A test device and method for measuring electrical parameters of capacitor core under multiple influencing factors

Abstract

The present invention discloses a test device and method for measuring the electrical parameters of a capacitor core under multiple influencing factors, including a sealed container and a sealed cover, the upper end of the sealed container is open, the sealed cover is detachably closed with a sealed cover, a fixed frame for fixing the capacitor core is installed inside the sealed container, an oil filling port, a vacuum valve and a sealed terminal are installed on the sealed cover, an oil filling port is installed with an oil filling valve, and the capacitor core is connected to the sealed terminal through a cable. The established test platform for measuring the equivalent electrical parameters of the capacitor core under multiple influencing factors can analyze multiple factors affecting the equivalent electrical parameters of the CVT capacitor unit, find out the influence of each influencing factor on the capacitance of the capacitor core and the power frequency dielectric loss value, so as to further deduce the influence of factors such as temperature, moisture, and aging on the CVT metering accuracy, and provide a reliable basis for the CVT metering error.

Description

Technical Field

[0001] The invention belongs to the technical field of CVT test equipment, and relates to a device and method for measuring the electrical parameters of a capacitor core under multiple influencing factors. Background Art

[0002] Capacitor voltage transformer (CVT) has the advantages of simple insulation structure, high insulation strength and light weight. As a voltage monitoring device, its measurement results are an important basis for secondary measurement, relay protection and monitoring equipment. In recent years, CVT has been widely used in complex environmental areas, and there are problems such as error tolerance, instability, insulation performance degradation and high failure rate. During the long-term operation of CVT, the electromagnetic unit is relatively stable, while the electrical parameters of the capacitor unit will be affected by factors such as temperature, aging and moisture, which will cause the capacitance and dielectric loss value of the capacitor voltage divider unit to change, thereby causing CVT measurement errors. As the main component of the CVT capacitor unit, the capacitor core is used as the experimental object, and the influence of temperature, aging and moisture on the equivalent electrical parameters (capacitance, dielectric loss factor) of the CVT capacitor unit is studied as one of the key research contents.

[0003] At present, most of the research on capacitor core aging test is aimed at the capacitor core of transformer bushing. For the capacitor core of CVT, the two structures are very different. If the existing research results are used to analyze the impact of CVT capacitor unit, its accuracy and reliability cannot meet the requirements. Therefore, the influence of factors such as temperature, moisture, and aging on the equivalent electrical parameters of CVT capacitor unit needs further research.

[0004] At present, due to the complexity of the CVT working environment, the equivalent electrical parameters (capacitance and dielectric loss factor) of the CVT capacitor unit are more susceptible to environmental factors than the electromagnetic unit, thus causing measurement errors. However, the current aging tests on capacitor cores are mostly tests on bushing capacitor cores, and there is a lack of aging tests on the CVT capacitor unit structure. The present invention aims at the capacitor core in the CVT capacitor voltage divider unit, establishes a test platform for measuring the equivalent electrical parameters of the capacitor core under multiple influencing factors, and studies and analyzes the influence of temperature, moisture and aging on the equivalent electrical parameters of the CVT capacitor unit. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a test device and a test method for measuring the electrical parameters of a capacitor core under multiple influencing factors, so as to solve the problems existing in the prior art.

[0006] The technical solution adopted by the present invention is: a test device for measuring the electrical parameters of a capacitor core under multiple influencing factors, including a sealed container and a sealing cover, the upper end of the sealed container is open, the sealing cover is detachably closed with a sealing cover, a fixing frame for fixing the capacitor core is installed inside the sealed container, an oil filling port, a vacuum valve and a sealing terminal are installed on the sealing cover, an oil filling port is installed with an oil filling valve, and the capacitor core is connected to the sealing terminal through a cable.

[0007] Preferably, the sealed container comprises a bottom plate and a cylindrical side wall sealed and fixedly connected to the bottom plate, and the cylindrical side wall is made of a transparent material.

[0008] Preferably, the fixing frame comprises two insulating plates, a connecting rod and a locking nut. The two insulating plates are pressed on the upper and lower ends of the capacitor core and the connecting rod is passed through the two insulating plates and then locked by the locking nut. Threads are provided at both ends of the connecting rod.

[0009] Preferably, the two insulating plates are both provided with metal plates, and the metal plates are provided with connection terminals.

[0010] Preferably, the above-mentioned capacitor core electrical parameter measurement test device under multiple influencing factors also includes a temperature sensor, which is built into the capacitor core.

[0011] Preferably, an oil pillow is also installed on the sealing cover.

[0012] Preferably, the sealing cover is sealed and connected to a flange provided at the top of the sealing container by bolts.

[0013] A test method for measuring the electrical parameters of a capacitor core under multiple influencing factors, the method includes a test method for measuring the change characteristics of capacitance at different temperatures, a test method for measuring the change characteristics of capacitance under different moisture levels, and a test method for measuring the dielectric loss of the capacitor core under power frequency.

[0014] The test method for measuring the change characteristics of capacitance at different temperatures includes the following steps:

[0015] (1) Place the capacitor core in a 110℃ / 50Pa vacuum oven and dry it for 48 hours;

[0016] (2) Fix the capacitor core with a fixing frame of two insulating plates, place it in a sealed container, and close the sealing cover;

[0017] (3) Use the measurement without oil injection or the measurement with oil injection. If no oil injection is used, jump directly to step (5);

[0018] (4) Inject the dehydrated capacitor oil into the test device through the oil filling port of the test device. Leave the capacitor in the test device for 48 hours to allow the capacitor to be fully immersed in the oil:

[0019] (5) Place the entire test device in a high-temperature constant temperature test chamber, control other external conditions to be the same, and measure the capacitance of the capacitor at room temperature of 10°C, 20°C, 40°C, 60°C, and 80°C, with each heating period lasting 1 hour;

[0020] (6) Use high temperature resistant wires to connect the electrodes at both ends of the capacitor and extend them outside the high temperature constant temperature test chamber through insulating rods to achieve real-time measurement at higher temperatures;

[0021] (7) Set the multimeter to the capacitance measurement mode, connect the two probes of the multimeter to the two leads of the capacitor, and measure the capacitance values ​​with and without oil filling;

[0022] (8) Replace the multimeter with a dielectric response meter, measure the frequency domain dielectric spectrum of the capacitor core, and extract the dielectric loss value at the power frequency.

[0023] The test method for measuring the change characteristics of capacitance under different water content includes the following steps:

[0024] (1) Place the capacitor core in a 110℃ / 50Pa vacuum oven and dry it for 48 hours;

[0025] (2) Fix the capacitor core with a fixing frame of two insulating plates, place it in a sealed container, and close the sealing cover;

[0026] (3) Capacitor oils with initial moisture contents of 10 ppm, 20 ppm, 30 ppm and 40 ppm (obtained by moisture absorption of new capacitor oil at room temperature) were prepared, and the moisture quality of the capacitor oils was measured using a Karl Fischer titrator;

[0027] (4) Inject the prepared capacitor oil sample into the test device through the oil filling port. Leave the capacitor in the test device for 48 hours to allow the capacitor to be fully immersed in the oil.

[0028] (5) Use high temperature resistant wires to connect the electrodes at both ends of the capacitor through insulating rods and extend them outside the high temperature test chamber, and set the temperature to room temperature;

[0029] (6) Set the multimeter to the capacitance measurement range, connect the two test leads of the multimeter to the two leads of the capacitor, and measure the capacitance value;

[0030] (7) Replace the multimeter with a dielectric response meter, measure the frequency domain dielectric spectrum of the capacitor core, and extract the dielectric loss value at the power frequency.

[0031] Beneficial effects of the present invention: Compared with the prior art, the effects of the present invention are as follows:

[0032] 1) The established test platform for measuring the equivalent electrical parameters of capacitor cores under multiple influencing factors can analyze multiple factors affecting the equivalent electrical parameters of CVT capacitor units, find out the influence of each influencing factor on the capacitance and power frequency dielectric loss value of the capacitor core, and further deduce the influence of temperature, moisture, aging and other factors on the CVT measurement accuracy, providing a reliable basis for CVT measurement errors;

[0033] 2) Inject capacitor oil through the oil filling valve and connect the vacuum pump through the vacuum valve to keep the device in a vacuum environment. At the same time, the measuring leads are fixed with terminal posts to prevent the influence of stray capacitance during multiple measurements. The whole test process has good sealing performance. The lead wires can be connected to a variety of measuring instruments through the terminal posts, such as using a six-and-a-half-digit multimeter to measure capacitance and a dielectric responder to measure capacitance dielectric loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the structure of the capacitance measuring device;

[0035] Figure 2 is a schematic diagram of an insulation board;

[0036] Figure 3 This is a wiring diagram for measuring the power frequency dielectric loss value of a capacitor core;

[0037] Figure 4 The flow chart of the test for measuring the capacitance variation characteristics and dielectric loss at different temperatures;

[0038] Figure 5 This is the flow chart of the capacitance variation characteristic measurement and dielectric loss measurement test under different moisture conditions. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0040] Example 1: Figure 1-3 As shown, a test device for measuring electrical parameters of a capacitor core under multiple influencing factors includes a sealed container 1 and a sealed cover 2. The upper end of the sealed container 1 is open, and the sealed cover 2 is detachably closed. A fixing frame 4 for fixing the capacitor core 3 is installed inside the sealed container 1, an oil filling port 5, a vacuum valve 6 and a sealed terminal 7 are installed on the sealing cover 2, an oil filling port 5 is installed with an oil filling valve 8, and the capacitor core 3 is connected to the sealed terminal 7 through a cable.

[0041] Preferably, the sealed container 1 comprises a bottom plate 101 and a cylindrical side wall 102 sealed and fixedly connected to the bottom plate 101. The cylindrical side wall 102 is made of transparent organic glass, which is convenient for observing the capacitance state inside the device.

[0042] Preferably, the fixing frame 4 comprises two insulating plates 401, a connecting rod 402 and a locking nut 403 made of epoxy resin material. The two insulating plates 401 are pressed on the upper and lower ends of the capacitor core 3 and are locked by the locking nut 403 after the connecting rod 402 passes through the two insulating plates 401. Threads are arranged at both ends of the connecting rod 402. The epoxy resin material is used, which has high insulation and compressive strength, and can avoid accidents such as leakage and breakdown. It has good heat resistance and will not deform as the test temperature increases. The heat resistance grade is F grade (155°C), and it has high mechanical strength. The locking nut and the connecting rod are made of epoxy resin material, and together with the upper and lower insulating plates, the capacitor core (length 11 cm, width 15 cm, height 1.3 cm) of the middle layer is fixed, which can avoid the influence of stray capacitance and ensure that the inter-electrode distance of the capacitor remains roughly unchanged during the test, thereby eliminating the influence of the change in capacitance caused by the change in the inter-electrode distance.

[0043] Preferably, a metal plate 404 is provided on each of the two insulating plates 401, and a wiring terminal 405 is provided on the metal plate 404. The specifications of the insulating plate are 22cm*18cm*5cm. The metal plate 404 and the wiring terminal 405 are made of aluminum alloy. The metal plate fixes the aluminum foil led out from the inside of the capacitor core on the insulating plate, and is connected to an external capacitance measuring meter through the wiring terminal, measuring lead and terminal post to realize the measurement of capacitance.

[0044] Preferably, the above-mentioned capacitor core electrical parameter measurement test device under multiple influencing factors also includes a temperature sensor, which is built into the capacitor core 3. A plurality of smaller temperature sensors (not shown in the figure) are installed inside the capacitor core. The influence of the temperature sensor on the capacitance can be ignored. When the readings of each temperature sensor are basically stable, the temperature average is taken to represent the actual temperature inside the capacitor core. After installing the capacitor core and the temperature sensor, use a vernier caliper to measure the upper and lower distances of the four corners of the two insulating plates to ensure that the capacitor is evenly stressed between the insulating plates.

[0045] Preferably, an oil pillow 9 is also installed on the sealing cover 2. The oil pillow plays the role of storing and replenishing oil, which can ensure that the sealed container is full of oil. At the same time, the contact area between the sealed container and the air is reduced, and the moisture, dust and oxidized oil stains absorbed from the air are deposited in the sealed container, thereby greatly slowing down the deterioration rate of the transformer oil.

[0046] Preferably, the sealing cover 2 is sealedly connected to a flange 11 disposed at the top of the sealed container 1 by bolts 10 .

[0047] Example 2: Figure 4-5As shown, a test method for measuring the electrical parameters of a capacitor core under multiple influencing factors includes a test method for measuring the change characteristics of capacitance and dielectric loss at different temperatures and a test method for measuring the change characteristics of capacitance and dielectric loss under different moisture levels.

[0048] The test method for measuring the change characteristics of capacitance and dielectric loss at different temperatures includes the following steps:

[0049] (1) Place the capacitor core in a 110℃ / 50Pa vacuum oven and dry it for 48 hours;

[0050] (2) Fix the capacitor core with a fixing frame of two insulating plates, place it in a sealed container, and close the sealing cover;

[0051] (3) Measurement without oil injection or with oil injection. If no oil injection (dodecylbenzene) is used, jump directly to step (5);

[0052] (4) Inject the dehydrated capacitor oil into the test device through the oil filling port of the test device. Leave the capacitor in the test device for 48 hours to allow the capacitor to be fully immersed in the oil:

[0053] (5) Place the entire test device in a high-temperature constant temperature test chamber, control other external conditions to be the same, and measure the capacitance of the capacitor at room temperature of 10°C, 20°C, 40°C, 60°C, and 80°C, with each heating period lasting 1 hour;

[0054] (6) Use high temperature resistant wires to connect the electrodes at both ends of the capacitor and extend them outside the high temperature constant temperature test chamber through insulating rods to achieve real-time measurement at higher temperatures;

[0055] (7) Set the multimeter to the capacitance measurement mode, connect the two probes of the multimeter to the two leads of the capacitor, and measure the capacitance values ​​with and without oil filling;

[0056] (8) Replace the multimeter with a dielectric response meter, such as Figure 3 The wiring shown is used to measure the frequency domain dielectric spectrum of the capacitor core and extract the dielectric loss value at the power frequency;

[0057] To ensure the repeatability of the test, each test was performed 2 to 3 times, and the repeated measurements were not performed on the same sample.

[0058] The test method for measuring the change characteristics of capacitance and dielectric loss under different moisture conditions includes the following steps:

[0059] (1) Place the capacitor core in a 110℃ / 50Pa vacuum oven and dry it for 48 hours;

[0060] (2) Fix the capacitor core with a fixing frame of two insulating plates, place it in a sealed container, and close the sealing cover;

[0061] (3) Capacitor oils with initial moisture contents of 10 ppm, 20 ppm, 30 ppm and 40 ppm (obtained by moisture absorption of new capacitor oil at room temperature) were prepared, and the moisture quality of the capacitor oils was measured using a Karl Fischer titrator;

[0062] (4) Inject the prepared capacitor oil sample into the test device through the oil filling port. Leave the capacitor in the test device for 48 hours to allow the capacitor to be fully immersed in the oil.

[0063] (5) Use high temperature resistant wires to connect the electrodes at both ends of the capacitor through insulating rods and extend them outside the high temperature test chamber, and set the temperature to room temperature;

[0064] (6) Set the multimeter to the capacitance measurement range, connect the two test leads of the multimeter to the two leads of the capacitor, and measure the capacitance value;

[0065] (7) Replace the multimeter with a dielectric response meter, such as Figure 3 The wiring shown is used to measure the frequency domain dielectric spectrum of the capacitor core and extract the dielectric loss value at the power frequency;

[0066] To ensure the repeatability of the test, each test was performed 2 to 3 times, and the repeated measurements were not performed on the same sample.

[0067] The entire capacitance measuring device is placed in a constant temperature box, and other external environments are kept the same. The temperature is changed, and the capacitance of the capacitor core is measured at different temperatures using a six-and-a-half-digit multimeter to obtain the capacitance value-temperature relationship curve of the capacitor core, extract the temperature coefficient of the capacitor core, and analyze its influence law. At the same time, the platform can measure the capacitance value of the capacitor core under different moisture and aging conditions, and analyze the influence of moisture and long-term aging on capacitance.

[0068] Using the DIRANA dielectric response instrument, capacitor cores at different temperatures, aging and moisture conditions were placed in the capacitance measurement device. Figure 3 Wiring, the DIRANA dielectric response instrument test cable is connected to both ends of the capacitor test device respectively, and the shielding end and the grounding cable are effectively grounded at the same time. The frequency domain dielectric spectrum of the capacitor core under different temperatures, aging and moisture levels can be measured, and the dielectric loss value of the capacitor core under the power frequency can be extracted, and the influence of temperature, aging and moisture on the dielectric loss value of the capacitor core can be analyzed.

[0069] The capacitance measuring device has a simple structure, is convenient for taking out and putting in samples during the test, has flexible combination and is easy to operate. It can effectively measure the influence of factors such as temperature, moisture, aging, etc. on the equivalent electrical parameters of the CVT capacitance unit, thereby analyzing the influence of factors such as temperature, moisture, aging, etc. on the CVT measurement error characteristics.

[0070] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A test method for measuring the electrical parameters of a capacitor core under multiple influencing factors, characterized by: The invention discloses a test device for measuring the electrical parameters of a capacitor core under multiple influencing factors, comprising a sealed container (1) and a sealed cover (2). The upper end of the sealed container (1) is open, and the sealed cover (2) is detachably sealed. A fixing frame (4) for fixing a capacitor core (3) is installed inside the sealed container (1). An oil filling port (5), a vacuum valve (6) and a sealed terminal (7) are installed on the sealed cover (2). An oil filling valve (8) is installed on the oil filling port (5). The capacitor core (3) is connected to the sealed terminal (7) through a cable. The fixing frame (4) comprises two insulating plates (401), a connecting rod (402) and a locking nut (403). The two insulating plates (401) are pressed on the upper and lower ends of the capacitor core (3) and the connecting rod (402) passes through the two insulating plates (401) and is locked by the locking nut (403). The connecting rod (402) is provided with threads at both ends; an oil pillow (9) is also installed on the sealing cover (2); and a temperature sensor is also included, which is built into the capacitor core (3); The method includes a test method for measuring the change characteristics of capacitance and dielectric loss at different temperatures and a test method for measuring the change characteristics of capacitance and dielectric loss at different moisture levels; The test method for measuring the change characteristics of capacitance and dielectric loss at different temperatures includes the following steps: (1) Place the capacitor core in a 110℃ / 50pa vacuum box and dry it for 48 hours; (2) Fix the capacitor core with a fixing frame of two insulating plates, place it in a sealed container, and cover it with a sealing cover; (3) Use non-oil injection or oil injection measurement. If no oil is injected, jump directly to step (5); (4) Inject the dehydrated capacitor oil into the test device through the oil injection port of the test device, and let the capacitor stand in the test device for 48 hours to allow the capacitor to be fully immersed in oil: (5) Place the entire test device in a high-temperature constant temperature test box, control other external conditions to be the same, select room temperature of 10℃, 20℃, 40℃, 60℃, and 80℃ to measure the capacitance of the capacitor, and maintain heating for 1 hour each time; (6) Use high-temperature resistant wires to connect the electrodes at both ends of the capacitor through insulating rods and extend them outside the high-temperature constant temperature test box; (7) Set the multimeter to the capacitance measurement mode, and connect the two test leads of the multimeter to the two leads of the capacitor, and measure the capacitance values ​​of the capacitor with and without oil filling; (8) Replace the multimeter with a dielectric response meter, measure the frequency domain dielectric spectrum of the capacitor core, and extract the dielectric loss value at the power frequency; The test method for measuring the capacitance variation characteristics and dielectric loss under different moisture conditions includes the following steps: (1) Place the capacitor core in a 110℃ / 50Pa vacuum oven and dry it for 48 hours; (2) Fix the capacitor core with a fixing frame of two insulating plates, place it in a sealed container, and close the sealing cover; (3) Capacitor oils with initial moisture contents of 10 ppm, 20 ppm, 30 ppm, and 40 ppm were prepared, and the moisture content of the capacitor oils was measured using a Karl Fischer titrator. (4) Inject the prepared capacitor oil sample into the test device through the oil filling port. Leave the capacitor in the test device for 48 hours to allow the capacitor to be fully immersed in the oil. (5) Use high-temperature resistant wires to connect the electrodes at both ends of the capacitor through insulating rods and extend them outside the high-temperature test chamber, and set the temperature to room temperature; (6) Set the multimeter to the capacitance measurement mode, connect the two test leads of the multimeter to the two leads of the capacitor, and measure the capacitance value; (7) Replace the multimeter with a dielectric response meter, measure the frequency domain dielectric spectrum of the capacitor core, and extract the dielectric loss value at the power frequency.

2. The test method of a capacitor core electrical parameter measurement test device under multiple influencing factors according to claim 1, characterized in that: The sealed container (1) comprises a bottom plate (101) and a cylindrical side wall (102) sealed and fixedly connected to the bottom plate (101), and the cylindrical side wall (102) is made of a transparent material.

3. The test method of a capacitor core electrical parameter measurement test device under multiple influencing factors according to claim 1, characterized in that: Metal plates (404) are provided on both insulating plates (401), and connection terminals (405) are provided on the metal plates (404).

4. The test method of a capacitor core electrical parameter measurement test device under multiple influencing factors according to claim 1, characterized in that: The sealing cover (2) is sealed and connected to a flange (11) provided at the top end of the sealing container (1) through bolts (10).

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