CN112485614B - Test method and device for withstand voltage of cable insulating material - Google Patents
Test method and device for withstand voltage of cable insulating material Download PDFInfo
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- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
- G01R31/1272—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation of cable, line or wire insulation, e.g. using partial discharge measurements
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Abstract
本申请公开了一种电缆绝缘材料的耐压测试方法及装置。其中，该方法包括：获取待测电缆的绝缘材料样本在预设时间范围内采集的工频击穿场强；获取待测电缆的绝缘材料样本在预设时间范围内采集的超低频击穿场强；基于第一击穿场强序列中的工频击穿场强确定绝缘材料样本的第一检测结果，指示绝缘材料样本是否通过工频耐压检测；基于第一检测结果确定绝缘材料样本的第二检测结果，指示绝缘材料样本是否通过超低频耐压检测；确定第一击穿场强序列和第二击穿场强序列之间的相关性，并基于相关性确定第二检测结果是否有效。本申请解决了由于缺乏超低频耐压试验检测标准，对电缆绝缘材料进行超低频耐压试验时难以确定试验结果的有效性的技术问题。
The present application discloses a method and a device for the withstand voltage test of a cable insulating material. Wherein, the method includes: obtaining the power frequency breakdown field strength collected by the insulating material sample of the cable to be tested within a preset time range; obtaining the ultra-low frequency breakdown field collected by the insulating material sample of the cable to be tested within the preset time range Determine the first test result of the insulating material sample based on the power frequency breakdown field strength in the first breakdown field strength sequence, indicating whether the insulating material sample passes the power frequency withstand voltage test; determine the insulation material sample based on the first test result. The second test result, indicating whether the insulating material sample passes the ultra-low frequency withstand voltage test; determine the correlation between the first breakdown field strength sequence and the second breakdown field strength sequence, and determine whether the second test result is valid based on the correlation . The present application solves the technical problem that it is difficult to determine the validity of the test results when the cable insulation material is subjected to the ultra-low frequency withstand voltage test due to the lack of detection standards for the ultra-low frequency withstand voltage test.
Description
Technical Field
The application relates to the technical field of power distribution networks, in particular to a withstand voltage test method and device for a cable insulating material.
Background
In recent years, in urban and rural power distribution network racks in China, Cross-Linked Polyethylene (XLPE) cables are widely used in urban power grids due to the advantages of good insulating property, easiness in manufacturing, convenience in installation, benefit for city and plant layout and the like, and a large number of 10kV medium-voltage power distribution cables are newly introduced in application occasions such as power grid power supply, subway power supply, high-speed rail power supply, wind power generation, photovoltaic power generation, electric vehicle charging pile power supply and the like. At present, the in-service time of domestic 10kV medium voltage distribution power cables gradually reaches 20 years and more, the service conditions, the aging degree and the expected service life of the in-service cables need to be evaluated in advance according to the design expected service life of the cables from 30 years to 40 years, and the cables with different aging degrees are reasonably arranged for state maintenance. In addition, because of a plurality of factors which are not in place for the quality management of the power engineering in China, the engineering management level is not high, and a plurality of defects are buried when cables are laid and cable accessories are installed in construction units, so that the absolute number and the annual fault rate of sudden power failure in the operation of the cables are increased in nearly 5 years, under the double clamping impact of bath curve effect of equipment life and low common and poor accessory installation quality, the annual fault frequency and average fault rate of a plurality of 10kV distribution cables of basic units are in an ascending situation, a scientific cross-linked cable aging state evaluation technology and an index system are urgently needed, the method has the advantages that the operation conditions of the cable and the accessory equipment are effectively known, the local updating and maintenance plan is reasonably arranged, and further the power supply reliability and the operation life of the XLPE cable are improved.
At present, the most common methods for detecting the medium-voltage distribution cable are a power frequency withstand voltage Test, an OWTS (Oscillating Wave Test System) partial discharge detection and a 2500V megger insulation resistance detection. The dc withstand voltage test is no longer recommended because it can generate space residual charge in the cable insulation material, resulting in partial discharge and breakdown in the cable. . OWTS partial discharge detection equipment is complicated and inconvenient to use on site. The insulation resistance detection uses a 2500V insulation megger, the data is inaccurate, and the applied direct current voltage is low, so that the insulation change condition under high voltage cannot be reflected. The equivalent capacitance of the cable is large, the requirement of a power frequency voltage withstand test on the capacity of the test voltage generator is high, the capacity of the test voltage generator cannot be met on site, and the voltage withstand test can be performed by using 0.1Hz ultralow frequency voltage. However, at present, no detection standard for the withstand voltage test under the ultralow frequency voltage of the cable exists in China, and the work is difficult to carry out.
In view of the above problems, no effective solution has been proposed.
Disclosure of Invention
The embodiment of the application provides a method and a device for testing the voltage resistance of a cable insulating material, which at least solve the technical problem that the effectiveness of a test result is difficult to determine when the ultralow frequency voltage resistance test is performed on the cable insulating material due to the lack of the detection standard of the ultralow frequency voltage resistance test.
According to an aspect of an embodiment of the present application, there is provided a method for testing a withstand voltage of a cable insulating material, including: acquiring power frequency breakdown field intensity acquired by an insulating material sample of a cable to be detected within a preset time range to obtain a first breakdown field intensity sequence, wherein the breakdown field intensity in the first breakdown field intensity sequence is the power frequency breakdown field intensity acquired at each acquisition moment within the preset time range; acquiring ultra-low frequency breakdown field intensity of an insulation material sample of the cable to be detected, which is acquired within the preset time range, to obtain a second breakdown field intensity sequence, wherein the breakdown field intensity in the second breakdown field intensity sequence is the ultra-low frequency breakdown field intensity acquired at each acquisition moment within the preset time range; determining a first detection result of the insulating material sample based on the power frequency breakdown field intensity in the first breakdown field intensity sequence, wherein the first detection result is used for indicating whether the insulating material sample passes power frequency withstand voltage detection or not; determining a second detection result of the insulating material sample based on the first detection result, wherein the second detection result is used for indicating whether the insulating material sample passes the ultra-low frequency voltage-resistant detection or not; determining a correlation between the first breakdown field strength sequence and the second breakdown field strength sequence, and determining whether the second detection result is valid based on the correlation.
Optionally, determining a correlation between the first breakdown field strength sequence and the second breakdown field strength sequence comprises: calculating a Pearson correlation coefficient between the first breakdown field strength sequence and the second breakdown field strength sequence; a significance level P value is determined by hypothesis testing based on the pearson correlation coefficient, and the significance level P value is compared to a first threshold.
Optionally, determining whether the second detection result is valid based on the correlation includes: determining that the second detection result is valid when the significance level P value is less than the first threshold and the Pearson correlation coefficient is greater than a second threshold.
Optionally, in case the significance level P-value is smaller than the first threshold value, the greater the pearson correlation coefficient, the stronger the correlation between the first and second breakdown field strength sequence.
Optionally, in the method, the breakdown field strengths in the first breakdown field strength sequence and the second breakdown field strength sequence are obtained by immersing the insulating material sample in the same type of insulating liquid for testing, and the dielectric constant of the insulating liquid is greater than that of air.
Optionally, obtaining the power frequency breakdown field strength of the insulation material sample of the cable to be tested, which is collected within a preset time range, includes: and performing power frequency breakdown test on a preset number of breakdown points in the insulating material sample at each acquisition moment to obtain a first group of breakdown voltages, determining a first Weibull distribution failure probability based on the first group of breakdown voltages, and determining the power frequency breakdown field strength of the current breakdown test based on the first Weibull distribution failure probability.
Optionally, obtaining the ultra-low frequency breakdown field strength of the insulation material sample of the cable to be tested, which is collected within the preset time range, includes: and performing an ultra-low frequency breakdown test on a preset number of breakdown points in the insulating material sample at each acquisition moment to obtain a second group of breakdown voltages, determining a second Weibull distribution failure probability based on the second group of breakdown voltages, and determining the ultra-low frequency breakdown field strength of the current breakdown test based on the second Weibull distribution failure probability.
Optionally, the sample of insulating material comprises: the cable body of the cable to be tested and the connector of the cable to be tested.
According to another aspect of the embodiments of the present application, there is also provided a device for testing a withstand voltage of a cable insulating material, including: the first acquisition module is used for acquiring the power frequency breakdown field intensity of an insulating material sample of a cable to be detected, which is acquired within a preset time range, so as to obtain a first breakdown field intensity sequence, wherein the breakdown field intensity in the first breakdown field intensity sequence is the power frequency breakdown field intensity acquired at each acquisition moment within the preset time range; the second acquisition module is used for acquiring the ultralow frequency breakdown field intensity of the insulating material sample of the cable to be detected, which is acquired within the preset time range, so as to obtain a second breakdown field intensity sequence, wherein the breakdown field intensity in the second breakdown field intensity sequence is the ultralow frequency breakdown field intensity acquired at each acquisition moment within the preset time range; the first determining module is used for determining a first detection result of the insulating material sample based on the power frequency breakdown field intensity in the first breakdown field intensity sequence, and the first detection result is used for indicating whether the insulating material sample passes power frequency withstand voltage detection or not; a second determination module, configured to determine a second detection result of the insulating material sample based on the first detection result, where the second detection result is used to indicate whether the insulating material sample passes the ultra-low frequency withstand voltage detection; a detection module for determining a correlation between the first breakdown field strength sequence and the second breakdown field strength sequence and determining whether the second detection result is valid based on the correlation.
Optionally, the detecting module is further configured to calculate a pearson correlation coefficient between the first breakdown field strength sequence and the second breakdown field strength sequence; performing hypothesis testing based on the Pearson correlation coefficient to determine a significance level P value, and comparing the significance level P value to a first threshold; and determining that the second detection result is valid when the significance level P value is less than the first threshold and the pearson correlation coefficient is greater than a second threshold.
Optionally, in the apparatus, both breakdown field strengths in the first breakdown field strength sequence and the second breakdown field strength sequence are obtained by immersing the insulating material sample in the same type of insulating liquid for testing, and a dielectric constant of the insulating liquid is greater than that of air.
According to another aspect of the embodiments of the present application, there is also provided a non-volatile storage medium, where the non-volatile storage medium includes a stored program, and when the program runs, the apparatus where the non-volatile storage medium is located is controlled to execute the above-mentioned method for testing the withstand voltage of the cable insulation material.
In the embodiment of the application, the power frequency breakdown field strength collected in a preset time range by an insulating material sample of a cable to be tested is obtained; acquiring the ultra-low frequency breakdown field strength of an insulation material sample of a cable to be detected, which is acquired within a preset time range; determining a first detection result of the insulating material sample based on the power frequency breakdown field intensity in the first breakdown field intensity sequence, and indicating whether the insulating material sample passes power frequency withstand voltage detection or not; determining a second detection result of the insulating material sample based on the first detection result, indicating whether the insulating material sample passes the ultra-low frequency withstand voltage detection; and determining the correlation between the first breakdown field strength sequence and the second breakdown field strength sequence, and determining whether the second detection result is effective or not based on the correlation, so that the technical effect of confirming the effectiveness of the ultralow frequency voltage-withstand test data by using the ultralow frequency voltage-withstand test data is realized, and the technical problem that the effectiveness of the test result is difficult to determine when the ultralow frequency voltage-withstand test is performed on the cable insulating material due to the lack of the detection standard of the ultralow frequency voltage-withstand test is solved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
fig. 1 is a schematic flow chart of a method for testing the withstand voltage of a cable insulation material according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of a voltage withstand testing device for a cable insulating material according to an embodiment of the present application.
Detailed Description
In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Example 1
According to an embodiment of the present application, there is provided a method for voltage withstand testing of a cable insulation material, it should be noted that the steps shown in the flowchart of the drawings may be executed in a computer system such as a set of computer executable instructions, and that although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in an order different from that shown or described herein.
Fig. 1 is a method for withstand voltage test of a cable insulating material according to an embodiment of the present application, and as shown in fig. 1, the method includes at least steps S102 to S110, where:
step S102, acquiring power frequency breakdown field intensity of an insulation material sample of a cable to be detected, wherein the power frequency breakdown field intensity is acquired within a preset time range, and acquiring a first breakdown field intensity sequence.
And the breakdown field intensity in the first breakdown field intensity sequence is the power frequency breakdown field intensity acquired at each acquisition moment within a preset time range.
And step S104, acquiring the ultralow frequency breakdown field intensity of the insulation material sample of the cable to be detected, which is acquired within a preset time range, and acquiring a second breakdown field intensity sequence.
And the breakdown field intensity in the second breakdown field intensity sequence is the ultralow frequency breakdown field intensity acquired at each acquisition moment in a preset time range.
In an embodiment of the present application, an insulation material sample includes: the cable body of the cable to be tested and the joint of the cable to be tested. It is understood that, for controlling the variable, the breakdown field strengths of the first and second series of breakdown field strengths are measured by immersing the sample of insulating material in the same type of insulating fluid having a dielectric constant greater than that of air.
Specifically, the method for acquiring the power frequency breakdown field intensity and the ultralow frequency breakdown field intensity of the insulating material sample of the cable to be tested, which are acquired within a preset time range, comprises the following steps: performing power frequency breakdown test on a preset number of breakdown points in the insulating material sample at each acquisition moment to obtain a first group of breakdown voltages, determining a first Weibull distribution failure probability based on the first group of breakdown voltages, and determining the power frequency breakdown field strength of the current breakdown test based on the first Weibull distribution failure probability; all the on-frequency breakdown field strengths constitute a first breakdown field strength sequence. Meanwhile, performing an ultralow frequency breakdown test on a preset number of breakdown points in the insulating material sample at each acquisition moment to obtain a second group of breakdown voltages, determining a second Weibull distribution failure probability based on the second group of breakdown voltages, and determining the ultralow frequency breakdown field strength of the current breakdown test based on the second Weibull distribution failure probability; all the ultralow frequency breakdown field strengths constitute a second breakdown field strength sequence. Specifically, the weibull distribution failure probability corresponds to a breakdown field strength, and after the weibull distribution failure probability is determined, the breakdown field strength corresponding to the weibull distribution failure probability can be determined.
It should be noted that, because the magnitude of the breakdown voltage depends on the combined action of various factors, the breakdown voltage value measured by the test generally has a very large dispersion, and in order to obtain an accurate breakdown voltage, the breakdown field strength is calculated by using the weibull distribution failure probability. According to the regulation of GB _ T29310-2012, when the number of breakdown points is more than 12, the breakdown experiment under the power frequency alternating current voltage generally adopts two-parameter Weibull distribution, and the expression of the distribution function is
In the formula: f-percentage of breakdown; t-breakdown field strength; α -a scale parameter; beta-shape parameter.
When t ═ α, f (t) ═ 0.632, i.e., 63.2% of the samples failed, and broke down, where α is also known as the characteristic lifetime.
And S106, determining a first detection result of the insulating material sample based on the power frequency breakdown field intensity in the first breakdown field intensity sequence.
Wherein the first detection result is used for indicating whether the insulating material sample passes the ultra-low frequency withstand voltage detection.
Step S108, determining a second detection result of the insulating material sample based on the first detection result.
And the second detection result is used for indicating whether the insulating material sample passes the power frequency withstand voltage detection or not.
Step S110, a correlation between the first breakdown field strength sequence and the second breakdown field strength sequence is determined, and whether the second detection result is valid is determined based on the correlation.
Generally, evaluating whether two variables are correlated includes a significance level and a correlation coefficient: the significance level, i.e. P-value, was first examined, and in general P-values less than 0.05 were significant, and as long as significant, it was concluded that: rejection of the original hypothesis is irrelevant, meaning that the two sets of data are significantly correlated; secondly, checking a correlation coefficient, wherein the correlation coefficient is a Pearson correlation coefficient, the Pearson correlation coefficient is used for measuring whether two data sets are on the same line or not, and is used for measuring the linear relation between distance variables, and the closer the correlation coefficient is to 1 or-1, namely the larger the absolute value is, the stronger the correlation is; the closer the correlation coefficient is to 0, i.e., the smaller the absolute value is, the weaker the correlation is.
The pearson correlation coefficient between two variables is defined as the quotient of the covariance and the standard deviation between the two variables: the calculation formula is as follows:
where cov (X, Y) denotes the sample covariance, σxSample standard deviation, σ, representing XySample standard deviations for Y are indicated. The following are the calculation formulas for covariance and standard deviation, respectively. Since it is the sample covariance and the sample standard deviation, the denominator uses n-1,
due to the fact thatX＝E(X)，
Y is also similar, and E [ (X-E (X)) (Y-E (Y)))]Since e (xy) -e (x) e (y), the correlation coefficient may be expressed as
Pearson's correlation coefficient for sample
In an embodiment of the application, determining a correlation between the first breakdown field strength sequence and the second breakdown field strength sequence comprises: calculating a Pearson correlation coefficient between the first breakdown field strength sequence and the second breakdown field strength sequence, performing hypothesis test according to the Pearson correlation coefficient to determine a significance level P value, and comparing the significance level P value with a first threshold value; determining whether the second detection result is valid based on the correlation, including: the second detection result is determined to be valid when the significance level P value is less than the first threshold value and the pearson correlation coefficient is greater than the second threshold value. If the significance level P value is greater than the first threshold value, or if the significance level P value is less than the first threshold value but the pearson correlation coefficient is also less than the second threshold value, then the second detection result is determined to be invalid.
It should be noted that, under the condition that the significant level P value is smaller than the first threshold, the larger the pearson correlation coefficient is, the stronger the correlation between the first breakdown field strength sequence and the second breakdown field strength sequence is, that is, the stronger the correlation between the cable ultra-low frequency withstand voltage test data and the power frequency withstand voltage test data is, the effective the cable ultra-low frequency withstand voltage test data is, and the cable ultra-low frequency withstand voltage test data can be used to reflect the insulation level of the cable.
In the specific test analysis of ultralow frequency voltage resistance and power frequency voltage resistance of the cable, because all insulating materials or electrical equipment can only keep the insulating property below a certain electric field intensity, when the electric field intensity exceeds a certain limit, the insulating materials can lose the insulating property instantly, so that the whole equipment is damaged. Therefore, the dielectric strength is the most fundamental parameter of the insulation characteristics, the magnitude of the voltage applied to the sample at breakdown is referred to as the breakdown voltage, and the field strength at the corresponding point is referred to as the breakdown field strength. For flat plate samples, the breakdown field strength can be calculated using the following formula:
in the formula: eBBreakdown field strength, kV/mm; u shapeB-breakdown voltage, kV; d is the thickness of the sample, mm.
In order to ensure that breakdown of the sample occurs in a uniform electric field, the test electrode system and the specification of the sample have certain requirements. For a punctured sample, the shape of the sample is required to be uniform, the thickness of the sample cannot be too large, if the sample is too thick, the breakdown voltage is too large, the measured data dispersity of the breakdown voltage is large, the area of the sample cannot be too small, and the area of the sample is larger than that of an electrode so as to reduce the occurrence of surface slipping; for the electrode system, besides manufacturing a ball-ball electrode to increase the uniformity thereof and ensure that the electric field at the edge of the electrode does not change too much, the factor of air discharge at the edge of the electrode needs to be considered, the air breakdown field strength at the edge of the electrode is lower than that of the tested sample and breakdown occurs first, so that partial discharge occurs and the breakdown voltage value of the sample is affected.
In an optional implementation scheme, the boosting mode selected in the test is rapid boosting, the boosting rate is 500V/s, and the boosting mode is sequentially performed in a zigzag dotting mode during breakdown. The method comprises the steps of immersing a transformer oil in a soaking sample and an electrode system, standing for 10min until no bubbles exist on the surface of an oil layer, connecting the sample and the electrode system into a high-voltage system, performing breakdown test, discharging at high voltage and ground by using a discharging rod during each sample change to eliminate residual charges, checking whether breakdown points are subjected to penetrating breakdown or not so as to prevent surface flashover from occurring and influence the accuracy of test measurement, and regularly cleaning bubbles near the electrode and the sample and carbon black generated by the breakdown.
And recording the breakdown voltage data and the thickness of each group of samples, and calculating the breakdown field intensity. Because the breakdown voltage depends on the combined action of a plurality of factors, the measured breakdown voltage value generally has great dispersion, and in order to obtain accurate breakdown voltage, the number of breakdown points of each sample is 15, which accords with the Weibull distribution. And adopting Minitab software to calculate the breakdown field intensity by the Weibull distribution failure probability of the breakdown field intensity.
Data of the cable sample breakdown test within 20 days are obtained and recorded in the following table, and it can be seen that the power frequency of the cable sample and the ultralow frequency breakdown field strength have the same change trend and are reduced along with the increase of the soaking time, but the breakdown field strength at the ultralow frequency is reduced more obviously. And (3) calculating the correlation coefficient r of the two groups of data to be 0.985, tr to be 12.792, checking the critical value distribution table by t test to obtain P <0.05, and rejecting the original hypothesis to be irrelevant, which means that the two groups of data are significantly correlated. The correlation coefficient of the two groups of data in the text is 0.985, and the data belong to strong correlation. Namely, the data of the ultralow frequency withstand voltage test is effective, and the ultralow frequency withstand voltage test can replace the power frequency withstand voltage test.
| Time of immersion in water | Ultra-low frequency breakdown field intensity kV/mm | Power frequency breakdown field strength V/mm |
| Day 0 | 67.450 | 37.260 |
| 0.5 day | 65.613 | 36.894 |
| 1 day | 61.428 | 36.017 |
| 3 days | 59.533 | 35.898 |
| 7 days | 57.683 | 35.756 |
| 13 days | 56.115 | 35.270 |
| 20 days | 55.542 | 34.957 |
In the actual test of the cable, the power frequency withstand voltage test of the XLPE cable with the voltage class of 10kV specified in GBT 12706.2-2008 'rated voltage 1kV to 35kV extruded insulation power cable and accessories' indicates that: the power frequency test voltage is 3.5U0, the duration time is 5 minutes, the requirement is that the insulation has no breakdown, and the withstand voltage test is passed. According to an optional embodiment of the application, after a 108-meter cable (comprising a terminal connector and an intermediate connector) is manufactured, a power frequency voltage withstand test is performed according to the national standard, and the result is that the power frequency voltage withstand test is passed.
According to the ultralow frequency withstand voltage test regulation of an XLPE cable with a voltage class of 10kV in ultralow frequency (0.1Hz) withstand voltage test specifications of 35kV and the following crosslinked polyethylene insulated power cables: test voltage peak value was 3U0, test time: and (5) 60min, if the insulation is required to have no breakdown, the voltage withstand test is passed. In an alternative embodiment of the present application, after a 108-meter cable (including a terminal connector and an intermediate connector) is manufactured, an ultra-low frequency withstand voltage test is performed according to the regulations of the national standard, and the result is that the ultra-low frequency withstand voltage test is passed. In summary, the ultra-low frequency voltage withstand test is effective and can replace power frequency voltage withstand test.
In the embodiment of the application, the power frequency breakdown field strength collected in a preset time range by an insulating material sample of a cable to be tested is obtained; acquiring the ultra-low frequency breakdown field strength of an insulation material sample of a cable to be detected, which is acquired within a preset time range; determining a first detection result of the insulating material sample based on the power frequency breakdown field intensity in the first breakdown field intensity sequence, and indicating whether the insulating material sample passes power frequency withstand voltage detection or not; determining a second detection result of the insulating material sample based on the first detection result, indicating whether the insulating material sample passes the ultra-low frequency withstand voltage detection; and determining the correlation between the first breakdown field strength sequence and the second breakdown field strength sequence, and determining whether the second detection result is effective or not based on the correlation, so that the technical effect of confirming the effectiveness of the ultralow frequency voltage-withstand test data by using the ultralow frequency voltage-withstand test data is realized, and the technical problem that the effectiveness of the test result is difficult to determine when the ultralow frequency voltage-withstand test is performed on the cable insulating material due to the lack of the detection standard of the ultralow frequency voltage-withstand test is solved.
Example 2
According to an embodiment of the present application, there is provided a device for withstand voltage testing of cable insulation material, as shown in fig. 2, the device at least includes a first obtaining module 20, a second obtaining module 22, a first determining module 24, a second determining module 26 and a detecting module 28, wherein:
the first obtaining module 20 is configured to obtain a power frequency breakdown field strength of an insulation material sample of a cable to be detected, which is collected within a preset time range, to obtain a first breakdown field strength sequence, where the breakdown field strength in the first breakdown field strength sequence is the power frequency breakdown field strength collected at each collection time within the preset time range.
The second obtaining module 22 is configured to obtain the ultra-low frequency breakdown field strength of the insulation material sample of the cable to be detected, which is collected within a preset time range, to obtain a second breakdown field strength sequence, where the breakdown field strength in the second breakdown field strength sequence is the ultra-low frequency breakdown field strength collected at each collection time within the preset time range.
In the embodiment of the application, the breakdown field strengths in the first breakdown field strength sequence and the second breakdown field strength sequence are obtained by soaking an insulating material sample in the same type of insulating liquid for testing, and the dielectric constant of the insulating liquid is greater than that of air.
The first determining module 24 is configured to determine a first detection result of the insulating material sample based on the power frequency breakdown field strength in the first breakdown field strength sequence, where the first detection result is used to indicate whether the insulating material sample passes power frequency withstand voltage detection;
and a second determination module 26, configured to determine a second detection result of the insulating material sample based on the first detection result, where the second detection result is used to indicate whether the insulating material sample passes the ultra-low frequency withstand voltage detection.
A detection module 28 for determining a correlation between the first breakdown field strength sequence and the second breakdown field strength sequence and determining whether the second detection result is valid based on the correlation.
In the embodiment of the present application, the detection module 28 is further configured to calculate a pearson correlation coefficient between the first breakdown field strength sequence and the second breakdown field strength sequence; performing hypothesis testing according to the Pearson correlation coefficient to determine a significance level P value, and comparing the significance level P value with a first threshold value; and determining that the second detection result is valid when the significance level P value is less than the first threshold and the pearson correlation coefficient is greater than the second threshold.
It should be noted that, reference may be made to the relevant description in embodiment 1 for a preferred implementation of this embodiment, and details are not described here again.
Example 3
According to an embodiment of the application, a nonvolatile storage medium is further provided, and the nonvolatile storage medium includes a stored program, wherein when the program runs, a device where the nonvolatile storage medium is located is controlled to execute the above method for testing the withstand voltage of the cable insulation material.
Optionally, the apparatus in which the non-volatile storage medium is controlled when the program is running executes the following steps: acquiring power frequency breakdown field intensity acquired by an insulating material sample of a cable to be detected within a preset time range to obtain a first breakdown field intensity sequence, wherein the breakdown field intensity in the first breakdown field intensity sequence is the power frequency breakdown field intensity acquired at each acquisition moment within the preset time range; acquiring ultra-low frequency breakdown field intensity acquired by an insulating material sample of a cable to be detected within a preset time range to obtain a second breakdown field intensity sequence, wherein the breakdown field intensity in the second breakdown field intensity sequence is the ultra-low frequency breakdown field intensity acquired at each acquisition moment within the preset time range; determining a first detection result of the insulating material sample based on the breakdown field intensity in the first breakdown field intensity sequence, wherein the first detection result is used for indicating whether the insulating material sample passes power frequency withstand voltage detection or not; determining a second detection result of the insulating material sample based on the first detection result, wherein the second detection result is used for indicating whether the insulating material sample passes the ultra-low frequency withstand voltage detection; a correlation between the first breakdown field strength sequence and the second breakdown field strength sequence is determined and based on the correlation it is determined whether the second detection result is valid.
It should be noted that, reference may be made to the relevant description in embodiment 1 for a preferred implementation of this embodiment, and details are not described here again.
The above-mentioned serial numbers of the embodiments of the present application are merely for description and do not represent the merits of the embodiments.
In the above embodiments of the present application, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
In the embodiments provided in the present application, it should be understood that the disclosed technology can be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units may be a logical division, and in actual implementation, there may be another division, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, units or modules, and may be in an electrical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or a part of or all or part of the technical solution contributing to the prior art may be embodied in the form of a software product stored in a storage medium, and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method described in the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic or optical disk, and other various media capable of storing program codes.
The foregoing is only a preferred embodiment of the present application and it should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.
Claims (10)
1. A method for testing the withstand voltage of a cable insulating material is characterized by comprising the following steps:
acquiring power frequency breakdown field intensity acquired by an insulating material sample of a cable to be detected within a preset time range to obtain a first breakdown field intensity sequence, wherein the breakdown field intensity in the first breakdown field intensity sequence is the power frequency breakdown field intensity acquired at each acquisition time within the preset time range;
acquiring ultra-low frequency breakdown field intensity of an insulation material sample of the cable to be detected, which is acquired within the preset time range, to obtain a second breakdown field intensity sequence, wherein the breakdown field intensity in the second breakdown field intensity sequence is the ultra-low frequency breakdown field intensity acquired at each acquisition moment within the preset time range;
determining a first detection result of the insulating material sample based on the power frequency breakdown field intensity in the first breakdown field intensity sequence, wherein the first detection result is used for indicating whether the insulating material sample passes power frequency withstand voltage detection or not;
determining a second detection result of the insulating material sample based on the first detection result, wherein the second detection result is used for indicating whether the insulating material sample passes the ultra-low frequency withstand voltage detection;
determining a correlation between the first breakdown field strength sequence and the second breakdown field strength sequence, and determining whether the second detection result is valid based on the correlation.
2. The method of claim 1,
determining a correlation between the first and second sequences of breakdown field strengths, comprising: calculating a Pearson correlation coefficient between the first breakdown field strength sequence and the second breakdown field strength sequence; performing hypothesis testing based on the Pearson correlation coefficient to determine a significance level P value, and comparing the significance level P value to a first threshold;
determining whether the second detection result is valid based on the correlation, including: determining that the second detection result is valid when the significance level P value is less than the first threshold and the Pearson correlation coefficient is greater than a second threshold.
3. The method according to claim 2, characterized in that the greater the pearson correlation coefficient, the stronger the correlation between the first and second breakdown field strength sequence in case the significance level P-value is smaller than the first threshold value.
4. The method of claim 1, wherein the breakdown field strengths of the first and second sequences of breakdown field strengths are each measured by immersing the sample of insulating material in the same type of insulating fluid having a dielectric constant greater than that of air.
5. The method of claim 1,
the power frequency breakdown field intensity of the insulation material sample of the cable to be tested, which is collected within the preset time range, is obtained, and the method comprises the following steps: performing power frequency breakdown test on a preset number of breakdown points in the insulating material sample at each acquisition moment to obtain a first group of breakdown voltages, determining a first Weibull distribution failure probability based on the first group of breakdown voltages, and determining the power frequency breakdown field strength of the current breakdown test based on the first Weibull distribution failure probability;
acquiring the ultra-low frequency breakdown field strength of the insulation material sample of the cable to be detected, which is acquired within the preset time range, and the method comprises the following steps: and performing an ultra-low frequency breakdown test on a preset number of breakdown points in the insulating material sample at each acquisition moment to obtain a second group of breakdown voltages, determining a second Weibull distribution failure probability based on the second group of breakdown voltages, and determining the ultra-low frequency breakdown field strength of the breakdown test based on the second Weibull distribution failure probability.
6. The method according to any one of claims 1 to 5, wherein the sample of insulating material comprises: the cable body of the cable to be tested and the joint of the cable to be tested.
7. A withstand voltage testing device of a cable insulation material is characterized by comprising:
the first acquisition module is used for acquiring the power frequency breakdown field intensity of an insulating material sample of a cable to be detected, which is acquired within a preset time range, so as to obtain a first breakdown field intensity sequence, wherein the breakdown field intensity in the first breakdown field intensity sequence is the power frequency breakdown field intensity acquired at each acquisition moment within the preset time range;
the second acquisition module is used for acquiring the ultralow frequency breakdown field intensity of the insulating material sample of the cable to be detected, which is acquired within the preset time range, so as to obtain a second breakdown field intensity sequence, wherein the breakdown field intensity in the second breakdown field intensity sequence is the ultralow frequency breakdown field intensity acquired at each acquisition moment within the preset time range;
the first determining module is used for determining a first detection result of the insulating material sample based on the power frequency breakdown field intensity in the first breakdown field intensity sequence, and the first detection result is used for indicating whether the insulating material sample passes power frequency withstand voltage detection or not;
a second determination module, configured to determine a second detection result of the insulation material sample based on the first detection result, where the second detection result is used to indicate whether the insulation material sample passes the ultra-low frequency withstand voltage detection;
a detection module for determining a correlation between the first breakdown field strength sequence and the second breakdown field strength sequence and determining whether the second detection result is valid based on the correlation.
8. The apparatus of claim 7, wherein the detection module is further configured to calculate a Pearson correlation coefficient between the first sequence of breakdown field strengths and the second sequence of breakdown field strengths; performing hypothesis testing based on the Pearson correlation coefficient to determine a significance level P value, and comparing the significance level P value to a first threshold; and determining that the second detection result is valid when the significance level P value is less than the first threshold and the pearson correlation coefficient is greater than a second threshold.
9. The apparatus of claim 7, wherein the breakdown field strengths of the first and second sequences of breakdown field strengths are each measured by immersing the sample of insulating material in the same type of insulating fluid having a dielectric constant greater than that of air.
10. A nonvolatile storage medium, characterized in that the nonvolatile storage medium includes a stored program, wherein when the program runs, a device in which the nonvolatile storage medium is located is controlled to execute the method for testing the withstand voltage of the cable insulation material according to any one of claims 1 to 6.
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| CN116307677B (en) * | 2022-11-25 | 2023-09-12 | 南方电网调峰调频发电有限公司检修试验分公司 | Early warning type determining method, device and medium for insulation of generator stator bar |
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| CN100568003C (en) * | 2006-10-13 | 2009-12-09 | 中国华北电力集团公司天津市电力公司 | Crosslinking polyethylene-insulated cable insulation diagnostic apparatus |
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