A test device and method for a capacitor of an epoxy glass cloth tube voltage transformer

Abstract

The application discloses a kind of test device and method of capacitor for epoxy glass cloth tube voltage transformer, including test sleeve, the capacitor to be measured is arranged in the test sleeve, the cavity for accommodating filling gas is formed between the test sleeve and the capacitor to be measured, upper end cover and lower end cover are arranged at the both ends of the test sleeve, the top end cover of the capacitor to be measured is connected with upper end cover by mounting plate, the bottom end cover of the capacitor to be measured is connected with lower end cover by spring wire, inflation port, pressure gauge and valve for controlling inflation port are arranged on the upper end cover.The application will greatly reduce production manufacturing cost, and the repeated use of test equipment is also convenient for workshop production, reduces outsourcing test commission, transfer, test cost and other operations, greatly reduces manufacturing cost.

Description

Technical Field

[0001] This invention relates to the technical field of voltage transformers, electronic transformers, DC voltage dividers, and equalizing capacitors for switching, and particularly to a test apparatus and method for capacitors used in epoxy glass tube voltage transformers. Background Technology

[0002] A voltage transformer (VT) is a device used to transform voltage. It mainly provides voltage to measuring instruments and relay protection devices to measure line voltage, power, and electrical energy.

[0003] Electronic voltage transformers (EVTs) are a new generation of power measurement and protection equipment, distinct from traditional electromagnetic voltage transformers (PTs). They are primarily used in smart grids, digital substations, and high-voltage / ultra-high-voltage transmission systems to proportionally convert high voltage and high current in power systems into low-level digital or analog signals for use in measurement, metering, relay protection, and monitoring systems. They are one of the core foundational devices for realizing the digitalization and intelligentization of power grids. EVTs use high-precision resistive or capacitive voltage dividers to proportionally reduce primary high voltage to a low-voltage signal, which is then signal-conditioned and converted from analog to digital for output. Capacitive voltage divider types can also function as coupling capacitors to achieve carrier communication.

[0004] A voltage divider, also commonly known as an AC / DC voltage divider, capacitive voltage divider, or RC voltage divider, is a specialized instrument used to measure high-voltage AC and DC power frequencies. It consists of the voltage divider body and the measuring instrument. Employing a balanced equipotential shielded structure, it converts the measured high voltage into a low-voltage signal through the voltage division principle of built-in capacitors. It also performs harmonic and temperature monitoring and is primarily used in power systems and electrical and electronic equipment manufacturing.

[0005] In high-voltage, ultra-high-voltage, and extra-high-voltage fields, capacitors are mainly used at the breaking points of circuit breakers to improve electric field distribution and voltage uniformity, thereby increasing the breaking capacity of the circuit breaker and extending its service life. Currently, gas-insulated switchgear (GIS) is commonly used in substations and switching stations. It consists of circuit breakers, disconnecting switches, grounding switches, current transformers, voltage transformers, surge arresters, busbars, connectors, and outgoing terminals. All these devices or components are enclosed in a grounded metal casing filled with SF6 gas at a certain pressure. With the development of green, environmentally friendly, and low-carbon power, N2, clean air, or mixed environmentally friendly gases have partially replaced SF6 gas; complete replacement will still take some time.

[0006] Electronic transformers, DC voltage dividers, and capacitors for switching are generally installed inside voltage dividers or GIS, or used inside test chambers. Since there is no need to consider external environmental pollution, non-metallic epoxy glass tubing is often used as the equipment shell. Considering the absolute clearance, it has the characteristics of beautiful appearance, light weight, and convenient processing and manufacturing.

[0007] The equalizing capacitors for open circuit breakers are connected in parallel at the circuit breaker terminals and are generally installed in parallel beside the circuit breaker bushings. Considering the temperature, humidity, and pollution of the external environment, porcelain bushings or composite bushings are often selected as the outer shell material. Both porcelain bushings and composite bushings are equipped with large and small umbrellas to meet the requirements for external insulation and altitude correction.

[0008] Due to limitations in equipment footprint and installation space, the equalizing capacitors for open circuit breakers are generally designed to be thinner or have a smaller margin, taking cost into consideration. When the voltage level is high, the equalizing capacitors for open circuit breakers cannot meet the on-site requirements. In this case, equalizing capacitors for GIS are generally selected and installed inside the GIS. Therefore, projects often use capacitors with epoxy glass tubing shells. Before delivery, partial discharge and insulation tests such as power frequency withstand voltage, lightning impulse voltage, and switching impulse voltage must be completed and accepted.

[0009] Currently, after producing capacitors with epoxy glass tube casings, manufacturers of capacitors and transformers still need to conduct routine tests such as capacitance and dielectric loss measurement, partial discharge, and insulation tests before delivering them to users. Considering the operating environment and the limitation of the epoxy glass tube casing in withstanding high external insulation test voltages, capacitor products require specific consideration of testing equipment and methods when undergoing partial discharge and insulation tests (including power frequency withstand voltage, lightning impulse voltage, and switching impulse voltage). Depending on the usage conditions, capacitors are typically tested inside GIS or AC / DC voltage dividers. However, for companies that only produce capacitors, purchasing one or more GIS or AC / DC voltage divider testing systems is prohibitively expensive.

[0010] Epoxy glass tubing capacitors, used in AC / DC voltage dividers and GIS (Gas Insulated Switchgear), are employed for voltage division, equalization, harmonic measurement, temperature monitoring, and high-frequency harmonic tolerance studies. These capacitors are typically installed internally and filled with N2, clean air, or a mixture of environmentally friendly gases. After filling, a certain pressure is maintained. The outer surface of the capacitors is typically covered with unsupported epoxy glass tubing. However, unsupported epoxy glass tubing cannot be directly used for tests such as insulation and partial discharge testing. Therefore, simulating operating conditions or outsourcing testing to a third party is necessary. For companies that only manufacture capacitors, purchasing testing equipment for one or more GIS and AC / DC voltage dividers is prohibitively expensive. Outsourcing routine testing for each unit to a third party inevitably increases manufacturing and fulfillment costs and introduces uncontrollable factors, negatively impacting the company's overall market image. Summary of the Invention

[0011] The purpose of this invention is to provide a testing device and method for capacitors used in epoxy glass tube voltage transformers, so as to solve the problems existing in the prior art and facilitate manufacturers to test the performance of capacitors after manufacturing, such as during partial discharge and insulation tests (including power frequency withstand voltage, lightning impulse voltage, switching impulse voltage, etc.).

[0012] To achieve the above objectives, the present invention adopts the following technical solution: A testing device for a capacitor used in an epoxy glass tube voltage transformer includes a test sleeve, in which a capacitor to be tested is placed. A cavity for accommodating filling gas is formed between the test sleeve and the capacitor to be tested. An upper end cover and a lower end cover are provided at both ends of the test sleeve. The top end cover of the capacitor to be tested is connected to the upper end cover via a mounting plate. The bottom end cover of the capacitor to be tested is connected to the lower end cover via a spring wire. An inflation port, a pressure gauge, and a valve for controlling the inflation port are provided on the upper end cover.

[0013] Furthermore, both ends of the capacitor under test are provided with capacitor equalization rings for balancing the internal electric field distribution, and a device equalization ring is provided on the top of the outside of the test device.

[0014] Furthermore, the filling gas is pure N2, clean air, or a mixture of environmentally friendly gases.

[0015] Furthermore, the test sleeve is made of ceramic or composite material, and the test sleeve is provided with large and small umbrellas on its outer side, which are evenly distributed.

[0016] Furthermore, sealing gaskets are provided between the test sleeve and the upper and lower end caps.

[0017] Furthermore, the test sleeve is connected to the upper and lower end caps, the top end cap of the capacitor under test is connected to the mounting plate, the mounting plate is connected to the upper end cap, the bottom end cap of the capacitor under test is connected to the spring wire, and the spring wire is connected to the lower end cap by fixing bolts.

[0018] Furthermore, the pressure gauge is equipped with a pressure relief device.

[0019] Furthermore, the air inlet and the valve are mounted on the upper end cover via a first base. The first base communicates with the cavity and is connected to the upper end cover via a sealing gasket or by welding.

[0020] Furthermore, the pressure gauge is mounted on the upper end cover via a second base, the second base being in communication with the cavity, and the second base being connected to the upper end cover via a sealing gasket, or by welding.

[0021] A test method for a capacitor used in an epoxy glass tube voltage transformer involves: After evacuating the air from the cavity through the inflation port, closing the valve and maintaining a constant pressure inside the test sleeve; opening the valve and injecting filling gas into the test sleeve through the inflation port; when the pressure gauge reading reaches 0.4~0.6 MPa, closing the valve and maintaining a constant pressure; transporting the test apparatus to a test chamber; applying a test voltage to the high-voltage end of the test apparatus; and grounding or connecting a test module such as an impedance box or Rogowski coil to the low-voltage end of the test apparatus; and completing the insulation and partial discharge tests of the epoxy glass tube voltage transformer capacitor within the required test time; after the test, recovering the filling gas inside the test sleeve through the valve and inflation port to ensure that the pressure inside the test sleeve is at normal atmospheric pressure.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects: Capacitors with epoxy glass tube shells are used in AC / DC voltage dividers and GIS for voltage division, voltage equalization, harmonic measurement, temperature monitoring, and high-frequency harmonic tolerance studies. However, the capacitors used in these devices are all installed inside them and filled with N2, clean air, or mixed environmentally friendly gases, and a certain pressure is injected and maintained. The outer surface of the capacitor is made of epoxy glass tube without a protective umbrella.

[0023] Due to the limitations of the operating conditions and requirements of epoxy glass tube capacitors without umbrellas, especially at higher voltages, directly applying voltage to the aforementioned equipment can damage the capacitor under test, the testing equipment, and the testing personnel. Therefore, for routine testing of capacitors at higher voltages, it is necessary to install them inside the equipment for testing, or purchase equipment of the same voltage rating for testing. Testing may damage or even destroy expensive equipment, thus requiring the purchase of multiple sets of equipment for capacitor testing. In other words, while the design cost of capacitors is relatively low, routine and special tests before delivery are very expensive. This invention designs a testing device that simplifies costs (without affecting the effectiveness of pre-delivery testing), and the device is reusable and will not damage the equipment. If routine testing for each unit is outsourced to a third party, it will inevitably increase manufacturing and fulfillment costs and introduce uncontrollable factors, affecting the company's overall market image.

[0024] This invention employs a testing device for capacitors in epoxy glass tube voltage transformers, which significantly reduces manufacturing costs. The reusability of the testing equipment also facilitates workshop production, reducing outsourcing testing, transportation, and testing fees, thus greatly lowering manufacturing costs. This invention effectively solves the problem of testing methods and equipment for partial discharge and insulation routine tests in capacitor and transformer manufacturing enterprises. It helps manufacturing enterprises reduce investment in testing equipment and devices, optimize site and production line layout, and reduce cost increases such as transportation and outsourcing testing caused by the lack of testing equipment, thereby reducing operating costs and alleviating the pressure on manufacturing enterprises. Simultaneously, it enables timely and effective delivery of manufactured products to users.

[0025] This invention is simple to operate, convenient to install and transport, and has the function of recovering gas inside the test sleeve, ensuring that the internal pressure of the test sleeve is normal atmospheric pressure after the test, eliminating safety hazards for operators, test personnel and equipment, and is an environmentally friendly testing device. This testing device is safe and reliable, will not pose safety hazards to assembly and operation personnel, and will not affect the assembly and testing environment. Attached Figure Description

[0026] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0027] Figure 1 This is a schematic diagram of a test apparatus for a capacitor used in an epoxy glass tube voltage transformer according to the present invention.

[0028] Among them, 1-capacitor to be tested, 2-test sleeve, 3-upper end cover, 4-lower end cover, 5-sealing gasket, 6-mounting plate, 7-1-capacitor equalizing ring, 7-2 device equalizing ring, 8-spring wire, 9-inflation port, 10-valve, 11-pressure gauge, 12-filling gas. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] Example 1 This invention provides a test apparatus for a capacitor used in an epoxy glass cloth tube voltage transformer. The capacitor's casing is made of epoxy glass cloth tube, and both ends of the epoxy glass cloth tube are fitted with stainless steel end caps. Sealing gaskets are placed between the end caps and the epoxy glass cloth tube. An expansion joint for temperature compensation is installed at the end caps. The outer sides of the two end caps are fixed to the epoxy glass cloth tube using aluminum alloy or stainless steel flanges, and the flanges and epoxy glass cloth tube are sealed and fixed with resin adhesive. The capacitor contains an insulating oil and is pressurized for compensation.

[0032] The test apparatus includes a test sleeve 2, an upper end cap 3 and a lower end cap 4 of the test sleeve 2, a capacitor to be tested 1, and a capacitor equalizing ring 7-1 to balance the internal electric field distribution. To eliminate interference from external conditions and balance the distribution of the external electric field during the insulation test, an equalizing ring 7-2 is installed on the top of the outside of the test apparatus. Other components include a sealing gasket 5 between the test sleeve 2 and the end caps (upper end cap 3 and lower end cap 4), an air inlet 9 on the upper end cap 3, a valve 10 (which can be a rotary valve) on the upper end cap 3, a pressure gauge 11 on the upper end cap 3, a mounting plate 6 between the capacitor to be tested 1 and the upper end cap 3, and a spring wire 8 connecting the capacitor to be tested 1 and the lower end cap 4. Using a dedicated pressurized extraction device, filler gas 12 (pure N2, clean air, or a mixture of environmentally friendly gases) is injected into the test sleeve 1 through the air inlet 9 of the upper end cover 3. After maintaining a certain pressure, a partial discharge and insulation test of an epoxy glass cloth tube type capacitor can be performed. After the test is completed, the filler gas 12 inside the test sleeve 2 is collected through the recovery function of the dedicated pressurized extraction device to ensure the safety of the test personnel and equipment.

[0033] The capacitor to be tested 1 is installed inside the test sleeve 2. The test sleeve 2 is equipped with large and small umbrellas, and is generally divided into three types: ceramic sleeve, composite sleeve, and other materials with umbrellas.

[0034] The test sleeve 2, the upper end cap 3, and the lower end cap 4 are all equipped with sealing gaskets 5 and fixing bolts for reliable sealing.

[0035] The top of the capacitor under test 1 is fixed to the upper end cover 3 by the mounting plate 6. Fixing bolts are provided between the top of the capacitor under test 1 and the mounting plate 6, and between the mounting plate 6 and the upper end cover 3.

[0036] The capacitor equalizing ring 7-1 is installed at both ends of the capacitor 1 under test to balance the electric field distribution. The device equalizing ring 7-2 is installed on the top of the outside of the test device to eliminate interference from external conditions and balance the distribution of the external electric field during the insulation test.

[0037] The bottom of the capacitor under test 1 is connected to the lower end cover 4 by the spring wire 8. The spring wire 8 can realize the size compensation caused by the inconsistent height of the capacitor under test 1. Fixing bolts are provided between the bottom of the capacitor under test 1 and the spring wire 8, and between the spring wire 8 and the lower end cover 4.

[0038] The upper end cover 3 is provided with an air inlet 9, a valve 10, and a pressure gauge 11. The air inlet 9 has a self-sealing function. The pressure gauge 11 is an analog or digital display type and has a built-in pressure relief device. If the internal pressure exceeds the bearing capacity of the valve 10 and the pressure gauge 11, it will automatically release pressure to protect the safety of operators and equipment.

[0039] The inflation port 9 and the valve 10 are mounted on a first base, which is fixed to the upper end cover 3 by a sealing gasket 5 or directly welded to it. The valve 10 can control the amount of air entering and exiting the inflation port 9.

[0040] The pressure gauge 11 is mounted on another second base, which is fixed by a sealing gasket or directly welded to the upper end cover 3, and maintains a certain operating and safety distance from the first base of the air inlet and the rotary valve.

[0041] After the air inside is extracted through the air inlet 9 using a vacuum pump with a special pressurization extraction device, the valve 10 is automatically or manually closed, and the pressure inside the test sleeve 2 is kept constant.

[0042] A dedicated pressurization extraction device is used to inject filling gas 12 into the test sleeve 2 through the inflation port 9. During inflation, the valve 10 is opened automatically or manually. When the pressure value displayed on the pressure gauge 11 is 0.4~0.6 MPa, the valve 10 is closed automatically or manually and the pressure is kept constant.

[0043] The test device is transported to the test chamber. A test voltage is applied to the top (or high voltage) end of the test device, and the bottom (or low voltage) end of the test device is grounded or connected to test modules such as impedance boxes or Rogowski coils. The partial discharge and insulation tests such as power frequency withstand voltage, lightning impulse voltage, and switching impulse voltage of the epoxy glass tube shell capacitor are completed within the required test time.

[0044] After the test is completed, a special pressurized extraction device is used to recover the filling gas 12 inside the test sleeve 2 through the valve 10 and the air inlet 9, so as to ensure that the inside of the test sleeve 2 is at normal atmospheric pressure and eliminate safety hazards to operators and equipment.

[0045] Example 2 like Figure 1 As shown, the test apparatus for the capacitor of the epoxy glass cloth tube voltage transformer in this embodiment mainly includes the capacitor under test 1, test sleeve 2, upper end cover 3, lower end cover 4, sealing gasket 5, mounting plate 6, capacitor equalizing ring 7-1, device equalizing ring 7-2, spring wire 8, air inlet 9, valve 10, pressure gauge 11, and filling gas 12. The connection relationship and specific structure of each component are as follows: The test bushing 2, as the main supporting component of the device, is used to accommodate the capacitor 1 under test and form a sealed test space. It is made of porcelain (a composite bushing or other umbrella-shaped bushing can also be selected according to actual test requirements). The porcelain bushing has excellent insulation performance, high temperature resistance, and mechanical strength, and can adapt to the high voltage environment and different temperature conditions during the test. To further improve the insulation effect of the test bushing 2 and avoid the influence of the external environment (such as humidity and dust) on the test, the outer side of the test bushing 2 is provided with a structure of large and small umbrellas, which are alternately distributed. This can effectively increase the creepage distance of the test bushing 2, reduce surface leakage, and ensure the safety and accuracy of the test process.

[0046] The inside of the test sleeve 2 is a hollow structure. The capacitor under test 1 is placed vertically in the test sleeve 2, and an annular cavity is formed between the test sleeve 2 and the capacitor under test 1. This cavity is used to contain the filling gas 12 to simulate the gas insulation environment of the capacitor under test 1 in actual operation.

[0047] The test sleeve 2 is detachably connected to an upper end cap 3 and a lower end cap 4 at both ends to seal the internal cavity of the test sleeve 2. To ensure the sealing effect and prevent leakage of the filling gas 12, sealing gaskets 5 are provided between the test sleeve 2 and the upper end cap 3 and the lower end cap 4. The sealing gaskets 5 are made of high-pressure resistant and corrosion-resistant fluororubber, and their size matches the port size of the test sleeve 2 and the connection surface size of the upper end cap 3 and the lower end cap 4. After assembly, they can fit tightly to form a reliable sealing structure.

[0048] Both the upper end cap 3 and the lower end cap 4 are made of high-strength aluminum alloy, ensuring sufficient mechanical strength and good electrical conductivity, and can be used as electrode connection components during the test. The upper end cap 3 integrates an inflation port 9, a valve 10, and a pressure gauge 11, all of which are connected to the cavity inside the test sleeve 2, and are used for the injection and recovery of filling gas 12, the control of gas flow rate, and the real-time monitoring of the pressure inside the cavity, respectively.

[0049] The inflation port 9 and valve 10 are mounted on the upper cover 3 via a first base. The first base is made of stainless steel and has a through hole inside. One end of the through hole communicates with the internal cavity of the test sleeve 2, and the other end connects to the inflation port 9. Valve 10 is connected in series between the inflation port 9 and the first base to control the opening and closing of the inflation port 9. The first base and the upper cover 3 are sealed with a gasket (or welded connection as needed) to ensure that gas does not leak from the connection. The inflation port 9 uses a quick-connect structure, which can be easily connected to external inflation equipment and gas recovery equipment, improving the convenience of test operation.

[0050] Pressure gauge 11 is mounted on upper cover 3 via a second base, also made of stainless steel, with internal through holes to allow communication between pressure gauge 11 and the internal cavity of test sleeve 2, ensuring that pressure gauge 11 can accurately monitor the pressure value within the cavity in real time. The connection between the second base and upper cover 3 is the same as that between the first base and can be achieved using a sealing gasket or welding to ensure a tight seal. To prevent excessive pressure inside the cavity during the test, which could damage the device or cause a safety accident, pressure gauge 11 is equipped with a pressure relief device. When the pressure inside the cavity exceeds a set threshold, the pressure relief device automatically opens, releasing some gas to reduce the pressure to a safe range. It automatically closes after the pressure returns to normal, ensuring the safety of the test process.

[0051] The capacitor under test 1 is a dedicated capacitor for epoxy glass cloth tube voltage transformers. Its top end cover is connected to the upper end cover 3 via mounting plate 6. Mounting plate 6 is made of insulating material (such as epoxy glass cloth board) to prevent short circuits between capacitor under test 1 and upper end cover 3. Mounting plate 6 is connected to the top end cover of capacitor under test 1 and to the upper end cover 3 via fixing bolts. The fixing bolts are made of stainless steel. Ensure that the bolts are tightened during connection to prevent loosening due to vibration during the test, which would affect the stability of the test.

[0052] The bottom cap of the capacitor under test 1 is connected to the lower cap 4 via a spring wire 8. The spring wire 8 is made of a flexible conductive material, which not only enables the electrical connection between the capacitor under test 1 and the lower cap 4, but also accommodates slight displacement of the capacitor under test 1 during the test, avoiding damage to the capacitor due to a rigid connection. The spring wire 8 is connected to the bottom cap of the capacitor under test 1 and to the lower cap 4 via fixing bolts, and the connection points are also sealed to prevent gas leakage.

[0053] To balance the electric field distribution across the capacitor under test 1 and prevent local insulation damage due to electric field concentration, which could affect the accuracy of the test results, capacitor equalization rings 7-1 are installed at both ends of the capacitor under test 1. The capacitor equalization rings 7-1 have a circular ring structure, and their dimensions match the end cap dimensions of the capacitor under test 1. Fixed to the end caps at both ends of the capacitor under test 1, they effectively disperse the electric field intensity, making the electric field distribution more uniform and ensuring uniform stress on the capacitor under test 1 during the test. The test apparatus is equipped with an equalization ring 7-2, which also has a circular ring structure and is fixed to the upper end cap 3. This ring is used to eliminate interference from external conditions and balance the distribution of the external electric field during the insulation test.

[0054] The filling gas 12 filling the cavity between the test sleeve 2 and the capacitor under test 1 is selected from pure N2, clean air, or a mixture of environmentally friendly gases (such as a mixture of SF6 and N2, the mixing ratio of which can be adjusted according to test requirements). Among them, pure N2 has the advantages of wide availability, low cost, stable chemical properties, and good insulation performance, and is the preferred filling gas in this embodiment; clean air can reduce the influence of impurities on the test and is suitable for scenarios with high requirements for the test environment; the mixture of environmentally friendly gases can balance insulation performance and environmental protection according to test requirements, avoiding the use of harmful gases that will cause pollution to the environment.

[0055] To ensure the overall stability and sealing of the device, all components are connected using fixing bolts. Specifically, this includes: the connection between the test sleeve 2 and the upper end cover 3 and the lower end cover 4; the connection between the top end cover of the capacitor under test 1 and the mounting plate 6; the connection between the mounting plate 6 and the upper end cover 3; the connection between the bottom end cover of the capacitor under test 1 and the spring wire 8; and the connection between the spring wire 8 and the lower end cover 4. All fixing bolts have an anti-loosening structure, and anti-loosening washers are placed between the bolts and nuts during assembly to prevent the bolts from loosening due to vibration during the test, thus ensuring the sealing and connection reliability of the device.

[0056] Example 3 The test method in this embodiment is based on the test apparatus described in Embodiment 2, and is used to complete the partial discharge and insulation tests of capacitors used in epoxy glass tube voltage transformers. The specific steps are as follows: First, inspect all components of the test apparatus to confirm that the test sleeve 2, upper end cap 3, and lower end cap 4 are undamaged and free of cracks; the sealing gasket 5 is free of aging and deformation; the air inlet 9 and valve 10 are leak-free; the pressure gauge 11 is functioning normally; and the pressure release device is intact. Next, place the capacitor to be tested 1 vertically inside the test sleeve 2 and adjust its position to ensure it is centered within the test sleeve 2 and not in contact with its inner wall. Then, install the capacitor equalizing ring 7-1, mounting plate 6, and spring wire 8 in sequence, and tighten all components with fixing bolts to ensure reliable connection. Next, connect the upper end cap 3 and lower end cap 4 to the test sleeve 2, press the sealing gasket 5 to ensure a sealed cavity is formed inside the test sleeve 2, and then install the capacitor equalizing ring 7-2 onto the upper end cap 3.

[0057] Connect the external vacuum equipment to the air inlet 9, open valve 10, and start the vacuum equipment to slowly remove the air from the cavity inside the test sleeve 2. During the vacuuming process, monitor the pressure inside the cavity in real time using pressure gauge 11 until the pressure inside the cavity drops to 0.1 MPa (absolute pressure). Maintain the vacuum state for 5-10 minutes to ensure that the air inside the cavity is completely removed, avoiding any residual air from affecting the test results. After the vacuuming is complete, close valve 10 to maintain the vacuum state inside the test sleeve 2 and prevent external air from entering.

[0058] Disconnect the vacuum equipment and connect the external inflation device to the inflation port 9, ensuring a reliable seal. Open valve 10 and slowly inject the selected filling gas 12 into the test sleeve 2 through the inflation port 9. Control the inflation speed during the injection process to avoid a sudden increase in pressure inside the cavity due to excessive inflation, which could damage the device or the capacitor under test 1. Simultaneously, monitor the pressure value inside the cavity in real time using pressure gauge 11. When the pressure value displayed on pressure gauge 11 is 0.5 MPa (in this embodiment, the middle value within the range of 0.4~0.6 MPa is selected, and it can be adjusted to any value within this range according to the test requirements), immediately close valve 10 to stop inflation, and maintain the pressure inside the test sleeve 2 unchanged. Let it stand for 10-15 minutes and observe whether the reading of pressure gauge 11 is stable to confirm that there is no gas leakage.

[0059] After confirming that the internal pressure of test sleeve 2 is stable and leak-free, the entire test apparatus is transported to the test chamber. Following the partial discharge and insulation test standards for epoxy glass cloth-cased capacitors, the test instruments are connected, and partial discharge and insulation tests are performed on the capacitor under test 1. During the test, test data is monitored in real time, and key parameters such as the partial discharge quantity, insulation resistance, and breakdown voltage of the capacitor under test 1 are recorded to ensure the accuracy and completeness of the test data. If any abnormal reading is found on pressure gauge 11 during the test (such as a sudden increase or decrease in pressure), the test should be stopped immediately, the apparatus checked for leaks, and the test continued only after the fault has been rectified.

[0060] After the test, first disconnect the test instrument from the test device, connect the external gas recovery device to the inflation port 9, open valve 10, and slowly release the filling gas 12 inside the test sleeve 2. Collect the filling gas 12 into a dedicated container to prevent gas leakage and environmental pollution. During the release process, monitor the pressure inside the cavity in real time using pressure gauge 11 until the pressure drops to normal atmospheric pressure (0.1 MPa). Then close valve 10 and disconnect the gas recovery device. Subsequently, remove the upper end cover 3 and lower end cover 4, take out the capacitor 1 to be tested, clean and inspect all components of the test device, and properly store the sealing gasket 5, fixing bolts, and other components for future use.

[0061] The test device of this invention has a simple structure and is easy to assemble. It can accurately simulate the actual working environment of capacitors used in epoxy glass tube voltage transformers. Through the insulating effect of the filling gas, it ensures the safety of the test process and the accuracy of the test results. The test method has clear steps and standardized operation, and can effectively complete the partial discharge and insulation performance test of the capacitor under test. It is suitable for factory testing, type testing and field testing of various epoxy glass tube voltage transformer capacitors.

[0062] The above description only illustrates embodiments of the present invention, but should not be construed as covering the entire scope of protection of the present invention. Equivalent changes or modifications, or proportional enlargements or reductions made by the paradigm based on the design spirit of the present invention should all be considered to fall within the protection scope of the present invention.

[0063] 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 its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A test apparatus for capacitors used in epoxy glass tube voltage transformers, characterized in that, The test sleeve (2) is provided with a capacitor (1) to be tested. A cavity for accommodating filling gas (12) is formed between the test sleeve (2) and the capacitor (1). The test sleeve (2) is provided with an upper end cap (3) and a lower end cap (4) at both ends. The top end cap of the capacitor (1) to be tested is connected to the upper end cap (3) through a mounting plate (6). The bottom end cap of the capacitor (1) to be tested is connected to the lower end cap (4) through a spring wire (8). The upper end cap (3) is provided with an air inlet (9), a pressure gauge (11) and a valve (10) for controlling the air inlet (9).

2. The test apparatus for a capacitor used in an epoxy glass tube voltage transformer according to claim 1, characterized in that, Both ends of the capacitor under test (1) are provided with capacitor equalization rings (7-1) for balancing the internal electric field distribution, and the top of the outside of the test device is provided with device equalization rings (7-2).

3. The test apparatus for a capacitor used in an epoxy glass tube voltage transformer according to claim 1, characterized in that, The filling gas (12) is pure N2, clean air, or a mixture of environmentally friendly gases.

4. The test device for the capacitor of the epoxy glass cloth tube voltage transformer according to claim 1, characterized in that, The test sleeve (2) is made of porcelain or composite material, and the test sleeve (2) is provided with large and small umbrellas on the outside, which are evenly arranged.

5. The test device for the capacitor of the epoxy glass cloth tube voltage transformer according to claim 1, characterized in that, A sealing gasket (5) is provided between the test sleeve (2) and the upper end cap (3) and the lower end cap (4).

6. The test device for the capacitor of the epoxy glass cloth tube voltage transformer according to claim 1, characterized in that, The test sleeve (2) is connected to the upper end cover (3) and the lower end cover (4) by fixing bolts, the top end cover of the capacitor under test (1) is connected to the mounting plate (6), the mounting plate (6) is connected to the upper end cover (3), the bottom end cover of the capacitor under test (1) is connected to the spring wire (8), and the spring wire (8) is connected to the lower end cover (4).

7. The test device for the capacitor of the epoxy glass cloth tube voltage transformer according to claim 1, characterized in that, The pressure gauge (11) is equipped with a pressure relief device.

8. The test device for the capacitor of the epoxy glass cloth tube voltage transformer according to claim 1, characterized in that, The air inlet (9) and the valve (10) are mounted on the upper cover (3) via a first base. The first base is connected to the cavity and is connected to the upper cover (3) via a sealing gasket or by welding.

9. The test device for the capacitor of the epoxy glass cloth tube voltage transformer according to claim 1, characterized in that, The pressure gauge (11) is installed on the upper cover (3) via a second base. The second base is connected to the cavity and is connected to the upper cover (3) via a sealing gasket or by welding.

10. A test method of the capacitor for epoxy glass-braid tube voltage transformers, based on the test device of the capacitor for epoxy glass-braid tube voltage transformers according to any one of claims 1 to 9, characterized by, After the air inside the cavity is evacuated through the air inlet (9), the valve (10) is closed and the pressure inside the test sleeve (2) is kept constant. The valve (10) is opened and the filling gas (12) is injected into the test sleeve (2) through the air inlet (9). When the pressure value of the pressure gauge (11) is 0.4~0.6Mpa, the valve (10) is closed and the pressure is kept constant. The test device is transferred to the test chamber. The test voltage value is applied to the high voltage end of the test device, and the test module is grounded or connected to the low voltage end of the test device. The insulation and partial discharge test of the capacitor for the epoxy glass cloth tube voltage transformer is completed within the test time. After the test is completed, the filling gas (12) inside the test sleeve (2) is recovered through the valve (10) and the air inlet (9) to ensure that the pressure inside the test sleeve (2) is normal atmospheric pressure.

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