A method and system for testing dc support capacitors

Abstract

The application relates to a method and system for testing a DC supporting capacitor, comprising: applying a DC voltage and superimposing a rated power frequency ripple voltage to a DC supporting capacitor sample at a first preset temperature, continuing for a first preset interval to complete a first stage test; adjusting the temperature and the applied DC voltage until the capacitor value loss is greater than or equal to a preset capacitor value loss or until the capacitor average hourly decline value is less than a preset threshold after a preset withstand voltage time interval under the test conditions of a preset stop temperature and a preset stop voltage, and the second stage test is completed; modifying the applied DC voltage and superimposing the rated power frequency ripple voltage at the first preset temperature, continuing for a second preset interval to complete a third stage test; if the capacitor sample does not appear self-healing failure, does not appear shell burst and / or appears pressure switch action, performing a voltage test; if no breakdown and flashover occur, it is determined that the test is passed.

Description

Technical Field

[0001] This invention relates to the field of high voltage testing technology, and more specifically, to a method and system for testing DC-supported capacitors. Background Technology

[0002] DC support capacitors are core components of converters in flexible DC transmission projects. Considering performance requirements such as size and fire resistance, dry-type film capacitors are currently used. However, the reliability of existing domestically produced DC dry-type capacitors still has significant issues. The high-voltage DC support capacitors (2800V, 7500μF-10000μF) used in projects are all imported products, resulting in high equipment costs and long procurement cycles.

[0003] The current quality assessment methods for high-voltage dry-type capacitors include factory testing and type testing. Even with existing testing methods and conditions, products that pass the tests still frequently experience malfunctions during operation. This indicates a discrepancy between the existing testing methods and the actual operating conditions of high-voltage dry-type DC capacitors, suggesting deficiencies in the assessment content. Destructive testing is a crucial type test for capacitors, primarily verifying their safe operation within technical specification limits. Currently, there is no specific testing standard for DC-supported capacitors; therefore, the destructive testing method in GB / T 17702 "Power Electronic Capacitors" can be referenced. This involves applying a high DC voltage to the test sample at a relatively high temperature until the capacitance decays to below 10%, requiring the sample not to explode. This standard is generally used for power electronic capacitors with smaller capacitances, and the test method is not specifically defined. Using this method for destructive testing of DC-supported capacitors cannot achieve the purpose of assessing actual operational safety. Furthermore, the capacitance decay rate is slow according to the standard test procedure, and the testing time for large-capacity DC-supported capacitors is very long, potentially exceeding six months. The testing process also carries the risk of explosion.

[0004] Therefore, for destructive testing of DC-supported capacitors, a test method that can evaluate their performance according to actual working conditions is required. Furthermore, the test process needs to be optimized to improve test efficiency, reduce time consumption, and enhance test safety. Summary of the Invention

[0005] This invention proposes a method and system for evaluating DC support capacitors, in order to solve the problem of how to evaluate DC support capacitors used in flexible DC converter valves.

[0006] To address the above problems, according to one aspect of the present invention, a method for evaluating a DC-supported capacitor is provided, the method comprising:

[0007] At a first preset temperature, a DC voltage equal to a first preset multiple of the rated DC voltage is applied to the DC-supported capacitor test specimen, and a rated power frequency ripple voltage is superimposed on it. This process is continued for a first preset period of time to complete the first stage test. After the first stage test is completed, the capacitance change of the test specimen is measured.

[0008] The temperature and applied DC voltage are adjusted according to the preset temperature adjustment step size and the preset DC voltage adjustment step size to carry out the second stage test. The capacitance of the capacitor sample is tested at preset time intervals until the capacitance value loss is greater than or equal to the preset capacitance value loss, or until the average hourly capacitance drop is less than the preset threshold after a preset withstand voltage time period under the test conditions of preset stop temperature and preset stop voltage, thus completing the second stage test.

[0009] At the first preset temperature, a DC voltage of a second preset multiple of the rated DC voltage is applied to the DC-supported capacitor test specimen and a rated power frequency ripple voltage is superimposed on it for a second preset period of time to complete the third stage test.

[0010] If the capacitor test specimen does not exhibit self-healing failure, does not show shell cracking, and / or does not exhibit pressure switch operation, then the capacitor test specimen is cooled to ambient temperature before conducting voltage tests between terminals and between terminals and the shell.

[0011] If the capacitor test specimen does not experience breakdown or flashover during the voltage test, then the capacitor test specimen is deemed to have passed the test.

[0012] Preferably, in the second stage of testing, the temperature adjustment range is [50℃, 70℃], and the DC voltage adjustment range is [1.3U]. NDC 1.6U NDC The preset temperature adjustment step size is 5℃; the preset capacitance loss is 90%; among which, U NDC This is the rated DC voltage of the capacitor.

[0013] Preferably, the method further includes:

[0014] During the second phase of testing, the test conditions were modified according to the capacitance decay rate, including:

[0015] For diaphragm type capacitor samples, if the average hourly capacitance decrease is less than a first preset percentage, the temperature or DC voltage should be increased according to the current test conditions.

[0016] For non-separator type capacitor test specimens, if the average hourly decrease in capacitance is less than the second preset percentage, the temperature or DC voltage is increased according to the current test conditions; if the average hourly decrease in capacitance is greater than or equal to the third preset percentage, the test is paused and the power is cut off for a third preset period of time, and then the voltage is reduced by one level according to the current conditions and the test continues; wherein, if the current voltage is the lowest test voltage at that temperature, the current voltage is maintained unchanged.

[0017] Preferably, the method further includes:

[0018] If, during the first, second, and / or third stage of testing, the capacitor sample exhibits self-healing failure and / or casing cracking, then the capacitor sample is directly deemed to have failed the test; and / or

[0019] If the capacitor test specimen experiences breakdown and flashover during the voltage test, it is determined that the capacitor test specimen has failed the test.

[0020] Preferably, the method further includes:

[0021] During the first, second, and / or third stage tests, the DC charging current of the capacitor sample is monitored. If the DC charging current exceeds a preset current under steady-state conditions, it is determined that the capacitor sample has experienced self-healing failure, and the test is terminated directly; and / or

[0022] If, during the first, second, and / or third stage of testing, a DC voltage or AC voltage cannot be applied to the capacitor sample, it is determined that a self-healing failure has occurred inside the sample, and the test is terminated directly.

[0023] According to another aspect of the present invention, a system for evaluating a DC-supported capacitor is provided, the system comprising:

[0024] The first-stage test unit is used to apply a DC voltage equal to a first preset multiple of the rated DC voltage and superimposed with a rated power frequency ripple voltage to the DC-supported capacitor test specimen at a first preset temperature for a first preset period of time to complete the first-stage test, and to measure the capacitance change of the test specimen after the first-stage test is completed.

[0025] The second-stage test unit is used to adjust the temperature and applied DC voltage according to the preset temperature adjustment step size and preset DC voltage adjustment step size to perform the second-stage test, and to test the capacitance of the capacitor sample at preset time intervals until the capacitance value loss is greater than or equal to the preset capacitance value loss, or until the average hourly capacitance drop is less than the preset threshold after a preset withstand voltage time period under the test conditions of preset stop temperature and preset stop voltage, thus completing the second-stage test.

[0026] The third-stage test unit is used to apply a DC voltage of a second preset multiple of the rated DC voltage and superimpose the rated power frequency ripple voltage to the DC-supported capacitor test sample at the first preset temperature for a second preset period of time to complete the third-stage test.

[0027] The voltage test unit is used to perform voltage tests between terminals and between terminals and the casing after cooling the capacitor test sample to ambient temperature if the capacitor test sample does not exhibit self-healing failure, casing cracking, and / or pressure switch activation.

[0028] The assessment result determination unit is used to determine that the capacitor test sample passes the assessment if no breakdown or flashover occurs during the voltage test.

[0029] Preferably, in the second stage test unit, during the second stage test, the temperature adjustment range is [50℃, 70℃], and the DC voltage adjustment range is [1.3U]. NDC 1.6U NDC The preset temperature adjustment step size is 5℃; the preset capacitance loss is 90%; among which, U NDC This is the rated DC voltage of the capacitor.

[0030] Preferably, the second-stage test unit is further used for:

[0031] During the second phase of testing, the test conditions were modified according to the capacitance decay rate, including:

[0032] For diaphragm type capacitor samples, if the average hourly capacitance decrease is less than a first preset percentage, the temperature or DC voltage should be increased according to the current test conditions.

[0033] For non-separator type capacitor test specimens, if the average hourly decrease in capacitance is less than the second preset percentage, the temperature or DC voltage is increased according to the current test conditions; if the average hourly decrease in capacitance is greater than or equal to the third preset percentage, the test is paused and the power is cut off for a third preset period of time, and then the voltage is reduced by one level according to the current conditions and the test continues; wherein, if the current voltage is the lowest test voltage at that temperature, the current voltage is maintained unchanged.

[0034] Preferably, the assessment result determination unit further includes:

[0035] If, during the first, second, and / or third stage of testing, the capacitor sample exhibits self-healing failure and / or casing cracking, then the capacitor sample is directly deemed to have failed the test; and / or

[0036] If the capacitor test specimen experiences breakdown and flashover during the voltage test, it is determined that the capacitor test specimen has failed the test.

[0037] Preferably, the system further includes: a monitoring unit, used for:

[0038] During the first, second, and / or third stage tests, the DC charging current of the capacitor sample is monitored. If the DC charging current exceeds a preset current under steady-state conditions, it is determined that the capacitor sample has experienced self-healing failure, and the test is terminated directly; and / or

[0039] If, during the first, second, and / or third stage of testing, a DC voltage or AC voltage cannot be applied to the capacitor sample, it is determined that a self-healing failure has occurred inside the sample, and the test is terminated directly.

[0040] This invention provides a method and system for testing a DC-supported capacitor, comprising: applying a DC voltage equal to a first preset multiple of the rated DC voltage and superimposing a rated power frequency ripple voltage to a DC-supported capacitor test specimen at a first preset temperature, for a first preset time interval to complete a first stage test, and measuring the capacitance change of the test specimen after the first stage test; adjusting the temperature and the applied DC voltage according to preset temperature adjustment steps and preset DC voltage adjustment steps to perform a second stage test, and testing the capacitance of the capacitor test specimen at preset time intervals until the capacitance loss is greater than or equal to a preset capacitance loss, or until the test reaches a preset stop temperature and preset stop voltage. Under the given conditions, the second stage test is completed when the average hourly decrease in capacitance is less than a preset threshold after a preset withstand voltage period. At the first preset temperature, a DC voltage equal to a second preset multiple of the rated DC voltage is applied to the DC-supported capacitor test specimen, superimposed with a rated power frequency ripple voltage, for a second preset period to complete the third stage test. If the capacitor test specimen does not exhibit self-healing failure, casing cracking, or pressure switch activation, it is cooled to ambient temperature before conducting voltage tests between terminals and between terminals and the casing. If the capacitor test specimen does not experience breakdown or flashover during the voltage test, it is determined that the capacitor test specimen has passed the test. The method of this invention can perform destructive testing on DC-supported capacitors according to actual operating conditions. Through an optimized test process, it improves test efficiency, significantly shortens test time, and achieves the goal of assessing the safety performance of capacitor test specimens. It also avoids serious explosions of the test specimens, ensuring the safety of the test process. It can be directly applied to type testing of large-capacity DC-supported capacitors. Attached Figure Description

[0041] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0042] Figure 1 A flowchart of a method 100 for evaluating a DC support capacitor according to an embodiment of the present invention.

[0043] Figure 2 A flowchart illustrating the evaluation of a DC-supported capacitor according to an embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of the structure of a system 300 for evaluating a DC support capacitor according to an embodiment of the present invention. Detailed Implementation

[0045] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0046] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0047] Figure 1 This is a flowchart of a method 100 for evaluating a DC-supported capacitor according to an embodiment of the present invention. Figure 1 As shown, the method for evaluating DC-supported capacitors provided by this invention can perform destructive testing on DC-supported capacitors under actual operating conditions. Through an optimized test process, it improves test efficiency and significantly shortens test time while achieving the goal of evaluating the safety performance of the capacitor test specimen. It also avoids serious explosions of the test specimen, ensuring the safety of the test process. This method can be directly applied to type testing of large-capacity DC-supported capacitors. The method 100 for evaluating DC-supported capacitors provided by this invention begins at step 101. In step 101, at a first preset temperature, a DC voltage equal to a first preset multiple of the rated DC voltage is applied to the DC-supported capacitor test specimen, and a rated power frequency ripple voltage is superimposed on it. This process continues for a first preset period to complete the first stage test. After the first stage test is completed, the capacitance change of the test specimen is measured.

[0048] The method of this invention utilizes the characteristic that the actual operating conditions of a DC-supported capacitor are characterized by DC superimposed ripple. It employs a superimposed AC / DC voltage method to conduct destructive testing on the test specimen. Corresponding to the actual operating conditions of the DC-supported capacitor, a destructive test is conducted by applying a DC voltage superimposed with a power frequency AC voltage to the test specimen capacitor. This ensures that the test conditions are equivalent to the operating conditions, guaranteeing that the evaluation results better reflect the actual operating performance of the test specimen. During the pressurization process, the AC voltage maintains the rated power frequency ripple voltage of the capacitor constant, while the DC voltage gradually increases according to the decrease in the test specimen capacitance as the test progresses, and the ambient temperature is adjusted accordingly.

[0049] The destructive test process for DC-supported capacitors is divided into three stages. The test specimen only needs to pass all three stages; it is not required that the capacitance must be reduced to below 10%. In each stage, different DC voltages are applied to the capacitor under different ambient temperatures, and a rated power frequency ripple voltage is superimposed on it.

[0050] In an embodiment of the present invention, in the first stage, because the sample is in relatively good condition at the beginning of the destructive test, a higher ambient temperature and a higher voltage are applied in the first stage to allow the sample to enter the capacity decay stage as quickly as possible. In the first test stage, the first preset temperature is 70°C, the first preset multiple is 1.3, and the first preset time period is 24 hours.

[0051] Combination Figure 2 As shown, in the first test phase, the test conditions were 70°C, and an application of 1.3U was made to the sample. NDC The DC voltage is superimposed with the rated power frequency ripple voltage, and after 24 hours, the change in the capacitance of the test sample is measured, and then the test proceeds to the second stage; among which, U NDC This is the rated DC voltage of the capacitor.

[0052] In step 102, the temperature and applied DC voltage are adjusted according to the preset temperature adjustment step size and the preset DC voltage adjustment step size to perform the second stage test. The capacitance of the capacitor sample is tested at preset time intervals until the capacitance loss is greater than or equal to the preset capacitance loss, or until the average hourly capacitance drop is less than the preset threshold after a preset withstand voltage time period under the test conditions of preset stop temperature and preset stop voltage, thus completing the second stage test.

[0053] Preferably, in the second stage of testing, the temperature adjustment range is [50℃, 70℃], and the DC voltage adjustment range is [1.3U]. NDC 1.6U NDC The preset temperature adjustment step size is 5℃; the preset capacitance loss is 90%; among which, U NDC This is the rated DC voltage of the capacitor.

[0054] Preferably, the method further includes:

[0055] During the second phase of testing, the test conditions were modified according to the capacitance decay rate, including:

[0056] For diaphragm type capacitor samples, if the average hourly capacitance decrease is less than a first preset percentage, the temperature or DC voltage should be increased according to the current test conditions.

[0057] For non-separator type capacitor test specimens, if the average hourly decrease in capacitance is less than the second preset percentage, the temperature or DC voltage is increased according to the current test conditions; if the average hourly decrease in capacitance is greater than or equal to the third preset percentage, the test is paused and the power is cut off for a third preset period of time, and then the voltage is reduced by one level according to the current conditions and the test continues; wherein, if the current voltage is the lowest test voltage at that temperature, the current voltage is maintained unchanged.

[0058] In the embodiments of the present invention, the second stage is the main stage of the destructive test, which accelerates the aging of the sample to achieve capacity decay. In order to avoid self-healing failure caused by the accumulation of self-healing heat inside the sample under AC and DC superimposed voltage, the second stage adopts a step-by-step temperature and pressure increase method.

[0059] Combination Figure 2 As shown, the temperature range is 55℃-70℃, and the voltage range is 1.3-1.6U. NDC Superimpose the rated power frequency ripple and measure the capacitance of the capacitor sample every 10-24 hours until the capacitance loss exceeds 90%, or when the test conditions are raised to 70℃, 1.3U NDC If, after 10-24 hours of withstand voltage testing, the average hourly decrease in capacitance of the test sample is less than 0.1%, then the test sample will proceed to the third stage.

[0060] In an embodiment of the present invention, during the second-stage stepped temperature and voltage increase process, the criterion for changing the test conditions is the capacitance decay rate, and different criteria are used depending on whether the sample is a separator membrane or a non-separator membrane. Specifically, for separator membrane samples, if the average capacitance decreases by less than 0.1% per hour (a first preset percentage), the temperature or voltage is increased according to the current test conditions; for non-separator membrane samples, if the average capacitance decreases by less than 0.03% per hour (a second preset percentage), the temperature or voltage is increased according to the current test conditions. To avoid excessively high internal temperatures caused by rapid self-healing of the sample, for non-separator membrane samples, if the average capacitance decreases by more than or equal to 0.2% per hour (a third preset time period), the test is paused and the power is cut off for 24 hours, and then the voltage is reduced by one level according to the current conditions (if the current voltage is the lowest test voltage at that temperature, the current voltage is maintained) and the test continues.

[0061] In step 103, at the first preset temperature, a DC voltage equal to a second preset multiple of the rated DC voltage is applied to the DC support capacitor test sample, and a rated power frequency ripple voltage is superimposed on it for a second preset period of time to complete the third stage test.

[0062] For large-capacity DC-supported capacitors, most test samples cannot achieve a capacitance loss of over 90% in a short period of time. Therefore, in the embodiments of this invention, a third stage is set up to conduct a withstand test on the test sample under extreme conditions. Figure 2As shown, if the sample passes this stage of the test, it can be considered that the capacitor sample is unlikely to experience destructive failure during its lifespan. The third stage of the test maintains a temperature of 70°C and applies 1.4U of [a specific chemical] to the sample. NDC The test was completed after 50 hours by superimposing the rated power frequency ripple voltage.

[0063] In step 104, if the capacitor test sample does not exhibit self-healing failure, does not exhibit casing cracking, and / or exhibits pressure switch operation, then the capacitor test sample is cooled to ambient temperature before voltage tests are performed between terminals and between terminals and the casing.

[0064] In an embodiment of the present invention, if the test sample exhibits self-healing failure, shell cracking, or pressure switch activation during the phased test, the test can be terminated. Specifically, this includes:

[0065] (1) During the test, pay attention to the condition of the outer shell of the test sample, record the deformation of the outer shell, and end the test when the outer shell cracks or explodes.

[0066] (2) Monitor the DC charging current of the test specimen during the test. If the DC charging current exceeds 200mA under steady state, the capacitor test specimen is considered to have self-healing failure and the test can be terminated.

[0067] (3) If a DC voltage or AC voltage cannot be applied to the test sample during the test, that is, the self-healing failure occurs inside the capacitor test sample, the test can be terminated.

[0068] (4) For test specimens equipped with pressure switches, if the pressure switch is activated, the power supply can be stopped, the test phase can be ended directly, and subsequent steps can be carried out.

[0069] In step 105, if the capacitor test sample does not experience breakdown or flashover during the voltage test, then the capacitor test sample is determined to have passed the test.

[0070] Preferably, the method further includes:

[0071] If, during the first, second, and / or third stage of testing, the capacitor sample exhibits self-healing failure and / or casing cracking, then the capacitor sample is directly deemed to have failed the test; and / or

[0072] If the capacitor test specimen experiences breakdown and flashover during the voltage test, it is determined that the capacitor test specimen has failed the test.

[0073] Preferably, the method further includes:

[0074] During the first, second, and / or third stage tests, the DC charging current of the capacitor sample is monitored. If the DC charging current exceeds a preset current under steady-state conditions, it is determined that the capacitor sample has experienced self-healing failure, and the test is terminated directly; and / or

[0075] If, during the first, second, and / or third stage of testing, a DC voltage or AC voltage cannot be applied to the capacitor sample, it is determined that a self-healing failure has occurred inside the sample, and the test is terminated directly.

[0076] In an embodiment of the present invention, the conditions for the capacitor test sample to pass the test are that the capacitor test sample does not explode, does not experience self-healing failure, and does not experience breakdown or flashover during the withstand voltage process between test sample terminals and between terminals and the casing.

[0077] Therefore, combining Figure 2 As shown, in an embodiment of the present invention, after completing the three-stage test, the test sample is cooled to ambient temperature and subjected to voltage tests between terminals and between terminals and the casing to determine whether the capacitor test sample experiences breakdown and flashover during the voltage tests between terminals and between terminals and the casing. If the capacitor test sample does not experience breakdown and flashover during the voltage tests, then the capacitor test sample is deemed to have passed the test.

[0078] Therefore, in the embodiments of the present invention, the conditions for the capacitor test sample to pass the test are to simultaneously meet the following: (1) the test sample shell does not crack during the test and does not experience self-healing failure, that is, the steady-state DC charging current does not exceed 200mA and there is no situation where DC or AC voltage cannot be applied; (2) the capacitor test sample does not experience breakdown and flashover during the voltage test.

[0079] In an embodiment of the present invention, if the capacitor test specimen exhibits a self-healing failure and / or a casing rupture during the first stage test, the second stage test, and / or the third stage test, the capacitor test specimen is directly determined to have failed the test. Furthermore, if the capacitor test specimen experiences breakdown and flashover during the voltage test, the capacitor test specimen is determined to have failed the test.

[0080] In embodiments of the present invention, it is also necessary to monitor the DC charging current of the capacitor test specimen during the first stage test, the second stage test, and / or the third stage test. If the DC charging current exceeds the preset current under steady-state conditions, it is determined that the capacitor test specimen has experienced self-healing failure, and the test is terminated directly. And / or during the first stage test, the second stage test, and / or the third stage test, if a DC voltage or AC voltage cannot be applied to the capacitor test specimen, it is determined that a self-healing failure has occurred inside the test specimen, and the test is terminated directly.

[0081] The method of the present invention applies a superimposed AC and DC voltage, which is equivalent to the actual operating conditions of a DC-supported capacitor, and can make the destructive test results better reflect the actual operating conditions of the product.

[0082] The method of this invention divides the destructive test into three stages, which is consistent with the product performance change pattern. While ensuring the accuracy of the test results, it can significantly shorten the destructive test cycle and improve the efficiency of product type testing.

[0083] The method of the present invention monitors the DC charging current of the test sample in real time during the test, and identifies the internal self-healing failure of the test sample in a timely manner by the change of the charging current. This can effectively avoid the sudden occurrence of a serious explosion of the test sample, greatly improve the safety of destructive testing, and protect test equipment and personnel.

[0084] The method of this invention can be used to conduct destructive testing on large-capacity DC-supported capacitors, and has important application value in improving the accuracy and efficiency of product type testing.

[0085] Figure 3 This is a schematic diagram of the structure of a system 300 for evaluating a DC-supported capacitor according to an embodiment of the present invention. Figure 3 As shown, the system 300 for evaluating DC support capacitors provided in this embodiment of the invention includes: a first-stage testing unit 301, a second-stage testing unit 302, a third-stage testing unit 303, a voltage testing unit 304, and an evaluation result determination unit 305.

[0086] Preferably, the first stage test unit 301 is used to apply a DC voltage of a first preset multiple of the rated DC voltage and superimpose a rated power frequency ripple voltage to the DC supported capacitor test sample at a first preset temperature for a first preset period of time to complete the first stage test, and to measure the capacitance change of the test sample after the first stage test is completed.

[0087] Preferably, the second-stage test unit 302 is used to adjust the temperature and applied DC voltage according to a preset temperature adjustment step size and a preset DC voltage adjustment step size to perform the second-stage test, and to test the capacitance of the capacitor sample at preset time intervals until the capacitance loss is greater than or equal to the preset capacitance loss, or until the average hourly capacitance decrease is less than a preset threshold after a preset withstand voltage time period under the test conditions of preset stop temperature and preset stop voltage, thus completing the second-stage test.

[0088] Preferably, in the second stage test unit 302, during the second stage test, the temperature adjustment range is [50℃, 70℃], and the DC voltage adjustment range is [1.3U]. NDC 1.6UNDC The preset temperature adjustment step size is 5℃; the preset capacitance loss is 90%; among which, U NDC This is the rated DC voltage of the capacitor.

[0089] Preferably, the second-stage test unit 302 is further configured to:

[0090] During the second phase of testing, the test conditions were modified according to the capacitance decay rate, including:

[0091] For diaphragm type capacitor samples, if the average hourly capacitance decrease is less than a first preset percentage, the temperature or DC voltage should be increased according to the current test conditions.

[0092] For non-separator type capacitor test specimens, if the average hourly decrease in capacitance is less than the second preset percentage, the temperature or DC voltage is increased according to the current test conditions; if the average hourly decrease in capacitance is greater than or equal to the third preset percentage, the test is paused and the power is cut off for a third preset period of time, and then the voltage is reduced by one level according to the current conditions and the test continues; wherein, if the current voltage is the lowest test voltage at that temperature, the current voltage is maintained unchanged.

[0093] Preferably, the third-stage test unit 303 is used to apply a DC voltage of a second preset multiple of the rated DC voltage and superimpose a rated power frequency ripple voltage to the DC support capacitor sample at the first preset temperature for a second preset period of time to complete the third-stage test.

[0094] Preferably, the voltage test unit 304 is used to perform voltage tests between terminals and between terminals and the casing after cooling the capacitor test sample to ambient temperature if the capacitor test sample does not exhibit self-healing failure, casing cracking, and / or pressure switch activation.

[0095] Preferably, the assessment result determination unit 305 is used to determine that the capacitor test sample passes the assessment if the capacitor test sample does not experience breakdown or flashover during the voltage test.

[0096] Preferably, the assessment result determination unit 305 further includes:

[0097] If, during the first, second, and / or third stage of testing, the capacitor sample exhibits self-healing failure and / or casing cracking, then the capacitor sample is directly deemed to have failed the test; and / or

[0098] If the capacitor test specimen experiences breakdown and flashover during the voltage test, it is determined that the capacitor test specimen has failed the test.

[0099] Preferably, the system further includes: a monitoring unit, used for:

[0100] During the first, second, and / or third stage tests, the DC charging current of the capacitor sample is monitored. If the DC charging current exceeds a preset current under steady-state conditions, it is determined that the capacitor sample has experienced self-healing failure, and the test is terminated directly; and / or

[0101] If, during the first, second, and / or third stage of testing, a DC voltage or AC voltage cannot be applied to the capacitor sample, it is determined that a self-healing failure has occurred inside the sample, and the test is terminated directly.

[0102] The system 300 for evaluating DC support capacitors in an embodiment of the present invention corresponds to the method 100 for evaluating DC support capacitors in another embodiment of the present invention, and will not be described again here.

[0103] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0104] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

[0105] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0106] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0107] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0108] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for evaluating DC-supported capacitors, characterized in that, The method includes: At a first preset temperature, a DC voltage equal to a first preset multiple of the rated DC voltage is applied to the DC-supported capacitor test specimen, and a rated power frequency ripple voltage is superimposed on it. This process is continued for a first preset period of time to complete the first stage test, allowing the DC-supported capacitor test specimen to enter the capacitance decay stage. After the first stage test is completed, the capacitance change of the test specimen is measured. The temperature and applied DC voltage are adjusted according to the preset temperature adjustment step size and the preset DC voltage adjustment step size to carry out the second stage test. The capacitance of the capacitor sample is tested at preset time intervals until the capacitance value loss is greater than or equal to the preset capacitance value loss, or until the average hourly capacitance drop is less than the preset threshold after a preset withstand voltage time period under the test conditions of preset stop temperature and preset stop voltage, thus completing the second stage test. At the first preset temperature, a DC voltage of a second preset multiple of the rated DC voltage is applied to the DC supported capacitor test specimen and a rated power frequency ripple voltage is superimposed on it for a second preset period of time to complete the third stage test, and the DC supported capacitor test specimen is subjected to an endurance test under extreme conditions. If the capacitor test specimen does not exhibit self-healing failure, does not show shell cracking, and / or does not exhibit pressure switch operation, then the capacitor test specimen is cooled to ambient temperature before conducting voltage tests between terminals and between terminals and the shell. If the capacitor test specimen does not experience breakdown or flashover during the voltage test, then the capacitor test specimen is deemed to have passed the test. Among them, the second preset time period is longer than the first preset time period; the second preset multiple is greater than the first preset multiple.

2. The method according to claim 1, characterized in that, In the second phase of testing, the temperature adjustment range was [50℃, 70℃], and the DC voltage adjustment range was [1.3U]. NDC 1.6U NDC The preset temperature adjustment step size is 5℃; the preset capacitance loss is 90%; among which, U NDC This is the rated DC voltage of the capacitor.

3. The method according to claim 1, characterized in that, The method further includes: During the second phase of testing, the test conditions were modified according to the capacitance decay rate, including: For diaphragm type capacitor samples, if the average hourly capacitance decrease is less than a first preset percentage, the temperature or DC voltage should be increased according to the current test conditions. For non-separator type capacitor test specimens, if the average hourly decrease in capacitance is less than the second preset percentage, the temperature or DC voltage is increased according to the current test conditions; if the average hourly decrease in capacitance is greater than or equal to the third preset percentage, the test is paused and the power is cut off for a third preset period of time, and then the voltage is reduced by one level according to the current conditions and the test continues; wherein, if the current voltage is the lowest test voltage at that temperature, the current voltage is maintained unchanged.

4. The method according to claim 1, characterized in that, The method further includes: If, during the first, second, and / or third stage of testing, the capacitor sample exhibits self-healing failure and / or casing cracking, then the capacitor sample is directly deemed to have failed the test; and / or If the capacitor test specimen experiences breakdown and flashover during the voltage test, it is determined that the capacitor test specimen has failed the test.

5. The method according to claim 1, characterized in that, The method further includes: During the first, second, and / or third stage tests, the DC charging current of the capacitor sample is monitored. If the DC charging current exceeds a preset current under steady-state conditions, it is determined that the capacitor sample has experienced self-healing failure, and the test is terminated directly; and / or If, during the first, second, and / or third stage of testing, a DC voltage or AC voltage cannot be applied to the capacitor sample, it is determined that a self-healing failure has occurred inside the sample, and the test is terminated directly.

6. A system for evaluating DC-supported capacitors, characterized in that, The system includes: The first-stage test unit is used to apply a DC voltage of a first preset multiple of the rated DC voltage and superimpose the rated power frequency ripple voltage on the DC supported capacitor test specimen at a first preset temperature for a first preset period of time to complete the first-stage test, allowing the DC supported capacitor test specimen to enter the capacitance decay stage, and measuring the capacitance change of the test specimen after the first-stage test is completed. The second-stage test unit is used to adjust the temperature and applied DC voltage according to the preset temperature adjustment step size and preset DC voltage adjustment step size to perform the second-stage test, and to test the capacitance of the capacitor sample at preset time intervals until the capacitance value loss is greater than or equal to the preset capacitance value loss, or until the average hourly capacitance drop is less than the preset threshold after a preset withstand voltage time period under the test conditions of preset stop temperature and preset stop voltage, thus completing the second-stage test. The third-stage test unit is used to apply a DC voltage of a second preset multiple of the rated DC voltage and superimpose the rated power frequency ripple voltage to the DC supported capacitor test specimen at the first preset temperature for a second preset period of time to complete the third-stage test and conduct a withstand test on the DC supported capacitor test specimen under extreme conditions. The voltage test unit is used to perform voltage tests between terminals and between terminals and the casing after cooling the capacitor test sample to ambient temperature if the capacitor test sample does not exhibit self-healing failure, casing cracking, and / or pressure switch activation. The assessment result determination unit is used to determine that the capacitor test sample passes the assessment if no breakdown or flashover occurs during the voltage test. Among them, the second preset time period is longer than the first preset time period; the second preset multiple is greater than the first preset multiple.

7. The system according to claim 6, characterized in that, In the second stage test unit, the temperature adjustment range is [50℃, 70℃], and the DC voltage adjustment range is [1.3U]. NDC 1.6U NDC The preset temperature adjustment step size is 5℃; the preset capacitance loss is 90%; among which, U NDC This is the rated DC voltage of the capacitor.

8. The system according to claim 6, characterized in that, The second-stage test unit is also used for: During the second phase of testing, the test conditions were modified according to the capacitance decay rate, including: For diaphragm type capacitor samples, if the average hourly capacitance decrease is less than a first preset percentage, the temperature or DC voltage should be increased according to the current test conditions. For non-separator type capacitor test specimens, if the average hourly decrease in capacitance is less than the second preset percentage, the temperature or DC voltage is increased according to the current test conditions; if the average hourly decrease in capacitance is greater than or equal to the third preset percentage, the test is paused and the power is cut off for a third preset period of time, and then the voltage is reduced by one level according to the current conditions and the test continues; wherein, if the current voltage is the lowest test voltage at that temperature, the current voltage is maintained unchanged.

9. The system according to claim 6, characterized in that, The assessment result determination unit also includes: If, during the first, second, and / or third stage of testing, the capacitor sample exhibits self-healing failure and / or casing cracking, then the capacitor sample is directly deemed to have failed the test; and / or If the capacitor test specimen experiences breakdown and flashover during the voltage test, it is determined that the capacitor test specimen has failed the test.

10. The system according to claim 6, characterized in that, The system further includes: a monitoring unit, used for: During the first, second, and / or third stage tests, the DC charging current of the capacitor sample is monitored. If the DC charging current exceeds a preset current under steady-state conditions, it is determined that the capacitor sample has experienced self-healing failure, and the test is terminated directly; and / or If, during the first, second, and / or third stage of testing, a DC voltage or AC voltage cannot be applied to the capacitor sample, it is determined that a self-healing failure has occurred inside the sample, and the test is terminated directly.

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