Cable insulation layer defect identification and positioning method based on air gap discharge theory

Abstract

The invention relates to the technical field of cable insulation layer defect identification and positioning, in particular to a cable insulation layer defect identification and positioning method, device and system based on an air gap discharge theory. According to the cable insulation layer defect identification and positioning method, an equivalent circuit diagram of a cable and an air gap is established; mounting annular electrodes at two ends of the to-be-detected cable insulating layer; applying a processing frequency voltage so that the equivalent air gap field intensity does not have a preset threshold value; and repeating multiple experiments and observing the discharge times, if the discharge times are lower than a given upper limit, determining that the cable insulation layer is intact, and otherwise, determining that the cable has obvious insulation layer defects. According to the method, scanning is carried out along the extension direction of the cable, segment-by-segment detection is carried out, and effective identification and positioning of the cable insulation defect are finally realized. According to the invention, effective identification of the defects of the insulating layer and accurate positioning of the defects of the insulating layer under the condition of small samples are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of cable insulation layer defect identification and location, and in particular to a method, device and system for cable insulation layer defect identification and location based on the air gap discharge theory. Background Art

[0002] With the development of urbanization, the use scale of power cables has gradually increased. However, since power cables are laid underground, compared with overhead lines, their environment is more humid and enclosed, and they are often affected by surface construction. This makes power cables more likely to have insulation layer defects, resulting in serious power transmission accidents such as electric leakage and short circuit.

[0003] Currently, the detection methods for cable insulation layer defects include the traveling wave method, the dielectric loss angle method, the leakage current method, etc. Among them, for the traveling wave method, due to the small change in the insulation parameters of aged cables, the measurement accuracy is usually low; the dielectric loss angle method is more sensitive to external interference, and there is a problem of high requirements for the detection environment; the leakage current method has great difficulty in detecting local defects and low detection accuracy for small holes and damages. In addition, the above detection methods have problems such as complex principles and high device costs.

[0004] In summary, the existing technology has problems of low defect detection accuracy, high difficulty and high cost. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problems of low defect detection accuracy, high difficulty and high cost in the existing technology.

[0006] To solve the above technical problem, the present invention provides a method for cable insulation layer defect identification and location, including:

[0007] Construct an equivalent circuit model of air gap discharge of the insulation layer defect of the target insulated cable;

[0008] Repeatedly excite the electrodes at both ends of the cable section to be measured of the insulated cable to apply a power frequency voltage to the cable section to be measured so that the peak value of the air gap field strength in the equivalent circuit reaches a preset threshold, and record the number of times of air gap discharge phenomena occurring in the cable section to be measured of the insulated cable;

[0009] Judge the defect state of the cable section to be measured of the insulated cable according to the total number of times of air gap discharge phenomena occurring in the cable section to be measured of the insulated cable.

[0010] Preferably, the construction of the equivalent circuit model of air gap discharge of the insulation layer defect of the target insulated cable includes:

[0011] Construct an equivalent circuit of air gap discharge of the insulation layer defect of the target insulated cable, and the equivalent circuit is composed of an air gap defect part, a non-air gap normal part and the remaining part connected in series inside the insulation layer of the target insulated cable and connected in parallel;

[0012] Based on the equivalent circuit, an equivalent circuit model for the air-gap discharge of the insulation layer defect of the target insulated cable is constructed according to the relative permittivity of the target insulated cable.

[0013] Preferably, the peak value of the power frequency voltage is not less than the product of the field strength of the air-gap defect part and the total length of the cable, or not less than the product of the field strength of the non-air-gap normal part, the length of the cable, and the ratio of the relative permittivity of the air-gap defect part to the non-air-gap normal part.

[0014] Preferably, the steps of repeatedly exciting the electrodes at both ends of the insulated cable section to be tested to apply a power frequency voltage to the insulated cable section to be tested so that the peak value of the air-gap field strength in the equivalent circuit reaches a preset threshold value, and recording the number of times of air-gap discharge phenomena occurring in the insulated cable to be tested include:

[0015] Step a: After controlling the voltage of the electrodes at both ends of the insulated cable section to be tested to gradually rise to not less than the peak value of the power frequency voltage, and making the peak value of the air-gap field strength in the equivalent circuit reach the preset threshold value, record the number of times of air-gap discharge phenomena occurring in the insulated cable to be tested within the first preset time period;

[0016] Step b: After the recording is completed, control the voltage of the electrodes at both ends of the insulated cable section to be tested to gradually decrease to 0V;

[0017] Step c: Repeat steps a-b every second preset time period;

[0018] Step d: Statistically calculate the total number of times of air-gap discharge phenomena occurring in the insulated cable to be tested.

[0019] Preferably, the determination of the defect state of the insulated cable section to be tested according to the total number of times of air-gap discharge phenomena occurring in the insulated cable to be tested includes:

[0020] When the total number is not greater than the preset upper limit, it is determined that the defect of the insulation layer of the target insulated cable is small;

[0021] When the total number is greater than the preset upper limit, it is determined that the defect of the insulation layer of the target insulated cable is large.

[0022] Preferably, after determining that the defect of the insulation layer of the target insulated cable is large, it includes:

[0023] Control the electrodes at both ends of the insulated cable section to be tested to slide the same unit distance in the same direction step by step according to the cable line;

[0024] Control the electrodes to detect the number of times of air-gap discharge phenomena occurring in the insulated cable section between the current electrodes every time they slide until the detection of the entire cable section is completed;

[0025] Locate the insulated cable section where the number of times of air-gap discharge phenomena exceeds the preset upper limit as the defect point.

[0026] The present invention also provides a device for identifying and locating cable insulation layer defects, including:

[0027] An equivalent circuit model construction module, configured to construct an equivalent circuit model for the air-gap discharge of the insulation layer defect of the target insulated cable;

[0028] A pressurization test module, configured to repeatedly excite the electrodes at both ends of the insulated cable segment to be tested to apply a power frequency voltage to the insulated cable segment to be tested so that the peak value of the air-gap field strength in the equivalent circuit reaches a preset threshold, and record the number of times of air-gap discharge phenomena occurring in the insulated cable to be tested;

[0029] A defect detection module, configured to judge the defect state of the insulated cable segment to be tested according to the total number of times of air-gap discharge phenomena occurring in the insulated cable to be tested.

[0030] Preferably, the defect detection module includes:

[0031] A first detection unit, configured to determine that the defect of the insulation layer of the target insulated cable is small when the total number is not greater than a preset upper limit;

[0032] A second detection unit, configured to determine that the defect of the insulation layer of the target insulated cable is large when the total number is greater than the preset upper limit.

[0033] Preferably, the device for identifying and locating cable insulation layer defects further includes a defect location module, and the defect location module includes:

[0034] A judgment unit, configured to determine to perform a defect location operation when the defect of the insulation layer of the target insulated cable is large;

[0035] An electrode sliding control unit, configured to control the electrodes at both ends of the insulated cable segment to be tested to slide in the same direction by the same unit distance step by step along the cable line;

[0036] A sliding detection unit, configured to control the number of times of air-gap discharge phenomena occurring in the insulated cable segment between the current electrodes to be detected each time the electrode slides until the detection of the entire cable segment is completed;

[0037] A defect location unit, configured to locate the insulated cable segment where the number of times of air-gap discharge phenomena exceeds the preset upper limit as the defect point.

[0038] The present invention also provides a system for identifying and locating cable insulation layer defects, including:

[0039] A voltage source;

[0040] A voltage regulating device, connected to the voltage source;

[0041] An electrode, connected to the voltage regulating device;

[0042] A trolley having the same track as the target insulated cable line and its control device are connected to the electrode;

[0043] A cable insulation layer defect identification and positioning device as described above is connected to the voltage regulating device and the control device of the trolley.

[0044] The above technical solution of the present invention has the following advantages compared with the prior art:

[0045] For the cable insulation layer defect identification and positioning method of the present invention, an equivalent circuit diagram of the cable and the air gap is established; annular electrodes are installed at both ends of the cable insulation layer to be measured; an industrial frequency voltage is applied so that the equivalent air gap field strength does not exceed a preset threshold; the experiment is repeated multiple times and the number of discharges is observed. If the number of discharges is lower than the given upper limit, it is considered that the cable insulation layer is intact, otherwise it is considered that there are obvious insulation layer defects in the cable. According to the above method, a scan is performed along the cable extension direction for segment-by-segment detection, and finally an effective identification and positioning of the cable insulation defect are realized. The present invention realizes an effective identification of the insulation layer defect and an accurate positioning of the insulation layer defect under the condition of a small sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to specific embodiments of the present invention in conjunction with the drawings, where:

[0047] Figure 1 is a flowchart of the implementation of a cable insulation layer defect identification and positioning method provided by the present invention;

[0048] Figure 2 is the equivalent circuit diagram established in the embodiment of the present invention;

[0049] Figure 3 is a schematic diagram of a cable insulation layer defect identification and positioning system provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] The core of the present invention is to provide a cable insulation layer defect identification and positioning method, device, equipment and computer storage medium, which effectively improves the accuracy of cable insulation layer defect detection and reduces the difficulty and cost.

[0051] In order to enable those skilled in the art to better understand the solution of the present invention, the following further details the present invention in conjunction with the drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0052] Please refer to Figure 1 , Figure 1 , which is the implementation flowchart of a method for identifying and locating cable insulation layer defects provided by the present invention. The specific operation steps are as follows:

[0053] S101: Construct an equivalent circuit model for the air-gap discharge of the insulation layer defect of the target insulated cable;

[0054] S102: Repeatedly excite the electrodes at both ends of the insulated cable section to be measured to apply a power frequency voltage to the insulated cable section to be measured so that the peak value of the air-gap field strength in the equivalent circuit reaches a preset threshold, and record the number of times of air-gap discharge phenomena occurring in the insulated cable to be measured;

[0055] S103: Judge the defect state of the insulated cable section to be measured according to the total number of air-gap discharge phenomena occurring in the insulated cable to be measured.

[0056] Based on the above embodiments, this embodiment elaborates on step S101 in detail:

[0057] In some embodiments, constructing an equivalent circuit model for the air-gap discharge of the insulation layer defect of the target insulated cable includes:

[0058] Construct an equivalent circuit for the air-gap discharge of the insulation layer defect of the target insulated cable, and the equivalent circuit is composed of a series of air-gap defect parts and non-air-gap normal parts inside the insulation layer of the target insulated cable and the remaining parts in parallel;

[0059] Based on the equivalent circuit, construct an equivalent circuit model for the air-gap discharge of the insulation layer defect of the target insulated cable according to the relative permittivity of the target insulated cable.

[0060] It should be noted that the permittivity of the cable insulation layer refers to the permittivity of the same material as the cable insulation layer at the same temperature and the same humidity as the detection scenario.

[0061] In one embodiment, query the relative permittivity ε of the insulated cable sample;

[0062] In some embodiments, through the equivalent circuit model, from the continuity of current, it can be obtained that:

[0063]

[0064] In the formula, U 1 , U 2 are the partial voltages of the air-gap defect part and the non-air-gap normal part respectively, while X 1 and X 2 are the impedance values of the air-gap defect part and the non-air-gap normal part respectively. According to the equivalent circuit, the expressions of X 1 and X 2 are:

[0065]

[0066] Wherein, X 1 and X 2 are the impedance values of the air-gap defect part and the non-air-gap normal part respectively, R 1 and R 2 are the resistance values of the air-gap defect part and the non-air-gap normal part respectively, j is the imaginary unit, w is the power frequency angular velocity, C 1 and C 2 are the equivalent capacitance values of the air-gap defect part and the non-air-gap normal part respectively.

[0067] Among them, ε 0 is the vacuum permittivity, k is the electrostatic constant, S is the equivalent cross-sectional area of the insulating layer, d and L are the equivalent length of the air-gap defect part and the total length of the cable respectively.

[0068] Based on the above embodiments, this embodiment will elaborate on step S102:

[0069] This embodiment selects a certain length of cable and arranges circular electrodes at both ends of the insulating cable to be measured;

[0070] In some embodiments, the electrodes at both ends of the insulating cable segment to be measured are repeatedly excited to apply a power frequency voltage to the insulating cable segment to be measured so that the peak value of the air-gap field strength in the equivalent circuit reaches a preset threshold, and the number of times of the air-gap discharge phenomenon (i.e., current mutation) occurring in the insulating cable to be measured is recorded, including:

[0071] Step a: After controlling the voltage of the electrodes at both ends of the insulating cable segment to be measured to gradually increase to not less than the peak value of the power frequency voltage, and when the peak value of the air-gap field strength in the equivalent circuit reaches the preset threshold, record the number of times of the air-gap discharge phenomenon occurring in the insulating cable to be measured within the first preset time period;

[0072] Step b: After the recording is completed, control the voltage of the electrodes at both ends of the insulating cable segment to be measured to gradually decrease to 0V;

[0073] Step c: Repeat steps a - b every second preset time period;

[0074] Step d: Statistically count the total number of times of the air-gap discharge phenomenon occurring in the insulating cable to be measured.

[0075] In a specific embodiment, the preset threshold is 30 KV / cm, which can be adjusted according to the actual situation, and the specific value is not limited in this embodiment.

[0076] In some embodiments, the peak value U of the power frequency voltage is not less than the field strength E 1The product of the total length of the cable, or not less than the field strength E of the normal part of the non-air gap 2 The product of the cable length and the ratio of the relative dielectric constant of the air gap defect part to the non-air gap normal part ε; The method for confirming the power frequency voltage peak is as follows:

[0077] Depend on:

[0078]

[0079] We can get:

[0080]

[0081] That is, the ratio of the field strengths of the two depends only on the ratio of their relative dielectric constants. Since d is extremely small compared to L, we can get:

[0082]

[0083] That is, the peak value of the power frequency voltage should not be less than the above calculation result.

[0084] In a specific embodiment, the first preset time length may be, for example, 10 seconds, which may be adjusted according to actual conditions. The present embodiment does not specifically limit its value. Specifically, the voltage across the electrodes is slowly increased to a value not lower than the peak voltage value calculated above, and 10 seconds are waited to observe whether air gap discharge occurs across the electrodes (i.e., a sudden change in current). If discharge occurs, it is recorded. Then the electrode voltage is gradually reduced to 0V, and the above experiment is performed again after a certain period of time.

[0085] Based on the above embodiments, this embodiment describes step S103 in detail:

[0086] The air gap discharge probability can be obtained by the ratio of the discharge number to the test number, and it can be judged whether the width of the equivalent air gap defect is greater than a given threshold, and then whether the insulation condition of the cable section is good.

[0087] In some embodiments, judging the defect state of the insulated cable segment to be tested according to the total number of times the air gap discharge phenomenon occurs in the insulated cable to be tested includes:

[0088] When the total number of times is not greater than a preset upper limit, it is determined that the insulation layer defect of the target insulated cable is relatively small;

[0089] When the total number of times is greater than a preset upper limit, it is determined that the insulation layer of the target insulated cable has a large defect.

[0090] In a specific embodiment, the number of experiments can be, for example, 10 times, and the preset upper limit can be, for example, 5 times. It can be adjusted according to the actual situation, and this embodiment does not make specific limitations in this regard. Specifically, after repeating the above experiment 10 times, count the number of times of air-gap discharge. If the number of discharges is less than 5 times, it is considered that the insulation layer defect of the insulated cable is small; otherwise, it is considered that the insulation defect of the insulated cable is large.

[0091] Based on the above embodiments, after determining that the insulation layer of the target insulated cable has a large defect, it includes:

[0092] Control the electrodes at both ends of the insulated cable section to be measured to slide the same unit distance in the same direction step by step according to the cable line;

[0093] Control the electrodes to detect the number of times of air-gap discharge phenomenon in the insulated cable section between the current electrodes every time they slide until the detection of the entire cable section is completed;

[0094] Locate the insulated cable section where the number of times of air-gap discharge phenomenon exceeds the preset upper limit as the defect point.

[0095] In a specific embodiment, the unit distance can be, for example, 10 cm. This embodiment does not make specific limitations in this regard. Specifically, perform the air-gap discharge detection as described in step S102 on the cable to be measured every 10 cm, and gradually identify the insulation layer defects of each cable section by observing the discharge phenomenon, thereby identifying the insulation layer defects of the entire cable section and locating the defect points.

[0096] Based on the above embodiments, this embodiment will illustrate the present invention in detail with specific experiments:

[0097] Step S1: The insulating layer material of the cable to be measured is cross-linked polyethylene material, and the dielectric constant ∈ = 2.2 of the cable to be measured is obtained. Based on this, an equivalent circuit model of the insulated cable and its defects is established as Figure 2 shown as

[0098] In the figure, R 1 , R 2 are the resistance values of the non-air-gap part and the air-gap part respectively, C 1 , C 2 are the equivalent capacitance values of the non-air-gap part and the air-gap part respectively, R 3 , C 3 are the resistance and equivalent capacitance values of the rest in parallel with these two parts.

[0099] In the figure, the expressions of C 1 and C 2 are:

[0100]

[0101] ∈ 0ε₀ is the vacuum permittivity, k is the electrostatic constant, S is the equivalent cross-sectional area of the insulating layer, and d and L are the equivalent length of the air gap part and the total length of the cable, respectively.

[0102] Step S2: Select a cable with a length of 10 cm and arrange annular electrodes at both ends of the insulated cable.

[0103] Step S3: Apply voltage at both ends of the electrode so that the air gap field strength in the corresponding model is not less than 30 KV / cm, and observe whether there is air gap discharge during the voltage application process. The specific applied voltage is calculated by the following formula:

[0104]

[0105] Since the cable is scanned every 10 cm, the applied voltage can be calculated to be 660 KV.

[0106] Step S4: As shown in Table 1, repeat the above voltage application process ten times and record the number of times of air gap discharge. If the number of discharges is less than 5 times, it is considered that the insulation layer defect of the cable is small and no subsequent positioning operation is required. If the number of occurrences is greater than or equal to 5 times, it is considered that the insulation layer defect of the cable is large. The number of discharges finally measured in this experiment is 7 times, so it is considered that the insulation layer defect of the cable is large and the next positioning operation is required.

[0107] Table 1 Test results of Experiment 1

[0108]

[0109]

[0110] Step S5: Conduct a scan of the insulation layer defect along the cable extension direction. The specific method is as follows:

[0111] Install the electrode on a trolley along the cable line track, and conduct the air gap discharge detection as described in Step S3 every 10 cm for the cable to be tested. By observing the discharge phenomenon and recording the number of air gap discharges, gradually identify the insulation layer defect of each section of the cable through Step S4. After the identification is completed, the trolley moves forward 10 cm, and then execute the above detection process again, and thus locate the defect point.

[0112] In this example, the specific positioning operation is as shown in the following table:

[0113] The position of an initial electrode (denoted as electrode A) is the coordinate zero point, and the direction from this electrode to another electrode (denoted as electrode B) is the positive direction. Conduct the discharge test as shown in Table 2:

[0114] Table 2 Test results of Experiment 2

[0115] Position of Electrode A / cm Position of Electrode B / cm Applied Voltage / kV Is the number of discharges greater than 5 times? 0 10 663.4 No 10 20 673.1 No 20 30 668.1 Yes 30 40 664.2 No 40 50 668.0 No 50 60 664.3 No 60 70 665.6 No 70 80 660.5 No 80 90 661.8 No 90 100 666.2 No

[0116] The position range of the insulation layer defect finally obtained in this example is (20 cm, 30 cm), and the error is less than 10 cm. It can be seen that this method can effectively locate the defects of the cable insulation layer, and the test device is simple and the positioning accuracy is high.

[0117] The embodiment of the present invention also provides a device for identifying and locating defects in a cable insulation layer; the specific device may include:

[0118] An equivalent circuit model construction module, configured to construct an equivalent circuit model for the air gap discharge of the insulation layer defect of the target insulated cable;

[0119] A voltage application test module, configured to repeatedly excite the electrodes at both ends of the insulated cable segment to be tested to apply a power frequency voltage to the insulated cable segment to be tested so that the peak value of the air gap field strength in the equivalent circuit reaches a preset threshold, and record the number of times of air gap discharge phenomena occurring in the insulated cable to be tested;

[0120] A defect detection module, configured to judge the defect state of the insulated cable segment to be tested according to the total number of times of air gap discharge phenomena occurring in the insulated cable to be tested.

[0121] Based on the above embodiments, the equivalent circuit model construction module includes:

[0122] An equivalent circuit construction unit, configured to construct an equivalent circuit for the air gap discharge of the insulation layer defect of the target insulated cable, and the equivalent circuit is composed of an air gap defect part, a non-air gap normal part and the remaining part connected in series inside the insulation layer of the target insulated cable and connected in parallel;

[0123] An equivalent circuit model construction unit, configured to construct an equivalent circuit model for the air gap discharge of the insulation layer defect of the target insulated cable based on the equivalent circuit according to the relative permittivity of the target insulated cable.

[0124] Based on the above embodiments, the voltage application test module includes:

[0125] A voltage application test unit, configured to control the voltage of the electrodes at both ends of the insulated cable segment to be tested to gradually rise to not less than the peak value of the power frequency voltage, and after the peak value of the air gap field strength in the equivalent circuit reaches a preset threshold, record the number of times of air gap discharge phenomena occurring in the insulated cable to be tested within a first preset time period; after the recording is completed, control the voltage of the electrodes at both ends of the insulated cable segment to be tested to gradually drop to 0 V;

[0126] A loop control unit, configured to repeat steps a-b every second preset time period;

[0127] A statistics unit, configured to count the total number of times of air gap discharge phenomena occurring in the insulated cable to be tested.

[0128] Based on the above embodiments, the defect detection module includes:

[0129] A first detection unit, configured to determine that the defect of the insulating layer of the target insulating cable is small when the total number of times does not exceed a preset upper limit;

[0130] A second detection unit, configured to determine that the defect of the insulating layer of the target insulating cable is large when the total number of times exceeds the preset upper limit.

[0131] Based on the above embodiments, the device further includes a defect location module, and the defect location module includes:

[0132] A judgment unit, configured to perform a defect location operation when it is determined that the defect of the insulating layer of the target insulating cable is large;

[0133] An electrode sliding control unit, configured to control the electrodes at both ends of the insulating cable section to be measured to slide in the same direction by the same unit distance step by step along the cable line;

[0134] A sliding detection unit, configured to control the electrodes to detect the number of times of air gap discharge phenomenon occurring in the insulating cable section between the current electrodes each time the electrodes slide, until the detection of the entire cable section is completed;

[0135] A defect location unit, configured to locate the insulating cable section where the number of times of air gap discharge phenomenon exceeds the preset upper limit as the defect point.

[0136] As Figure 3 , a specific embodiment of the present invention further provides a cable insulating layer defect identification and location system, which is characterized by including:

[0137] A voltage source;

[0138] A voltage regulating device, connected to the voltage source;

[0139] Electrodes, connected to the voltage regulating device;

[0140] A trolley having a track identical to the target insulating cable line and its control device, connected to the electrodes;

[0141] A cable insulating layer defect identification and location device as described above, connected to the voltage regulating device and the control device of the trolley.

[0142] A specific embodiment of the present invention further provides a cable insulating layer defect identification and location device, including: a memory for storing a computer program; a processor for implementing the steps of the above-mentioned cable insulating layer defect identification and location method when executing the computer program.

[0143] A specific embodiment of the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned method for identifying and locating cable insulation layer defects are implemented.

[0144] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0145] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0146] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device implements the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0147] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Therefore, the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0148] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A method for identifying and locating defects in cable insulation layers, characterized in that: include: Construct an equivalent circuit model of air gap discharge in insulation layer defects of target insulated cables; Repeatedly stimulating the electrodes at both ends of the insulated cable segment to be tested to apply a power frequency voltage to the insulated cable segment to be tested so that the peak value of the air gap field intensity in the equivalent circuit reaches a preset threshold value, and recording the number of times the air gap discharge phenomenon occurs in the insulated cable to be tested; The defect state of the insulated cable section to be tested is determined according to the total number of times the air gap discharge phenomenon occurs in the insulated cable to be tested.

2. The cable insulation layer defect identification and positioning method according to claim 1, characterized in that: The equivalent circuit model of the insulation layer defect air gap discharge of the target insulated cable is constructed as follows: Constructing an equivalent circuit of the air gap discharge of the insulation layer defect of the target insulated cable, wherein the equivalent circuit is composed of the air gap defect part connected in series and the non-air gap normal part connected in parallel with the remaining part inside the insulation layer of the target insulated cable; Based on the equivalent circuit, an equivalent circuit model of air gap discharge of insulation layer defects of the target insulation cable is constructed according to the relative dielectric constant of the target insulation cable.

3. The cable insulation layer defect identification and positioning method according to claim 1, characterized in that: The peak value of the power frequency voltage is not less than the product of the field strength of the air gap defective part and the total length of the cable, or is not less than the product of the field strength of the non-air gap normal part and the cable length and the ratio of the relative dielectric constant of the air gap defective part to the non-air gap normal part.

4. The cable insulation layer defect identification and positioning method according to claim 3 is characterized in that: The repeatedly exciting the electrodes at both ends of the insulated cable segment to be tested to apply a power frequency voltage to the insulated cable segment to be tested so that the peak value of the air gap field intensity in the equivalent circuit reaches a preset threshold value, and recording the number of times the air gap discharge phenomenon occurs in the insulated cable to be tested includes: Step a: After controlling the voltage of the electrodes at both ends of the insulated cable segment to be tested to gradually increase to a value not lower than the peak value of the power frequency voltage, and after making the peak value of the air gap field strength in the equivalent circuit reach a preset threshold value, the number of times the air gap discharge phenomenon occurs in the insulated cable to be tested within a first preset time length is recorded; Step b: After recording is completed, the voltage of the electrodes at both ends of the insulated cable segment to be tested is controlled to gradually decrease to 0V; Step c: Repeat steps ab at intervals of a second preset time length; Step d: Count the total number of times the air gap discharge phenomenon occurs in the insulated cable to be tested.

5. The cable insulation layer defect identification and positioning method according to claim 1, characterized in that: The method of judging the defect state of the insulated cable section to be tested according to the total number of times the air gap discharge phenomenon occurs in the insulated cable to be tested comprises: When the total number of times is not greater than a preset upper limit, it is determined that the insulation layer defect of the target insulated cable is relatively small; When the total number of times is greater than a preset upper limit, it is determined that the insulation layer of the target insulated cable has a large defect.

6. The cable insulation layer defect identification and location method according to claim 5, characterized in that: The step of determining that the insulation layer of the target insulated cable has a large defect includes: Control the electrodes at both ends of the insulated cable segment to be tested to slide gradually in the same direction by the same unit distance according to the cable route; Each time the electrodes slide, the number of times the air gap discharge occurs in the insulated cable segment between the current electrodes is detected until the detection of the entire cable segment is completed; The insulated cable section where the number of air gap discharge phenomena exceeds a preset upper limit is located as a defect point.

7. A cable insulation layer defect identification and positioning device, characterized in that: include: An equivalent circuit model building module is used to build an equivalent circuit model of air gap discharge of insulation layer defects of target insulated cables; A pressure test module is used to repeatedly stimulate the electrodes at both ends of the insulated cable segment to be tested to apply a power frequency voltage to the insulated cable segment to be tested so that the peak value of the air gap field intensity in the equivalent circuit reaches a preset threshold value, and record the number of times the air gap discharge phenomenon occurs in the insulated cable to be tested; The defect detection module is used to determine the defect state of the insulated cable section to be tested according to the total number of times the air gap discharge phenomenon occurs in the insulated cable to be tested.

8. The cable insulation layer defect identification and positioning device according to claim 7, characterized in that: The defect detection module comprises: A first detection unit, configured to determine that the defect of the insulation layer of the target insulated cable is small when the total number of times is not greater than a preset upper limit; The second detection unit is used to determine that the insulation layer of the target insulated cable has a large defect when the total number of times is greater than a preset upper limit.

9. The cable insulation layer defect identification and positioning device according to claim 8, characterized in that: The cable insulation layer defect identification and positioning device further includes a defect positioning module, and the defect positioning module includes: A judgment unit, used to determine that when the insulation layer defect of the target insulated cable is relatively large, a defect location operation is performed; The electrode sliding control unit is used to control the electrodes at both ends of the insulated cable segment to be tested to slide gradually in the same direction by the same unit distance according to the cable line; A sliding detection unit, used to control the electrodes to slide each time, and detect the number of times the air gap discharge phenomenon occurs in the insulated cable segment between the current electrodes until the detection of the entire cable segment is completed; The defect location unit is used to locate the insulated cable section where the number of air gap discharge phenomena exceeds a preset upper limit as a defect point.

10. A cable insulation layer defect identification and positioning system, characterized in that: include: Voltage source; A voltage regulating device connected to the voltage source; an electrode connected to the voltage regulating device; A trolley having the same track as the target insulated cable line and a control device thereof, connected to the electrode; A cable insulation layer defect identification and positioning device as described in claim 9, connected to the voltage regulating device and the control device of the trolley.

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