A high-voltage cable for detecting space charge on-line, a detection method and a manufacturing method

Abstract

The application provides a high-voltage cable for detecting space charge, a detection method and a manufacturing method. The outer sheath is provided with two second circumferential seams and three second axial seams; the two side edges of the fixed sheath part are hinged to the connecting side edges of two detachable outer sheath blocks, and a switching mechanism is arranged between the opening and closing side edges of the two detachable outer sheath blocks; and the buffer sleeve is provided with two spaced first circumferential seams and a first axial seam. The outer sheath is divided into a fixed sheath part and two detachable outer sheath blocks, so as to form an openable and closable detection window; the fixed sheath part is integrally connected with the outer sheath, and the two detachable outer sheath blocks are hinged to the fixed sheath part, so that the detection window can be quickly opened and closed, and the switching mechanism is locked to cooperate with the first circumferential seam and the first axial seam of the buffer sleeve, so that the buffer sleeve can be opened synchronously with the detection window.

Description

Technical Field

[0001] This invention relates to the field of power equipment testing technology, and more specifically, to a high-voltage cable for online detection of space charge, a testing method, and a manufacturing method. Background Technology

[0002] The accumulation of space charge inside the main insulation of high-voltage cables is one of the key factors leading to insulation aging and breakdown faults. Long-term accumulation of space charge distorts the electric field distribution, accelerates the deterioration of insulation materials, and in severe cases, can cause partial discharge or even insulation breakdown, directly threatening the safe and stable operation of the power grid. In recent years, with the widespread application of high-voltage direct current (HVDC) transmission technology, the problem of space charge accumulation in the main insulation of 110kV and above high-voltage cables has become increasingly prominent, becoming a key cause of cable breakdown faults. After a fault occurs, the entire cable line needs to be replaced, which is not only costly and time-consuming to repair, but also seriously affects the reliability of power supply and the normal operation of cities. Therefore, regular detection of space charge in the main insulation of high-voltage cables is an important means of predicting the insulation condition of cables and preventing faults. Research on online non-destructive testing technology for space charge in the main insulation of high-voltage cables has significant engineering implications.

[0003] Current technologies for detecting space charge in the main insulation of high-voltage cables mainly include thermal diffusion method, pressure wave method, electroacoustic pulse method, and photoelectric method. Among these, the electroacoustic pulse method (PEA) utilizes high-frequency narrow pulses to induce mechanical displacement of the charge. By receiving the acoustic signal generated by this mechanical displacement and converting it into an electrical signal, the distribution of space charge can be determined. This method is currently the most widely used space charge measurement method.

[0004] Current research on electroacoustic pulse methods largely focuses on offline detection techniques, while online detection methods require further exploration. Existing detection schemes mainly suffer from the following two types of technical limitations: The first type is offline sample collection and testing, which requires removing the cable from the line. This not only interrupts the power supply and affects the normal power supply of the power grid, but also deviates from the actual operating conditions such as load and temperature. The measurement results deviate from the actual charge accumulation state, and the testing process is cumbersome and inefficient.

[0005] The second category is online detection methods. Existing online detection solutions are easily obstructed by structures such as the cable's outer sheath and metal shielding layer, resulting in severe signal attenuation and insufficient accuracy in locating and quantitatively analyzing space charge, making it difficult to meet the needs of rapid and efficient on-site detection. Some online detection devices require damaging the cable's surface structure, making post-detection sealing restoration difficult and easily introducing new safety hazards such as moisture intrusion and electric field distortion. Furthermore, the devices have poor structural adaptability, only compatible with specific cable specifications, limiting their versatility.

[0006] Chinese patent CN113740624A discloses an embedded detection device comprising a grounded metal shielding box, a carbon black semiconductor lower electrode, a piezoelectric sensor, and a strap fixing structure. This device embeds the detection components onto the main insulation surface by partially peeling away the cable's outer sheath and shielding layer, and uses an electroacoustic pulse method to collect space charge signals for testing. However, this device requires peeling away the cable's surface structure, and restoration relies on sealant after testing. The sealing performance is difficult to maintain in consistency with the original cable, easily leading to safety hazards such as moisture intrusion and electric field distortion. Furthermore, the peeling and restoration process is time-consuming, affecting detection efficiency.

[0007] In summary, existing technologies for detecting space charge in the main insulation of high-voltage cables suffer from drawbacks. Offline detection requires power outages and cable disconnection, is detached from actual operating conditions, and is inefficient. Online detection, on the other hand, faces limitations such as requiring damage to the cable's surface structure, difficulty in restoration, complex equipment, poor adaptability, and insufficient portability. Therefore, achieving rapid, accurate, and online detection of space charge in the main insulation without damaging the cable's main structure or affecting its normal operation is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0008] In view of this, the present invention proposes a high-voltage cable for online detection of space charge, a detection method, and a manufacturing method, aiming to solve the problems of existing offline detection of space charge in the main insulation of high-voltage cables requiring power outage and cable disconnection, and online detection requiring damage to the surface structure, which is difficult to restore, has complex equipment, is cumbersome to operate, and has low detection efficiency.

[0009] On one hand, this invention proposes a high-voltage cable for online detection of space charge. The cable includes: a cable body and a buffer sleeve and an outer sheath sequentially sleeved on the cable body; wherein the outer sheath has two axially spaced second circumferential seams and three circumferentially spaced second axial seams located between the two second circumferential seams, each second axial seam extending axially from one of the second circumferential seams to the other; the two circumferential seams and the three axial seams together divide the outer sheath between the two second circumferential seams into three outer sheath blocks; wherein two of the three outer sheath blocks are detachable structures, serving as detection windows on the outer sheath, and the remaining outer sheath block is a fixed sheath portion, fixedly connected to the outer sheath on the cable body; the fixed sheath portion... The two sides of the buffer sleeve are respectively hinged to the connecting sides of the two detachable outer sheath blocks. A switching mechanism is provided between the opening and closing sides of the two detachable outer sheath blocks to control the opening and closing of the two detachable outer sheath blocks. When the switching mechanism is opened, the two detachable outer sheath blocks can rotate and open towards the outer periphery of the cable body. The buffer sleeve is provided with two spaced first circumferential seams and a first axial seam. The first axial seam extends axially from one of the first circumferential seams to the other first circumferential seam. When the two detachable outer sheath blocks are opened outward, the area on the buffer sleeve located between the two first circumferential seams can open from the first axial seam towards the outer periphery of the cable body to expose the surface of the cable body and realize online detection of space charge.

[0010] Furthermore, in the aforementioned high-voltage cable for online detection of space charge, each of the second circumferential seams is an arc segment extending circumferentially, and the fixed sheath portion is integrally connected with the outer sheath on both sides of the two second circumferential seams.

[0011] Furthermore, in the aforementioned high-voltage cable for online detection of space charge, the two second circumferential seams correspond one-to-one with the two first circumferential seams, and the corresponding second circumferential seams and first circumferential seams are located on the same cross-section of the cable body.

[0012] Furthermore, in the aforementioned high-voltage cable for online detection of space charge, the corresponding second circumferential seam and the first circumferential seam are aligned at their starting points and ending points in the circumferential direction.

[0013] Furthermore, in the aforementioned high-voltage cable for online detection of space charge, the central angle of the fixed sheath portion is 90°, and the central angle of both of the two detachable outer sheath blocks is 135°.

[0014] Furthermore, in the aforementioned high-voltage cable for online detection of space charge, the two sides of the fixed sheath are respectively hinged to the connecting sides of the two detachable outer sheath blocks via hinges.

[0015] Furthermore, in the aforementioned high-voltage cable for online detection of space charge, the switching mechanism is a locking structure or a snap-on structure.

[0016] Furthermore, the aforementioned high-voltage cable for online detection of space charge.

[0017] Furthermore, the aforementioned high-voltage cable for online detection of space charge.

[0018] The present invention provides a high-voltage cable for online detection of space charge.

[0019] On the other hand, the present invention proposes an online detection method for space charge in high-voltage cables. The online detection method for high-voltage cables using the aforementioned online space charge detection method includes the following steps: activating the switching mechanism of the high-voltage cable for online space charge detection, causing two detachable outer sheath blocks to rotate and open towards the outer periphery of the cable body; opening the area on the buffer sleeve located between the two first circumferential seams from the first axial seam towards the outer periphery of the cable body, exposing the surface of the cable body; attaching the detection probe to the exposed surface of the cable body, applying an excitation signal, and acquiring the space charge response signal; after detection, resetting the buffer sleeve to wrap around the outer periphery of the cable body, closing the two detachable outer sheath blocks, and locking the switching mechanism to restore the outer sheath structure.

[0020] Furthermore, in the above-mentioned online detection method for space charge in high-voltage cables, the applied excitation signal is a high-frequency narrow pulse electrical signal, which causes mechanical displacement of the space charge inside the main insulation of the cable. The detection probe receives the acoustic wave signal generated by the mechanical displacement of the charge and converts it into an electrical signal to obtain the distribution of space charge.

[0021] Furthermore, this invention proposes a method for manufacturing a high-voltage cable for online detection of space charge. This method includes the following steps: cutting two axially spaced second circumferential slits on the outer sheath of the cable body; cutting three circumferentially spaced second axial slits between the two second circumferential slits; each second axial slit extending axially from one second circumferential slit to the other, thereby dividing the outer sheath between the two second circumferential slits into three outer sheath blocks, where two outer sheath blocks serve as detachable detection windows, and the other as a fixed sheath portion; installing hinge structures between the two sides of the fixed sheath portion and the connecting sides of the two detachable outer sheath blocks; installing a switching mechanism between the opening and closing sides of the two detachable outer sheath blocks; and cutting two spaced first circumferential slits and one first axial slit on the buffer sleeve, the first axial slit extending axially from one first circumferential slit to the other.

[0022] The high-voltage cable, detection method, and manufacturing method for online detection of space charge provided by this invention, by setting two second circumferential seams and three second axial seams on the outer sheath, divides the axial region between the two second circumferential seams of the outer sheath into a fixed sheath part and two detachable outer sheath blocks, forming an openable detection window, avoiding the need to completely cut or peel off the outer sheath to expose the main insulation; by integrally connecting the fixed sheath part with the outer sheath, and hinged the two detachable outer sheath blocks to the fixed sheath part respectively, the detection window can be quickly opened and closed, and locked by a switching mechanism, in conjunction with the first circumferential seam and the first axial seam preset on the buffer sleeve. The design incorporates a gap, allowing the buffer sleeve to open synchronously with the detection window. This enables the exposure and restoration of the main insulation without any auxiliary tools, solving the problems of complex structure, cumbersome operation, and low detection efficiency of existing detection devices. By integrating the detection window into the original outer sheath structure of the cable, the outer sheath can be restored completely after detection simply by closing the sheath block and locking the switch mechanism, eliminating the need for sealant or other restoration processes. This fundamentally avoids the safety hazards of moisture intrusion and electric field distortion. Furthermore, because the fixed sheath section remains continuously connected, the overall strength and sealing performance of the outer sheath are preserved, solving the problems of poor sealing performance and long-term operational risks associated with existing embedded detection devices. Therefore, this embodiment achieves rapid, accurate, and online detection of space charge in the main insulation without power outages, cable disconnection, or damage to the cable's main structure.

[0023] In addition, the cable provided in this embodiment also has the following technical effects: First, by using a hinged and switching mechanism design for the two detachable outer sheath blocks, the operator only needs to perform three steps to expose the main insulation: open the switching mechanism, rotate the sheath block outward, and flip up the buffer sleeve. After the test is completed, the reverse operation can be performed to restore it. No special tools are required throughout the process, making it convenient to operate. A single person can complete the test, which significantly reduces the skill requirements and labor intensity of on-site testing personnel.

[0024] Secondly, the size and central angle ratio of the detection window can be adaptively designed according to the outer diameter of the cable. By adjusting the arc length and axial spacing of the second circumferential seam, it can match cables with different cross-sections of 110kV, 220kV and even higher voltage levels. It has good versatility and strong adaptability and is suitable for cables of different specifications.

[0025] Third, the detection window can directly expose the main insulation surface, and the detection probe can fit closely to it, resulting in high positioning accuracy. This avoids the attenuation and scattering of the acoustic signal by the outer sheath and buffer sleeve, significantly improving the positioning accuracy and quantitative analysis accuracy of space charge, and resulting in less attenuation of the detection signal.

[0026] Fourth, the detection window structure can be repeatedly opened and closed, and the sealing structure can maintain good sealing performance after multiple operations. It can be reused without replacing parts after each test, which greatly reduces the maintenance cost of long-term testing.

[0027] Fifth, the detection window does not change the detection principle of the electroacoustic pulse method or the usage of existing detection probes. It is directly compatible with commercially available PEA detection systems, without the need to develop additional dedicated detection instruments, making it easy to promote and apply in existing cable lines with low promotion difficulty.

[0028] Sixth, the detection window can be opened at any time, and maintenance personnel can conduct periodic or online monitoring of the cable as needed to keep abreast of the dynamics of space charge accumulation, detect latent fault signs such as electric field distortion in advance, provide data support for condition-based maintenance, and effectively reduce the risk of unplanned power outages. Attached Figure Description

[0029] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of the structure of a high-voltage cable for online detection of space charge provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a high-voltage cable for online detection of space charge provided in an embodiment of the present invention; Figure 3A flowchart illustrating the online detection method for space charge in high-voltage cables provided in an embodiment of the present invention; Figure 4 A flowchart illustrating a method for manufacturing a high-voltage cable for online detection of space charge, as provided in an embodiment of the present invention. Explanation of reference numerals in the attached figures: 1-Cable body, 11-Copper conductor, 12-Semi-conductive binding tape, 13-Semi-conductive inner shielding layer, 14-Insulation layer, 15-Semi-conductive outer shielding layer, 2-Buffer sleeve, 3-Outer sheath, 31-Metallic sheath, 32-Outer protective sleeve, 301-Fixed sheath part, 302-Removable outer sheath block, 4-Hinged connector, 5-Switching mechanism, 6-Fixed connector, 7-Detection platform. Detailed Implementation

[0030] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] Cable Example: See Figures 1 to 2 This figure illustrates a preferred structure of a high-voltage cable for online space charge detection provided by an embodiment of the present invention. As shown, the high-voltage cable for online space charge detection includes: a cable body 1 and a buffer sleeve 2 and an outer sheath 3 sequentially sleeved on the cable body 1; wherein, The outer sheath 3 is provided with two axially spaced second circumferential seams and three circumferentially spaced second axial seams located between the two second circumferential seams. Each second axial seam extends axially from one of the second circumferential seams to the other. The two circumferential seams and the three axial seams together divide the outer sheath 3 between the two second circumferential seams into three outer sheath blocks. Among the three outer sheath blocks, two outer sheath blocks are detachable structures and serve as detection windows on the outer sheath 3. The remaining outer sheath block is a fixed sheath part 301, which is fixedly connected to the outer sheath 3 on the cable body 1.

[0032] Specifically, the cable body 1 is the core structure of the high-voltage power cable, including, from the inside out, a copper conductor 11, a semi-conductive binding tape 12, a semi-conductive inner shielding layer 13, an insulation layer 14, and a semi-conductive outer shielding layer 15. A buffer sleeve 2 is fitted around the outer periphery of the cable body 1, typically made of semi-conductive material, such as a semi-conductive tape, a semi-conductive water-resistant tape, or a water-blocking buffer layer, used to buffer mechanical stress, uniformly distribute the electric field, and suppress partial discharge during cable operation. An outer sheath 3 is fitted around the outer periphery of the buffer sleeve 2, and may include, from the inside out, a metal sheath 31 and an outer protective sleeve 32. The outer protective sleeve 32 may be made of insulating materials such as polyethylene or polyvinyl chloride, used to protect the internal structure of the cable from external mechanical damage, moisture intrusion, and environmental corrosion.

[0033] In this embodiment, the second circumferential seam is a cut extending circumferentially along the outer sheath 3. Two second circumferential seams are arranged at intervals along the cable axis so that the outer sheath 3 between the two second circumferential seams forms an arc-shaped cutting zone. In this embodiment, both second circumferential seams are arc segments extending circumferentially to avoid axially cutting the outer sheath 3. Preferably, the starting and ending points of the two second circumferential seams can be aligned. The second axial seam is a cut extending axially along the outer sheath 3. Three second axial seams are distributed at intervals circumferentially. Each second axial seam starts from one second circumferential seam and extends axially along the outer sheath 3 to the other second circumferential seam. In particular, two second axial seams can be respectively set at the starting and ending points of the two second circumferential seams, that is, the two second circumferential seams and the two second axial seams enclose a rectangular cutting area, and the cutting area is separated from the original outer sheath 3. Another section is set within the cutting area, which divides the outer sheath 3 within the cutting area into two independent outer sheath blocks. Each outer sheath block has an arc-shaped plate structure. The outer sheath 3 located axially between the two circumferential seams and outside the cutting area is also an arc-shaped plate structure, which is an integral structure with the original outer sheath 3. That is, it is not cut into a fixed sheath part 301. The fixed sheath part 301 is not completely separated during the cutting process, but remains integrally connected with the original outer sheath 3 of the cable, equivalent to a part of the original outer sheath 3. That is, the fixed sheath part 301 is integrally connected with the outer sheath 3 on both sides of the two second circumferential seams. In this embodiment, the outer protective sleeve 32 blocks in each arc-shaped plate structure can be bonded to the outer wall of the corresponding metal sheath 31. The two arc-shaped plate structure outer sheath blocks are detachable structures, which are located on both sides of the fixed sheath part 301, forming an openable detection window. When space charge detection is required, the two detachable outer sheath blocks 302 can be opened outward to expose the inner buffer sleeve 2; after the detection is completed, the two detachable outer sheath blocks 302 can be closed again to restore the integrity of the outer sheath 3.

[0034] The two sides of the fixed sheath part 301 are respectively hinged to the connecting sides of the two detachable outer sheath blocks 302. A switch mechanism 5 is provided between the opening and closing sides of the two detachable outer sheath blocks 302 to control the opening and closing of the two detachable outer sheath blocks 302. When the switch mechanism 5 is opened, the two detachable outer sheath blocks 302 can be rotated to open in the direction of the outer periphery of the cable body 1.

[0035] Specifically, the fixed sheath 301 is connected to the two detachable outer sheath blocks 302 via a hinge connector 4. In this embodiment, the hinge connector 4 can be a hinge, with one hinge plate fixed to one side wall of the fixed sheath 301 and the other hinge plate fixed to the connecting side wall of the detachable outer sheath block 302. The hinge pin is located outside the fixed sheath 301 and the detachable outer sheath block 302, allowing the detachable outer sheath block 302 to rotate outward around the hinge pin. A switching mechanism 5 is provided between the opening and closing sides (i.e., side walls) of the two detachable outer sheath blocks 302. This switching mechanism 5 can adopt a locking structure, a snap-on structure, or a latching structure, and is used to lock and close the two detachable outer sheath blocks 302 after the test is completed. When testing is required, the operator manually opens the switch mechanism 5 to release the locking state, and then pulls the two detachable outer sheath blocks 302 outward to rotate them around the hinge axis in the direction of the outer periphery of the cable to open them, exposing the inner buffer sleeve 2.

[0036] The buffer sleeve 2 is provided with two spaced first circumferential seams and a first axial seam. The first axial seam extends axially from one of the first circumferential seams to the other first circumferential seam. When the two detachable outer sheath blocks 302 are opened outward, the area on the buffer sleeve 2 located between the two first circumferential seams can be opened from the first axial seam toward the outer periphery of the cable body 1 to expose the surface of the cable body 1 and realize online detection of space charge.

[0037] Specifically, the first circumferential seam on the buffer sleeve 2 extends circumferentially along the buffer sleeve 2. Two first circumferential seams are spaced apart axially, corresponding one-to-one with the second circumferential seams. The positions of the corresponding second circumferential seams and first circumferential seams are also aligned, especially on the same cross-section of the cable body 1, with the starting and ending points aligned circumferentially. This ensures that when the removable outer sheath block on the outer sheath 3 is opened, the corresponding flip-up area on the buffer sleeve 2 can be accurately exposed, facilitating quick positioning of the detection area by operators and improving detection efficiency. Simultaneous cutting is also possible. The first axial seam extends axially along the buffer sleeve 2, with its two ends connecting to the two first circumferential seams, thereby forming an openable detection area on the buffer sleeve 2. In this embodiment, the first axial seam can be located between the starting and ending points of the second circumferential seam, so that the buffer sleeve 2 can be opened outward from both sides of the first axial seam, improving opening efficiency. After the two removable outer sheath blocks on the outer sheath 3 are opened outward, the operator can manually flip or lift the portion of the buffer sleeve 2 located between the two first circumferential seams along the first axial seam, thereby exposing the main insulation surface of the cable body 1. At this time, the detection probe can be directly attached to the exposed surface of the cable body 1, and a high-frequency narrow pulse electrical signal can be applied to cause mechanical displacement of the space charge inside the cable main insulation. The detection probe receives the acoustic wave signal generated by the mechanical displacement of the charge and converts it into an electrical signal, thereby obtaining the space charge distribution and realizing online detection of space charge. It should be noted that each of the second circumferential seams and the first circumferential seams is not a complete annular seam extending around the entire circumference, but rather an arc segment shape, that is, there is a certain interval between the two ends of the seam, and the start and end points of the seam are located within the same circumferential area of ​​the outer sheath 3.

[0038] In this embodiment, the central angle corresponding to the fixed sheath 301 is 90°, and the central angles corresponding to the two detachable outer sheath blocks 302 are 135° respectively.

[0039] Specifically, on the cross-section of the outer sheath 3, the three outer sheath blocks are distributed according to different central angle ratios. The fixed sheath part 301 occupies a 90° central angle, and the two detachable outer sheath blocks 302 each occupy a 135° central angle, which makes the opening area of ​​the detection window larger, making it easier for operators to fully expose the surface of the cable's main insulation for the installation and operation of the detection probe. At the same time, the fixed sheath part 301 maintains a continuous 90° connection area to ensure the overall structural strength and stability of the outer sheath 3.

[0040] In this embodiment, the two detachable outer sheath blocks 302 are provided with sealing structures to form a seal with the fixed sheath part 301 and the outer surface of the cable body 1 after the switch mechanism 5 is closed.

[0041] Specifically, a sealing strip or gasket is provided on the inner edge or connecting contact surface of the detachable outer sheath block 302. The sealing strip can be made of elastic materials such as rubber or silicone. When the two detachable outer sheath blocks 302 are closed and the switching mechanism 5 is locked, the sealing structure fits tightly against the side of the fixed sheath part 301 and the outer surface of the cable body 1, forming a complete sealing system. This ensures that the detection window area has the same waterproof, moisture-proof, and dustproof performance as the original cable outer sheath 3 when closed, avoiding safety hazards such as moisture intrusion and decreased insulation performance introduced by cutting the outer sheath 3.

[0042] In this embodiment, the window opening length is less than or equal to 50cm, and can be particularly 20cm to 30cm. That is to say, the axial seam length is less than or equal to 50cm, and can be particularly 20cm to 30cm.

[0043] In summary, the high-voltage cable for online detection of space charge provided in this embodiment, by setting two second circumferential seams and three second axial seams on the outer sheath 3, divides the axial region of the outer sheath 3 between the two second circumferential seams into a fixed sheath part 301 and two detachable outer sheath blocks 302, forming an openable detection window, thus avoiding the need to completely cut or peel off the outer sheath 3 to expose the main insulation; by integrally connecting the fixed sheath part 301 with the outer sheath 3 and hinged the two detachable outer sheath blocks 302 to the fixed sheath part 301 respectively, the detection window can be quickly opened and closed. At the same time, the switch mechanism 5 is used for locking, and in conjunction with the first circumferential seam and the first axial seam preset on the buffer sleeve 2, the buffer sleeve 2 can be opened synchronously with the detection window, completing the main detection without any auxiliary tools. The insulation exposure and restoration method solves the problems of complex structure, cumbersome operation, and low detection efficiency of existing detection devices. It also addresses the issues of offline detection of space charge in the main insulation of high-voltage cables requiring power outages and cable disconnection, and online detection requiring damage to the surface structure, resulting in difficult restoration, complex devices, cumbersome operation, and low detection efficiency. By integrating the detection window into the original outer sheath 3 structure of the cable, the outer sheath 3 can be restored completely after detection simply by closing the sheath block and locking the switch mechanism 5, without the need for sealant or other restoration processes. This fundamentally avoids the safety hazards of moisture intrusion and electric field distortion. Furthermore, because the fixed sheath part 301 remains continuously connected, the overall strength and sealing performance of the outer sheath 3 are preserved, solving the problems of poor sealing performance and long-term operational risks associated with existing embedded detection devices. Therefore, this embodiment achieves rapid, accurate, and online detection of space charge in the main insulation without power outages and cable disconnection, and without damaging the main cable structure 1.

[0044] In addition, the cable provided in this embodiment also has the following technical effects: First, by using the hinge and switching mechanism 5 design of the two detachable outer sheath blocks 302, the operator only needs to open the switching mechanism 5, rotate the sheath block outward, and flip up the buffer sleeve 2 to expose the main insulation. After the test is completed, the reverse operation can be performed to restore it. No special tools are required throughout the process, making the operation convenient. A single person can complete the test, which significantly reduces the skill requirements and labor intensity of on-site testing personnel.

[0045] Secondly, the size and central angle ratio of the detection window can be adaptively designed according to the outer diameter of the cable. By adjusting the arc length and axial spacing of the second circumferential seam, it can match cables with different cross-sections of 110kV, 220kV and even higher voltage levels. It has good versatility and strong adaptability and is suitable for cables of different specifications.

[0046] Third, the detection window can directly expose the main insulation surface, and the detection probe can fit closely to it, resulting in high positioning accuracy. This avoids the attenuation and scattering of the acoustic signal by the outer sheath 3 and the buffer sleeve 2, significantly improving the positioning accuracy and quantitative analysis accuracy of space charge, and resulting in less attenuation of the detection signal.

[0047] Fourth, the detection window structure can be repeatedly opened and closed, and the sealing structure can maintain good sealing performance after multiple operations. It can be reused without replacing parts after each test, which greatly reduces the maintenance cost of long-term testing.

[0048] Fifth, the detection window does not change the detection principle of the electroacoustic pulse method or the usage of existing detection probes. It is directly compatible with commercially available PEA detection systems, without the need to develop additional dedicated detection instruments, making it easy to promote and apply in existing cable lines with low promotion difficulty.

[0049] Sixth, the detection window can be opened at any time, and maintenance personnel can conduct periodic or online monitoring of the cable as needed to keep abreast of the dynamics of space charge accumulation, detect latent fault signs such as electric field distortion in advance, provide data support for condition-based maintenance, and effectively reduce the risk of unplanned power outages.

[0050] Example of detection method: See Figure 3 This is a flowchart illustrating the online detection method for space charge in high-voltage cables provided in this embodiment of the invention. The detection method uses the aforementioned online space charge detection high-voltage cable to perform online detection of space charge in the high-voltage cable. As shown in the figure, the detection method includes the following steps: Step S201: Open the sheath window by activating the switching mechanism of the high-voltage cable for online detection of space charge, causing the two detachable outer sheath blocks to rotate and open towards the outer periphery of the cable body.

[0051] Specifically, preparatory work before testing can begin. First, confirm that the high-voltage cable is in operation, and record current load current, ambient temperature, and other operating parameters. Clean dust and debris from the surface of the testing window, and check the sealing condition of the hinges and switch mechanism 5 to ensure there is no moisture or damage. Prepare the space charge detection equipment, adjust the equipment parameters, and ensure the compatibility of the detection probe with the cable's main insulation, i.e., the cable body 1. Next, open the sheath window. First, locate the switch mechanism 5, manually release the locking state, and then pull outwards the two detachable outer sheath blocks 302, causing them to rotate around the hinge axis to open. Figure 2 The right-side detachable outer sheath block 302 rotates clockwise, while the left-side detachable outer sheath block 302 rotates counterclockwise. Because the detachable outer sheath blocks 302 are connected to the fixed sheath part 301 via hinges, the rotation process is smooth and stable. The two detachable outer sheath blocks 302, when opened, are located on either side of the cable body 1 (e.g., Figure 2 (As shown on the left and right sides), revealing the inner buffer sleeve 2.

[0052] In step S202, the inner window is opened by opening the area between the two first circumferential seams on the buffer sleeve from the first axial seam toward the outer periphery of the cable body, exposing the surface of the cable body.

[0053] Specifically, locate the first axial seam on the buffer sleeve 2, and manually fold or lift the portion of the buffer sleeve 2 located between the two first circumferential seams outwards along the first axial seam. Because the buffer sleeve 2 has a certain degree of flexibility, it remains open after being folded up, exposing the main insulation surface of the cable body 1. At this point, the detection window is fully open, and the detection probe installation position is ready. The high-voltage cable can be placed on the detection platform 7 and secured using the fixing connector 6. The fixing connector 6 can be a binding strap, which can pass through the second circumferential seam where the two hinges are located, and wrap around the folded or lifted buffer sleeve 2, i.e., between the buffer sleeve 2 and the cable body 1, and secure it to the detection platform 7.

[0054] In the online detection step S203, the detection probe is attached to the exposed surface of the cable body, an excitation signal is applied, and the space charge response signal is collected.

[0055] Specifically, the electroacoustic pulse detection probe, i.e., the space charge detection probe, is tightly attached to the exposed surface of the main insulation of the cable. After adjusting the probe's position and angle, the detection equipment is started. A high-frequency narrow pulse electrical signal is applied to the main insulation of the cable through the detection probe, causing mechanical displacement of the space charge inside the main insulation. The acoustic signal generated by the charge displacement is received by the piezoelectric sensor in the detection probe. The space charge signal is collected according to preset detection parameters, converted into an electrical signal, and output to the signal processing unit to record the detection data. During the detection process, the cable's operating status is monitored in real time. If any abnormality occurs, the detection is immediately stopped and the detection window is closed. The applied excitation signal is a high-frequency narrow pulse electrical signal that causes mechanical displacement of the space charge inside the main insulation of the cable. The detection probe receives the acoustic signal generated by the mechanical displacement of the charge and converts it into an electrical signal to obtain the space charge distribution.

[0056] In step S204, after the test is completed, the buffer sleeve is reset and wrapped around the outer periphery of the cable body, the two detachable outer sheath blocks are closed and the switch mechanism is locked to restore the outer sheath structure.

[0057] Specifically, after the inspection is completed, the flipped-up buffer sleeve 2 is first re-covered around the outer perimeter of the cable body 1 to restore its original position. Then, the two detachable outer sheath blocks 302 are pushed inward to rotate and close around the hinge axis until the opening and closing sides of the two detachable outer sheath blocks 302 contact each other. Finally, the switch mechanism 5 is operated to lock and fix the two detachable outer sheath blocks 302. Finally, the sealing status of the hinge window and the switch assembly is checked. Because the detachable outer sheath blocks 302 are equipped with a sealing structure, after closing, they can form a reliable seal with the fixed sheath part 301 and the outer surface of the cable body 1, restoring the original protective performance of the cable outer sheath 3. After restoration, the inspection results are recorded, the inspection data and restoration status are compiled, and an inspection report is generated to provide a basis for the detection and evaluation of cable space charge.

[0058] In summary, the online detection method for space charge of high-voltage cables provided in this embodiment divides the axial region between the two second circumferential seams and three second axial seams on the outer sheath 3 into a fixed sheath part 301 and two detachable outer sheath blocks 302, forming an openable detection window. This avoids the need to completely cut or peel off the outer sheath 3 to expose the main insulation. By integrally connecting the fixed sheath part 301 with the outer sheath 3 and hinged the two detachable outer sheath blocks 302 to the fixed sheath part 301, the detection window can be quickly opened and closed. Simultaneously, the switching mechanism 5 locks the window in place, which works in conjunction with the first circumferential seam and the buffer sleeve 2. The first axial slit allows the buffer sleeve 2 to open synchronously with the detection window, enabling the exposure and restoration of the main insulation without any auxiliary tools. This solves the problems of complex structure, cumbersome operation, and low detection efficiency of existing detection devices. By integrating the detection window into the original outer sheath 3 structure of the cable, the outer sheath 3 can be restored to its complete state simply by closing the sheath block and locking the switch mechanism 5 after detection, without the need for applying sealant or other restoration processes. This fundamentally avoids the safety hazards of moisture intrusion and electric field distortion. At the same time, because the fixed sheath part 301 remains continuously connected, the overall strength and sealing performance of the outer sheath 3 are preserved, solving the problems of poor sealing performance and long-term operational risks of existing embedded detection devices. Therefore, this embodiment achieves rapid, accurate, and online detection of space charge in the main insulation without power outages or cable disconnection, and without damaging the structure of the cable body 1.

[0059] Example of manufacturing method: See Figure 4 This is a flowchart illustrating the manufacturing method of a high-voltage cable for online space charge detection provided in this invention. As shown, the manufacturing method mainly includes four steps: cable pretreatment, annular partition marking, hinged window and switch installation, and sealing treatment. The entire process does not damage the core structure of the cable's main insulation and shielding layer. Specifically, it may include the following steps: In cutting step S301, two axially spaced second circumferential seams are cut on the outer sheath outside the cable body, and three circumferentially spaced second axial seams are cut between the two second circumferential seams. Each second axial seam extends axially from one of the second circumferential seams to the other, thereby dividing the outer sheath between the two second circumferential seams into three outer sheath blocks, two of which serve as detachable inspection windows and the other as a fixed sheath part.

[0060] Specifically, the cable is first pre-treated. The high-voltage cable section to be inspected is selected, and dust and oil are cleaned from the cable surface to ensure the outer sheath is free of damage, bulges, or other defects. Considering the cable's operational safety and stability, the window length is typically 20cm to 30cm, and should not exceed 50cm. In other words, the axial gap length should be less than or equal to 50cm, especially 20cm to 30cm. Next, annular zoning is performed using a laser rangefinder and angle marker. Centered on the cable axis, the annular cross-section of the cable in the inspection area is divided into three sector areas with angles of 135°, 135°, and 90° respectively. A special marker pen is used to mark the zoning boundary lines along the cable axis, with the marking length matching the designed length of the inspection window, ensuring clear zoning boundaries and an angle error ≤ ±1°. Finally, cutting is performed. The outer sheath 3 is cut along the two boundary lines of the area using a cable outer sheath 3 circumferential cutter. The cutting depth is equal to the thickness of the outer sheath 3. Specifically, in the area between the two second circumferential seams, three axial seams are cut along the axis, each extending from one second circumferential seam to the other, dividing the outer sheath 3 in this area into three independent outer sheath blocks. The middle outer sheath block is the fixed sheath part 301, and the two outer sheath blocks on either side are the detachable inspection windows.

[0061] In hinge installation step S302, hinge structures are installed between the two sides of the fixed sheath and the connecting sides of the two detachable outer sheath blocks.

[0062] Specifically, one side of the hinge plate is fixed to the side wall of the fixed sheath 301 by screws, rivets or adhesive, and the other side of the hinge plate is fixed to the connecting side, i.e. the side wall, of the detachable outer sheath block 302, so that the detachable outer sheath block 302 can rotate around the hinge axis.

[0063] In switch installation step S303, the switch mechanism is installed between the opening and closing sides of the two removable outer sheath blocks.

[0064] Specifically, locking or snap fastener components are installed on the opening and closing sides of the detachable outer sheath block 302 to ensure that the two detachable outer sheath blocks 302 can be locked and fixed by the switch mechanism 5 after they are closed.

[0065] In the slit cutting step S304, two spaced first circumferential slits and a first axial slit are cut on the buffer sleeve. The first axial slit extends axially from one of the first circumferential slits to the other first circumferential slit.

[0066] Specifically, after the outer sheath 3 is cut to form a detection window, the inner buffer sleeve 2 is cut through the opening on the outer sheath 3. During cutting, it is necessary to ensure that the main insulation layer 14 of the cable body 1 is not damaged. Two first circumferential slits and one first axial slit are cut on the buffer sleeve 2 to form a flip-up detection area, resulting in the aforementioned high-voltage cable for online detection of space charge. When cutting to form two second circumferential slits, the two second circumferential slits are made to correspond one-to-one with the two first circumferential slits and are located on the same cross-section of the cable body 1. That is, when cutting the second circumferential slits on the outer sheath 3, a positioning fixture or visual positioning system is used to ensure that the second circumferential slits correspond axially to the first circumferential slits to be cut on the buffer sleeve 2, so as to ensure that the opening positions of the outer sheath 3 and the buffer sleeve 2 can be accurately aligned when the detection window is opened subsequently.

[0067] For specific cutting methods, please refer to the specific structure of the high-voltage cable for online detection of space charge mentioned above. It will not be described in detail in this embodiment.

[0068] The high-voltage cable and its detection device, detection method, and manufacturing method provided in this embodiment achieve rapid, accurate, and online detection of space charge in the main insulation without damaging the main structure of the cable or affecting its normal operation. This effectively solves the technical problems in the prior art where offline detection requires power outage and cable disconnection, and online detection requires damage to the surface structure and is difficult to restore. It has the advantages of convenient operation, high detection efficiency, good reliability, and wide applicability, and provides strong technical support for high-voltage cable insulation condition assessment and fault prevention.

[0069] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0070] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0071] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A high-voltage cable for online detection of space charge, characterized in that, include: The cable body, and a buffer sleeve and an outer sheath sequentially fitted onto the cable body; wherein... The outer sheath has two axially spaced second circumferential seams and three circumferentially spaced second axial seams located between the two second circumferential seams. Each second axial seam extends axially from one of the second circumferential seams to the other. The two circumferential seams and the three axial seams together divide the outer sheath between the two second circumferential seams into three outer sheath blocks. Among the three outer sheath blocks, two are detachable structures, serving as detection windows on the outer sheath, and the remaining outer sheath block is a fixed sheath part, fixedly connected to the outer sheath on the cable body. The two sides of the fixed sheath are respectively hinged to the connecting sides of the two detachable outer sheath blocks. A switch mechanism is provided between the opening and closing sides of the two detachable outer sheath blocks to control the opening and closing of the two detachable outer sheath blocks. When the switch mechanism is opened, the two detachable outer sheath blocks can rotate to open in the direction of the outer periphery of the cable body. The buffer sleeve is provided with two spaced-apart first circumferential seams and a first axial seam. The first axial seam extends axially from one of the first circumferential seams to the other first circumferential seam. When the two detachable outer sheath blocks are opened outward, the area on the buffer sleeve located between the two first circumferential seams can be opened from the first axial seam toward the outer periphery of the cable body to expose the surface of the cable body and realize online detection of space charge.

2. The high-voltage cable for online detection of space charge according to claim 1, characterized in that, Each of the second circumferential seams is an arc segment extending circumferentially, and the fixed sheath portion is integrally connected with the outer sheaths on both sides of the two second circumferential seams.

3. The high-voltage cable for online detection of space charge according to claim 2, characterized in that, The two second circumferential seams correspond one-to-one with the two first circumferential seams, and the corresponding second circumferential seams and first circumferential seams are located on the same cross-section of the cable body.

4. The high-voltage cable for online detection of space charge according to claim 3, characterized in that, The corresponding second circumferential seam and the first circumferential seam are aligned at their starting points and ending points in the circumferential direction.

5. The high-voltage cable for online detection of space charge according to any one of claims 1 to 4, characterized in that, The central angle of the fixed sheath is 90°, and the central angle of the two detachable outer sheath blocks is 135°.

6. The high-voltage cable for online detection of space charge according to any one of claims 1 to 4, characterized in that, The two sides of the fixed sheath are respectively hinged to the connecting sides of the two detachable outer sheath blocks via hinges.

7. The high-voltage cable for online detection of space charge according to any one of claims 1 to 4, characterized in that, The switching mechanism is a locking structure or a snap-on structure.

8. A method for online detection of space charge in high-voltage cables, characterized in that, The high-voltage cable for online detection of space charge as described in any one of claims 1 to 7 comprises the following steps: The switching mechanism of the high-voltage cable for online detection of space charge is activated, causing the two detachable outer sheath blocks to rotate and open towards the outer periphery of the cable body; Open the area of ​​the buffer sleeve located between the two first circumferential seams from the first axial seam toward the outer periphery of the cable body to expose the surface of the cable body. The detection probe is attached to the exposed surface of the cable body, an excitation signal is applied, and the space charge response signal is collected; After the test is completed, the buffer sleeve is reset and wrapped around the outer periphery of the cable body, the two detachable outer sheath blocks are closed and the switching mechanism is locked to restore the outer sheath structure.

9. The online detection method for space charge in high-voltage cables according to claim 8, characterized in that, The applied excitation signal is a high-frequency narrow pulse electrical signal, which causes mechanical displacement of the space charge inside the main insulation of the cable. The detection probe receives the acoustic signal generated by the mechanical displacement of the charge and converts it into an electrical signal to obtain the space charge distribution.

10. A method for manufacturing a high-voltage cable for online detection of space charge, characterized in that, Includes the following steps: Two axially spaced second circumferential slits are cut into the outer sheath outside the cable body, and three circumferentially spaced second axial slits are cut between the two second circumferential slits. Each second axial slit extends axially from one of the second circumferential slits to the other, thereby dividing the outer sheath between the two second circumferential slits into three outer sheath blocks, two of which serve as detachable inspection windows and the other as a fixed sheath part. Hinges are installed between the two sides of the fixed sheath and the connecting sides of the two detachable outer sheath blocks. A switch mechanism is installed between the opening and closing sides of the two removable outer sheath blocks; Two spaced-apart first circumferential seams and a first axial seam are cut into the buffer sleeve, the first axial seam extending axially from one of the first circumferential seams to the other first circumferential seam.

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