Equivalent Test Apparatus and Method for Insulation Strength of Internal Interface of GIS Cable Terminal

Abstract

This invention relates to an equivalent testing device and method for the interfacial insulation strength of GIS cable terminals. The device includes a high-voltage power supply, a partial discharge acquisition device, a test electrode system, and a microscopic observation system. The test electrode system includes a pressure application workpiece, an acrylic pad, a foil strain gauge, a pressure transducer, a prefabricated copper foil electrode, and a test sample. The acrylic pad has a three-layer acrylic pad structure, with the test sample and foil strain gauge placed between the layers. The test sample is placed using a layered arrangement of silicone rubber and epoxy resin sheets, with a prefabricated copper foil electrode bonded in the middle. The high-voltage needle electrode and the grounding plate electrode of the prefabricated copper foil electrode are respectively connected to the high-voltage side and the grounding side of the high-voltage power supply. This invention uses a prefabricated copper foil electrode, which ensures a tight fit between the electrode and the double-layer insulation medium, solving the problem of significant air gaps caused by the inability to adhere the double-layer insulation medium. It can be widely used for testing interfacial insulation strength and the failure process.

Description

Technical Field

[0001] This invention belongs to the field of high-voltage equipment technology, and relates to GIS cable terminals, particularly a device and method for equivalent testing of the internal interface insulation strength of GIS cable terminals. Background Technology

[0002] High-voltage GIS is a high-voltage power distribution device that uses SF6 gas as the insulating medium and is composed of high-voltage electrical equipment such as circuit breakers and disconnectors. Due to its compact structure, high reliability, and convenient maintenance, high-voltage GIS has become the best equipment for power conversion in ultra-high voltage and extra-high voltage substations and is widely used in power transmission and transformation projects in my country.

[0003] GIS cable terminals are an essential type of terminal in GIS switchgear. They employ a dry-type design and use SF6 gas as external insulation, offering advantages such as compact structure, easy maintenance, and stable performance. However, with the occurrence of extreme weather in recent years (temperatures as low as -40°C), GIS cable terminal failures have become frequent. Unlike past failures, recent failures show a clear correlation between the timing of the failures and the temperature. Statistics show that on the day of the cold wave alone, three GIS terminal breakdown accidents occurred, seriously affecting the safe and stable operation of the power grid. Disassembly of the faulty terminals revealed the following characteristics: no obvious discharge channels were found in the cable body and inside the stress cone, while obvious discharge and high-temperature burning marks were present at the interface between the stress cone and the epoxy bushing. The preliminary assessment is that the interface breakdown was caused by a decrease in the interface insulation strength. Changes in the mating state of the insulation interface are a key factor affecting the overall insulation performance of the terminal. Considering the order-of-magnitude difference in the coefficients of thermal expansion between silicone rubber and epoxy resin, interface performance may decline due to thermal expansion mismatch in low-temperature environments. Therefore, in order to explore the breakdown damage characteristics of the insulation interface under different interface pressures and to explain the mechanism of terminal failure under extreme weather conditions, it is urgent to propose an equivalent test platform for the insulation strength of GIS cable terminal interfaces to test the insulation interface failure process and its damage characteristics under different pressures. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an equivalent test device and method for the insulation strength of the internal interface of a GIS cable terminal, which can perform real-time synchronous testing of the partial discharge characteristics, failure rate, and failure morphology during the insulation interface failure process under different pressures.

[0005] The present invention solves the existing technical problems by adopting the following technical solution:

[0006] An equivalent test device for the internal interface insulation strength of a GIS cable terminal includes a high-voltage power supply, a partial discharge acquisition device, a test electrode system, and a microscopic observation system;

[0007] The high-voltage power supply provides the test voltage for the test electrode system and the applied voltage phase for the partial discharge acquisition equipment;

[0008] The partial discharge acquisition device acquires the discharge pulse current of the test electrode system in real time and obtains the partial discharge characteristics based on the applied voltage phase.

[0009] The test electrode system includes a pressure application workpiece, an acrylic pad, a foil strain gauge, a pressure transducer, a prefabricated copper foil electrode, and a test sample. The pressure application workpiece provides pressure to the acrylic pad. The acrylic pad has a three-layer acrylic pad structure, with the test sample and foil strain gauge placed between the layers. The test sample is placed using a layered method of silicone rubber and epoxy resin sheets, with a prefabricated copper foil electrode attached in the middle. The high-voltage needle electrode and the grounding plate electrode of the prefabricated copper foil electrode are respectively connected to the high-voltage side and the grounding side of the high-voltage power supply. The foil strain gauge is connected to the pressure transducer, which is used to measure the applied pressure of the pressure application workpiece.

[0010] The microscopic observation system includes a cold light source and an electron microscope. The cold light source is installed directly below the test electrode system, and the electron microscope is installed directly above the test electrode system. The light source direction of the cold light source and the electron microscope are perpendicular to the surface of the sample to be tested.

[0011] Furthermore, the high-voltage power supply includes a transformer, a voltage regulator, a current-limiting resistor, and a voltage divider. The voltage regulator, transformer, and current-limiting resistor are connected in sequence. The other end of the current-limiting resistor is connected to the voltage divider and the high-voltage needle electrode of the test electrode system. The other end of the voltage divider is connected to the partial discharge acquisition device to provide it with the applied voltage phase.

[0012] Furthermore, the transformer is a 0-100kV partial discharge-free transformer; the voltage divider is a 1000:1 RC voltage divider.

[0013] Furthermore, the partial discharge acquisition device includes an HFCT sensor, a signal processor, and a computer. The HFCT sensor is concentrically connected to the ground wire of the test electrode system to acquire the discharge pulse current in real time and transmit it to the signal processor. The signal processor synchronizes the acquired discharge pulse current and the applied voltage phase and transmits the processed data to the computer.

[0014] Furthermore, the workpiece to which the pressure is applied consists of a frame, upper and lower clamping plates, and a worm gear. The upper and lower clamping plates include two upper clamping plates and two lower clamping plates. The two lower clamping plates are symmetrically fixed to the bottom of the inner side of the frame. The two upper clamping plates are respectively installed together with the lower ends of the two worm gears. The upper ends of the two worm gears are installed on the upper end of the frame. The worm gears are used to adjust the pressure between the upper and lower clamping plates.

[0015] Furthermore, the prefabricated copper foil electrode includes a high-voltage needle electrode, an auxiliary positioning part, and a ground plane electrode, wherein the auxiliary positioning part ensures the spacing between the high-voltage needle electrode and the ground plane electrode.

[0016] Furthermore, the distance between the high-pressure needle electrode and the grounding electrode is 2mm, and the width and length of the high-pressure needle electrode satisfy a ratio of 1:2.

[0017] A test method for an equivalent test device for the internal interface insulation strength of a GIS cable terminal includes the following steps:

[0018] Step 1: Cut the polished epoxy resin sheet and silicone rubber sheet into square test samples;

[0019] Step 2: Adhere the prefabricated copper foil electrode to the surface of the epoxy resin sample sheet, remove the auxiliary positioning part, and then slowly cover the square test sample onto the surface of the epoxy resin sample sheet from one side, ensuring that there are no obvious air bubbles at the bonding interface.

[0020] Step 3: Place the bonded test sample in the first gap of the three-layer acrylic pad, place the foil strain gauge in the second gap of the three-layer acrylic pad, and connect the foil strain gauge to the pressure transducer.

[0021] Step 4: Place the assembled three-layer acrylic pad, foil strain gauge and test sample into the pressure application workpiece, and adjust the applied pressure to a specific value using the worm gear;

[0022] Step 5: Adjust the cold light source and electron microscope to be perpendicular to the surface of the sample, and focus on the middle position between the high-pressure needle electrode and the ground plane electrode. Adjust the light intensity of the cold light source until the interface of the sample to be tested can be clearly observed.

[0023] Step 6: Connect the high-voltage needle electrode and the grounding electrode to the high-voltage side and the grounding side of the high-voltage power supply. Adjust the voltage regulator to control the applied voltage and observe the interface marking state in real time. After the interface marks start, keep the applied voltage unchanged. Then turn on the electron microscope and signal processor to record the interface electrical trace damage morphology and partial discharge characteristics in real time until the test sample is broken down.

[0024] Step 7: After the test sample breaks down, adjust the voltage regulator to zero and turn off the electron microscope and signal processor. The test is now complete.

[0025] The advantages and positive effects of this invention are:

[0026] This invention features a rational design, employing prefabricated copper foil electrodes instead of existing needle-plate electrodes. This ensures a tight fit between the electrodes and the double-layer insulating medium, significantly reducing air gaps near the electrodes and resolving the problem of noticeable air gaps due to the inability to achieve proper adhesion between the double-layer insulating medium. Furthermore, the testing device can perform real-time synchronous testing of the partial discharge characteristics, failure rate, and failure morphology during the insulation interface failure process under different pressures. It overcomes the limitation of existing testing platforms providing limited test data. Its testing method is simple, accurate, and reliable, and can be widely used for testing interface insulation strength and failure processes. Attached Figure Description

[0027] Figure 1 This is a structural diagram of the prefabricated copper foil electrode of the present invention;

[0028] Figure 2 This is a structural diagram of the test electrode system of the present invention;

[0029] Figure 3 This is a schematic diagram of the overall structure of the equivalent test device of the present invention;

[0030] Figure 4 This is a diagram showing the synchronous test results of the electrical tracking damage process and partial discharge characteristics at the insulation interface according to the present invention;

[0031] Among them, 1-high pressure needle electrode, 2-auxiliary positioning part, 3-grounding plate electrode, 4-current limiting resistor, 5-transformer, 6-voltage divider, 7-voltage regulator, 8-electron microscope, 9-workpiece under pressure, 10-acrylic pad, 11-foil strain gauge, 12-prefabricated copper foil electrode, 13-halogen cold light source, 14-pressure converter, 15-HFCT sensor, 16-signal processor, 17-computer, 9.1-frame, 9.2-upper and lower clamping plates, 9.3-worm gear. Detailed Implementation

[0032] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] An equivalent test device for the internal interface insulation strength of a GIS cable terminal, such as Figures 1 to 3 As shown, it consists of a high-voltage power supply, a partial discharge acquisition device, an experimental electrode system, and a microscopic observation system.

[0034] The high-voltage power supply includes a 0-100kV partial discharge-free transformer (5), a voltage regulator (7), a current-limiting resistor (4), and a voltage divider (6). The current-limiting resistor (4) is a 2MΩ current-limiting resistor used to prevent overcurrent. The voltage divider (6) is a 1000:1 RC divider used to measure the applied voltage in real time and provide the applied voltage phase to the signal processor (16).

[0035] The partial discharge acquisition device includes an HFCT sensor (15), a signal processor (16), and a computer (17). The HFCT sensor (15) is concentrically connected to the ground wire of the test electrode system to acquire the discharge pulse current in real time and transmit it to the signal processor (16). The signal processor (16) synchronizes the acquired discharge pulse current with the applied voltage phase and transmits the processed data to the computer (17).

[0036] The test electrode system includes a pressure application workpiece (9), an acrylic pad (10), a foil strain gauge (11), a pressure converter (14), a prefabricated copper foil electrode (12), and a test sample. In this embodiment, the pressure application workpiece (9) is a JIN FENG-Q19D device. The pressure application workpiece (9) consists of a frame (9-1), upper and lower clamping plates (9-2), and worm gears (9-3). The upper and lower clamping plates (9-2) include two upper clamping plates and two lower clamping plates. The two lower clamping plates are symmetrically fixed to the bottom of the inner side of the frame (9-1). The two upper clamping plates are respectively installed together with the bottom of the two worm gears (9-3). The upper ends of the two worm gears (9-3) are installed on the upper end of the frame (9-1). The upper clamping plates can be adjusted up and down by means of the worm gears (9-3). Among them, the acrylic pad (10) is installed between the upper and lower clamping plates (9-2) in the pressure-applying workpiece (9), and the applied pressure is adjusted by the worm gear (9-3).

[0037] The acrylic pad (10) is a three-layer acrylic pad (10) structure, with the test sample and foil strain gauge (11) placed between the layers of the acrylic pad. The test sample is an epoxy resin / silicone rubber sample sheet, which is placed in a stacked manner of silicone rubber and epoxy resin sheets, with a prefabricated copper foil electrode (12) pasted in the middle. The high-voltage needle electrode (1) and the grounding electrode (3) of the prefabricated copper foil electrode (12) are respectively connected to the high-voltage side and the grounding side of the high-voltage power supply; the foil strain gauge (11) is connected to a pressure transducer (14), which applies pressure for measurement.

[0038] The prefabricated copper foil electrode (12) is fabricated using laser cutting technology, and its structure is as follows: Figure 1 As shown, the whole assembly includes a high-pressure needle electrode (1), an auxiliary positioning part (2), and a grounding electrode (3); the auxiliary positioning part (2) ensures that the high-pressure needle electrode (1) and the grounding electrode (3) are strictly controlled at a distance of 2 mm. After the prefabricated copper foil electrode (12) is attached to the sample to be tested, the auxiliary positioning part (2) is removed with a cutter. Except for the high-pressure needle electrode (1) and the grounding electrode (3) needing to maintain a given distance and the high-pressure needle electrode width and length needing to meet a ratio of 1:2, the dimensions of the other parts can be adjusted according to the size of the sample to be tested. In this example, the following is selected: Figure 1 The dimensions are marked in the middle.

[0039] The microscopic observation system includes a halogen cold light source (13) and an electron microscope (8). The halogen cold light source (13) is installed directly below the test electrode system, and the electron microscope (8) is installed directly above the test electrode system. The light source direction of the halogen cold light source (13) and the electron microscope (8) should be strictly perpendicular to the surface of the sample to obtain clear observation results.

[0040] Based on the above-mentioned equivalent test device for the internal interface insulation strength of GIS cable terminals, this invention also proposes an equivalent test method for the internal interface insulation strength of GIS cable terminals, comprising the following steps:

[0041] Step 1: Cut the polished epoxy resin sheet and silicone rubber sheet into 4cm*4cm square test samples.

[0042] Step 2, Figure 1 The prefabricated copper foil electrode shown is bonded to the surface of the epoxy resin sample sheet, and the auxiliary positioning part (2) is removed. Then, the silicone rubber sample sheet is slowly placed on the surface of the epoxy resin sample sheet from one side to ensure that there are no obvious bubbles at the bonding interface.

[0043] Step 3: Place the bonded test sample in the first gap of the three-layer acrylic pad (10), place the foil strain gauge (11) in the second gap of the three-layer acrylic pad (10), and connect the foil strain gauge (11) to the pressure converter (14).

[0044] Step 4: Place the assembled three-layer acrylic pad (10), foil strain gauge (11), and test sample into the pressure application workpiece (9), and adjust the applied pressure to a specific value using a worm gear. The pressure sensor output unit is kg. Therefore, the interface pressure is calculated based on the sample size and according to Equation 1.

[0045]

[0046] In the formula, P is the interface pressure (MPa), M is the pressure sensor reading (kg), and g is the acceleration due to gravity (9.8 m / s²). 2 S is the surface area of ​​the sample (m²) 2 ).

[0047] Step 5: Adjust the halogen cold light source (13) and electron microscope (8) to be perpendicular to the surface of the sample, and focus on the middle position between the high-pressure needle electrode (1) and the grounding electrode (3). Adjust the light intensity of the halogen cold light source (13) until the interface of the sample to be tested can be clearly observed.

[0048] Step 6: Connect the high-voltage needle electrode (1) and the grounding electrode (3) to the high-voltage side and grounding side of the high-voltage power supply. Adjust the voltage regulator (7) to control the applied voltage and observe the interface marking state in real time. After the interface marks appear, keep the applied voltage constant. Then turn on the electron microscope (8) and signal processor (16) to record the interface electrical trace damage morphology and partial discharge characteristics in real time until the sample breaks down. Figure 4 As shown.

[0049] Step 7: After the sample breaks down, adjust the voltage regulator (7) to zero and turn off the electron microscope (8) and signal processor (16). The test is now complete. If you want to continue testing, return to step 1 and repeat process 1-7.

[0050] The above steps can be used to perform the equivalent test of the insulation strength of the internal interface of the GIS cable terminal.

[0051] It should be emphasized that the embodiments described in this invention are illustrative rather than limiting. Therefore, this invention includes, but is not limited to, the embodiments described in the specific implementation. Any other implementations derived by those skilled in the art based on the technical solutions of this invention are also within the scope of protection of this invention.

Claims

1. An equivalent test device for the internal interface insulation strength of a GIS cable terminal, characterized in that: This includes a high-voltage power supply, partial discharge acquisition equipment, test electrode system, and microscopic observation system; The high-voltage power supply provides the test voltage for the test electrode system and the applied voltage phase for the partial discharge acquisition equipment; The partial discharge acquisition device acquires the discharge pulse current of the test electrode system in real time and obtains the partial discharge characteristics based on the applied voltage phase. The test electrode system includes a pressure application workpiece, an acrylic pad, a foil strain gauge, a pressure transducer, a prefabricated copper foil electrode, and a test sample. The pressure application workpiece provides pressure to the acrylic pad. The acrylic pad has a three-layer acrylic pad structure, with the test sample and foil strain gauge placed between the layers. The test sample is placed using a layered method of silicone rubber and epoxy resin sheets, with a prefabricated copper foil electrode attached in the middle. The high-voltage needle electrode and the grounding plate electrode of the prefabricated copper foil electrode are respectively connected to the high-voltage side and the grounding side of the high-voltage power supply. The foil strain gauge is connected to the pressure transducer, which is used to measure the applied pressure of the pressure application workpiece. The workpiece to which the pressure is applied consists of a frame, upper and lower clamping plates, and a worm gear. The upper and lower clamping plates include two upper clamping plates and two lower clamping plates. The two lower clamping plates are symmetrically fixed to the bottom of the inner side of the frame. The two upper clamping plates are respectively installed together with the lower ends of the two worm gears. The upper ends of the two worm gears are installed on the upper end of the frame. The worm gears are used to adjust the pressure between the upper and lower clamping plates. The prefabricated copper foil electrode includes a high-pressure needle electrode, an auxiliary positioning part, and a ground plane electrode. The auxiliary positioning part ensures the distance between the high-pressure needle electrode and the ground plane electrode. The microscopic observation system includes a cold light source and an electron microscope. The cold light source is installed directly below the test electrode system, and the electron microscope is installed directly above the test electrode system. The light source direction of the cold light source and the electron microscope are perpendicular to the surface of the sample to be tested.

2. The equivalent test device for the internal interface insulation strength of GIS cable terminals according to claim 1, characterized in that: The high-voltage power supply includes a transformer, a voltage regulator, a current-limiting resistor, and a voltage divider. The voltage regulator, transformer, and current-limiting resistor are connected in sequence. The other end of the current-limiting resistor is connected to the voltage divider and the high-voltage needle electrode of the test electrode system. The other end of the voltage divider is connected to a partial discharge acquisition device to provide it with the applied voltage phase.

3. The equivalent test device for the internal interface insulation strength of GIS cable terminals according to claim 2, characterized in that: The transformer is a 0~100 kV partial discharge-free transformer; the voltage divider is a 1000:1 RC voltage divider.

4. The equivalent test device for the internal interface insulation strength of GIS cable terminals according to claim 1, characterized in that: The partial discharge acquisition device includes an HFCT sensor, a signal processor, and a computer. The HFCT sensor is concentrically connected to the ground wire of the test electrode system and is used to acquire the discharge pulse current in real time and transmit it to the signal processor. The signal processor synchronizes the acquired discharge pulse current and the applied voltage phase and transmits the processed data to the computer.

5. The equivalent test device for the internal interface insulation strength of GIS cable terminals according to claim 1, characterized in that: The distance between the high-pressure needle electrode and the grounding electrode is 2mm, and the width and length of the high-pressure needle electrode meet the ratio of 1:

2.

6. A test method for an equivalent test device for the internal interface insulation strength of a GIS cable terminal as described in any one of claims 1-5, characterized in that: Includes the following steps: Step 1: Cut the polished epoxy resin sheet and silicone rubber sheet into square test samples; Step 2: Adhere the prefabricated copper foil electrode to the surface of the epoxy resin sample sheet, remove the auxiliary positioning part, and then slowly cover the square test sample onto the surface of the epoxy resin sample sheet from one side, ensuring that there are no obvious air bubbles at the bonding interface. Step 3: Place the bonded test sample in the first gap of the three-layer acrylic pad, place the foil strain gauge in the second gap of the three-layer acrylic pad, and connect the foil strain gauge to the pressure transducer. Step 4: Place the assembled three-layer acrylic pad, foil strain gauge and test sample into the pressure application workpiece, and adjust the applied pressure to a specific value using the worm gear; Step 5: Adjust the cold light source and electron microscope to be perpendicular to the surface of the sample, and focus on the middle position between the high-pressure needle electrode and the ground plane electrode. Adjust the light intensity of the cold light source until the interface of the sample to be tested can be clearly observed. Step 6: Connect the high-voltage needle electrode and the grounding electrode to the high-voltage side and the grounding side of the high-voltage power supply. Adjust the voltage regulator to control the applied voltage and observe the interface marking state in real time. After the interface marks start, keep the applied voltage unchanged. Then turn on the electron microscope and signal processor to record the interface electrical trace damage morphology and partial discharge characteristics in real time until the test sample is broken down. Step 7: After the test sample breaks down, adjust the voltage regulator to zero and turn off the electron microscope and signal processor. The test is now complete.

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