CN-115932426-B - Method and system for checking direct-current supporting capacitor

CN115932426BCN 115932426 BCN115932426 BCN 115932426BCN-115932426-B

Abstract

The invention relates to a method and a system for checking a direct current support capacitor, wherein the method comprises the steps of applying direct current voltage to a direct current support capacitor sample at a first preset temperature and superposing rated power frequency ripple voltage for a first preset interval to finish a first-stage test, adjusting the temperature and the applied direct current voltage until capacitance loss is greater than or equal to preset capacitance loss or until capacitance average hourly reduction value is smaller than a preset threshold value after the preset withstand voltage time period under the test conditions of the preset stop temperature and the preset stop voltage to finish a second-stage test, modifying the applied direct current voltage at the first preset temperature and superposing the rated power frequency ripple voltage for a second preset interval to finish a third-stage test, and performing a voltage test if no self-healing failure phenomenon, no shell burst phenomenon and/or no pressure switch action phenomenon occur in the capacitor sample, and determining that the capacitor sample passes the check if breakdown and flashover do not occur.

Inventors

DAI MIN
ZHOU JIAO
LI PENG
YAN FEI
HUANG XIANG
YANG WEIMIN

Assignees

中国电力科学研究院有限公司

Dates

Publication Date: 20260508
Application Date: 20220324

Claims (10)

1. A method of evaluating a dc support capacitor, the method comprising: Applying a DC voltage with the magnitude of a rated DC voltage of a first preset multiple to a DC supporting capacitor sample at a first preset temperature, superposing the rated power frequency ripple voltage, and continuing the first preset interval to finish the first-stage test, so that the DC supporting capacitor sample enters a capacity attenuation stage, and measuring the capacity change of the sample after the first-stage test is finished; According to a preset temperature adjustment step length and a preset direct current voltage adjustment step length, adjusting the temperature and the applied direct current voltage so as to perform a second-stage test, and testing the capacitance of the capacitor test article according to a preset time interval until the capacitance loss is greater than or equal to the preset capacitance loss or until the average hourly capacitance drop value is smaller than a preset threshold value after a preset withstand voltage time period under the test conditions of the preset stop temperature and the preset stop voltage, and completing the second-stage test; applying a DC voltage with the second preset multiple of rated DC voltage to the DC supporting capacitor sample at the first preset temperature, superposing the rated power frequency ripple voltage, and continuing the second preset interval to finish the third-stage test, and performing a tolerance test on the DC supporting capacitor sample by adopting a limit condition; If the capacitor test sample does not have self-healing failure, shell explosion and/or pressure switch action, cooling the capacitor test sample to the ambient temperature and then carrying out voltage tests between terminals and between the terminals and the shells; if the capacitor test product is not broken down and flashover in the voltage test process, determining that the capacitor test product passes the examination; The second preset time period is greater than the first preset time period, and the second preset multiple is greater than the first preset multiple.
2. The method of claim 1, wherein in the second stage test, the temperature is adjusted in the range of [50 ℃ and 70 ℃, the direct current voltage is adjusted in the range of [1.3U NDC ,1.6U NDC ], the preset temperature adjustment step is 5 ℃, the preset capacitance loss is 90%, and wherein U NDC is the rated direct current voltage of the capacitor.
3. The method according to claim 1, wherein the method further comprises: in the second stage of testing, the test conditions are changed according to the capacitance decay rate, including: For a separator type capacitor sample, if the average drop of capacitance per hour is less than a first preset percentage, increasing the temperature or DC voltage according to the current test conditions; for a capacitor sample of a non-separation film type, if the average drop of capacitance per hour is smaller than a second preset percentage, the temperature or the direct current voltage is increased according to the current test condition, and if the average drop of capacitance per hour is larger than or equal to a third preset percentage, the test is stopped, after the power is off for a third preset period, the first voltage is reduced according to the current condition, and the test is continued, wherein if the current voltage is the lowest test voltage at the temperature, the current voltage is maintained unchanged.
4. The method according to claim 1, wherein the method further comprises: When the first stage test, the second stage test and/or the third stage test are/is performed, if the self-healing failure phenomenon and/or the shell burst phenomenon of the capacitor test sample occur, directly determining that the capacitor test sample fails to pass the examination, and/or If the capacitor test sample breaks down and flashover occurs in the voltage test process, determining that the capacitor test sample does not pass the examination.
5. The method according to claim 1, wherein the method further comprises: Monitoring the DC charging current of the capacitor test sample during the first stage test, the second stage test and/or the third stage test, if the DC charging current exceeds a preset current under a steady state condition, determining that the capacitor test sample has self-healing failure, directly ending the test, and/or And in the process of performing the first stage test, the second stage test and/or the third stage test, if the condition that the direct current voltage or the alternating current voltage cannot be applied to the capacitor test sample occurs, determining that self-healing failure occurs in the test sample, and directly ending the test.
6. A system for evaluating a dc support capacitor, the system comprising: The first stage test unit is used for applying a direct current voltage with a rated direct current voltage of which the magnitude is a first preset multiple to the direct current support capacitor sample at a first preset temperature, superposing the rated power frequency ripple voltage for a first preset interval to finish the first stage test, enabling the direct current support capacitor sample to enter a capacity attenuation stage, and measuring the capacitance change of the sample after the first stage test is finished; the second stage test unit is used for adjusting the temperature and the applied direct current voltage according to a preset temperature adjustment step length and a preset direct current voltage adjustment step length so as to perform a second stage test, and testing the capacitance of the capacitor test article according to a preset time interval until the capacitance loss is greater than or equal to the preset capacitance loss or until the average capacitance drop value per hour is smaller than a preset threshold value after a preset withstand voltage time period under the test conditions of the preset stop temperature and the preset stop voltage, so as to complete the second stage test; The third stage test unit is used for applying a direct current voltage with the magnitude being a second preset multiple of the rated direct current voltage to the direct current support capacitor sample at the first preset temperature, superposing the rated power frequency ripple voltage, and continuing the second preset interval to finish the third stage test, and performing a tolerance test on the direct current support capacitor sample by adopting a limit condition; the voltage test unit is used for carrying out voltage tests between terminals and between the terminals and the shells after the capacitor sample is cooled to the ambient temperature if the capacitor sample does not have self-healing failure, shell explosion and/or pressure switch action; the assessment result determining unit is used for determining that the capacitor sample passes the assessment if the capacitor sample is not broken down and flashover in the voltage test process; The second preset time period is greater than the first preset time period, and the second preset multiple is greater than the first preset multiple.
7. The system of claim 6, wherein in the second stage test unit, the temperature adjustment range is [50 ℃ and 70 ℃, the direct current voltage adjustment range is [1.3U NDC ,1.6U NDC ], the preset temperature adjustment step is 5 ℃, the preset capacitance loss is 90%, and wherein U NDC is the rated direct current voltage of the capacitor.
8. The system of claim 6, wherein the second stage test unit is further configured to: in the second stage of testing, the test conditions are changed according to the capacitance decay rate, including: For a separator type capacitor sample, if the average drop of capacitance per hour is less than a first preset percentage, increasing the temperature or DC voltage according to the current test conditions; for a capacitor sample of a non-separation film type, if the average drop of capacitance per hour is smaller than a second preset percentage, the temperature or the direct current voltage is increased according to the current test condition, and if the average drop of capacitance per hour is larger than or equal to a third preset percentage, the test is stopped, after the power is off for a third preset period, the first voltage is reduced according to the current condition, and the test is continued, wherein if the current voltage is the lowest test voltage at the temperature, the current voltage is maintained unchanged.
9. The system according to claim 6, wherein the assessment result determination unit further comprises: When the first stage test, the second stage test and/or the third stage test are/is performed, if the self-healing failure phenomenon and/or the shell burst phenomenon of the capacitor test sample occur, directly determining that the capacitor test sample fails to pass the examination, and/or If the capacitor test sample breaks down and flashover occurs in the voltage test process, determining that the capacitor test sample does not pass the examination.
10. The system of claim 6, further comprising a monitoring unit for: Monitoring the DC charging current of the capacitor test sample during the first stage test, the second stage test and/or the third stage test, if the DC charging current exceeds a preset current under a steady state condition, determining that the capacitor test sample has self-healing failure, directly ending the test, and/or And in the process of performing the first stage test, the second stage test and/or the third stage test, if the condition that the direct current voltage or the alternating current voltage cannot be applied to the capacitor test sample occurs, determining that self-healing failure occurs in the test sample, and directly ending the test.

Description

Method and system for checking direct-current supporting capacitor Technical Field The invention relates to the technical field of high-voltage tests, in particular to a method and a system for checking a direct-current support capacitor. Background The direct-current supporting capacitor is a core component of the flexible direct-current transmission engineering converter, and dry film capacitors are adopted at present in consideration of the performance requirements of volume, fire resistance and the like. The reliability of the existing domestic direct current dry capacitor is also greatly problematic, and the high-voltage direct current support capacitor (2800V, 7500 mu F-10000 mu F) used in engineering is an imported product, and has the problems of high equipment cost, long purchase period and the like. The existing quality assessment modes of the high-voltage dry capacitor are factory tests, type tests and the like, and products with qualified test results still frequently fail in operation under the existing test methods and conditions, so that the existing test methods are different from the actual operation conditions of the high-voltage dry direct-current capacitor, and the assessment content has defects. The damage test is a key type test item of the capacitor, and mainly tests whether the capacitor can safely work within the range of the limit value of the technical specification, and as no test standard aiming at the direct current support capacitor exists at present, the damage test method of GB/T17702 'power electronic capacitor' can only be referred, and a higher direct current voltage is applied to a test sample at a higher temperature until the capacitance of the test sample is attenuated to be below 10%, so that the test sample is required not to burst. The standard is generally used for the power electronic capacitor with smaller capacitance, the test method is not specifically defined, the purpose of checking the actual operation safety cannot be achieved by adopting the method to perform the destructive test on the direct current support capacitor, the capacitance of the sample drops slowly according to the standard test flow, the test time required for the large-capacity direct current support capacitor is very long, more than half a year is needed, and the explosion risk exists in the test process. Therefore, for the damage test of the direct current support capacitor, the performance of the direct current support capacitor can be checked according to a test method corresponding to the actual working condition, and the test flow needs to be optimized, so that the test efficiency is improved, the time consumption is reduced, and the test safety is improved. Disclosure of Invention The invention provides a method and a system for checking a direct-current support capacitor, which are used for solving the problem of how to check the direct-current support capacitor for a flexible direct-current converter valve. In order to solve the above problems, according to an aspect of the present invention, there is provided a method of checking a dc support capacitor, the method comprising: Applying a direct current voltage with a rated direct current voltage of which the magnitude is a first preset multiple to a direct current supporting capacitor sample at a first preset temperature, superposing the rated power frequency ripple voltage for a first preset interval to finish a first-stage test, and measuring the capacitance change of the sample after the first-stage test is finished; According to a preset temperature adjustment step length and a preset direct current voltage adjustment step length, adjusting the temperature and the applied direct current voltage so as to perform a second-stage test, and testing the capacitance of the capacitor test article according to a preset time interval until the capacitance loss is greater than or equal to the preset capacitance loss or until the average hourly capacitance drop value is smaller than a preset threshold value after a preset withstand voltage time period under the test conditions of the preset stop temperature and the preset stop voltage, and completing the second-stage test; applying a DC voltage with the second preset multiple of the rated DC voltage to the DC supporting capacitor sample at the first preset temperature, and superposing the rated power frequency ripple voltage for a second preset interval to finish the third-stage test; If the capacitor test sample does not have self-healing failure, shell explosion and/or pressure switch action, cooling the capacitor test sample to the ambient temperature and then carrying out voltage tests between terminals and between the terminals and the shells; if the capacitor test sample does not break down and flashover in the voltage test process, determining that the capacitor test sample passes the examination. Preferably, in the second stage test, the temperature adjustment range is [50 ℃ and 70