Measuring device and method applied to frequency domain dielectric spectrum test

Abstract

The invention discloses a measuring device and method applied to a frequency domain dielectric spectrum test, the top of a measuring device body is provided with an air inlet valve, an air outlet valve and a measuring electrode interface, the bottom of an inner cavity is provided with a high-voltage electrode gasket, the upper surface of the high-voltage electrode gasket is provided with a high-voltage electrode, and the inner cavity is provided with a measuring electrode above the high-voltage electrode. The measuring electrode is connected with the measuring electrode interface through a wire, the measuring electrode is sleeved with a protection electrode, the outer diameter of the protection electrode is not larger than that of the high-voltage electrode, an annular cavity is formed between the measuring electrode and the protection electrode, the top face of the measuring electrode is connected with a measuring electrode gasket, and the lower surface of the measuring electrode gasket is fixedly connected with the top face of the protection electrode. A pressure balance hole is formed in the corresponding portion, above the annular cavity, of the measuring electrode gasket, and an integral structure formed by connecting the measuring electrode, the measuring electrode gasket and the protection electrode is connected with the top of the measuring device body through an elastic connecting structure. And the inner cavity of the measuring device body is also provided with a temperature control system for controlling the temperature of the insulating oil added into the measuring device body.

Description

Technical Field

[0001] The present invention belongs to the field of electrical insulation testing, and in particular relates to a measuring device and method for frequency domain dielectric spectrum testing. Background Art

[0002] With the rapid development of ultra-high voltage AC and DC transmission systems, dielectric insulation materials are increasingly being used in ultra-high voltage DC and ultra-high voltage DC transmission and transformation equipment. Transformers and bushings are critical components in the power transmission and transformation process, and their healthy operation is crucial to the safety and stability of power grid operations. The internal insulation of transformers and bushings primarily consists of oil-paper insulation, and its service life depends on the insulation performance of this system. Over long-term operation, the oil-paper insulation of transformers and bushings gradually ages or becomes damp due to factors such as temperature, electric fields, moisture, and mechanical stress, leading to a decrease in insulation performance.

[0003] In recent years, with the advancement of nondestructive testing technology, dielectric response techniques, represented by frequency-domain dielectric spectroscopy (FDS), have been widely used in the insulation evaluation of oil-paper insulation equipment. Compared with traditional testing methods, FDS offers advantages such as low noise susceptibility, rich information, and a narrow measurement bandwidth. However, the electrode systems currently used for frequency-domain dielectric spectroscopy testing of oil-paper insulation are often limited by the electrode system and temperature control system, failing to achieve both test accuracy and temperature control precision, thus compromising the accuracy and reliability of the experiment. Current oil-impregnated paper insulation testing uses a relatively small amount of oil, making it difficult to accurately simulate the actual operating environment, resulting in significant discrepancies between the measured dielectric properties and the actual oil-paper properties. Furthermore, during actual operation, the temperature of oil-paper insulation fluctuates continuously due to factors such as operating current and heat dissipation. Therefore, there is a need for a temperature-controlled measurement device and method for frequency-domain dielectric spectroscopy testing that can accurately control the temperature of the oil-paper insulation and assess the dielectric properties of oil-impregnated paper used in transformers or bushings under simulated operating conditions. Such a device will help to conduct in-depth research on the frequency-dependent characteristics of the dielectric constant and dielectric loss factor of oil-impregnated paper materials at different temperatures, accurately evaluate the aging status of oil-paper insulation, and thus improve the safety and reliability of transformers and bushings. Summary of the Invention

[0004] In order to solve the technical difficulties that the existing test electrode system and temperature control system cannot meet at the same time, the purpose of the present invention is to provide a measurement device and method for frequency domain dielectric spectrum testing. The present invention can measure the dielectric constant and dielectric loss factor of oil-paper insulation as a function of frequency at different temperatures, and study the influence of temperature on the dielectric properties of dielectric materials.

[0005] The technical solution adopted in the present invention is as follows: A measuring device for frequency domain dielectric spectrum testing includes a sealed measuring device body, wherein an air inlet valve, an air outlet valve and a measuring electrode interface are provided on the top of the measuring device body, a high-voltage electrode gasket is provided at the bottom of the inner cavity of the measuring device body, and a high-voltage electrode is provided on the upper surface of the high-voltage electrode gasket. A measuring electrode is provided above the high-voltage electrode in the inner cavity of the measuring device body, and the measuring electrode and the measuring electrode interface are connected by a wire. A protective electrode is provided on the outer sleeve of the measuring electrode, and the outer diameter of the protective electrode is not larger than the outer diameter of the high-voltage electrode. An annular chamber is formed between the outer wall of the measuring electrode and the inner wall of the protective electrode. The top surface of the measuring electrode is connected to the measuring electrode gasket, and the lower surface of the measuring electrode gasket is fixedly connected to the top surface of the protective electrode. A pressure balancing hole is opened on the measuring electrode gasket at a corresponding position above the annular chamber. The integral structure formed by the measuring electrode, the measuring electrode gasket and the protective electrode is connected to the top of the measuring device body by an elastic connection structure. The inner cavity of the measuring device body is also provided with a temperature control system for controlling the temperature of insulating oil added to the measuring device body.

[0006] Preferably, an elastic layer is provided between the measuring electrode and the measuring electrode gasket, and when the measuring electrode and the protective electrode do not apply pressure to the oil-immersed paper sample, the lower end of the measuring electrode protrudes from the lower end of the protective electrode.

[0007] Preferably, the elastic layer and the measuring pole are connected via a ball joint.

[0008] Preferably, the shape of the protective electrode is cylindrical, and the upper end of the protective electrode is provided with an outer flange; The elastic connection structure includes a support spring, a pressure spring and a support bolt. The outer flange is provided with a plurality of support bolts evenly distributed around the outer flange. The upper ends of the support bolts are threadedly connected to the top of the measuring device body, and the lower ends of the support bolts pass through the outer flange. The diameter of the through holes provided on the outer flange for the support bolts to pass through is larger than the diameter of the support bolts. The outer flange can slide up and down along the support bolts. All support bolts are distributed around the periphery of the measuring electrode gasket, and the support spring and pressure spring are arranged between the upper surface of the measuring electrode gasket and the top of the measuring device body. The support spring and pressure spring are both in a compressed state.

[0009] Preferably, the measuring device body includes a measuring device base and a measuring device top cover. The measuring device base is a container having a lower bottom, side walls and an inner cavity. The top of the measuring device base is open. The inner cavity of the measuring device base serves as the inner cavity of the measuring device body, and the measuring device top cover serves as the top of the measuring device body. The measuring device base and the measuring device top cover are detachably sealed by fixing bolts and a sealing ring.

[0010] Preferably, the temperature control system includes a thermocouple, a heating belt, a thermocouple temperature measurement system, a heating belt temperature control system and a controller. The thermocouple is arranged in the inner cavity of the measuring device body and is used to detect the temperature of the insulating oil in the inner cavity of the measuring device body. The thermocouple temperature measurement system is connected to the thermocouple, and the thermocouple temperature measurement system is used to parse the detection signal of the thermocouple into temperature information and display it; the heating belt is arranged on the outside of the measuring device body and is used to heat the measuring device body and the insulating oil in the inner cavity of the measuring device body. The heating belt temperature control system is connected to the heating belt, and the heating belt temperature control system is used to control the heating power of the heating belt; the thermocouple temperature measurement system and the heating belt temperature control system are both connected to the controller, and the controller is used to receive the temperature information parsed by the thermocouple temperature measurement system, and send an instruction to increase the heating power or maintain the heating power to the heating belt temperature control system according to the temperature information, and the heating belt temperature control system controls the heating power of the heating belt according to the instruction sent by the controller.

[0011] Preferably, the measuring device for frequency domain dielectric spectrum testing of the present invention further comprises a dielectric spectrometer, and the dielectric spectrometer is connected to the measuring electrode interface and the high voltage electrode via wires.

[0012] Preferably, the measuring device applied to the frequency domain dielectric spectrum test of the present invention also includes a data measurement and control system, which is connected to the measuring pole interface and the high-voltage pole through a wire. The data measurement and control system includes a voltage testing unit, a current testing unit and a data processing unit. The data processing unit is used to perform data analysis and processing based on the data of the voltage testing unit and the current testing unit to obtain the variation characteristics of the dielectric constant and dielectric loss factor of the oil-immersed paper sample under experimental conditions with the test frequency.

[0013] Preferably, the measuring electrode, the protective electrode and the high-voltage electrode are all made of stainless steel, and the high-voltage electrode gasket and the measuring electrode gasket are both made of polytetrafluoroethylene.

[0014] The present invention also provides a measurement method for frequency domain dielectric spectrum testing, which is performed using the measurement device for frequency domain dielectric spectrum testing described above, and includes the following steps: Add insulating oil to the surface of the high-voltage electrode so that the surface of the high-voltage electrode is covered with an insulating oil film. Place the prepared oil-impregnated paper sample on the insulating oil film on the surface of the high-voltage electrode, remove the bubbles between the oil-impregnated paper sample and the surface of the high-voltage electrode, and then add an appropriate amount of insulating oil to the measuring device body; The whole structure consisting of the measuring electrode, the measuring electrode gasket and the protective electrode is installed into the measuring device body, so that the measuring electrode, the protective electrode and the high-voltage electrode clamp the oil-impregnated paper sample, and then the measuring device body is sealed. At this time, the liquid level of the insulating oil in the measuring device body is above the measuring electrode gasket; Then, the gas in the inner cavity of the measuring device body is extracted through the air outlet valve, so that the air in the annular chamber, between the measuring electrode and the oil-immersed paper sample, between the high-voltage electrode and the oil-immersed paper sample, between the protective electrode and the oil-immersed paper sample, and the bubbles in the insulating oil are all discharged. Then, inert gas is injected into the inner cavity of the measuring device body through the air inlet valve until the pressure of the inert gas is equal to the atmospheric pressure of the surrounding environment of the inner cavity of the measuring device body, and then the injection of inert gas is stopped; The insulating oil in the inner cavity of the measuring device is controlled to a preset temperature through the temperature control system, and then the dielectric spectrum test is started. The preset experimental parameters are applied to the oil-immersed paper sample through the high-voltage electrode and the measuring electrode, and the voltage and current signals of the oil-immersed paper sample are measured and collected. According to the voltage and current signals of the oil-immersed paper sample, the change characteristics of the dielectric constant and dielectric loss factor of the oil-immersed paper sample at the preset temperature with the test frequency are analyzed.

[0015] The present invention has the following beneficial effects: The present invention is applied to a measuring device for frequency domain dielectric spectrum testing. By providing an air outlet valve and an air inlet valve, the air in the measuring device body can be extracted and a protective gas can be injected, thereby eliminating the interference of air during the measurement process and avoiding the adverse effects of local discharge caused by the reduction of internal air pressure on the dielectric property measurement of the oil-immersed paper sample. Unlike the traditional method of fixing the sample with bolts, the present invention transmits the elastic force of the elastic connection structure to the measuring electrode and the protective electrode through the measuring electrode gasket, thereby pressing the oil-immersed paper sample between the measuring electrode and the high-voltage electrode to ensure that the measuring electrode and the high-voltage electrode can fit tightly with the sample, thereby improving the accuracy and reliability of the test results. The protective electrode in the present invention is sleeved on the outside of the measuring electrode, so the size of the protective electrode is larger than that of the measuring electrode. Therefore, the present invention can use oil-impregnated paper samples of larger sizes. Through the pressing effect of the protective electrode on the oil-impregnated paper sample, the measuring electrode and the oil-impregnated paper sample can be fully contacted, avoiding the problem in the prior art that when the oil-impregnated paper sample is pressed by the measuring electrode and the high-voltage electrode, the oil-impregnated paper sample is easily deviated, resulting in a part of the area between the measuring electrode and the high-voltage electrode not being covered by the oil-impregnated paper sample, and then discharge occurs between the measuring electrode and the high-voltage electrode. In addition, since the protective electrode is a witch when in use The demon is grounded, so there must be sufficient spacing between the outer wall of the measuring electrode and the inner wall of the protective electrode. In the present invention, an annular chamber is formed between the outer wall of the measuring electrode and the inner wall of the protective electrode. The lower surface of the measuring electrode gasket is fixedly connected to the top surface of the protective electrode. Therefore, the annular chamber is prone to contain air, which will affect the accuracy of the experimental results. To this end, the measuring electrode gasket of the present invention is provided with a pressure balance hole at a corresponding position above the annular chamber. In this way, when the gas in the inner cavity of the measuring device body is extracted through the air outlet valve, the air in the annular chamber can be discharged from the pressure balance hole. In addition, the pressure of the insulating oil needs to be consistent with the external atmospheric pressure during the experiment. To this end, the pressure balance hole can connect the insulating oil in the annular chamber with the insulating oil outside the protective electrode, thereby ensuring that the air pressure of all the insulating oil in the measuring device body of the present invention is consistent with the external atmospheric pressure, thereby ensuring the experimental results. At the same time, the existence of the pressure balance hole also has an important function, which is to enable the measuring electrode and the protective electrode to fully contact with the oil-immersed paper sample to avoid gaps between them. The specific principle is as follows: when the gas in the inner cavity of the measuring device body is extracted through the air outlet valve, the measuring electrode and the protective electrode can be made to lightly press the surface of the oil-immersed paper sample. In the process of extracting the gas from the inner cavity of the measuring device body, the gas in the annular chamber overflows upward from the pressure balance hole. In this process, a certain negative pressure will be formed at the lower end of the measuring electrode and the protective electrode. Due to the existence of this negative pressure, the insulating oil outside the protective electrode will flow along the gap between the measuring electrode, the protective electrode and the oil-immersed paper sample, and then push the air between the measuring electrode, the protective electrode and the oil-immersed paper sample into the annular chamber, and then overflow upward from the pressure balance hole.Therefore, the present invention can exhaust the air in the insulating oil, the air between the oil-impregnated paper sample and the high-voltage pole, and the air between the measuring pole and the protective pole and the oil-impregnated paper sample as much as possible, thereby ensuring the reliability of the experimental structure. In addition, by setting up a temperature control system, the insulating oil can be heated to a preset temperature to obtain the change characteristics of the dielectric constant and dielectric loss factor of the oil-impregnated paper sample with the test frequency at the preset temperature. In summary, the present invention can measure the change characteristics of the dielectric constant and dielectric loss factor of oil-paper insulation with frequency at different temperatures, and study the influence of temperature on the dielectric properties of dielectric materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the overall structure of the measuring device of the present invention applied to frequency domain dielectric spectrum testing; Figure 2 It is a schematic structural diagram of the top cover of the measuring device of the present invention; Figure 3 It is a schematic diagram of the structure of the electrode parts (measuring electrode, high voltage electrode, protection electrode) of the measuring device of the present invention; Figure 4 It is a schematic diagram of the installation structure of the measuring device of the present invention; In the figure: 1 is the measuring electrode interface, 2 is the air outlet valve, 3 is the sealing ring, 4 is the support spring, 5 is the heating belt, 6 is the support bolt, 7 is the thermocouple, 8 is the measuring electrode, 9 is the high-voltage electrode, 10 is the high-voltage electrode gasket, 11 is the measuring device base, 12 is the oil-impregnated paper sample, 13 is the protective electrode, 131 is the outer flange, 14 is the measuring electrode gasket, 15 is the pressure spring, 16 is the base threaded hole, 17 is the fixing bolt, 18 is the air inlet valve, 19 is the measuring device top cover, 20 is the ball joint, 21 is the voltage test unit, 22 is the thermocouple temperature measurement system, 23 is the data measurement and control system, 24 is the current test unit, 25 is the dielectric spectrometer, 26 is the heating belt temperature control system, and 27 is the annular chamber. DETAILED DESCRIPTION

[0017] The present invention is further described below with reference to the accompanying drawings and embodiments.

[0018] Reference Figure 1 、 Figure 2 and Figure 4The measurement device for frequency domain dielectric spectrum testing of the present invention includes a data measurement and control system 23, a dielectric spectrum testing system 25, a thermocouple temperature measurement system 22, and a heating belt temperature control system 26. The data measurement and control system 23 is connected to the control system 23, the measuring electrode interface 1, and the high-voltage electrode 9 via wires, and includes a voltage test unit 21, a current test unit 24, and a data processing unit. The data processing unit controls experimental conditions and parameters, collects signals returned by the voltage test unit and the current test unit, and analyzes the changing characteristics of the dielectric constant and dielectric loss factor of the oil-immersed paper sample 12 at different temperatures as a function of the test frequency.

[0019] The dielectric spectrum test system includes a dielectric spectrometer 25 and a measuring device body. The top of the measuring device body is provided with an air inlet valve 18, an air outlet valve 2 and a measuring electrode interface 1. The bottom of the inner cavity of the measuring device body is provided with a high-voltage electrode gasket 10. The upper surface of the high-voltage electrode gasket 10 is provided with a high-voltage electrode 9. The inner cavity of the measuring device body is provided with a measuring electrode 8 above the high-voltage electrode 9. The measuring electrode 8 is connected to the measuring electrode interface 1 through a wire. The outer sleeve of the measuring electrode 8 is provided with a protective electrode 13. The outer diameter of the protective electrode 13 is not greater than the outer diameter of the high-voltage electrode 9. The outer wall of the measuring electrode 8 An annular chamber 27 is formed between the inner wall of the measuring electrode 8 and the guard electrode 13. A measuring electrode gasket 14 is connected to the top surface of the measuring electrode 8. The lower surface of the measuring electrode gasket 14 is fixedly connected to the top surface of the guard electrode 13. The measuring electrode gasket 14 has a pressure balancing hole at a corresponding position above the annular chamber 27. The integrated structure formed by the measuring electrode 8, measuring electrode gasket 14, and guard electrode 13 is connected to the top of the measuring device body via an elastic connection structure. The inner cavity of the measuring device body also houses a temperature control system for controlling the temperature of the insulating oil added to the measuring device body. A dielectric spectrometer 25 is connected to the measuring electrode interface 1 and the high-voltage electrode 9 via wires. The measuring device body consists of a measuring device base 11 and a measuring device cover 19. The measuring device base 11 is a container with a lower bottom, sidewalls, and an inner cavity. The top of the measuring device base 11 is open, and the inner cavity of the measuring device base 11 serves as the inner cavity of the measuring device body, while the measuring device cover 19 serves as the top of the measuring device body. The measuring device base 11 and the measuring device cover 19 are removably sealed by fixing bolts 17 and a sealing ring 3. The measuring electrode interface 1 is located in the center of the measuring device cover 19 and is connected to the dielectric spectrometer 25 via measuring wires. It receives the current and voltage signals flowing through the oil-impregnated paper sample and represents the low-voltage end of the experimental circuit. The air outlet valve 2 and the air inlet valve 18 are both located on the measuring device cover 19. To simulate the vacuum environment of the transformer oil-paper operation, the air in the oil cup three-electrode measuring device was evacuated through the air outlet valve 2 during the experiment. This also prevents the influence of partial discharge caused by the reduced air pressure on the test results. Before the test, nitrogen was injected into the oil cup three-electrode measuring device through the air inlet valve 18 until the internal air pressure equalized with the external ambient pressure. The sealing ring 3 is located between the measuring device top cover 19 and the measuring device base 11 and fits tightly with both to achieve sealing of the measuring device.The protective electrode 13 is cylindrical in shape, with an outer flange 131 at its upper end. The elastic connection structure includes a support spring 4, a pressure spring 15, and support bolts 6. Several support bolts 6 are evenly distributed around the outer flange 131. The upper ends of the support bolts 6 are threadedly connected to the top of the measuring device body, and the lower ends of the support bolts 6 extend through the outer flange 131. The through-holes in the outer flange 131, through which the support bolts 6 pass, have a larger diameter than the support bolts 6, allowing the outer flange 131 to slide up and down along the support bolts 6. All support bolts 6 are distributed around the periphery of the measuring electrode gasket 14. The support spring 4 and pressure spring 15 are positioned between the upper surface of the measuring electrode gasket 14 and the top of the measuring device body, and are both compressed. The support and pressure springs are selected to have a large diameter and a moderate spring rate, and the surface material of the springs is non-corrosive and non-detachable under high temperature conditions. Specifically, two support springs 4 and two pressure springs 15 are provided. Both support springs 4 and pressure springs 15 are located between the measuring device top cover 19 and the measuring electrode gasket 14 and are loosely connected to the upper and lower contact surfaces. The support springs 4 provide support, separating the measuring device top cover 19 from the measuring electrode gasket 14 and are assembled first, with the pressure springs 15 assembled later to increase pressure. The measuring electrode gasket 14 is provided with fine air holes as pressure balance holes to maintain the air pressure between the protective electrode 13 and the measuring electrode 8 cavity and the air pressure outside the protective electrode 13, ensuring that there is no difference in the insulating oil level inside. Four support bolts 6 are provided. The upper ends of the four support bolts 6 are fixedly connected to the measuring device top cover 19 by threads, and the lower ends that contact the protective electrode 13 are smooth bolts. This facilitates the vertical adjustment of the measuring electrode 8 and protective electrode 13 according to the thickness of the sample during measurement. The measuring electrode 8 and protective electrode 13 are both located on the upper side of the oil-impregnated paper sample 12 and fit tightly against it. The measuring electrode 8 is connected to the measuring electrode interface 1 via a measuring lead. The upper end of the measuring electrode 8 is elastically connected to the measuring electrode gasket 14 via an elastic layer (e.g., a rubber spring structure). This allows for light contact between the oil-impregnated paper sample 12, the measuring electrode 8, and the high-voltage electrode 9 during the initial stage of vacuuming, facilitating the complete removal of bubbles from the oil-impregnated paper sample 12. Specifically, when the measuring electrode 8 and the protective electrode 13 are not applying pressure to the oil-impregnated paper sample 12, the lower end of the measuring electrode 8 protrudes beyond the lower end of the protective electrode 13, meeting this requirement. The upper end of the protective electrode 13 is in contact with the lower end of the measuring electrode gasket 14, and the elastic force generated by the deformation of the support spring 4 and the pressure spring 15 is transmitted through the measuring electrode gasket 14 to the measuring electrode 8 and the protective electrode 13.Furthermore, a ball hinge 20 is used at the upper end of the measuring electrode 8, that is, the elastic layer is connected to the measuring electrode 8 via the ball hinge 20. The electrode position can be adjusted promptly according to the uneven surface of the oil-impregnated paper sample 12, ensuring close contact between the measuring electrode 8, the protective electrode 13, and the high-voltage electrode 9 and the oil-impregnated paper sample 12. At the same time, the vertical position of the measuring electrode 8 and the protective electrode 13 can be adjusted according to the thickness of the oil-impregnated paper sample 12. The ball hinge 20 can be set at the lower end of the rubber spring structure. The support bolt 6 limits the measuring electrode 8 and the protective electrode 13, so that the measuring electrode 8 and the protective electrode 13 can only move vertically according to the thickness of the oil-impregnated paper sample 12, but cannot move horizontally. The oil-impregnated paper sample 12 is located between the measuring electrode 8 and the high-voltage electrode 9, and the upper end is in contact with the protective electrode 13. The high-voltage electrode 9 is connected to the dielectric spectrometer via the high-voltage electrode wire and belongs to the high-voltage end of the experimental circuit. The high-voltage electrode gasket 10 is made of polytetrafluoroethylene, with the upper end bonded to the high-voltage electrode 9 and the lower end fixedly connected to the measuring device base 11. Its supporting and insulating functions separate the high-voltage electrode 9 at the high-voltage end from the measuring device base 11 at the ground end. The fixing bolts 17 are located on the measuring device top cover 19 and are symmetrically distributed at equal intervals. By connecting with the base threaded holes 16, the pressure is transmitted to the contact surface between the measuring device top cover 19 and the sealing ring 3, and the sealing ring 3 and the measuring device base 11, thereby achieving the sealing of the entire measuring device. The sealing ring is made of nitrile rubber material suitable for transformer oil. The measuring electrode, protective electrode and high-voltage electrode are all made of stainless steel that is resistant to high temperature, corrosion-resistant and easy to conduct electricity. The contact surface with the oil-impregnated paper sample needs to be ground and polished in advance.

[0020] The temperature control system includes a thermocouple 7, a heating belt 5, a thermocouple temperature measurement system 22, a heating belt temperature control system 26 and a controller. The thermocouple 7 is arranged in the inner cavity of the measuring device body and is used to detect the temperature of the insulating oil in the inner cavity of the measuring device body. The thermocouple temperature measurement system 22 is connected to the thermocouple 7. The thermocouple temperature measurement system 22 is used to parse the detection signal of the thermocouple 7 into temperature information and display it; the heating belt 5 is arranged outside the measuring device body and is used to heat the measuring device body and the insulating oil in the inner cavity of the measuring device body. The heating belt temperature control system 26 is connected to the heating belt 5. The heating belt temperature control system 26 is used to control the heating power of the heating belt 5; the thermocouple temperature measurement system 22 and the heating belt temperature control system 26 are both connected to the controller. The controller is used to receive the temperature information analyzed by the thermocouple temperature measurement system 22, and send an instruction to increase the heating power or maintain the heating power to the heating belt temperature control system 26 according to the temperature information. The heating belt temperature control system 26 controls the heating power of the heating belt 5 according to the instruction sent by the controller. In the experiment, an appropriate amount of insulating oil is first added to the surface of the high-voltage electrode 9. The prepared oil-impregnated paper sample 12 is placed on the upper surface of the high-voltage electrode 9. The air bubbles between the oil-impregnated paper sample 12 and the surface of the high-voltage electrode 9 are removed. Then, insulating oil is added to the measuring device. The insulating oil height should be at least 3 cm above the probe tip of the measuring thermocouple 7 and at least 3 cm below the top cover 19 of the measuring device. When measuring the spectral characteristics of the oil-impregnated paper sample 12 at a specific temperature, the heating belt temperature control system is first turned on. Considering the heat dissipation of the measuring device itself, the heating temperature of the heating belt 5 is set slightly higher than the desired test temperature until the temperature display instrument connected to the measuring thermocouple 7 reaches the test temperature. The heating temperature of the heating belt 5 is then adjusted to the test temperature (within 5°C) until the temperature of the thermocouple 7 reaches the test temperature and remains stable for a period of time. At this point, the sample temperature is at the desired test temperature. The data measurement and control system can then be started, and the sample parameters, voltage, test frequency, and other experimental parameters can be input to begin the test. The temperature control system connected to the heating belt should have a temperature control accuracy within ±1°C and appropriate heating power to ensure that the insulating oil and oil-impregnated paper samples are quickly heated and stabilized to the test temperature. The measurement accuracy of the measuring thermocouple should be within ±1°C, and the measuring probe should be immersed in the insulating oil during the test.

[0021] Reference Figure 3The electrode structure of the measuring device of the present invention includes a measuring electrode 8, a protective electrode 13, a high-voltage electrode 9, and a high-voltage electrode gasket 10. Due to the pressure of the support spring 4 and the pressure spring 15, the measuring electrode 8 presses the oil-immersed paper sample 12 tightly against the high-voltage electrode 9, ensuring the accuracy of the capacitance of the oil-immersed paper sample 12. The lower end of the protective electrode 13 contacts the upper surface of the oil-immersed paper sample 12 and is located on the periphery of the measuring electrode 8, preventing the measuring electrode 8 from directly contacting the high-voltage electrode 9, and playing an insulating and protective role. When used in conjunction with the ball head hinge 20 made of stainless steel, the position of the measuring electrode 8 can be accurately adjusted according to the uneven surface of the oil-immersed paper sample 12, ensuring that the measuring electrode 8, the protective electrode 13 and the high-voltage electrode 9 can fit tightly with the sample. The high-voltage electrode gasket 10 is located between the high-voltage electrode 9 and the base 11 of the measuring device, separating the high-voltage end and the ground end, and playing an insulating and protective and supporting role.

[0022] To measure the variations in the dielectric constant and dissipation factor of oil-impregnated paper samples at different temperatures as a function of test frequency and improve test accuracy, an AC voltage exceeding 1,000 volts must be applied to the sample. The dielectric spectrometer on this measurement device can provide high AC voltage, with an output voltage of up to 2 kV. Furthermore, all components of the measurement device, except for the measuring electrode 8, the oil-impregnated paper sample 12, and the high-voltage electrode 9, are grounded.

[0023] The present invention also provides a measurement method for frequency domain dielectric spectrum testing, comprising the following steps: Add insulating oil to the surface of the high-voltage electrode 9 so that the surface of the high-voltage electrode 9 is covered with an insulating oil film. Place the prepared oil-impregnated paper sample 12 on the insulating oil film on the surface of the high-voltage electrode 9, remove the bubbles between the oil-impregnated paper sample 12 and the surface of the high-voltage electrode 9, and then add an appropriate amount of insulating oil to the measuring device body; The whole structure formed by connecting the measuring electrode 8, the measuring electrode gasket 14 and the protective electrode 13 is installed in the measuring device body, so that the measuring electrode 8, the protective electrode 13 and the high-voltage electrode 9 clamp the oil-impregnated paper sample 12, and then the measuring device body is sealed. At this time, the liquid level of the insulating oil in the measuring device body is above the measuring electrode gasket 14; The gas in the inner cavity of the measuring device body is then extracted through the outlet valve 2, so that the air in the annular chamber 27, between the measuring electrode 8 and the oil-immersed paper sample 12, between the high-voltage electrode 9 and the oil-immersed paper sample 12, between the protective electrode 13 and the oil-immersed paper sample 12, and the bubbles in the insulating oil are all discharged. Then, inert gas is injected into the inner cavity of the measuring device body through the inlet valve 18 until the pressure of the inert gas is equal to the atmospheric pressure of the surrounding environment of the inner cavity of the measuring device body, and then the injection of inert gas is stopped; The insulating oil in the inner cavity of the measuring device body is controlled to a preset temperature by the temperature control system, and then the dielectric spectrum test is started. The preset experimental parameters are applied to the oil-impregnated paper sample 12 through the high-voltage electrode 9 and the measuring electrode 8, and the voltage and current signals of the oil-impregnated paper sample 12 are measured and collected. According to the voltage and current signals of the oil-impregnated paper sample 12, the change characteristics of the dielectric constant and dielectric loss factor of the oil-impregnated paper sample 12 at the preset temperature with the test frequency are analyzed.

[0024] The present invention provides a measurement device and method for frequency-domain dielectric spectroscopy testing. By providing an air outlet valve and an air inlet valve to evacuate air from the measurement device and inject nitrogen, this eliminates air interference and prevents the adverse effects of partial discharge caused by reduced internal air pressure on the dielectric property measurement of oil-impregnated paper samples. A sealing ring is provided between the top cover and the base of the measurement device, leveraging the elastic force of support and pressure springs to achieve a secure seal. Unlike conventional methods of securing samples with bolts, the present invention transfers the elastic force of the support and pressure springs through a measuring electrode gasket to the measuring electrode and guard electrode, pressing the oil-impregnated paper sample tightly between the measuring electrode and the high-voltage electrode. Combined with a stainless steel ball-jointed hinge, the measuring electrode position can be precisely adjusted to accommodate uneven sample surfaces, ensuring a tight fit between the measuring electrode and the high-voltage electrode, improving the accuracy and reliability of test results. A measuring thermocouple is installed in the top cover of the measurement device and connected to a temperature display instrument to monitor the temperature of the insulating oil inside in real time. Furthermore, a power-adjustable heating tape is installed around the periphery of the measurement device base, transferring heat to the insulating oil and the oil-impregnated paper sample through the rapid thermal conductivity of the metal. The thermocouple temperature measurement system and the heating belt temperature control system work together to solve the problem of traditional measurement devices' difficulty in rapidly heating and stably controlling the temperature of oil-impregnated paper systems containing large amounts of insulating oil. In summary, the measurement device and method for frequency-domain dielectric spectrum testing of the present invention offer advantages such as excellent sealing performance, close fit between the sample and the electrode, and rapid temperature rise and stable temperature control. This provides a new and effective means for measuring the variations in the dielectric constant and dielectric loss factor of oil-impregnated paper samples at different temperatures as a function of test frequency, and has promising application prospects.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A measuring device for frequency domain dielectric spectrum testing, characterized in that: The invention comprises a sealed measuring device body, wherein the top of the measuring device body is provided with an air inlet valve (18), an air outlet valve (2) and a measuring electrode interface (1), the bottom of the inner cavity of the measuring device body is provided with a high-voltage electrode gasket (10), the upper surface of the high-voltage electrode gasket (10) is provided with a high-voltage electrode (9), the inner cavity of the measuring device body is provided with a measuring electrode (8) above the high-voltage electrode (9), the measuring electrode (8) and the measuring electrode interface (1) are connected by a wire, the outer sleeve of the measuring electrode (8) is provided with a protective electrode (13), the outer diameter of the protective electrode (13) is not greater than the outer diameter of the high-voltage electrode (9), and the outer wall of the measuring electrode (8) is in contact with the protective electrode. An annular chamber (27) is formed between the inner walls of the protective pole (13), the top surface of the measuring pole (8) is connected to the measuring pole gasket (14), the lower surface of the measuring pole gasket (14) is fixedly connected to the top surface of the protective pole (13), and the measuring pole gasket (14) is provided with a pressure balance hole at a corresponding position above the annular chamber (27). The overall structure formed by connecting the measuring pole (8), the measuring pole gasket (14) and the protective pole (13) is connected to the top of the measuring device body through an elastic connection structure. The inner cavity of the measuring device body is also provided with a temperature control system for controlling the temperature of the insulating oil added to the measuring device body.

2. The measuring device for frequency domain dielectric spectrum testing according to claim 1, characterized in that: An elastic layer is provided between the measuring electrode (8) and the measuring electrode gasket (14). When the measuring electrode (8) and the protective electrode (13) do not apply pressure to the oil-immersed paper sample (12), the lower end of the measuring electrode (8) protrudes from the lower end of the protective electrode (13).

3. The measuring device for frequency domain dielectric spectrum testing according to claim 2, characterized in that: The elastic layer and the measuring pole (8) are connected via a ball joint (20).

4. The measuring device for frequency domain dielectric spectrum testing according to claim 1, characterized in that: The protective electrode (13) is cylindrical in shape, and an outer flange (131) is provided at the upper end of the protective electrode (13); The elastic connection structure includes a support spring (4), a pressure spring (15) and a support bolt (6); the outer flange (131) is evenly provided with a plurality of the support bolts (6) in the circumference thereof; the upper end of the support bolt (6) is threadedly connected to the top of the measuring device body; the lower end of the support bolt (6) passes through the outer flange (131); the diameter of the through hole provided on the outer flange (131) for the support bolt (6) to pass through is larger than the diameter of the support bolt (6); and the outer flange (131) can slide up and down along the support bolt (6); All support bolts (6) are distributed around the periphery of the measuring electrode gasket (14), and the support spring (4) and the pressure spring (15) are arranged between the upper surface of the measuring electrode gasket (14) and the top of the measuring device body, and the support spring (4) and the pressure spring (15) are both in a compressed state.

5. The measuring device for frequency domain dielectric spectrum testing according to claim 1, characterized in that: The measuring device body comprises a measuring device base (11) and a measuring device top cover (19). The measuring device base (11) is a container having a bottom, side walls and an inner cavity. The top of the measuring device base (11) is open. The inner cavity of the measuring device base (11) serves as the inner cavity of the measuring device body, and the measuring device top cover (19) serves as the top of the measuring device body. The measuring device base (11) and the measuring device top cover (19) are detachably sealed and connected via fixing bolts (17) and a sealing ring (3).

6. The measuring device for frequency domain dielectric spectrum testing according to claim 1, characterized in that: The temperature control system comprises a thermocouple (7), a heating belt (5), a thermocouple temperature measurement system (22), a heating belt temperature control system (26) and a controller. The thermocouple (7) is arranged in the inner cavity of the measuring device body and is used to detect the temperature of the insulating oil in the inner cavity of the measuring device body. The thermocouple temperature measurement system (22) is connected to the thermocouple (7). The thermocouple temperature measurement system (22) is used to resolve the detection signal of the thermocouple (7) into temperature information and display it; the heating belt (5) is arranged outside the measuring device body and is used to control the insulation of the measuring device body and the inner cavity of the measuring device body. The oil is heated, and the heating belt temperature control system (26) is connected to the heating belt (5), and the heating belt temperature control system (26) is used to control the heating power of the heating belt (5); the thermocouple temperature measurement system (22) and the heating belt temperature control system (26) are both connected to a controller, and the controller is used to receive temperature information analyzed by the thermocouple temperature measurement system (22), and send an instruction to increase the heating power or maintain the heating power to the heating belt temperature control system (26) according to the temperature information, and the heating belt temperature control system (26) controls the heating power of the heating belt (5) according to the instruction sent by the controller.

7. The measuring device for frequency domain dielectric spectrum testing according to claim 1, characterized in that: It also includes a dielectric spectrometer (25), which is connected to the measuring electrode interface (1) and the high-voltage electrode (9) through a wire.

8. The measuring device for frequency domain dielectric spectrum testing according to claim 1, characterized in that: The data measurement and control system (23) is connected to the measuring electrode interface (1) and the high-voltage electrode (9) through a wire. The data measurement and control system (23) includes a voltage test unit (21), a current test unit (24) and a data processing unit. The data processing unit is used to perform data analysis and processing based on the data of the voltage test unit (21) and the current test unit (24) to obtain the change characteristics of the dielectric constant and dielectric loss factor of the oil-immersed paper sample (12) under experimental conditions as a function of the test frequency.

9. The measuring device for frequency domain dielectric spectrum testing according to claim 1, characterized in that: The measuring electrode (8), the protective electrode (13) and the high-voltage electrode (9) are all made of stainless steel, and the high-voltage electrode gasket (10) and the measuring electrode gasket (14) are all made of polytetrafluoroethylene.

10. A measurement method for frequency domain dielectric spectrum testing, characterized in that: The measurement method is performed using the measurement device for frequency domain dielectric spectrum testing according to any one of claims 1 to 9, and includes the following steps: Add insulating oil to the surface of the high-voltage electrode (9) so that the surface of the high-voltage electrode (9) is covered with an insulating oil film, place the prepared oil-impregnated paper sample (12) on the insulating oil film on the surface of the high-voltage electrode (9), remove the bubbles between the oil-impregnated paper sample (12) and the surface of the high-voltage electrode (9), and then add an appropriate amount of insulating oil to the measuring device body; The whole structure formed by connecting the measuring electrode (8), the measuring electrode gasket (14) and the protective electrode (13) is installed in the measuring device body, so that the measuring electrode (8), the protective electrode (13) and the high-voltage electrode (9) clamp the oil-immersed paper sample (12), and then the measuring device body is sealed. At this time, the liquid level of the insulating oil in the measuring device body is located above the measuring electrode gasket (14); Then, the gas in the inner cavity of the measuring device body is extracted through the outlet valve (2), so that the air in the annular chamber (27), between the measuring electrode (8) and the oil-immersed paper sample (12), between the high-voltage electrode (9) and the oil-immersed paper sample (12), between the protective electrode (13) and the oil-immersed paper sample (12), and the bubbles in the insulating oil are all discharged. Then, inert gas is injected into the inner cavity of the measuring device body through the inlet valve (18), and the injection of inert gas is stopped when the gas pressure of the inert gas is equal to the atmospheric pressure of the surrounding environment of the inner cavity of the measuring device body; The insulating oil in the inner cavity of the measuring device body is controlled to a preset temperature by a temperature control system, and then the dielectric spectrum test is started. By applying preset experimental parameters to the oil-immersed paper sample (12) through the high-voltage electrode (9) and the measuring electrode (8), the voltage and current signals of the oil-immersed paper sample (12) are measured and collected, and the dielectric constant and dielectric loss factor of the oil-immersed paper sample (12) at the preset temperature are analyzed according to the voltage and current signals of the oil-immersed paper sample (12). Changes in the test frequency.

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