollution-free and clean effect.
[0047] The pressure inside the sealed cavity 1 is displayed by pressure gauge 16. Pressure gauge 16 is connected to the sealed cavity 1 via pressure gauge connector 20. When the absolute pressure inside the sealed cavity 1 is below 60 Pa, first close the vacuum valve 30, then close the rotary vane vacuum pump 23. Incorrect closing sequence will cause oil in the rotary vane vacuum pump 23 to enter the sealed cavity 1 through the vacuum valve 30. After evacuation, open the SF6 filling valve 18. Connect the SF6 cylinder to the quick-connect fitting 19 (connected to the inlet of the SF6 filling valve 18) via a PU tube to fill the sealed cavity 1 with SF6 gas. The adjustable needle valve 17 at the inlet of the SF6 filling valve 18 can control the filling speed of the SF6 gas. The SF6 gas can be filled at 0.1 MPa-0.2 MPa. After the SF6 gas filling is complete, close the SF6 filling valve 18 and begin the voltage application experiment.
[0048] The electrostatic probe 35 is mounted on the telescopic end of the telescopic mechanism via the probe clamp 11. Before applying voltage, ensure the electrostatic probe is positioned on the turntable 8 to avoid interference from the electrostatic probe's charge accumulation on the surface of the epoxy-impregnated paper core model 33 during the experiment. The turntable 8 is connected to the sealed cavity 1 and is grounded. The electrostatic probe 35 can complete the zero-calibration operation 3mm outside the base plate 8. The diameter of the turntable 8 is the same as the diameter of the epoxy-impregnated paper core model 33. After the zero-calibration operation is completed, the telescopic mechanism can drive the electrostatic probe 35 to move vertically only in the y-axis direction to complete the measurement of the surface potential of the epoxy-impregnated paper core model 33. The y-axis direction is consistent with the central axis direction of the epoxy-impregnated paper core model 33.
[0049] The rotary motion servo motor 14 in the turntable drive mechanism is fixed to the bottom of the sealed cavity 1 by the rotary motion servo motor mounting base 10. The output shaft of the rotary motion servo motor 14 is equipped with a planetary reducer 13. The planetary reducer 13 reduces the speed of the rotary motion servo motor 14 and increases the output torque. The output end of the planetary reducer 13 is connected to the rotary transmission assembly 6. The rotary transmission assembly 6 passes through the bottom of the sealed cavity 1 and is sealed to the sealed cavity 1. The planetary reducer 13 can drive the turntable 8 to rotate the epoxy impregnated paper core model 33 through the rotary transmission assembly 6. The rolling pulley on the grounding assembly 3 and the rotating tip 12 can ensure the normal rotation of the epoxy impregnated paper core model 33 inside the sealed cavity 1. The telescopic mechanism includes a linear motion servo motor 15 and a linear motion servo motor mounting base 9. The linear motion servo motor 15 is fixed to the bottom of the sealed cavity 1 via the linear motion servo motor mounting base 9. The telescopic end is located inside the sealed cavity 1. The electrostatic probe 35 is fixed to the upper end (i.e., the telescopic end) of the linear motion servo motor 15 via an insulated probe clamp 11. The electrostatic probe 35 can be driven by the linear motion servo motor 15 to move linearly up and down. The electrostatic probe 35 is perpendicular to the surface of the epoxy-impregnated paper core model 33, and the distance between the detection end of the electrostatic probe 35 and the surface of the epoxy-impregnated paper core model 33 is 3mm. The detailed measurement process of the surface potential of the epoxy-impregnated paper core model 33 is as follows:
[0050] The electrostatic probe 35 passes through the probe wiring flange 29 on the sealed cavity 1. During measurement, the linear motion servo motor 15 drives the electrostatic probe 35 to first complete the voltage zeroing operation at the turntable 8 position, so that the zero potential of the electrostatic probe 35 corresponds to the ground potential of the sealed cavity 1. After the voltage zeroing operation is completed, the linear motion servo motor 15 drives the electrostatic probe 35 to move from the lowest end of the core epoxy impregnated paper core model 33 to a preset distance at the lower edge of the flange 34 and then stops. This preset distance should ensure that the electrostatic probe 35 does not contact the lower edge of the flange 34, and is generally 10cm. During this process, the electrostatic probe 35 performs a linear measurement of the surface potential of the core epoxy impregnated paper core model 33. Then, the rotation servo motor 14 drives the turntable 8 to rotate, so that the turntable 8 drives the epoxy impregnated paper core model 33 to rotate at a constant speed of 1°. After rotation, the linear motion servo motor 15 drives the electrostatic probe 35 to move at a constant speed from 10mm below the lower edge of the flange 34 to the lowest point of the epoxy impregnated paper core model 33. Then, the rotary servo motor 14 drives the turntable 8 to rotate, causing the turntable 8 to rotate the epoxy impregnated paper core model 33 by another 1° at a constant speed. The linear motion servo motor 15 then drives the electrostatic probe 35 from the lowest point of the epoxy impregnated paper core model 33 to a preset distance below the lower edge of the flange 34 and stops. The linear motion servo motor 15 and the rotary servo motor 14 work together to ensure that the electrostatic probe 35 completes the measurement of the surface potential of the lower half of the epoxy impregnated paper core model 33 according to the above scanning method. Since the epoxy impregnated paper core model 33 is symmetrical on both sides of the mounting flange 34, only the surface potential of the lower half of the epoxy impregnated paper core model 33 needs to be tested. This invention enables the vertical motion of the electrostatic probe in the y-direction to be coordinated with the rotational motion of the core in the z-axis by using a linear motion servo motor 15 and a rotary servo motor 14. The surface potential of the core model can be measured by using two servo motors, which reduces the complexity of motion control and reduces the influence of redundant metal devices in the sealed cavity on the study of the charge accumulation characteristics of the core surface.
[0051] The control box 24 is used to send motion commands to the linear motion servo motor 15 and the rotary servo motor 14 to control the movement of the electrostatic probe 35 and the epoxy impregnated paper core model 33, thereby completing the measurement of the surface potential of the epoxy impregnated paper core model 33. At the same time, the control box 24 transmits the measured surface potential data to the industrial control computer 25 for processing and storage, and displays the measured potential curve on the display screen 26.
[0052] In the above-described embodiment of the present invention, the connecting device inside the sealed cavity 1 adopts a detachable structure. By replacing the connecting parts, it can also be used for surface potential measurement of gas through-wall bushings and single-post insulator models in GIL pipe racks. The sealed cavity 1 can also be equipped with a vacuum fiber optic connector 27, which facilitates the development of optical probes for measuring surface potential.
[0053] The surface potential measurement system for the epoxy-impregnated paper core model of the ultra-high voltage through-wall bushing described in this embodiment is used to measure the surface potential of the ultra-high voltage bushing core model according to the following steps:
[0054] Step 1: Before the experiment, first wipe the surface of the epoxy-impregnated paper core model 33 clean with anhydrous ethanol to remove dust and other impurities, preventing interference with the measurements. Then wrap the epoxy-impregnated paper core model 33 in clean aluminum foil and place it in a vacuum drying oven for one week at 80°C. This minimizes the interference caused by moisture on the epoxy-impregnated paper core model 33.
[0055] Step 2: After the epoxy impregnated paper core model 33 has dried, install and fix the epoxy impregnated paper core model 33 inside the sealed cavity 1. After installation, first check whether the electrostatic probe 35 is 1mm-3mm away from the surface of the epoxy impregnated paper core model 33, and whether the probe clamp 11 is firmly fixed. Before vacuuming, turn on the linear motion servo motor 15 and the rotary servo motor 14, and check whether the operation process of the linear motion servo motor 15 and the rotary servo motor 14 is correct.
[0056] Step 3: After checking the linear motion servo motor 15 and the rotary servo motor 14, close the cavity door 31 and tighten it with the fastening bolts 32. Perform a vacuuming operation on the sealed cavity 1. Then, according to the experimental requirements, fill it with SF6 gas at 0.1MPa-0.2MPa. At this time, ground the high-voltage end of the high-voltage insulating sleeve 2 and measure the initial surface potential of the epoxy impregnated paper core model 33 below the flange 34. Since the flange 34 is fitted outside the epoxy impregnated paper core model 33 and in contact with the grounding tap, when the surface potential amplitude of the epoxy impregnated paper core model 33 below the flange 34 is less than 10V, it can be considered that the charge on the surface of the epoxy impregnated paper core model 33 has been basically dissipated, and a pressure test can be carried out for a certain period of time. Otherwise, the epoxy impregnated paper core model 33 needs to be placed in the SF6 environment and the high-voltage end of the high-voltage insulating sleeve 2 needs to be grounded so that the charge on the surface of the epoxy impregnated paper core model 33 can be dissipated through the grounding end.
[0057] Step 4: The DC voltage input from high-voltage insulating bushing 2 can be selected within ±40kV to conduct a charge accumulation experiment for a certain period of time. Before applying voltage, check that the circuit connections are correct to ensure experimental safety.
[0058] Step 5: Two minutes before the end of the experiment, start the industrial computer 25, control box 24, and electrometer to put the equipment into normal operation, measurement, and data acquisition state. During this stage, the electrostatic probe should be calibrated to zero.
[0059] Step 6: After the experiment, turn off the high-voltage power supply, touch the inlet terminal of the high-voltage insulating bushing 2 with a grounding rod, and suspend the grounding wire at the high-voltage inlet terminal to change the high potential during the pressurization process to ground potential. Then, quickly start the measurement program to allow the electrostatic probe 35 to complete the measurement of the surface potential of the epoxy impregnated paper core model 33. This measurement is called the initial measurement.
[0060] Step 7: After the initial measurement is completed, the surface potential of the epoxy impregnated paper core model 33 can be measured again every 1 hour to investigate the dissipation characteristics of the surface potential of the epoxy impregnated paper core model 33 under the experimental conditions.
[0061] Step 8: Analyze the experimental data. The surface data of the epoxy-impregnated paper core model 33 under different air pressures, voltage amplitudes, and pressurization durations are exported and analyzed. Combined with the simulation model, the accumulation and dissipation characteristics of the surface charge of the epoxy-impregnated paper core model 33 with respect to parameters such as air pressure, voltage amplitude, and pressurization duration are analyzed. This is of great significance for studying the charge accumulation and dissipation mechanism at the interface between the UHV bushing core and SF6, exploring effective methods to suppress charge accumulation, reducing the risk of surface flashover of the bushing core, and maintaining the stable operation of the UHV bushing.
Claims
1. A surface potential measurement system for epoxy-impregnated paper core model of ultra-high voltage through-wall bushing, characterized in that, The system includes a sealed cavity (1), a high-voltage insulating sleeve (2), a grounding assembly (3), a turntable (8), a telescopic mechanism, a main gas filling and discharging pipe assembly (5), an electrostatic probe (35), and a flange (34). The flange (34) can be fitted onto the outside of the epoxy impregnated paper core model (33) and contact the grounding tap of the epoxy impregnated paper core model (33). The high-voltage insulating sleeve (2) is installed on the top of the sealed cavity (1) and penetrates the sealed cavity (1). The connection between the high-voltage insulating sleeve (2) and the sealed cavity (1) is insulated and sealed. One end of the grounding assembly (3) is fixedly connected to the sealed cavity (1), and the other end of the grounding assembly (3) can contact the outer surface of the flange (34). (2) The lower end of the conductor is connected to a rotating connection mechanism that can be rotatably connected to the upper end of the guide rod of the epoxy impregnated paper core model (33). The rotating connection mechanism is a conductor. The turntable (8) is installed in the sealed cavity (1) and located below the high-voltage insulating sleeve (2). An insulating support (4) that can be connected to the lower end of the guide rod of the epoxy impregnated paper core model (33) is installed on the upper part of the turntable (8). The electrostatic probe (35) is set in the sealed cavity (1). The electrostatic probe (35) is insulatedly installed at the movable end of the telescopic mechanism. The fixed end of the telescopic mechanism is connected to the sealed cavity (1). The telescopic direction of the telescopic mechanism is parallel to the rotating shaft of the turntable (8). The inflation and deflation manifold assembly (5) is connected to the sealed cavity (1). The grounding component (3) is connected to the flange (34) at one end with an elastic device. A rolling pulley is installed on the elastic device. The rolling pulley can contact the surface of the flange (34). The elastic device can keep the surface of the rolling pulley in contact with the surface of the flange (34). The rolling pulley is a conductor and is electrically connected to the sealing cavity (1). The rotating connection mechanism adopts a rotating tip (12), which is a conductor. The upper end of the rotating tip (12) is fixedly connected to the conductor inside the high-voltage insulating sleeve (2), and the lower end of the rotating tip (12) can be detachably electrically connected to the upper end of the guide rod of the epoxy impregnated paper core model (33).
2. The surface potential measurement system for epoxy-impregnated paper core model of ultra-high voltage through-wall bushing according to claim 1, characterized in that, It also includes a turntable drive mechanism for driving the turntable (8) to rotate. The turntable drive mechanism includes a rotary transmission assembly (6), a rotary motion servo motor (14), a rotary motion servo motor mounting base (10), and a reducer. The rotary transmission assembly (6) is installed at the bottom of the sealed cavity (1) and passes through the sealed cavity (1). The rotary transmission assembly (6) is rotatably connected to and sealed with the sealed cavity (1). The rotary motion servo motor mounting base (10) is installed outside the sealed cavity (1). The rotary motion servo motor (14) is installed on the rotary motion servo motor mounting base (10). The output shaft of the rotary motion servo motor (14) is connected to the input end of the rotary transmission assembly (6) through the reducer. The output end of the rotary transmission assembly (6) is connected to the turntable (8).
3. The surface potential measurement system for epoxy-impregnated paper core model of ultra-high voltage through-wall bushing according to claim 2, characterized in that, Both the turntable (8) and the rotary transmission assembly (6) are conductors. The turntable (8), the rotary transmission assembly (6) and the sealed cavity (1) are at the same potential. The diameter of the turntable (8) is the same as the outer diameter of the epoxy impregnated paper core model (33).
4. The surface potential measurement system for epoxy-impregnated paper core model of ultra-high voltage through-wall bushing according to claim 1, characterized in that, The electrostatic probe (35) is perpendicular to and coplanar with the axis of rotation of the turntable (8).
5. The surface potential measurement system for epoxy-impregnated paper core model of ultra-high voltage through-wall bushing according to claim 1, characterized in that, The inflation / deflation manifold assembly (5) includes an inflation valve, a vacuum valve (30), and a tee. One end of the tee is connected to the inner cavity of the sealed cavity (1), and the inflation valve and vacuum valve (30) are respectively installed at the other two ends of the tee.
6. The surface potential measurement system for epoxy-impregnated paper core model of ultra-high voltage through-wall bushing according to claim 1, characterized in that, A sight glass observation window (28) is provided on the sealed cavity (1).
7. The surface potential measurement system for epoxy-impregnated paper core model of ultra-high voltage through-wall bushing according to claim 1, characterized in that, A pressure gauge (16) is provided on the sealed cavity (1) for detecting the pressure inside the sealed cavity (1).
8. A method for measuring the surface potential of an epoxy-impregnated paper core model for ultra-high voltage through-wall bushings, characterized in that... This method employs the surface potential measurement system for the epoxy-impregnated paper core model of the ultra-high voltage through-wall bushing as described in any one of claims 1-7, and includes the following steps: Installation process: Fit a flange (34) around the epoxy impregnated paper core model (33) to be tested, so that the flange (34) contacts the grounding tap of the epoxy impregnated paper core model (33); after the flange (34) and the epoxy impregnated paper core model (33) are connected, connect the upper end of the guide rod of the epoxy impregnated paper core model (33) to the rotating connection mechanism, fix the lower end of the guide rod of the epoxy impregnated paper core model (33) to the upper end of the insulating support (4), and make the axis of the epoxy impregnated paper core model (33) coaxial with the axis of rotation of the turntable (8), and make the grounding component (3) contact the outer surface of the flange (34); after the epoxy impregnated paper core model (33) is installed, adjust the electrostatic probe (35) to maintain a preset distance from the epoxy impregnated paper core model (33); ground the lower end of the sealing cavity (1) and the insulating support (4); Gas filling and emptying process: After the installation process is completed, the sealing cavity (1) is sealed, and the inner cavity of the sealing cavity (1) is evacuated through the gas filling and emptying manifold assembly (5). When the vacuum degree in the sealing cavity (1) reaches the preset value, the gas filling and emptying manifold assembly (5) is switched to stop evacuation, and then insulating gas is filled into the sealing cavity (1). When the insulating gas in the sealing cavity (1) reaches the preset pressure, the gas filling and emptying manifold assembly (5) is switched to stop filling the insulating gas. Voltage measurement process: Before applying voltage, the position of the electrostatic probe (35) is adjusted by the telescopic mechanism, and the voltage of the electrostatic probe (35) is calibrated to 0. After the voltage calibration is completed, the preset voltage is applied to the epoxy impregnated paper core model (33) through the high voltage insulating sleeve (2), and then the surface potential of the epoxy impregnated paper core model (33) is measured. The process of measuring the surface potential of the epoxy-impregnated paper core model (33) includes the following steps: Step 1: Drive the electrostatic probe (35) through the telescopic mechanism to move the electrostatic probe (35) from the lower end of the epoxy impregnated paper core model (33) to the flange (34). The electrostatic probe (35) stops moving. During the movement, the electrostatic probe (35) measures the surface potential of the epoxy impregnated paper core model (33). Then, drive the epoxy impregnated paper core model (33) to rotate by a preset angle through the turntable (8). After that, the turntable (8) stops. Step 2: Drive the electrostatic probe (35) through the telescopic mechanism to return the electrostatic probe (35) to the lower end of the epoxy impregnated paper core model (33), and stop the movement of the electrostatic probe (35). During the movement, the electrostatic probe (35) measures the surface potential of the epoxy impregnated paper core model (33); then drive the epoxy impregnated paper core model (33) to rotate by a preset angle through the turntable (8). Step 3: Repeat steps 1 to 2 until the turntable (8) rotates at least once to complete the measurement of the surface potential of the epoxy impregnated paper core model (33).