Cable electric heating aging performance test equipment and test method thereof

Abstract

The invention discloses a cable electric heating aging performance test device and a test method thereof, and the test method comprises the steps: setting a test total period length D and a test time interval T, D being a whole time of T; the cables are segmented and divided into A, B and C groups and the A, B and C groups are marked; one section in the group A is subjected to standing treatment, the other cable sections are connected in series, constant voltage is applied to the series cables, and temperature control is carried out; the B group of cable sections are adopted to replace the A group of cable sections in sequence at the interval of time T, and the B group of cables replace the A group of cables; carrying out a constant-voltage aging test on the group C of cables by adopting the same voltage and test time interval as the group A of cables; repeating the steps, and performing a group test; and carrying out data analysis on the collected experimental data. According to the test process, the influence of the resistance parameter influence on the test process can be effectively eliminated, the test factors can be effectively separated in the subsequent analysis process, and the data acquisition mode has good scientificity and normalization.

Description

Technical Field

[0001] The invention relates to a cable electrothermal aging performance testing device and a testing method thereof, belonging to the technical field of cables. Background Art

[0002] In the power system, the cable is one of the main carriers for transmitting power, and its performance directly affects the safety and reliability of the power system. During long-term use, the cable will be affected by various environmental factors, such as temperature changes, chemical corrosion, mechanical stress, etc., which will cause the cable to age. Among them, electrothermal aging is a very important aspect. It is mainly caused by the heat generated by the current passing through the conductor. This heat accelerates the degradation of the insulation material, thereby affecting the service life of the cable. Traditional cable aging tests are usually carried out under laboratory conditions, including but not limited to constant temperature aging, thermal cycle aging and other methods. However, these methods often cannot fully simulate the complex conditions under actual operating conditions, especially for cables with new materials or complex structures, which require more accurate and practical aging test methods. The current electrothermal aging test does not take into account its heterogeneous mesoscopic effect under the test conditions, lacks the evolution law of the insulation breakdown failure process under the combined action of electricity and heat, and the analysis of insulation aging life, resulting in the lack of scientificity and normalization of the test design in the factor analysis process, and its test results are insufficient for the technical guidance of the engineering evaluation method of the remaining life of the cable cross-linked polyethylene insulation. Summary of the invention

[0003] The purpose of the present invention is to provide a cable aging performance testing method to solve the above technical problems.

[0004] The technical solution to achieve the purpose of the present invention is: a method for testing the electrical and thermal aging performance of a cable, comprising the following steps:

[0005] Determine the test time and test time interval T, where D is an integer multiple of T;

[0006] The model cable is segmented to obtain model cable segments, and the processed model cable segments are divided into four groups: A1, A2, B, and C and marked; the number of model cables is set to N A1 、N A2 、N B 、N C ;

[0007] In order to satisfy the replacement relationship and minimize the number of model cables, the quantitative relationship of the number of model cables in each group should satisfy N A1 =N A2 +1=N B +2=N C +2;

[0008] A model cable segment in group A1 is placed in a static state to obtain a static group;

[0009] Connect the remaining model cable segments in group A1 in series to form a path, apply a first constant voltage to the series cables, and perform temperature control at the same time to obtain a first initial path;

[0010] The first initial path is subjected to an electrothermal aging test, specifically: at each interval T, a model cable segment of the B group model cable segment is used to replace a model cable segment in the A1 group series cable of the first initial path, until a first preset number of the A1 group model cable segments are replaced by the B group model cable segments; and after the total test time D, an electrothermal aging model cable sample group is obtained;

[0011] The model cable segments in group A2 are connected in series to form a path, and a constant voltage is applied to the series cables to obtain a second initial path;

[0012] The second initial path is subjected to an aging test, specifically: at each interval T, a model cable segment of the C group model cable segment is used to replace a model cable segment in the A2 group series cable of the second initial path, until a second preset number of the A2 group model cable segments are replaced by the C group model cable segments; and an aging model cable sample group is obtained after a total test time D;

[0013] The model cable sections of the static group, the electrothermal aging model cable sample group, and the aging model cable sample group were subjected to margin withstand voltage breakdown tests respectively;

[0014] Analyze the margin voltage breakdown test data to obtain the cable electrical and thermal aging performance data.

[0015] During the test, the cables on the first initial path and the second initial path are passed through the temperature control device and connected to the voltage control device. During the test, the temperature parameters and voltage parameters are adjusted, and then the model cable is replaced segment by segment so that different model cable segments are subjected to different voltage and temperature effects. When the method is used for testing, the resistance of each path does not change during the test, and the overall homogeneity is strong. Compared with the existing method of using separate tests during the test of electrical and thermal aging factors, the parameters of the model cable segments are relatively stable and highly consistent during the test, and multiple test data sampling points are obtained under the same parameters due to the replacement, which can effectively eliminate the interference of the circuit performance on the test process, and can effectively separate the test factors in the subsequent analysis process, and the data collection method is more scientific and standardized.

[0016] Further or optionally, in order to make the test process close to the natural year time cycle, the total test time D is 360 days, the time interval T is 90 days, and the model cable segment is replaced with a replacement cycle close to one season during the test process. When the test start time is close to the season change time, the impact of seasonal factors on the test process can be effectively sorted out.

[0017] Further or optionally, in order to collect multi-point data and improve data reproducibility, the model cable is segmented into 5 segments in the A1 group and 4 segments in the A2 group, which are marked as A 21 , A 22 , A 23 , A 24 ; Group B has 3 segments, and Group C has 3 segments, marked as C1, C2, and C3 respectively; The replacement steps of Group B for Group A1 are: B1 replaces A 14 , B2 replaces A 13 , B3 replaces A 12 , A 11 After static treatment, A 15 No replacement is performed; the replacement procedure of group C for group A2 is C1 replacing A 24 , C2 replaces A 23 , C3 replaces A 22 , A 21 No replacement is made.

[0018] After completing the substitution, we get:

[0019] A 11 Being left to stand

[0020] A 12 , B3 parameters are the same; A 13 , B2 parameters are the same; A 14 , B1 parameters are the same; A 15 It is the full cycle test data;

[0021] A 21 , C3 parameters are the same; A 22 , C2 parameters are the same; A 23 , C1 parameters are the same; A 24 It is the full cycle test data;

[0022] During the test, except for the test start and end points, each point was sampled at least twice, with good data repeatability, which can effectively eliminate the influence of resistance and time factors on the test process.

[0023] Further or optionally, in order to simulate the actual working environment of the cable, the first constant voltage adopts a 35.5kV constant industrial frequency voltage, and the conductor temperature range in the model cable segment is controlled to be 90°C to 95°C. At this time, the test process is closer to the extreme working conditions in the actual project, and the data redundancy is higher after the test is completed.

[0024] Further or optionally, during the test process of Groups A1 and B, in order to make the temperature control of the internal conductor of the model cable segment more precise, a temperature control unit is used to control the temperature. During the test, the model cable segment is always controlled to be located inside the temperature control unit. Specifically, the temperature control unit is a through-hole transformer, and the uniform electric field inside it can effectively maintain the uniformity of its temperature. During the test, the temperature parameters of the internal conductor of the model cable segment are controlled by changing the through-hole transformer parameters.

[0025] Further or optionally, in the margin withstand voltage breakdown test, in order to achieve minimum density data sampling, the starting test voltage value is 35.5kV, and the voltage is upgraded at a voltage interval of 10kV per level, with each level being maintained for 5 minutes until the cable sample breaks down. In the actual test process, more accurate data sampling can be obtained by shortening the voltage interval step.

[0026] Further or optionally, in order to make the test environment closer to the actual working environment, the test voltage frequency is maintained at 49-51 Hz during the operation of the electrothermal aging test and the aging test, and the environmental test temperature is room temperature during the operation. During the actual test, the constant temperature of 20°C is not controlled, and the actual air temperature of the test environment shall prevail.

[0027] Further or optionally, in order to ensure that a minimum number of data collection samples are obtained, the electrothermal aging test and the aging test are performed at least once. Further, in order to improve the data reproduction performance, the electrothermal aging test and the aging test are performed three times. In actual tests, the total length of the cable can be set to 450 meters and evenly cut into sections of 10 meters. In this way, three groups of at least 45 data can be obtained.

[0028] Further or optionally, the present application also provides a cable electrothermal aging performance test device, which is used to implement the above-mentioned cable aging performance test method, and its overall structure is very simple, including a controller, a voltage source and a temperature control unit;

[0029] A controller, used to control the voltage of the voltage source and the temperature parameter of the temperature control unit, the controller being electrically connected to the voltage source and the temperature control unit;

[0030] A voltage source, used to provide the voltage during the test;

[0031] Temperature control unit, used to control the conductor temperature of the cable section during the test.

[0032] The specific test method is as follows: the temperature control unit used is a through-core transformer, and the above-mentioned cable electrothermal aging performance test method is implemented. During the test, the cable segment passes through the inside of the through-core transformer;

[0033] During the test, the series cables to be tested are passed through an equal number of feedthrough transformers;

[0034] During the test, the model cable segment is replaced and tested according to the steps of the above-mentioned cable electrothermal aging performance test method.

[0035] In the actual test process, the device can flexibly set the number of through-hole transformers according to the needs of data sampling. During the test, the through-hole transformers can be evenly arranged in a ring. For example, when the natural month is used as the data collection segmentation point, 12 data sampling points can be set. At this time, the 12 through-hole transformers are arranged in a different arrangement, and then 360 days are used as the total test time D, and 30 days are used as the time interval T for testing. It is only necessary to use a longer sample to be tested and cut it into the corresponding number of segments during the sample preparation stage.

[0036] By adopting the above technical solution, the present invention has the following beneficial effects:

[0037] (1) Compared with the prior art method of directly subjecting the model cable to aging test, the present application places the model cable in an environment closer to the actual application for testing. During the test, the cable of the same material is used to replace the test cable segment. During the test, the overall resistance of the loop does not change. During the test, the parameters are stable and consistent, and the fluctuation caused by the loop factors is smaller. In addition, due to the replacement, multiple test data sampling points are obtained under the same parameter, which can effectively eliminate the interference of the loop performance on the test process. In the subsequent analysis process, the test factors can be effectively separated, and the data collection and processing methods are more scientific and standardized.

[0038] (2) The total test time length D of this application is 360 days, and the test time interval is 90 days, which is closer to the natural time cycle. The test results are closer to the actual use environment and can effectively sort out the impact of seasonal factors on the test process.

[0039] (3) This application adopts a five-point test method. The same test conditions can be cleverly reproduced during the test process, with good data repeatability, which can effectively eliminate the influence of resistance and time factors on the test process.

[0040] (4) The constant voltage of the test in this application is 35.5 kV, and the test conductor temperature is 90°C to 95°C. At this time, the test process is closer to the extreme working conditions in actual engineering, and the data redundancy is higher after the test is completed.

[0041] (5) During the test process of this application, a through-hole transformer is used to control the temperature. During the test process, the model cable is always located inside the through-hole transformer. The uniform electric field inside the through-hole transformer can effectively maintain its temperature uniformity. During the test process, the temperature parameters of the conductor inside the model cable segment are controlled by changing the through-hole transformer parameters.

[0042] (6) This application upgrades at 10kV voltage intervals, with each level holding time being 5 minutes. Effective parameters can be obtained on the basis of ensuring the minimum number of data collection points. On this basis, shortening the voltage interval step can obtain more accurate sampling data.

[0043] (7) The test frequency of this application is 49-51 Hz, and the initial test temperature is room temperature, which is closer to the actual working environment.

[0044] (8) The present application also provides a cable aging performance testing device, which has a very flexible test time period and data sampling method, a simple structure, and can adapt to sampling of various test cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention is further described below in conjunction with the accompanying drawings and embodiments, wherein:

[0046] Figure 1 : Schematic diagram of the model cable replacement process;

[0047] Figure 2 : Simple diagram of the test process. DETAILED DESCRIPTION

[0048] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0049] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0050] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0052] In the description of the embodiments of the present invention, it should be understood that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is conventionally placed when used, or are the orientations or positional relationships conventionally understood by those skilled in the art. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0053] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The present invention is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the scope of protection of the present invention.

[0054] (Example 1)

[0055] See Figure 1 A method for testing the electrical and thermal aging performance of a cable in this embodiment comprises the following steps:

[0056] Take 450 meters of the sample to be tested, take 10 meters as a model cable segment, divide it into 45 even sections, and then divide it into three groups, namely 1#, 2# and 3#, each group is marked as 1# (A 11 , A 12 , A 13 , A 14 , A 15 , A 21 , A 22 , A 23 , A 24 ,B1,B2,B3,C1,C2,C3),2#(A 11 , A 12 , A 13 , A 14 , A 15 , A 21 , A 22 , A23 , A 24 ,B1,B2,B3,C1,C2,C3),3#(A 11 , A 12 , A 13 , A 14 , A 15 , A 21 , A 22 , A 23 , A 24 , B1, B2, B3, C1, C2, C3).

[0057] For the 1# model cable segment group, A 11 Perform static treatment, marked as 1# static group;

[0058] Then A 12 , A 13 , A 14 , A 15 After passing through the through-hole transformer, they are connected in series to form a path, and the parameters of the through-hole transformer are controlled to adjust the conductor parameters of the model cable segment to obtain a first initial path;

[0059] Replace A with B3, B2, and B1 on the 90th, 180th, and 270th days respectively. 12 , A 13 , A 14 , then the first initial path was removed on the 360th day to obtain the 1# electrothermal aging test group;

[0060] Then A 21 , A 22 , A 23 , A 24 Passing through the series connection to form a path, a second initial path is obtained;

[0061] Replace A with C1, C2, and C3 on the 90th, 180th, and 270th days, respectively. 21 , A 22 , A 23 , then the first initial path was removed on the 360th day to obtain the 1# aging test group;

[0062] The specific replacement process is as follows: Figure 1 The overall test process is as follows: Figure 2 shown.

[0063] The specific comparison method is shown in the following table, where the temperature is 90℃~95℃, and 90℃ is used for the 1# model cable segment group.

[0064]

[0065] The model cable segments obtained from the 1# static group, 1# electrothermal aging test group and 1# aging test group were subjected to margin withstand voltage breakdown tests. The frequency of the test voltage was 49-51Hz during the test. The test was carried out at room temperature. The initial test voltage was 35.5kV, which was applied between the conductor and the insulation shield and maintained for 5 minutes. Then the test voltage was increased step by step by 10kV per level and maintained for 5 minutes at each level until the cable sample broke down. The breakdown voltage was recorded, and the relationship between the breakdown data and the time-temperature-voltage was obtained. The data was cleaned, and a time-breakdown voltage trend relationship diagram was drawn to obtain the 1# data relationship table.

[0066] The same test steps were carried out on the 2# and 3# model cable segment groups, the voltage of the through-hole transformer was changed, and the conductor temperature was set to 93°C and 95°C respectively, and the 2# data relationship table and the 3# data relationship table were obtained.

[0067] The data in the 1# data relationship table, 2# data relationship table and 3# data relationship table are analyzed for consistency, abnormal data are eliminated, and the data are put into the data processing software for fitting processing to obtain the relationship between electric heating, voltage and withstand voltage.

[0068] The present application also relates to a cable aging performance test device, which is used to implement the above-mentioned cable electrothermal aging performance test method, specifically including a voltage source and a through-hole transformer. During the test, the model cable segment passes through the through-hole transformer, both of which are powered by the voltage source. During the actual test, the number of through-hole transformers is set according to the total test time and the time interval T.

[0069] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for testing the electrical and thermal aging performance of a cable, characterized in that: The steps include: Determine the test time and test time interval T, where D is an integer multiple of T; The model cable is segmented to obtain model cable segments, and the processed model cable segments are divided into four groups: A1, A2, B, and C and marked; the number of model cables is set to N A1 、N A2 、N B 、N C ; A model cable segment in group A1 is placed in a static state to obtain a static group; Connect the remaining model cable segments in group A1 in series to form a path, apply a first constant voltage to the series cables in group A1, and perform temperature control at the same time to obtain a first initial path; The first initial path is subjected to an electrothermal aging test, specifically: at each interval T, a model cable segment of the B group model cable segment is used to replace a model cable segment in the A1 group series cable of the first initial path, until a first preset number of the A1 group model cable segments are replaced by the B group model cable segments; after maintaining the total test time D, an electrothermal aging model cable sample group is obtained; Connecting the model cable segments in group A2 in series to form a path, applying a second constant voltage to the series-connected cables in group A2 to obtain a second initial path; The second initial path is subjected to an aging test, specifically: at each interval T, a model cable segment of the C group model cable segment is used to replace a model cable segment in the A2 group series cable of the second initial path, until a second preset number of the A2 group model cable segments are replaced by the C group model cable segments; and an aging model cable sample group is obtained after a total test time D; The model cable sections of the static group, the electrothermal aging model cable sample group, and the aging model cable sample group were subjected to margin withstand voltage breakdown tests respectively; Analyze the margin voltage breakdown test data to obtain the cable electrical and thermal aging performance data.

2. A cable electrothermal aging performance testing method according to claim 1, characterized in that: The total test time D is 360 days, and the time interval T is 90 days.

3. A cable electrothermal aging performance testing method according to claim 1, characterized in that: In the segmentation process of the model cable, the number of segments in group A1 is 5, which are marked as A 11 , A 12 , A 13 , A 14 , A 15 , A2 group has 4 segments, marked as A 21 , A 22 , A 23 , A 24 , Group B has 3 segments, marked as B1, B2, and B3, and Group C has 3 segments, marked as C1, C2, and C3. The replacement steps of Group B for Group A1 are: B1 replaces A 14 , B2 replaces A 13 , B3 replaces A 12 , A 11 After static treatment, A 15 No replacement is performed; the replacement procedure of group C for group A2 is C1 replacing A 24 , C2 replaces A 23 , C3 replaces A 22 , A 21 No replacement is made.

4. A cable electrothermal aging performance testing method according to claim 1, characterized in that: The first constant voltage adopts a constant power frequency voltage of 35.5 kV, and when temperature control is performed, the temperature range of the conductor in the model cable segment is controlled to be 90° C. to 95° C.

5. A cable electrothermal aging performance testing method according to claim 1, characterized in that: During the test of Group A1 and Group B, the temperature was controlled by a temperature control unit, and the corresponding model cable segment was always within the control range of the temperature control unit during the test.

6. A cable electrothermal aging performance testing method according to claim 1, characterized in that: In the margin withstand voltage breakdown test, the initial test voltage is 35.5kV, and the voltage is upgraded at a 10kV voltage interval, with each level being maintained for 5 minutes until the cable sample breaks down.

7. A method for testing the electrical and thermal aging performance of a cable according to any one of claims 1 to 5, characterized in that: During the operation of the electrothermal aging test and the aging test, the test voltage frequency is maintained at 49-51 Hz and the environmental test temperature is room temperature.

8. A method for testing the electrical and thermal aging performance of a cable according to any one of claims 1 to 5, characterized in that: The electrothermal aging test and aging test shall be carried out at least once.

9. A cable electrothermal aging performance testing method according to claim 8, characterized in that: The number of electric and thermal aging tests and aging tests is 3 times.

10. A cable aging performance testing device, characterized in that: Specifically include: controller, voltage source and temperature control unit; A controller, used to control the voltage of the voltage source and the temperature parameters of the temperature control unit to implement a cable electrothermal aging performance test method as described in any one of claims 1 to 9, wherein the controller is electrically connected to the voltage source and the temperature control unit; A voltage source, used to provide the voltage during the test; Temperature control unit, used to control the conductor temperature of the cable section during the test.

Images