A method for detecting defects in a high-voltage cable buffer layer

Abstract

This invention discloses a method for on-site detection of defects in the buffer layer of high-voltage cables and a novel electrode connector, belonging to the technical field of electrical equipment defect detection. The novel electrode connector includes a metal rod, an insulating shell slidably fitted onto the metal rod, and a pressure block disposed at one end of the metal rod; the pressure block is used to drive the end of the metal rod away from the pressure block to extend out of the insulating shell. This application solves the technical problem of effectively assessing defects in the buffer layer of high-voltage cables by measuring the buffer layer resistance of the high-voltage cable under test and comparing it with the resistance of a normal high-voltage cable buffer layer. Simultaneously, the novel connector avoids contact between the water-blocking strip in the high-voltage cable buffer layer and the metal rod during the measurement process, reducing the influence of the water-blocking strip on the measurement results.

Description

Technical Field

[0001] This invention relates to the field of electrical equipment defect detection, and in particular to a method for on-site detection of defects in the buffer layer of high-voltage cables. Background Technology

[0002] High-voltage cross-linked polyethylene (XLPE) cables are widely used in transmission lines for urban power grids and offshore wind power, and are one of the important pieces of equipment in new power systems. They are typically laid underground and are susceptible to damage from external forces such as municipal engineering projects, leading to moisture intrusion. To prevent water trees from forming on the cable insulation due to moisture, a semi-conductive buffer water-blocking strip is often installed between the insulation shielding layer and the metal sheath of the high-voltage cable as a longitudinal water-blocking buffer layer. This water-blocking strip is filled with water-blocking powder based on sodium polyacrylate.

[0003] When the buffer layer gets wet, its resistivity will increase significantly, leading to overheating and ablation or discharge ablation. At this time, a large number of ablation points and white powder (hereinafter referred to as "white powder") will be generated on the insulation shield, buffer layer and metal sheath of the high-voltage cable.

[0004] Testing revealed that the white powder is a high-resistance insulating material. Because the white powder is distributed between the originally conductive insulating shield layer and the metal sheath, it causes poor electrical contact between the insulating shield layer and the metal sheath. After the cable has been running for a long time, the temperature in some areas becomes too high. The temperature is conducted through the metal sheath, which manifests as a local temperature rise on the outside of the high-voltage cable. The temperature is conducted towards the conductor, which gradually develops into ablation defects, burns the main insulation, and eventually causes the cable body to break down.

[0005] Therefore, after a period of use, high-voltage cables need to undergo defect detection of their buffer layer. Currently, the main methods for detecting ablation defects in the buffer layer of high-voltage cables include partial discharge detection, X-ray digital imaging technology, and infrared thermal imaging detection.

[0006] Regarding the aforementioned technologies, the inventors believe that the shortcomings are as follows: partial discharge detection is easily affected by external electromagnetic signals, resulting in low sensitivity; X-ray digital imaging technology is prone to missing blind spots in the buffer layer imaging during practical use; and infrared thermal imaging detection is easily affected by external environmental factors such as room temperature. Therefore, none of the above three detection methods can effectively assess the defects in the buffer layer of high-voltage cables. Summary of the Invention

[0007] The purpose of this invention is to provide a method for on-site detection of defects in the buffer layer of high-voltage cables and a novel electrode connector, so as to effectively detect defects in the buffer layer of high-voltage cables.

[0008] To achieve the above objectives, the following technical solution is adopted:

[0009] A method for on-site detection of defects in the buffer layer of a high-voltage cable and a novel electrode connector, comprising a metal rod, an insulating shell slidably sleeved on the metal rod, and a pressure block disposed at one end of the metal rod;

[0010] The pressure block is used to drive the end of the metal rod away from the pressure block to extend out of the insulating shell.

[0011] Preferably, the inner wall of the insulating shell is provided with a limiting block for limiting the pressure block, and the limiting block has a through hole for the metal rod to pass through;

[0012] The pressure block is slidably connected to the inner wall of the insulating shell, and when the pressure block abuts against the limiting block, the end of the metal rod away from the pressure block extends out of the insulating shell.

[0013] Preferably, the limiting block is provided with a spring, the end of the spring away from the limiting block is connected to the pressure block, and the spring is sleeved on the outer wall of the metal rod.

[0014] A method for on-site detection of defects in the buffer layer of a high-voltage cable includes the following steps:

[0015] S1. Based on the outline of the corrugated aluminum sheath printed on the outer sheath of the high-voltage cable to be tested, mark the positions of the two corrugated aluminum sheath crests on the outer sheath, and the line connecting the two marks is parallel to the axis of the high-voltage cable.

[0016] S2. Drill holes at the two marked locations respectively, which are the first detection hole and the second detection hole. The drilling direction is perpendicular to the surface of the high-voltage cable. The first detection hole is drilled to the surface of the corrugated aluminum sheath, and the second detection hole is drilled to the surface of the insulation shielding layer.

[0017] S3. Clean the asphalt on the surface of the wrinkled aluminum sheath in the first test hole, and then use a high-pressure air gun to clean the first test hole and the second test hole respectively until the surface of the wrinkled aluminum sheath in the first test hole and the surface of the insulating shielding layer in the second test hole are completely exposed.

[0018] S4. Insert the conventional electrode connector into the first detection hole to make the conventional electrode connector electrically connected to the corrugated aluminum sheath. Insert the end of the new electrode connector away from the pressure block into the second detection hole. When the end of the insulating shell away from the pressure block approaches the insulating shielding layer, press the pressure block to push the metal rod so that the end of the metal rod away from the pressure block extends out of the insulating shell and is electrically connected to the insulating shielding layer.

[0019] S5. Connect the conventional electrode connector and the new electrode connector to the multimeter respectively, and record the resistance value displayed by the multimeter at this time;

[0020] S6. Pull out the conventional electrode connector and the new electrode connector, and repeat S4-S5 until sufficient resistance data is collected. Then, take the average value of the measured data as the contact resistance of the high-voltage cable buffer layer.

[0021] S7. The contact resistance of the high-voltage cable buffer layer is compared with the resistance value of the contact resistance of a normal high-voltage cable buffer layer measured in advance, thereby analyzing the defects of the high-voltage cable buffer layer.

[0022] S8. After the test is completed, disconnect the conventional electrode connector and the new electrode connector, reseal the first and second test holes with lead sealant, and then restore the outer sheath with heat-shrinkable plastic or waterproof tape.

[0023] Preferably, the high-pressure air gun uses inert gas to clean the first and second detection holes.

[0024] Preferably, the normal contact resistance value of the high-voltage cable buffer layer is 500Ω. If the measured contact resistance of the buffer layer is less than 500Ω, it is determined that the high-voltage cable buffer layer has no ablation or moisture defects. If the measured contact resistance of the buffer layer is between 500Ω and 1000Ω, it is determined that the high-voltage cable buffer layer contains a small amount of white powder or that the high-voltage cable has become damp. If the measured contact resistance of the buffer layer is greater than 1000Ω, it is determined that the high-voltage cable buffer layer contains a large amount of white powder or is severely damp, and needs to be repaired in time.

[0025] As can be seen from the above scheme, this invention inserts conventional electrode connectors and novel electrode connectors into a first detection hole and a second detection hole pre-drilled and cleaned on the surface of the high-voltage cable under test, respectively. This electrically connects the conventional electrode connector to the corrugated aluminum sheath and the novel electrode connector to the insulating shielding layer. Subsequently, the resistance of the buffer layer of the high-voltage cable under test is measured using a multimeter electrically connected to both the conventional and novel electrode connectors. By comparing the resistance of the buffer layer of the high-voltage cable under test with that of a normal high-voltage cable, the defects in the buffer layer of the high-voltage cable under test can be quickly analyzed.

[0026] Meanwhile, by measuring the resistance of the high-voltage cable buffer layer to analyze the defects of the buffer layer, the interference of external environmental factors on the measurement data can be effectively reduced, and missed detections can be avoided, thereby effectively assessing the defects of the high-voltage cable buffer layer.

[0027] Furthermore, since both the first and second detection holes are pre-cleaned, the surface of the wrinkled aluminum sheath in the first detection hole and the surface of the insulating shielding layer in the second detection hole are fully exposed, thereby ensuring good electrical contact between the conventional electrode connector and the new electrode connector and avoiding interference from white powder or other insulating impurities in the two detection holes.

[0028] Furthermore, after the new electrode connector is inserted into the second detection hole, the metal rod is extended from the insulating shell by the pressure block. This allows the insulating shell to effectively separate the metal rod from the water-blocking strip in the buffer layer during the insertion of the new electrode connector into the second detection hole, thus avoiding increased measurement error due to contact between the metal rod and the water-blocking strip.

[0029] Furthermore, the measuring instrument is portable and fast because it only uses a multimeter. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a cross-sectional view of the insulating shell of the novel electrode connector in an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the metal rod extending out of the insulating shell in an embodiment of the present invention.

[0033] Figure 3 This is a cross-sectional view of the longitudinal section of the high-voltage cable in an embodiment of the present invention.

[0034] Figure 4 This is a cross-sectional view of the high-voltage cable in an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached drawings: 1. New type of electrode connector; 11. Insulating shell; 12. Limiting block; 13. Pressure block; 14. Spring; 15. Metal rod; 2. Conventional electrode connector; 3. Multimeter; 4. High voltage cable; 41. Outer sheath; 42. Corrugated aluminum sheath; 43. Buffer layer; 44. Insulating shielding layer; 45. Insulating layer; 46. Conductor shielding layer; 47. Conductor. Detailed Implementation

[0036] This invention discloses a method for on-site detection of defects in the buffer layer of high-voltage cables and a novel electrode connector. The following is in conjunction with the appendix... Figure 1-4 The present invention will be described in further detail below.

[0037] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0038] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0039] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0040] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0042] This invention discloses a method for on-site detection of defects in the buffer layer of high-voltage cables and a novel electrode connector.

[0043] Reference Figure 1 A novel electrode connector 1 includes a metal rod 15, a pressure block 13 fixedly connected to one end of the metal rod 15, and an insulating shell 11 slidably sleeved on the metal rod 15, with the pressure block 13 slidably connected to the insulating shell 11.

[0044] When the pressure block 13 is pressed, the pressure block 13 can drive the metal rod 15 to slide inside the insulating shell 11.

[0045] Meanwhile, a limiting block 12 is fixed on the inner wall of the insulating shell 11. The limiting block 12 has a through hole for the metal rod 15 to pass through. In this embodiment, the through hole is adapted to the metal rod 15, and the maximum outline of the pressure block 13 parallel to the opening of the through hole is greater than the diameter of the through hole, so that the pressure block 13 cannot pass through the limiting block 12 through the through hole, thereby limiting the movement of the pressure block 13 by the limiting block 12.

[0046] In addition, a spring 14 is fixed on the side of the limiting block 12 near the pressure block 13. The spring 14 is sleeved on the outside of the metal rod 15, and the end of the spring 14 away from the limiting block 12 is fixedly connected to the pressure block 13.

[0047] Reference Figure 2 When the pressure block 13 is pushed closer to the limit block 12, the end of the metal rod 15 away from the pressure block 13 extends out of the insulating shell 11, at which time the spring 14 is compressed; when the pressure block 13 is released, the spring 14 extends and lifts the pressure block 13 and the metal rod 15, so that the metal rod 15 retracts back into the insulating shell 11.

[0048] Reference Figure 3 and Figure 4 The existing high-voltage cable 4, from the inside out, includes a conductor 47, a conductor 47 shielding layer 46, an insulation layer 45, an insulation shielding layer 44, a buffer layer 43, a corrugated aluminum sheath 42, and an outer sheath 41. A method for on-site detection of defects in the buffer layer of a high-voltage cable includes the following steps:

[0049] S1. Based on the outline of the corrugated aluminum sheath 42 printed on the outer sheath 41 of the high-voltage cable 4 under test, mark the two crest positions of the corrugated aluminum sheath 42 on the outer sheath 41, and the line connecting the two marks is parallel to the axis of the high-voltage cable 4.

[0050] S2. Drill holes at the two marked locations respectively, which are the first detection hole and the second detection hole. The drilling direction is perpendicular to the surface of the high-voltage cable 4. The first detection hole is drilled to the surface of the corrugated aluminum sheath 42, and the second detection hole is drilled to the surface of the insulating shielding layer 44.

[0051] S3. Clean the asphalt on the surface of the wrinkled aluminum sheath 42 in the first detection hole, and then use a high-pressure air gun filled with inert gas to clean the first detection hole and the second detection hole respectively until the surface of the wrinkled aluminum sheath 42 in the first detection hole and the surface of the insulating shielding layer 44 in the second detection hole are completely exposed.

[0052] S4. Insert the conventional electrode connector 2 into the first detection hole to make the conventional electrode connector 2 electrically connected to the corrugated aluminum sheath 42. Insert the end of the new electrode connector 1 away from the pressure block 13 into the second detection hole. When the end of the insulating shell 11 away from the pressure block 13 approaches the insulating shielding layer 44, press the pressure block 13 to push the metal rod 15 so that the end of the metal rod 15 away from the pressure block 13 extends out of the insulating shell 11 and is electrically connected to the insulating shielding layer 44.

[0053] S5. Connect the conventional electrode connector 2 and the new electrode connector 1 to the multimeter 3 respectively, and record the resistance value displayed by the multimeter 3 at this time;

[0054] S6. Release the pressure block 13 so that the pressure block 13 and the metal rod 15 automatically reset under the action of the spring 14. Pull out the conventional electrode connector 2 and the new electrode connector 1. Repeat S4-S5 until sufficient resistance data is collected. Then, take the average value of the measured data as the contact resistance of the buffer layer 43 of the high voltage cable 4.

[0055] S7. Compare the contact resistance of the buffer layer 43 of the high-voltage cable 4 with the pre-measured contact resistance of 500Ω for the normal high-voltage cable 4 buffer layer 43. If the measured contact resistance of the buffer layer 43 is less than 500Ω, it is determined that the high-voltage cable 4 buffer layer 43 has no ablation or moisture defects; if the measured contact resistance of the buffer layer 43 is between 500Ω and 1000Ω, it is determined that the high-voltage cable 4 buffer layer 43 contains a small amount of white powder or the high-voltage cable 4 has been damp; if the measured contact resistance of the buffer layer 43 is greater than 1000Ω, it is determined that the high-voltage cable 4 buffer layer 43 contains a large amount of white powder or is severely damp, and needs to be repaired in time.

[0056] S8. After the test is completed, pull out the conventional electrode connector 2 and the new electrode connector 1, reseal the first test hole and the second test hole with lead sealant, and then restore the outer sheath 41 with heat-shrinkable plastic or waterproof tape.

[0057] In this embodiment, the preferred distance between the first detection hole and the second detection hole is 1m, and the opening size of the first detection hole and the second detection hole is 1cm. 2 .

[0058] The implementation principle of the on-site detection method for defects in the buffer layer of high-voltage cables and the novel electrode joint of this invention is as follows:

[0059] Since the resistance of the buffer layer 43 can be regarded as a series connection of a large number of transverse resistances and a parallel connection of radial resistances, the contact resistance of the buffer layer 43 gradually tends to a certain resistance value as the length of the high-voltage cable 4 increases. Thus, by comparing the resistance of the buffer layer 43 of the high-voltage cable 4 under test with the normal value, the defects of the buffer layer 43 of the high-voltage cable 4 under test can be analyzed.

[0060] Meanwhile, by measuring the resistance of the buffer layer 43 of the high-voltage cable 4, the defect status of the buffer layer 43 can be analyzed, which can effectively reduce the interference of external environmental factors on the measurement data, avoid missed detection, and thus effectively assess the defect status of the buffer layer 43 of the high-voltage cable 4.

[0061] Furthermore, since both the first and second detection holes are pre-cleaned by a high-pressure air gun filled with inert gas, the surface of the wrinkled aluminum sheath 42 in the first detection hole and the surface of the insulating shielding layer 44 in the second detection hole are completely exposed. This ensures good electrical contact between the conventional electrode connector 2 and the novel electrode connector 1, preventing white powder or other insulating impurities in the two detection holes from interfering with the detection. At the same time, the inert gas prevents the gas from reacting with the internal material of the high-voltage cable 4 during air jetting.

[0062] Furthermore, after the new electrode connector 1 is inserted into the second detection hole, the metal rod 15 is extended from the insulating shell 11 by the pressure block 13. This allows the insulating shell 11 to effectively separate the metal rod 15 from the water-blocking strip in the buffer layer 43 during the insertion of the new electrode connector 1 into the second detection hole, thus avoiding increased measurement error due to contact between the metal rod 15 and the water-blocking strip.

[0063] Furthermore, the measuring instrument is easy to carry and has a fast testing speed because it only uses a multimeter 3.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for on-site detection of defects in the buffer layer of high-voltage cables, employing a novel electrode connector, characterized in that... The novel electrode connector includes: a metal rod (15), an insulating shell (11) slidably sleeved on the metal rod (15), and a pressure block (13) disposed at one end of the metal rod (15); The pressure block (13) is used to drive the metal rod (15) to extend out of the insulating shell (11) at one end away from the pressure block (13); Includes the following steps: S1. Based on the outline of the corrugated aluminum sheath (42) printed on the outer sheath (41) of the high-voltage cable (4) to be tested, mark the two crest positions of the corrugated aluminum sheath (42) on the outer sheath (41), and the line connecting the two marks is parallel to the axis of the high-voltage cable (4). S2. Drill holes at the two marked locations respectively, namely the first detection hole and the second detection hole. The drilling direction is perpendicular to the surface of the high-voltage cable (4). The first detection hole is drilled to the surface of the wrinkled aluminum sheath (42), and the second detection hole is drilled to the surface of the insulating shielding layer (44). S3. Clean the asphalt on the surface of the wrinkled aluminum sheath (42) in the first detection hole, and then use a high-pressure air gun to clean the first detection hole and the second detection hole respectively until the surface of the wrinkled aluminum sheath (42) in the first detection hole and the surface of the insulating shielding layer (44) in the second detection hole are completely exposed. S4. Insert the conventional electrode connector (2) into the first detection hole to make the conventional electrode connector (2) electrically connected to the corrugated aluminum sheath (42). Insert the end of the new electrode connector (1) away from the pressure block (13) into the second detection hole. When the end of the insulating shell (11) away from the pressure block (13) approaches the insulating shielding layer (44), press the pressure block (13) to push the metal rod (15) so that the end of the metal rod (15) away from the pressure block (13) extends out of the insulating shell (11) and is electrically connected to the insulating shielding layer (44). S5. Connect the conventional electrode connector (2) and the new electrode connector (1) to the multimeter (3) respectively, and record the resistance value displayed by the multimeter (3) at this time; S6. Pull out the conventional electrode connector (2) and the new electrode connector (1), repeat S4-S5 until sufficient resistance data is collected, and then use the average value of the measured data as the contact resistance of the buffer layer (43) of the high-voltage cable (4); S7. The contact resistance of the buffer layer (43) of the high-voltage cable (4) is compared with the resistance value of the contact resistance of the buffer layer (43) of the normal high-voltage cable (4) in advance to analyze the defects of the buffer layer (43) of the high-voltage cable (4); S8. After the test is completed, pull out the conventional electrode connector (2) and the new electrode connector (1), reseal the first test hole and the second test hole with lead sealant, and then restore the outer sheath (41) with heat shrink plastic or waterproof tape.

2. The method for detecting defects in a buffer layer of a high voltage cable in situ according to claim 1, characterized in that: The high-pressure air gun uses inert gas to clean the first and second detection holes.

3. The method for detecting defects in a buffer layer of a high voltage cable in situ according to claim 1, characterized in that: The contact resistance value of the buffer layer (43) of the normal high-voltage cable (4) is 500Ω. If the measured contact resistance of the buffer layer (43) is less than 500Ω, it is determined that the buffer layer (43) of the high-voltage cable (4) has no defects of burning or moisture. If the measured contact resistance of the buffer layer (43) is between 500Ω and 1000Ω, it is determined that there is a small amount of white powder in the buffer layer (43) of the high-voltage cable (4) or the high-voltage cable (4) has been damp. If the measured contact resistance of the buffer layer (43) is greater than 1000Ω, it is determined that there is a large amount of white powder in the buffer layer (43) of the high-voltage cable (4) or it is severely damp, and it needs to be repaired in time.

4. The method for detecting defects in a buffer layer of a high voltage cable in situ according to claim 1, characterized in that: The inner wall of the insulating shell (11) is provided with a limiting block (12) for limiting the pressure block (13), and the limiting block (12) has a through hole for the metal rod (15) to pass through. The pressure block (13) is slidably connected to the inner wall of the insulating shell (11), and when the pressure block (13) abuts against the limiting block (12), the end of the metal rod (15) away from the pressure block (13) extends out of the insulating shell (11).

5. The method for detecting defects in a buffer layer of a high voltage cable in situ according to claim 4, characterized in that: The limiting block (12) is provided with a spring (14), and one end of the spring (14) away from the limiting block (12) is connected to the pressure block (13). The spring (14) is sleeved on the outer wall of the metal rod (15).

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