Power cable withstand voltage test method, device and terminal based on withstand voltage equivalent analysis

Abstract

The present invention provides a method, device and terminal for withstand voltage testing of power cables based on withstand voltage equivalent analysis. The method comprises: using a 0.1 Hz cosine square wave voltage to perform a withstand voltage test on a target power cable to obtain an initial test result; correcting the initial test result according to a preset equivalent analysis result, and determining the corrected test result as the final test result of the target power cable. The process of obtaining the preset equivalent analysis result is to apply power frequency voltage and 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses, respectively, to perform a withstand voltage test; based on the obtained multiple groups of breakdown times and breakdown failure probabilities, obtain the Weibull distribution of power frequency voltage and 0.1 Hz cosine square wave voltage; based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution, perform an equivalence analysis to obtain an equivalent analysis result. On the basis of equivalent analysis, the present invention improves the accuracy of the withstand voltage test results.

Description

Technical Field

[0001] The present invention relates to the technical field of power cables, and in particular to a method, device and terminal for testing power cable withstand voltage based on withstand voltage equivalent analysis. Background Art

[0002] Power cables are used to transmit and distribute electrical energy. They are commonly used in urban underground power grids, power station lead-out lines, internal power supply for industrial and mining enterprises, and underwater transmission lines across rivers and seas. With the increasing requirements for power supply reliability, the use of power cables in urban power grids has also increased significantly.

[0003] In practical applications, power cables are mostly laid in direct burial or cable trenches, and are in contact with moisture or water for a long time. In addition, the power cable body and accessories will also experience a certain degree of insulation aging during long-term use, which can cause insulation failure of the power cable. The withstand voltage test is a basic test to assess the insulation performance of the cable, which can find larger defects inside the insulation. The withstand voltage test mainly includes an AC withstand voltage test using a 50Hz power frequency voltage and an ultra-low frequency withstand voltage test using a 0.1Hz cosine square wave voltage. The power cable has a large capacity, and using a 50Hz power frequency voltage for the withstand voltage test requires a large power, and the equipment is large in size, making on-site construction difficult. The 0.1Hz cosine square wave voltage is widely used in the withstand voltage test of power cables because of its small equipment size, low power demand, and polarity conversion wave close to the 50Hz power frequency voltage.

[0004] However, under the standard withstand voltage of 50 Hz power frequency voltage and 0.1 Hz cosine square wave voltage, the breakdown time and morphological characteristics of the breakdown channel of the power cable vary greatly with the difference in the residual insulation thickness of the power cable, resulting in inaccurate results of the withstand voltage test of 0.1 Hz cosine square wave voltage. Summary of the invention

[0005] The embodiments of the present invention provide a method, device and terminal for power cable withstand voltage testing based on withstand voltage equivalent analysis to solve the problem that the result of the current 0.1 Hz cosine square wave voltage withstand voltage test is not accurate enough.

[0006] In a first aspect, an embodiment of the present invention provides a method for testing a power cable withstand voltage based on withstand voltage equivalent analysis, comprising:

[0007] A 0.1Hz cosine square wave voltage is used to perform a withstand voltage test on the target power cable to obtain initial test results;

[0008] Correcting the initial test result according to the preset equivalent analysis result, and determining the corrected test result as the final test result of the target power cable;

[0009] Among them, the process of obtaining the preset equivalent analysis results is as follows: applying power frequency voltage and 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses, respectively, to carry out a withstand voltage test; according to multiple groups of breakdown times and breakdown failure probabilities obtained from the withstand voltage test, the Weibull distribution of power frequency voltage and 0.1 Hz cosine square wave voltage with different insulation residual thicknesses are obtained respectively; based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution, the equivalence of power frequency voltage and 0.1 Hz cosine square wave voltage is analyzed to obtain the equivalent analysis results.

[0010] In a possible implementation, a power frequency voltage and a 0.1 Hz cosine square wave voltage are applied to multiple groups of insulation defect models with different insulation residual thicknesses to perform a withstand voltage test, including:

[0011] Placing multiple groups of insulation defect models with different insulation residual thicknesses in the insulation oil in the test oil tank; wherein the liquid level of the insulation oil in the test oil tank is higher than the height of the insulation defect model;

[0012] Applying a power frequency voltage of a preset amplitude and a cosine square wave voltage of 0.1 Hz of a preset amplitude to multiple groups of insulation defect models with different insulation residual thicknesses;

[0013] When the power frequency voltage of the preset amplitude and the 0.1Hz cosine square wave voltage of the preset amplitude are reached respectively, the voltage is kept unchanged to test the withstand voltage time of the insulation defect model of the target group insulation residual thickness; wherein the insulation defect model of the target group insulation residual thickness is any one of multiple groups of insulation defect models with different insulation residual thicknesses.

[0014] In a possible implementation, a 0.1 Hz cosine square wave voltage is used to perform a withstand voltage test on the target power cable to obtain initial test results, including:

[0015] A 0.1 Hz cosine square wave voltage is continuously applied to the target power cable. When the preset voltage value is reached, the timing starts and the preset voltage value is kept unchanged.

[0016] When the test voltage shows 0, the target power cable is broken down, the timing is stopped, and the initial withstand voltage time is obtained.

[0017] In a possible implementation, the initial test result is corrected according to the equivalent analysis result, and the corrected test result is determined as the final test result of the target power cable, including:

[0018] According to the withstand voltage time of the insulation defect model with the same insulation residual thickness under the power frequency voltage and the 0.1Hz cosine square wave voltage, the initial withstand voltage time of the initial test is corrected according to a preset ratio, and the corrected withstand voltage time is determined as the final test result of the target power cable.

[0019] In one possible implementation, the insulation defect model is a pin-plate electrode defect model;

[0020] The needle-plate electrode defect model includes:

[0021] A cross-linked polyethylene cable sheet is arranged between a high-voltage electrode and a low-voltage electrode; wherein the high-voltage electrode and the low-voltage electrode are made of brass;

[0022] One end of the tungsten needle electrode passes through the high-voltage electrode and is inserted into the cross-linked polyethylene cable pressing sheet, and the other end is set on the screw-in dial; the screw-in dial is rotated to adjust the depth of the tungsten needle electrode inserted into the cross-linked polyethylene cable pressing sheet to obtain insulation defect models with different insulation residual thicknesses.

[0023] In a possible implementation, the multiple groups of insulation defect models with different insulation residual thicknesses include insulation defect models with insulation residual thicknesses of 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm.

[0024] In one possible implementation, the Weibull distribution is:

[0025]

[0026] Among them, t is the breakdown time, F(t) is the breakdown failure probability, α is the scale parameter, and β is the shape parameter.

[0027] In a second aspect, an embodiment of the present invention provides a power cable withstand voltage test device based on withstand voltage equivalent analysis, comprising:

[0028] The initial test module is used to perform a withstand voltage test on the target power cable using a 0.1 Hz cosine square wave voltage to obtain an initial test result;

[0029] A correction module, used to correct the initial test result according to a preset equivalent analysis result, and determine the corrected test result as the final test result of the target power cable;

[0030] Among them, the process of obtaining the preset equivalent analysis results is as follows: applying power frequency voltage and 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses, respectively, to carry out a withstand voltage test; according to multiple groups of breakdown times and breakdown failure probabilities obtained from the withstand voltage test, the Weibull distribution of power frequency voltage and 0.1 Hz cosine square wave voltage with different insulation residual thicknesses are obtained respectively; based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution, the equivalence of power frequency voltage and 0.1 Hz cosine square wave voltage is analyzed to obtain the equivalent analysis results.

[0031] In a possible implementation, the method further includes:

[0032] The withstand voltage test module is used to apply power frequency voltage and 0.1Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses to perform withstand voltage tests;

[0033] A distribution generation module is used to obtain Weibull distributions of power frequency voltage and 0.1 Hz cosine square wave voltage of different insulation residual thicknesses according to multiple groups of breakdown times and breakdown failure probabilities obtained from the withstand voltage test;

[0034] The equivalent analysis module is used to analyze the equivalence of power frequency voltage and 0.1Hz cosine square wave voltage based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution, and obtain the equivalent analysis results;

[0035] Withstand voltage test module, also used for

[0036] Placing multiple groups of insulation defect models with different insulation residual thicknesses in the insulation oil in the test oil tank; wherein the liquid level of the insulation oil in the test oil tank is higher than the height of the insulation defect model;

[0037] Applying a power frequency voltage of a preset amplitude and a cosine square wave voltage of 0.1 Hz of a preset amplitude to multiple groups of insulation defect models with different insulation residual thicknesses;

[0038] When the power frequency voltage of the preset amplitude and the 0.1Hz cosine square wave voltage of the preset amplitude are reached respectively, the voltage is kept unchanged to test the withstand voltage time of the insulation defect model of the target group insulation residual thickness; wherein the insulation defect model of the target group insulation residual thickness is any one of multiple groups of insulation defect models with different insulation residual thicknesses.

[0039] In a possible implementation, the initial test module is also used to

[0040] A 0.1 Hz cosine square wave voltage is continuously applied to the target power cable. When the preset voltage value is reached, the timing starts and the preset voltage value is kept unchanged.

[0041] When the test voltage shows 0, the target power cable is broken down, the timing is stopped, and the initial withstand voltage time is obtained.

[0042] In a possible implementation, the correction module is also used to

[0043] According to the withstand voltage time of the insulation defect model with the same insulation residual thickness under the power frequency voltage and the 0.1Hz cosine square wave voltage, the initial withstand voltage time of the initial test is corrected according to a preset ratio, and the corrected withstand voltage time is determined as the final test result of the target power cable.

[0044] In one possible implementation, the insulation defect model is a pin-plate electrode defect model;

[0045] The needle-plate electrode defect model includes:

[0046] A cross-linked polyethylene cable sheet is arranged between a high-voltage electrode and a low-voltage electrode; wherein the high-voltage electrode and the low-voltage electrode are made of brass;

[0047] One end of the tungsten needle electrode passes through the high-voltage electrode and is inserted into the cross-linked polyethylene cable pressing sheet, and the other end is set on the screw-in dial; the screw-in dial is rotated to adjust the depth of the tungsten needle electrode inserted into the cross-linked polyethylene cable pressing sheet to obtain insulation defect models with different insulation residual thicknesses.

[0048] In a possible implementation, the multiple groups of insulation defect models with different insulation residual thicknesses include insulation defect models with insulation residual thicknesses of 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm.

[0049] In one possible implementation, the Weibull distribution is:

[0050]

[0051] Among them, t is the breakdown time, F(t) is the breakdown failure probability, α is the scale parameter, and β is the shape parameter.

[0052] In a third aspect, an embodiment of the present invention provides a terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the method described in the first aspect or any possible implementation manner of the first aspect are implemented.

[0053] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0054] In an embodiment of the present invention, first, a 0.1 Hz cosine square wave voltage is used to perform a withstand voltage test on the target power cable to obtain an initial test result. Then, the initial test result is corrected according to the preset equivalent analysis result, and finally, the corrected test result is determined as the final test result of the target power cable. Among them, the process of obtaining the preset equivalent analysis result includes, first, applying power frequency voltage and 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses, respectively, to perform a withstand voltage test; then, according to multiple groups of breakdown times and breakdown failure probabilities obtained from the withstand voltage test, the Weibull distribution of power frequency voltage and 0.1 Hz cosine square wave voltage with different insulation residual thicknesses is obtained respectively. Finally, based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution, the equivalence of the power frequency voltage and the 0.1 Hz cosine square wave voltage is analyzed to obtain an equivalent analysis result. In this way, firstly, the equivalence of the power frequency voltage and the 0.1Hz cosine square wave voltage is analyzed to obtain the equivalence analysis result, and then the power cable can be tested on the basis of the equivalence analysis result to ensure the accuracy of the withstand voltage test result. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0056] Figure 1 is a flowchart of a process for obtaining a preset equivalent analysis result provided by an embodiment of the present invention;

[0057] Figure 2 It is a structural schematic diagram of a pin-plate electrode defect model with highly controllable insulation residual thickness provided by an embodiment of the present invention;

[0058] Figure 3 is a Weibull distribution diagram of breakdown time under power frequency voltage provided by an embodiment of the present invention;

[0059] Figure 4 is a Weibull distribution diagram under a 0.1 Hz cosine square wave voltage provided by an embodiment of the present invention;

[0060] Figure 5 is a front view of the morphological features of the breakdown channel provided by an embodiment of the present invention;

[0061] Figure 6 is a side view of the morphological features of the breakdown channel provided by an embodiment of the present invention;

[0062] Figure 7It is a flow chart of the implementation of the power cable withstand voltage test method based on withstand voltage equivalent analysis provided by an embodiment of the present invention;

[0063] Figure 8 It is a structural schematic diagram of a power cable withstand voltage test device based on withstand voltage equivalent analysis provided by an embodiment of the present invention;

[0064] Fig. 9 is a schematic diagram of a terminal provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0065] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0066] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0067] Most of the breakdown accidents of cross-linked polyethylene (XLPE) cables are closely related to the main insulation of the power cable system. The withstand voltage test is a basic test to assess the insulation performance of the cable. It is a handover test that must be carried out before the power cable is put into operation. It can find the larger defects inside the power cable.

[0068] The pin-plate electrode defect is a typical defect in power cables and one of the main reasons for cable insulation breakdown. The pin-plate electrode defect will form an extremely uneven electric field inside the power cable, seriously reducing the breakdown voltage of the power cable.

[0069] The power cable insulation withstand voltage test is a basic test to assess the insulation performance of power cables and is a handover test that must be conducted before the power cables are put into operation. The withstand voltage test voltage types mainly include AC withstand voltage, DC withstand voltage and 0.1Hz ultra-low frequency withstand voltage. However, due to differences in test voltage, test model and statistical methods, the test results are also biased or even inconsistent.

[0070] Based on the above problems, an embodiment of the present invention provides a power cable voltage withstand testing method based on voltage withstand equivalence analysis. Before introducing the power cable voltage withstand testing method, it is first necessary to perform a voltage withstand equivalence analysis, and use the preset equivalent analysis results to perform subsequent power cable testing.

[0071] Here, we first introduce the steps of the process of obtaining the preset equivalent analysis results, such as Figure 1 As shown:

[0072] Step S110, applying power frequency voltage and 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses, respectively, to perform a withstand voltage test.

[0073] In some embodiments, multiple groups of insulation defect models with different insulation residual thicknesses include insulation defect models with insulation residual thicknesses of 0.2 mm, 0.3 mm, 0.4 mm and 0.5 mm. Other insulation defect models with different insulation residual thicknesses can also be produced according to actual power cable testing requirements.

[0074] Optionally, the insulation defect model can be a needle-plate electrode defect model. The needle-plate electrode defect model is an important model for studying extremely non-uniform electric field discharges, but no specific regulations are given in the relevant standards. Most of the needle electrodes in the traditional needle-plate electrode defect model use a long needle directly inserted into the XLPE sample. Since XLPE has a certain hardness, the insertion depth and angle are not easy to control, especially the insertion depth, which has a great influence on the electrode electric field distribution. This leads to unsatisfactory control of the distance between the needle electrode and the plate electrode, that is, the residual insulation thickness, and poor consistency of the electric field distribution at the needle tip position, resulting in a large dispersion of the test results.

[0075] To this end, the present invention provides a pin-plate electrode defect model with highly controllable insulation residual thickness, the overall structure of which is as follows: Figure 2 Specifically, the needle plate electrode defect model includes:

[0076] A cross-linked polyethylene cable pressing sheet 203 is arranged between a high-voltage electrode 202 and a low-voltage electrode 201, wherein the high-voltage electrode 202 and the low-voltage electrode 201 are made of brass. A tungsten needle electrode 205 has one end inserted through the high-voltage electrode 202 into the cross-linked polyethylene cable pressing sheet 203, and the other end is arranged on a screw-in dial 204. The screw-in dial 204 is rotated to adjust the depth of the tungsten needle electrode 205 inserted into the cross-linked polyethylene cable pressing sheet 203, and an insulation defect model with different insulation residual thickness is obtained.

[0077] First, a cross-linked polyethylene cable compression sheet 203 sample with a thickness of 2 mm and an area of ​​100 mm*100 mm is pressed tightly with a high-voltage electrode 202 and a low-voltage electrode 201. The high-voltage electrode 202 and the low-voltage electrode 201 are both made of equal-diameter electrodes specified in GB / T 1408.1-2016, with a specification of 25 mm×25 mm and a brass material with an edge chamfer of 3 mm. Then, a screw-in tungsten needle electrode 205 is inserted into the high-voltage electrode 202. The head diameter of the tungsten needle electrode 205 is 1 mm, the radius of curvature is 20 μm, and the tail is a screw with a pitch of 1 mm. Finally, the insertion depth of the tungsten needle electrode 205 is controlled by a screw-in dial 204 with a scale. The tungsten needle electrode 205 penetrates 0.1 mm for every 36° rotation. Since the needle tip is short, the pressure is reduced and its own deformation is very small. The screw-in structure can effectively control the insertion depth, and the residual insulation thickness is highly controllable. By controlling the insertion depth of the tungsten needle electrode 205, multiple groups of models with insulation residual thicknesses of 0.2 mm, 0.3 mm, 0.4 mm and 0.5 mm respectively can be prepared.

[0078] In some embodiments, first, in order to prevent the XLPE insulation sample from being affected by surface flashover when the insulation withstand voltage test is conducted in the air, the above-made multiple groups of insulation defect models with different insulation residual thicknesses are placed in the insulation oil in the test oil tank. The liquid level of the insulation oil in the test oil tank is higher than the height of the insulation defect model, and a pressure relief valve is provided on the top of the test oil tank to prevent explosion caused by a sudden increase in pressure at the moment of breakdown.

[0079] Then, a power frequency voltage with a preset amplitude and a cosine square wave voltage with a preset amplitude of 0.1 Hz are applied to the insulation defect models of the plurality of groups with different insulation residual thicknesses. Specifically, for a 10 kV power cable, when a withstand voltage test is performed for 60 minutes, a power frequency voltage with a preset amplitude of 2U0 and a cosine square wave voltage with a preset amplitude of 0.1 Hz of 2.5U0 can be used. To this end, taking the 10 kV power cable U0 as a reference, a power frequency voltage of 2U0 and a cosine square wave voltage of 0.1 Hz of 2.5U0 are applied to the insulation defect models with different insulation residual thicknesses.

[0080] Finally, when the power frequency voltage of the preset amplitude and the 0.1Hz cosine square wave voltage of the preset amplitude are reached respectively, the voltage is kept unchanged, and the withstand voltage time of the insulation defect model of the target group insulation residual thickness is tested. Specifically, when the voltage reaches the preset amplitude, the preset voltage amplitude is kept unchanged, and the timing is started. When the test voltage instantly becomes 0 volts, that is, the insulation defect model is broken down, the timing is stopped, which is the withstand voltage time of the corresponding model under the corresponding preset voltage.

[0081] Step S120, obtaining Weibull distributions of power frequency voltage and 0.1 Hz cosine square wave voltage with different insulation residual thicknesses according to multiple groups of breakdown times and breakdown failure probabilities obtained from the withstand voltage test.

[0082] In some embodiments, the most common distribution for solid insulation breakdown test data is Weibull distribution, which has wide applicability and is of great value for extreme value distribution types where failure occurs at the weakest point. The present invention processes withstand voltage test data using two-parameter Weibull distribution.

[0083]

[0084] Where t is the breakdown time, F(t) is the breakdown failure probability, α is the scale parameter, and β is the shape parameter. α refers to the breakdown time when the failure probability is 0.632, and β is the slope of the above formula, which indicates the dispersion of the test data. The larger β is, the smaller the variation range of the breakdown time is. The White method is used to calculate the values ​​of α and β. Figure 3 and Figure 4 As shown in the figure, they are the Weibull distribution diagrams under power frequency voltage and 0.1Hz cosine square wave voltage. Figure 3 Curve 1 is the Weibull distribution diagram of the insulation residual thickness sample with power frequency voltage of 0.2mm, Curve 2 is the Weibull distribution diagram of the insulation residual thickness sample with power frequency voltage of 0.3mm, Curve 3 is the Weibull distribution diagram of the insulation residual thickness sample with power frequency voltage of 0.4mm, and Curve 4 is the Weibull distribution diagram of the insulation residual thickness sample with power frequency voltage of 0.5mm. Figure 4 The curve in the figure is the Weibull distribution diagram of the insulation residual thickness sample with 0.2mm and 0.1Hz cosine square wave voltage.

[0085] It should be noted here that since the samples with insulation residual thickness of 0.3mm, 0.4mm and 0.5mm did not break down under the condition of 2.5U0 voltage and the longest action time of 3h, only the breakdown data statistics of the sample with insulation residual thickness of 0.2mm are given.

[0086] Step S130: Based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution, the equivalence of the power frequency voltage and the 0.1 Hz cosine square wave voltage is analyzed to obtain an equivalent analysis result.

[0087] In some embodiments, based on the above Weibull distribution Figure 3 and Figure 4, and the following Tables 1 and 2, it can be seen that for power frequency voltage, with the increase of residual insulation thickness, the α scale parameter and β shape parameter under 2U0 voltage gradually increase, the breakdown time gradually increases, and the variation range of the breakdown time gradually decreases. For 0.1Hz cosine square wave voltage, all defective samples did not break down under the condition of 2.5U0 voltage with the longest action time of 3h, so only the breakdown data statistics of the 0.2mm residual insulation thickness sample are given, which means that the withstand voltage of 2.5U0, for this type of defect, cannot be found under the prescribed withstand voltage time of 60min.

[0088] Among them, the scale parameters and shape parameters of the power frequency breakdown test are shown in Table 1.

[0089] Table 1

[0090] Insulation remaining thickness / mm α / min β 0.5 59.48 1.45 0.4 40.24 1.58 0.3 23.23 1.00 0.2 6.07 0.92

[0091] The scale parameters and shape parameters of the 0.1Hz cosine square wave breakdown test are shown in Table 2.

[0092] Table 2

[0093] Insulation remaining thickness / mm α / min β 0.2 348.62 1.11

[0094] For a residual insulation thickness of 0.5mm, the breakdown time is approximately 60 minutes. This means that for a 2U0 power frequency withstand voltage, the maximum residual thickness that can be found for this type of defect is 0.5mm. For a defect with a residual insulation thickness of 0.2mm, the power frequency voltage can complete the breakdown in just 6 minutes.

[0095] For the residual insulation thickness of 0.2mm, the breakdown time is about 345min, which is much longer than the breakdown time of about 6min under the action of power frequency voltage. This means that for this type of defect, it is impossible to find such defect under the prescribed withstand voltage time of 60min for 2.5U0 withstand voltage.

[0096] Further, such as Figure 5 and Figure 6 The front view and side view of the morphological features of the breakdown channel shown, where Figure 5 and Figure 6The left picture shows the morphological characteristics of the breakdown channel of the power frequency voltage, and the right picture shows the morphological characteristics of the breakdown channel of the 0.1Hz cosine square wave voltage. By observing the morphological characteristics of the breakdown channel, it can be seen that the diameter of the breakdown channel of the power frequency voltage is greater than that of the 0.1Hz cosine square wave voltage, the breakdown channel is relatively smooth, and the low-voltage electrode side of the breakdown channel has become significantly thicker, indicating that the energy injection at the moment of breakdown is relatively sufficient, and the XLPE material is fully vaporized during the breakdown process. However, the breakdown channel under the 0.1Hz cosine square wave voltage is relatively rugged, but relatively uniform, indicating that the energy injection at the time of breakdown is significantly small, the vaporization process is not sufficient, and the cumulative effect is not significant.

[0097] Through the equivalence analysis of the above power frequency voltage and the 0.1Hz cosine square wave voltage, it can be concluded that under the condition of the needle plate electrode defect model, the strength of the 0.1Hz cosine square wave voltage for the cable withstand voltage test is significantly lower than that of the power frequency voltage. Increasing the voltage of the cosine square wave, the frequency of the cosine square wave or increasing the test time will increase its strength for the cable withstand voltage test.

[0098] After obtaining the preset equivalent analysis results, the target power cable can be subjected to a withstand voltage test. Figure 7 As shown, the steps of the power cable withstand voltage test method based on withstand voltage equivalent analysis provided by the embodiment of the present invention include:

[0099] Step S710: Perform a withstand voltage test on the target power cable using a 0.1 Hz cosine square wave voltage to obtain an initial test result.

[0100] In some embodiments, a 0.1 Hz cosine square wave voltage is continuously applied to the target power cable, and when the preset voltage value 2.5U0 is reached, timing is started and the preset voltage value 2.5U0 is maintained unchanged;

[0101] When the test voltage shows 0, the target power cable is broken down, the timing is stopped, and the initial withstand voltage time is obtained.

[0102] Specifically, the test applied voltage was 30.75 kV, and a 0.1 Hz cosine square wave voltage was continuously applied to the target 10 kV power cable with an insulation residual thickness of 0.2 mm. When the preset voltage value 2.5U0 was reached, the withstand voltage breakdown time was 348.62 minutes.

[0103] Step S720: Correct the initial test result according to the preset equivalent analysis result, and determine the corrected test result as the final test result of the target power cable.

[0104] In some embodiments, based on the withstand voltage time of the insulation defect model with the same insulation residual thickness under the power frequency voltage and the 0.1 Hz cosine square wave voltage, the initial withstand voltage time of the initial test is corrected according to a preset ratio, and the corrected withstand voltage time is determined as the final test result of the target power cable.

[0105] Specifically, the strength of the cable withstand voltage test using the above-mentioned 0.1Hz cosine square wave voltage is significantly lower than that of the power frequency voltage. The breakdown time of a power cable with a residual insulation thickness of 0.2mm tested using a 0.1Hz cosine square wave voltage is 348.62 minutes, while when the same model is tested using a power frequency voltage, the breakdown time is only 6.07 minutes. To obtain accurate test results, the initial withstand voltage time tested using a 0.1Hz cosine square wave voltage must be corrected according to a preset ratio. The preset ratio is a number greater than 1 to obtain an accurate withstand voltage time. For power cables of different specifications, different test models, and different test voltages, the preset ratio here is not specifically limited. Users can limit it according to specific circumstances to ensure the accuracy of the test.

[0106] In some embodiments, the frequency of the cosine square wave can be increased, and the strength of the test on the cable withstand voltage can also be improved.

[0107] The same model as above was used to test the 0.5Hz cosine square wave at 2.5U0 voltage, and the test results are shown in Table 3. The scale parameters and shape parameters of the 0.5Hz cosine square wave breakdown test. It can be seen that increasing the frequency greatly reduces the breakdown time to about 37.1min, and the shape parameter β is also improved to a certain extent.

[0108] Table 3

[0109] Insulation remaining thickness / mm α / min β 0.2 37.10 1.21

[0110] By using the above equivalence analysis results, the original test results can be increased according to a preset ratio to obtain the accurate withstand voltage test time.

[0111] The voltage, frequency or test time of the cosine square wave can also be increased to improve the withstand voltage test strength, thereby improving the accuracy of the test.

[0112] The embodiment of the present invention provides a method for withstand voltage testing of power cables based on withstand voltage equivalent analysis. First, a 0.1 Hz cosine square wave voltage is used to perform a withstand voltage test on a target power cable to obtain an initial test result. Then, the initial test result is corrected according to a preset equivalent analysis result, and finally, the corrected test result is determined as the final test result of the target power cable. Among them, the process of obtaining the preset equivalent analysis result includes, first, applying power frequency voltage and 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses, respectively, to perform a withstand voltage test; then, according to multiple groups of breakdown times and breakdown failure probabilities obtained from the withstand voltage test, the Weibull distribution of power frequency voltage and 0.1 Hz cosine square wave voltage with different insulation residual thicknesses is obtained respectively. Finally, based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution, the equivalence of the power frequency voltage and the 0.1 Hz cosine square wave voltage is analyzed to obtain an equivalent analysis result. In this way, firstly, the equivalence of the power frequency voltage and the 0.1Hz cosine square wave voltage is analyzed to obtain the equivalence analysis result, and then the power cable can be tested on the basis of the equivalence analysis result to ensure the accuracy of the withstand voltage test result.

[0113] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0114] Based on the power cable withstand voltage test method based on withstand voltage equivalent analysis provided in the above embodiment, accordingly, the present invention also provides a specific implementation of a power cable withstand voltage test device based on withstand voltage equivalent analysis applied to the power cable withstand voltage test method based on withstand voltage equivalent analysis. Please refer to the following embodiments.

[0115] like Figure 8 As shown, a power cable withstand voltage test device 800 based on withstand voltage equivalent analysis is provided, and the device includes:

[0116] An initial test module 810 is used to perform a withstand voltage test on a target power cable using a 0.1 Hz cosine square wave voltage to obtain an initial test result;

[0117] A correction module 820, configured to correct the initial test result according to a preset equivalent analysis result, and determine the corrected test result as the final test result of the target power cable;

[0118] Among them, the process of obtaining the preset equivalent analysis results is as follows: applying power frequency voltage and 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses, respectively, to carry out a withstand voltage test; according to multiple groups of breakdown times and breakdown failure probabilities obtained from the withstand voltage test, the Weibull distribution of power frequency voltage and 0.1 Hz cosine square wave voltage with different insulation residual thicknesses are obtained respectively; based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution, the equivalence of power frequency voltage and 0.1 Hz cosine square wave voltage is analyzed to obtain the equivalent analysis results.

[0119] In a possible implementation, the method further includes:

[0120] A withstand voltage test module 830 is used to apply a power frequency voltage and a 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses to perform a withstand voltage test;

[0121] A distribution generation module 840 is used to obtain Weibull distributions of power frequency voltage and 0.1 Hz cosine square wave voltage of different insulation residual thicknesses according to multiple groups of breakdown times and breakdown failure probabilities obtained from the withstand voltage test;

[0122] An equivalent analysis module 850 is used to analyze the equivalence of the power frequency voltage and the 0.1 Hz cosine square wave voltage based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution to obtain an equivalent analysis result;

[0123] The withstand voltage test module 830 is also used for

[0124] Placing multiple groups of insulation defect models with different insulation residual thicknesses in the insulation oil in the test oil tank; wherein the liquid level of the insulation oil in the test oil tank is higher than the height of the insulation defect model;

[0125] Applying a power frequency voltage of a preset amplitude and a cosine square wave voltage of 0.1 Hz of a preset amplitude to multiple groups of insulation defect models with different insulation residual thicknesses;

[0126] When the power frequency voltage of the preset amplitude and the 0.1Hz cosine square wave voltage of the preset amplitude are reached respectively, the voltage is kept unchanged to test the withstand voltage time of the insulation defect model of the target group insulation residual thickness; wherein the insulation defect model of the target group insulation residual thickness is any one of multiple groups of insulation defect models with different insulation residual thicknesses.

[0127] In a possible implementation, the initial test module 810 is also used to

[0128] A 0.1 Hz cosine square wave voltage is continuously applied to the target power cable. When the preset voltage value is reached, the timing starts and the preset voltage value is kept unchanged.

[0129] When the test voltage shows 0, the target power cable is broken down, the timing is stopped, and the initial withstand voltage time is obtained.

[0130] In a possible implementation, the correction module 820 is further configured to

[0131] According to the withstand voltage time of the insulation defect model with the same insulation residual thickness under the power frequency voltage and the 0.1Hz cosine square wave voltage, the initial withstand voltage time of the initial test is corrected according to a preset ratio, and the corrected withstand voltage time is determined as the final test result of the target power cable.

[0132] In one possible implementation, the insulation defect model is a pin-plate electrode defect model;

[0133] The needle-plate electrode defect model includes:

[0134] A cross-linked polyethylene cable sheet is arranged between a high-voltage electrode and a low-voltage electrode; wherein the high-voltage electrode and the low-voltage electrode are made of brass;

[0135] One end of the tungsten needle electrode passes through the high-voltage electrode and is inserted into the cross-linked polyethylene cable pressing sheet, and the other end is set on the screw-in dial; the screw-in dial is rotated to adjust the depth of the tungsten needle electrode inserted into the cross-linked polyethylene cable pressing sheet to obtain insulation defect models with different insulation residual thicknesses.

[0136] In a possible implementation, the multiple groups of insulation defect models with different insulation residual thicknesses include insulation defect models with insulation residual thicknesses of 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm.

[0137] In one possible implementation, the Weibull distribution is:

[0138]

[0139] Among them, t is the breakdown time, F(t) is the breakdown failure probability, α is the scale parameter, and β is the shape parameter.

[0140] Fig. 9 is a schematic diagram of a terminal provided by an embodiment of the present invention. Fig. 9 As shown, the terminal 9 of this embodiment includes: a processor 90, a memory 91, and a computer program 92 stored in the memory 91 and executable on the processor 90. When the processor 90 executes the computer program 92, the steps in the above-mentioned embodiments of the power cable withstand voltage test method based on withstand voltage equivalent analysis are implemented, for example Figure 7 Alternatively, the processor 90 implements the functions of each module / unit in the above-mentioned device embodiments when executing the computer program 92, such as step 710 to step 720 shown in FIG. Figure 8Functions of modules 810 to 820 are shown.

[0141] Exemplarily, the computer program 92 may be divided into one or more modules 9, which are stored in the memory 91 and executed by the processor 90 to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program 92 in the terminal 9. For example, the computer program 92 may be divided into Figure 8 Modules 810 to 820 are shown.

[0142] The terminal 9 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The terminal 9 may include, but is not limited to, a processor 90 and a memory 91. Those skilled in the art will appreciate that Fig. 9 It is only an example of terminal 9 and does not constitute a limitation on terminal 9. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the terminal may also include input and output devices, network access devices, buses, etc.

[0143] The processor 90 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0144] The memory 91 may be an internal storage unit of the terminal 9, such as a hard disk or memory of the terminal 9. The memory 91 may also be an external storage device of the terminal 9, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the terminal 9. Further, the memory 91 may also include both an internal storage unit of the terminal 9 and an external storage device. The memory 91 is used to store the computer program and other programs and data required by the terminal. The memory 91 may also be used to temporarily store data that has been output or is to be output.

[0145] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0146] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0147] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0148] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0149] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0150] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0151] If the integrated module is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned embodiments of the power cable withstand voltage test method based on withstand voltage equivalent analysis can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practices in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practices, computer-readable media does not include electrical carrier signals and telecommunication signals.

[0152] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for testing power cable withstand voltage based on withstand voltage equivalent analysis, characterized in that: include: A 0.1Hz cosine square wave voltage is used to perform a withstand voltage test on the target power cable to obtain initial test results; Correcting the initial test result according to a preset equivalent analysis result, and determining the corrected test result as the final test result of the target power cable; Among them, the process of obtaining the preset equivalent analysis results is as follows: applying power frequency voltage and 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses, respectively, to perform a withstand voltage test; according to the multiple groups of breakdown times and breakdown failure probabilities obtained from the withstand voltage test, the Weibull distribution of the power frequency voltage and the 0.1 Hz cosine square wave voltage with different insulation residual thicknesses are obtained respectively; based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution, the equivalence of the power frequency voltage and the 0.1 Hz cosine square wave voltage is analyzed to obtain an equivalent analysis result.

2. The method for testing the power cable withstand voltage based on withstand voltage equivalent analysis according to claim 1, characterized in that: The method of applying a power frequency voltage and a 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses to perform a withstand voltage test includes: Placing a plurality of groups of insulation defect models with different insulation residual thicknesses in the insulation oil in a test oil tank; wherein the liquid level of the insulation oil in the test oil tank is higher than the height of the insulation defect models; Applying a power frequency voltage of a preset amplitude and a 0.1 Hz cosine square wave voltage of a preset amplitude to the plurality of groups of insulation defect models with different insulation residual thicknesses respectively; When the power frequency voltage of the preset amplitude and the 0.1 Hz cosine square wave voltage of the preset amplitude are reached respectively, the voltage is kept unchanged, and the withstand voltage time of the insulation defect model of the target group insulation residual thickness is tested; wherein, the insulation defect model of the target group insulation residual thickness is any one of the multiple groups of insulation defect models with different insulation residual thicknesses.

3. The power cable withstand voltage test method based on withstand voltage equivalent analysis according to claim 1, characterized in that: The method of performing a withstand voltage test on the target power cable using the 0.1 Hz cosine square wave voltage to obtain an initial test result includes: Continuously applying a 0.1 Hz cosine square wave voltage to the target power cable, and when a preset voltage value is reached, starting timing and maintaining the preset voltage value unchanged; When the test voltage shows 0, the target power cable is broken down, the timing is stopped, and the initial withstand voltage time is obtained.

4. The power cable withstand voltage test method based on withstand voltage equivalent analysis according to claim 1, characterized in that: The correcting the initial test result according to the equivalent analysis result, and determining the corrected test result as the final test result of the target power cable, comprises: According to the withstand voltage time of the insulation defect model with the same insulation residual thickness under the power frequency voltage and the 0.1 Hz cosine square wave voltage, the initial withstand voltage time of the initial test is corrected according to a preset ratio, and the corrected withstand voltage time is determined as the final test result of the target power cable.

5. The method for testing the power cable withstand voltage based on withstand voltage equivalent analysis according to claim 1, characterized in that: The insulation defect model is a needle-plate electrode defect model; The needle plate electrode defect model includes: A cross-linked polyethylene cable sheet disposed between a high-voltage electrode and a low-voltage electrode; wherein the high-voltage electrode and the low-voltage electrode are made of brass; A tungsten needle electrode has one end that passes through the high-voltage electrode and is inserted into the cross-linked polyethylene cable pressing sheet, and the other end is arranged on a screw-in dial; the screw-in dial is rotated to adjust the depth of the tungsten needle electrode inserted into the cross-linked polyethylene cable pressing sheet to obtain insulation defect models with different insulation residual thicknesses.

6. The method for testing the withstand voltage of a power cable based on withstand voltage equivalent analysis according to claim 1, characterized in that: The multiple groups of insulation defect models with different insulation residual thicknesses include insulation defect models with insulation residual thicknesses of 0.2 mm, 0.3 mm, 0.4 mm and 0.5 mm.

7. The power cable withstand voltage test method based on withstand voltage equivalent analysis according to any one of claims 1 to 6, characterized in that: The Weibull distribution is: Among them, t is the breakdown time, F(t) is the breakdown failure probability, α is the scale parameter, and β is the shape parameter.

8. A power cable withstand voltage test device based on withstand voltage equivalent analysis, characterized in that: include: The initial test module is used to perform a withstand voltage test on the target power cable using a 0.1 Hz cosine square wave voltage to obtain an initial test result; A correction module, used to correct the initial test result according to a preset equivalent analysis result, and determine the corrected test result as the final test result of the target power cable; Among them, the process of obtaining the preset equivalent analysis results is as follows: applying power frequency voltage and 0.1 Hz cosine square wave voltage to multiple groups of insulation defect models with different insulation residual thicknesses, respectively, to perform a withstand voltage test; according to the multiple groups of breakdown times and breakdown failure probabilities obtained from the withstand voltage test, the Weibull distribution of the power frequency voltage and the 0.1 Hz cosine square wave voltage with different insulation residual thicknesses are obtained respectively; based on the scale parameter, shape parameter and morphological characteristics of the breakdown channel in the Weibull distribution, the equivalence of the power frequency voltage and the 0.1 Hz cosine square wave voltage is analyzed to obtain an equivalent analysis result.

9. The power cable withstand voltage test device based on withstand voltage equivalent analysis according to claim 8, characterized in that: Also includes: The correction module is also used placing a plurality of groups of insulation defect models with different insulation residual thicknesses in the insulating oil in a test oil tank; Applying a power frequency voltage of a preset amplitude and a 0.1 Hz cosine square wave voltage of a preset amplitude to the plurality of groups of insulation defect models with different insulation residual thicknesses respectively; When the power frequency voltage of the preset amplitude and the 0.1 Hz cosine square wave voltage of the preset amplitude are reached respectively, the voltage is kept unchanged, and the withstand voltage time of the insulation defect model of the target group insulation residual thickness is tested; wherein, the insulation defect model of the target group insulation residual thickness is any one of the multiple groups of insulation defect models with different insulation residual thicknesses.

10. A terminal comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

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