Device and method for testing charge distribution and surface flashover characteristic of GIL insulator

Abstract

The invention discloses a device and method for testing charge distribution and GIL insulator surface flashover characteristics, and the device comprises a closed experiment cavity, an insulator rotating table is disposed in the middle of the interior of the closed experiment cavity, and the insulator rotating table is connected with a rotation control system and controls the vertical movement and rotation movement of the insulator rotating table. The top of the insulator rotating table is provided with a top clamp used for clamping an insulator, the corona pin is fixed to the upper portion in the closed experiment cavity through a three-dimensional fine adjustment support and connected with an external high-voltage power source through a high-voltage terminal, the probe is installed on the inner side of the cavity through a fixed rotating device, and the measuring face of the probe faces the surface of the insulator. The probe is used for scanning and detecting surface potential distribution, and a probe signal is led to the electrostatic potentiometer through a shielding cable and is recorded and processed in real time through an oscilloscope and a data acquisition system. A real electric field environment of a direct current GIL coaxial cylinder structure can be simulated to measure complex curved surface charge distribution, and a mapping model of a charge accumulation state and a surface flashover characteristic is established.

Description

Technical Field

[0001] This invention belongs to the field of surface flashover characteristic testing technology. The invention relates to a test device and method for charge distribution and surface flashover characteristics of GIL insulators. Background Technology

[0002] In high-voltage direct current (HVDC) gas-insulated metal-enclosed transmission lines (GILs), solid insulators are subjected to high unipolar electric fields for extended periods, leading to abnormal charge accumulation at the gas-solid interface and severe distortion of the surface electric field distribution. This phenomenon not only induces insulation failures such as surface flashover but also directly affects the long-term operational reliability of the equipment, becoming a key technical bottleneck restricting the development of DC GIL technology to higher voltage levels. However, the mechanism by which charge accumulation affects the surface withstand voltage of insulators remains unclear, and quantitative research methods are lacking, severely hindering the optimal design of insulation structures.

[0003] Existing technologies primarily focus on charge accumulation characteristics, failing to establish a quantitative correlation model between charge distribution and flashover voltage, thus unable to reveal the path of charge distortion electric field's influence on insulation failure. Regarding flashover experimental setups, traditional platforms employ flat electrodes or simplified insulation structures. However, the surface electric field distribution of basin-type insulators in actual operation is quite complex. Simplified models cannot reasonably represent the insulator as an equivalent, failing to recreate the true coaxial cylindrical electric field environment of a real GIL (Gas Insulator Voltage), leading to significant deviations between experimental results and actual operating conditions. Furthermore, the measurement of charge distribution on complex curved insulator surfaces is susceptible to charge dissipation interference. Existing scanning devices struggle to achieve dynamic tracking of curved surfaces while maintaining a constant spacing, affecting data accuracy. Summary of the Invention

[0004] In view of the shortcomings of existing devices in reproducing real working conditions and actively controlling charge variables, the purpose of this invention is to provide a test device and method for charge distribution and surface flashover characteristics of GIL insulators, which can simulate the real electric field environment of DC GIL coaxial cylindrical structure to measure the charge distribution of complex curved surfaces and establish a mapping model between charge accumulation state and surface flashover characteristics.

[0005] The technical solution to achieve the purpose of this invention is as follows: A testing device for charge distribution and surface flashover characteristics of GIL insulators includes a sealed experimental cavity. An insulator rotating platform is positioned in the center of the cavity. The rotating platform is connected to a rotation control system, which controls the vertical and rotational movement of the platform. A top clamp is positioned on the top of the rotating platform for clamping the insulator. Electrodes are positioned on the upper and lower sides of the top clamp and connected to a high-voltage power supply. A corona needle is fixed to the upper part of the sealed experimental cavity via a three-dimensional fine-tuning bracket for three-dimensional adjustment. The corona needle is connected to an external high-voltage power supply via a high-voltage terminal. A probe is mounted inside the cavity via a fixed rotating device, with its measuring surface facing the insulator surface. This probe is used to scan and detect the surface potential distribution. The probe signal is led to an electrostatic potentiometer via a shielded cable. The electrostatic potentiometer is connected to an oscilloscope and data acquisition system outside the cavity, and the data is recorded and processed in real time via the oscilloscope and data acquisition system.

[0006] In a preferred embodiment, the insulator rotary table includes a vertical motion module and a rotary motion module. The vertical motion module includes a stepper motor and a ball screw transmission mechanism to drive the insulator to translate vertically, so that each area of ​​the insulator surface can be aligned with the probe. The rotary motion module uses a servo motor to drive the top clamp to rotate around the axis via a coupling. The ball screw transmission mechanism of the vertical motion module is connected to the coupling via a fixed frame, and works with the probe to complete the ring-by-ring scanning of the insulator's annular surface.

[0007] In the preferred embodiment, the corona needle is a tungsten alloy corona needle with a tip curvature radius of less than 50 micrometers.

[0008] In a preferred embodiment, the corona needles comprise multiple needles arranged in an equilateral triangle to form a corona needle array. By synchronously applying voltage, the corona discharge scenario generated by insulation defects at multiple locations on the surface of the insulator is simulated.

[0009] In a preferred embodiment, the fixed rotation device for the probe includes a housing, the housing is provided with a support frame and a rotation mechanism, a rotating shaft is rotatably connected to the support frame, the rotation mechanism rotates by meshing with the rotating shaft through a rotating gear, and a probe is provided at the end of the rotating shaft.

[0010] In a preferred embodiment, the sealed experimental cavity is equipped with a vacuum pump or connected to an inert gas pipeline.

[0011] This invention also discloses a test method for charge distribution and surface flashover characteristics of GIL insulators, applied to the test apparatus for charge distribution and surface flashover characteristics of GIL insulators described in any of the above claims, comprising the following steps: The insulator is clamped in the top clamp of the test device, and the required vacuum environment is established in the sealed experimental cavity before the pressurization operation is performed. The probe and corona needle were retracted, and pressure was applied to the top and bottom of the insulator to simulate flashover during normal equipment operation. The corona needle was connected to the high-voltage end and placed close to the side of the insulator to simulate corona discharge caused by insulation defects. The relationship between injected charge and flashover under different pressure application methods was obtained. Different voltage levels were applied, and the flashover voltages corresponding to each voltage level were observed and recorded. These were then compared and analyzed with historical flashover data. Furthermore, the changes in flashover stable voltage under different temperatures were compared, and a mapping model between charge accumulation state and surface flashover characteristics was established.

[0012] In the preferred technical solution, the situations in which flashover occurs during normal operation of the simulated equipment include: The probe and corona needle were completely retracted to a fixed position that would not affect the electric field. Then, a high-voltage power supply was connected between the upper and lower electrodes of the insulator, and a DC voltage was applied at a constant boost rate until flashover occurred. The breakdown process under normal operating conditions of the equipment was simulated and its intrinsic flashover voltage was recorded.

[0013] In the preferred technical solution, the simulation of corona discharge caused by insulation defects includes: The corona needle is connected to the high-voltage output terminal. Its tip is positioned at a specified position on the side of the insulator and kept at a constant distance by a three-dimensional fine-tuning bracket. A voltage is continuously applied to perform stable corona discharge to pre-place space charge on the surface. Then, the corona voltage is quickly removed and the upper and lower electrodes are switched to apply voltage. The flashover voltage under this state is measured with the same voltage boosting procedure, so as to compare and analyze the effect of surface charge on the deterioration of insulation performance.

[0014] In the preferred technical solution, different voltage levels are applied, and the flashover voltage corresponding to each voltage level is observed and recorded, then compared and analyzed with historical flashover data; the changes in flashover stable voltage under different temperatures are also compared, including: Corona injection was performed at four voltage levels: 5kV, 15kV, 25kV, and 35kV. The flashover voltages at each voltage level were observed and recorded, and compared with historical flashover data. Simultaneously, a series of tests were conducted at five temperature points: 20℃, 40℃, 60℃, 80℃, and 100℃. The surface temperature of the samples was maintained, and the flashover stability voltage of the insulators in different temperature environments was measured to obtain the influence of temperature on the dynamic behavior of surface charge and the insulation failure threshold.

[0015] Compared with the prior art, the significant advantages of this invention are: This invention can simulate the real electric field environment of a DC GIL coaxial cylindrical structure to measure the charge distribution on complex curved surfaces, establish a mapping model between charge accumulation state and surface flashover characteristics, and reveal the influence mechanism of charge distribution on surface flashover characteristics.

[0016] To address the shortcomings of existing surface charge testing devices, which are mainly designed for planar sheet materials and are difficult to adapt to the three-dimensional morphology measurement of curved insulating components, this invention develops a multi-degree-of-freedom motion control system for supporting and positioning insulators, enabling quantitative measurement of the full surface charge distribution of curved insulators. Attached Figure Description

[0017] Figure 1 A schematic diagram of the test device for charge distribution and surface flashover characteristics of GIL insulators; Figure 2 This is a schematic diagram of an insulator structure; Figure 3 This is a schematic diagram of the insulator rotary table structure; Figure 4 This is a schematic diagram of the probe's fixed rotation device. Figure 5 These are the flashover voltages corresponding to different amplitudes of voltage under normal conditions. Figure 6 These are the flashover voltages at different temperatures under normal conditions. Figure 7 The effect of different temperatures on flashover voltage under defect conditions. Detailed Implementation

[0018] The principle of this invention is that the entire device, through the coordinated control of its various modules, can simulate the real electric field environment of a DC GIL coaxial cylindrical structure to measure the charge distribution on complex curved surfaces and establish a mapping model between charge accumulation state and surface flashover characteristics.

[0019] Example: like Figure 1 As shown, a test apparatus for charge distribution and surface flashover characteristics of GIL insulators includes a sealed experimental cavity 10. An insulator rotating platform 20 is disposed in the center of the sealed experimental cavity 10. The insulator rotating platform 20 is connected to a rotation control system, which controls the vertical and rotational movement of the insulator rotating platform. A top clamp 25 is disposed on the top of the insulator rotating platform 20 for clamping a curved insulator 30. The insulator 30 is as follows... Figure 2As shown, electrodes (not shown in the figure) are set on the upper and lower sides of the top clamp. The electrodes are connected to a high-voltage power supply. The corona needle 40 is fixed to the upper part of the sealed experimental cavity 10 through a three-dimensional fine-tuning bracket. The three-dimensional fine-tuning bracket is used for three-dimensional adjustment. The corona needle 40 is connected to an external high-voltage power supply through a high-voltage terminal. The probe 50 is installed inside the cavity 10 through a fixed rotation device. The measuring surface of the probe 50 faces the surface of the insulator 30 and is used to scan and detect the surface potential distribution. The probe signal is led to the electrostatic potentiometer 60 through a shielded cable. The electrostatic potentiometer 60 is connected to an oscilloscope and data acquisition system outside the cavity. The oscilloscope and data acquisition system record and process the data in real time.

[0020] The sealed experimental cavity 10 is made of stainless steel and is equipped with a vacuum pump or connected to an inert gas pipeline. Specifically, the sealed experimental cavity 10 has a volume of 1 m³ and is equipped with a quartz glass observation window (withstanding 0.8 MPa pressure), an electrode post adapter electrode (DC withstand voltage 20 kV), a pressure vacuum gauge (range 0-1 MPa), and a safety valve (threshold 0.8 MPa) to ensure a stable gas environment.

[0021] Gas environment treatment method for sealed experimental cavity 10: High-purity inert gas can be used to replace the air in the cavity instead of vacuum treatment. By controlling the flow rate and pressure of nitrogen, a clean and stable gas insulation environment can also be created to avoid interference from impurities in the air on charge accumulation.

[0022] The corona needle 40 is a tungsten alloy corona needle with a tip curvature radius of less than 50 micrometers. Its position can be adjusted using a three-dimensional fine-tuning bracket to align with a specific area on the insulator surface. The structure of the three-dimensional fine-tuning bracket can adopt an existing structure, which will not be described in detail here.

[0023] In a preferred embodiment, the corona needle 40 includes multiple needles arranged in an equilateral triangle to form a corona needle array. By synchronously applying voltage, the corona discharge scenario generated by insulation defects at multiple locations on the surface of the insulator is simulated.

[0024] Regarding the adjustment and optimization of the pressurization method: the original upper and lower flat plate electrodes can be replaced with arc-shaped electrodes that are compatible with the curved surface of the insulator.

[0025] A preferred embodiment, such as Figure 3As shown, the insulator rotary table 20 includes a vertical motion module and a rotary motion module. The vertical motion module includes a stepper motor 21 and a ball screw transmission mechanism 22, which drives the insulator 30 to translate vertically. The positioning resolution is 1 mm, and the effective stroke is 50 cm, ensuring that all areas of the insulator 30 surface can be aligned with the probe. The rotary motion module uses a servo motor 23 to drive the top clamp 25 to rotate around its axis via a coupling 24. The angular displacement control accuracy is 1°. The ball screw transmission mechanism 22 of the vertical motion module is connected to the coupling 24 via a fixed frame 26, and works with the probe 50 to complete the ring-by-ring scanning of the annular surface of the insulator 30. Based on the coordinated control of the linear and rotary motions, combined with the corona injection module and potential detection unit mounted on an independent adjustment bracket, quantitative measurement of the charge distribution across the entire surface of the curved insulator is achieved.

[0026] A preferred embodiment, such as Figure 4 As shown, the probe 50 is used to detect the charge generated by corona injection or other means. The fixed rotation device of the probe 50 includes a housing 51. The housing 51 is provided with a support frame 52 and a rotation mechanism 53. A rotating shaft 54 ​​is rotatably connected (e.g., a bearing) on ​​the support frame 52. The rotation mechanism 53 rotates by meshing with the rotating shaft 54 ​​through a rotating gear 55. The probe 50 is provided at the end of the rotating shaft 54.

[0027] The electrostatic potentiometer 60 can also be replaced by other non-contact electrostatic measuring instruments, such as electrostatic voltage scanners. By adjusting the scanning step size and sampling frequency, it is still possible to accurately collect the surface potential of the insulator and then convert it into charge distribution data.

[0028] The electrostatic potentiometer 60 amplifies, processes, and converts the surface potential signal sensed by the probe into a standard voltage signal. Subsequently, a high-precision oscilloscope and data acquisition system record and process the signal in real time, thus forming a complete integrated platform for charge injection, control, and measurement.

[0029] Another embodiment, a method for testing charge distribution and surface flashover characteristics of GIL insulators, includes the following steps: The insulator is clamped in the top clamp of the test device, and the required vacuum environment is established in the sealed experimental cavity before the pressurization operation is performed. The probe and corona needle were retracted, and pressure was applied to the top and bottom of the insulator to simulate flashover during normal equipment operation. The corona needle was connected to the high-voltage end and placed close to the side of the insulator to simulate corona discharge caused by insulation defects. The relationship between injected charge and flashover under different pressure application methods was obtained. Different voltage levels were applied, and the flashover voltages corresponding to each voltage level were observed and recorded. These were then compared and analyzed with historical flashover data. Furthermore, the changes in flashover stable voltage under different temperatures were compared, and a mapping model between charge accumulation state and surface flashover characteristics was established.

[0030] Before surface charge injection, the sample was cleaned with anhydrous ethanol to remove residual charge, and the pressurization operation was performed after establishing the required vacuum environment in the sealed experimental cavity.

[0031] The following are examples of flashover situations that may occur during normal operation of analog equipment: The probe and corona needle are completely retracted to a fixed position that does not affect the electric field. Then, a high-voltage power supply is connected between the upper and lower electrodes of the insulator, and a DC voltage is applied at a constant boost rate (e.g., 1 kV per second) until a flashover occurs. The breakdown process under normal operating conditions of the equipment is simulated and its intrinsic flashover voltage is recorded.

[0032] Furthermore, to simulate the charge accumulation effect caused by surface insulation defects, a corona needle was connected to the high-voltage output terminal. The tip of the needle was positioned at a specified location on the side of the insulator and kept at a constant distance (e.g., 2 mm) by a three-dimensional fine-tuning bracket. A voltage was continuously applied (e.g., for 60 seconds) to perform stable corona discharge to pre-place space charge on the surface. Then, the corona voltage was quickly removed and the upper and lower electrodes were switched to be pressurized. The flashover voltage under this state was measured with the same voltage boosting procedure, so as to compare and analyze the effect of surface charge on the deterioration of insulation performance.

[0033] Specifically, corona injection was performed at four voltage levels: 5kV, 15kV, 25kV, and 35kV. The flashover voltage corresponding to each voltage level was observed and recorded, and compared with historical flashover data. Simultaneously, a series of experiments were conducted at five temperature points: 20℃, 40℃, 60℃, 80℃, and 100℃. The surface temperature of the samples was maintained, and the flashover stability voltage of the insulators in different temperature environments was measured. The influence of temperature on the dynamic behavior of surface charge and the insulation failure threshold was obtained. The response relationship between charge accumulation behavior and flashover voltage under different voltage amplitudes and temperature conditions was obtained, thereby establishing a mapping model between charge accumulation state and surface flashover characteristics.

[0034] The specific analysis process is as follows: pass Figure 1 The platform simulates the charge distribution during normal operation and insulation damage operation, and analyzes its flashover voltage. First, for the insulator sample simulating normal operation, the flashover voltage corresponding to different amplitude voltages is calculated as follows: Figure 5 As shown, when different voltages are applied directly to the test specimens, their flashover voltages do not show a significant difference compared to those of specimens without charge accumulation, and both exhibit considerable dispersion. In contrast, the flashover voltages of specimens that have experienced flashover have lower dispersion and higher mean values. This suggests that the charge accumulated during flashover may help increase subsequent flashover voltages and enhance their stability.

[0035] according to Figure 6As shown, the flashover voltage of the sample changes with temperature after the flashover reaches a stable state. The data points in the figure are the average results of multiple experiments. Under high-temperature conditions, the degree of gas ionization is enhanced, and the carrier concentration increases, resulting in a greater actual amount of charge accumulating on the surface of the insulating medium than at low temperatures. However, due to the intensified thermal motion of gas molecules at high temperatures, the distribution of positive and negative charges on the medium surface tends to be more uniform, resulting in a relatively reduced net charge. Although the distortion effect of the smaller net charge on the original electric field is weaker, this only applies to the initial stage of flashover. During the further development of flashover, the large number of positive and negative charges distributed along the flashover path will interact with the charges inside the channel, ultimately affecting the formation of flashover. The greater actual accumulation of charge under high-temperature conditions significantly enhances the effect of this process.

[0036] For samples simulating insulation defects through corona discharge, the effect of different temperatures on flashover voltage is as follows: Figure 7 As shown, under relatively low temperature conditions, corona treatment causes a decrease in the flashover voltage of the sample. As the ambient temperature rises, the flashover voltage gradually increases; when the temperature exceeds 60℃, the flashover voltage of the corona-treated sample recovers to the flashover voltage value of the untreated state and remains stable throughout subsequent heating processes.

[0037] Experimental results show that neither direct pressure application nor weak corona treatment caused a significant change in the flashover voltage of the samples; however, the charge accumulation generated by the flashover process or high-intensity corona significantly affected the flashover characteristics of the samples. The residual charge after flashover not only helps to increase the flashover voltage of the samples but also enhances their stability.

[0038] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A testing device for the charge distribution and the surface flashover characteristics of GIL insulators, comprising a closed experimental cavity, characterized in that, The middle part of the closed experimental cavity is provided with an insulator rotating table, the insulator rotating table is connected with a rotating control system, the rotating control system controls vertical movement and rotating movement of the insulator rotating table, the top of the insulator rotating table is provided with a top clamp, the top clamp is used for clamping an insulator, electrodes are arranged on the upper and lower sides of the top clamp, the electrodes are connected with a high-voltage power supply, a corona needle is fixed to the upper part in the closed experimental cavity through a three-dimensional fine adjustment support, and the corona needle is used for scanning and detecting surface potential distribution, a probe signal is led to an electrostatic potential meter through a shielded cable, the electrostatic potential meter is connected with an oscilloscope and a data acquisition system outside the cavity, and the oscilloscope and the data acquisition system are used for real-time recording and processing.

2. The test device for charge distribution and GIL insulator surface flashover characteristics according to claim 1, characterized in that, The insulator rotating table comprises a vertical movement module and a rotating movement module, the vertical movement module comprises a stepping motor and a ball screw transmission mechanism, the ball screw transmission mechanism drives the insulator to move in the vertical direction, so that each region of the surface of the insulator can be aligned with the probe, and the rotating movement module drives the top clamp to rotate around the axis through a servo motor and a shaft coupling, and the ball screw transmission mechanism of the vertical movement module is connected with the shaft coupling through a fixing frame, so that the probe can complete circle-by-circle scanning of the annular surface of the insulator.

3. The test device for charge distribution and GIL insulator surface flashover characteristics according to claim 1, characterized in that, The corona needle is a tungsten alloy corona needle, and the curvature radius of the needle tip is less than 50 microns.

4. The test device for charge distribution and GIL insulator surface flashover characteristics according to claim 1, characterized in that, The corona needle comprises a plurality of corona needles, the plurality of corona needles are arranged in an equilateral triangle shape to form a corona needle array, and the corona needle array is used for simulating a corona discharge scene generated by multiple position insulation defects on the surface of the insulator by synchronously applying a voltage.

5. The test device for charge distribution and GIL insulator surface flashover characteristics according to claim 1, characterized in that, The fixing rotating device of the probe comprises a shell, the shell is provided with a support frame and a rotating mechanism, a rotating shaft is rotatably connected to the support frame, the rotating mechanism is engaged with the rotating shaft through a rotating gear to rotate, and the rotating shaft is provided with the probe at the end.

6. The test device for charge distribution and GIL insulator surface flashover characteristics according to claim 1, characterized in that, The closed experimental cavity is provided with a vacuumizing device or connected with an inert gas pipeline.

7. A method for testing the characteristics of surface flashover of a charge distribution and GIL insulator, applied to the testing device for the characteristics of surface flashover of a charge distribution and GIL insulator according to any one of claims 1-6, characterized in that, The method comprises the following steps: The insulator is clamped on the top clamp of the test device, and the pressurizing operation is performed after the required vacuum environment is established in the closed experimental cavity; The probe and the corona needle are retracted, the insulator is pressurized from top to bottom, the situation of flashover occurring during normal operation of the equipment is simulated, the corona needle is connected with the high-voltage end, the side of the insulator is approached, the situation of corona discharge generated by an insulation defect is simulated, and the relationship between injected electric charge and flashover under different pressurizing modes is obtained; Different levels of voltage are applied respectively, the corresponding flashover voltage of each voltage level is observed and recorded, and the historical flashover data is compared and analyzed; and the change of the stable voltage of flashover under different temperatures is compared, and a mapping model of the charge accumulation state and the surface flashover characteristics is established.

8. The method of claim 7, wherein the method further comprises: The situation of flashover occurring during normal operation of the equipment comprises: The probe and the corona needle are completely retracted to a fixed position without affecting the electric field, then the high-voltage power supply is connected between the upper and lower electrodes of the insulator, a direct current voltage is applied at a constant voltage increasing rate until flashover occurs, the breakdown process under the normal operation condition of the equipment is simulated, and the intrinsic flashover voltage is recorded.

9. The method of claim 8, wherein the method further comprises: The situation of corona discharge generated by an insulation defect comprises: The corona needle is connected to a high-voltage output end, and the tip thereof is positioned at a specified position on the side of the insulator and kept at a constant distance by a three-dimensional fine adjustment support, a voltage is continuously applied to stabilize the corona discharge to preset space charges on the surface, then the corona voltage is quickly removed and the upper and lower electrodes are switched to be pressurized, the flashover voltage in this state is measured by the same voltage rising procedure, and thus the influence of surface charges on the degradation of insulation performance is compared and analyzed.

10. The method of claim 7, wherein the method further comprises: Different levels of voltage are respectively applied, the flashover voltage corresponding to each voltage level is observed and recorded, and comparison and analysis are made with historical flashover data; and the change of the flashover stable voltage at different temperatures is compared, including: Corona injection is carried out at four voltage levels of 5 kV, 15 kV, 25 kV and 35 kV, the flashover voltage corresponding to each voltage level is observed and recorded, and comparison and analysis are made with historical flashover data; meanwhile, a series of tests are carried out at five temperature points of 20℃, 40℃, 60℃, 80℃ and 100℃, the surface temperature of the test sample is maintained, the flashover stable voltage of the insulator in different temperature environments is measured, and the influence law of temperature on the dynamic behavior of surface charges and the failure threshold of insulation is obtained.

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