A detection method for a rapid detection device for cross-linked polyethylene cable water tree resistance

Abstract

The present invention specifically relates to a detection method for a rapid detection device for the water tree resistance of a cross-linked polyethylene cable, and belongs to the technical field of power cable insulation detection. The problem to be solved is to provide a detection method for a detection device that can quickly detect and evaluate the water tree resistance of a cross-linked polyethylene cable. The technical scheme adopted is: an organic glass cylinder inside a constant temperature box is arranged above an insulating base, a NaCl solution is contained in the organic glass cylinder, an upper port cover thereof is closed with an organic glass cover, a copper electrode penetrates the organic glass cover, the upper end of the copper electrode is grounded, a plurality of cable samples penetrate the cylinder wall of the organic glass cylinder, one end of the cable sample is connected to a high-voltage fuse through a wire, and the high-voltage fuse is connected to a high-frequency high-voltage power supply through a wire; the present invention can complete the water tree aging test of a plurality of cable samples at one time, and solves the technical problem that the quality of the incoming cables cannot be controlled.

Description

Technical Field

[0001] The invention belongs to the technical field of power cable insulation detection, and in particular relates to a detection method of a rapid detection device for anti-water treeing ability of a cross-linked polyethylene cable. Background Art

[0002] In recent years, power grid companies have experienced a number of large-scale power outages caused by cable breakdown. Many cables often fail prematurely before their design life. Due to the lack of technical means for early detection of cable access, the quality of cables entering the network in the past was uneven, which may lead to premature breakdown accidents. Water tree aging is the main reason for the decline of cable insulation. The water tree resistance of cables has an important impact on the insulation life of cables. Therefore, the water tree resistance of cable insulation is an important indicator of insulation life and long-term operation reliability. Different cable design life and water tree resistance will lead to large differences in cable costs. Manufacturers may sacrifice life and water tree resistance to reduce costs, resulting in the quality of cables entering the network being difficult to guarantee, far from the expected service life. The low quality of cables entering the network has caused great pressure on the later operation and maintenance, increased huge operation and maintenance cost investment, and the later operation risks are uncontrollable.

[0003] The current cable network inspection project only involves some basic properties of the cable, such as geometric parameters, cross-linking degree, flame retardancy and basic electrical parameters, and there is no corresponding rapid detection method for the cable's ability to resist water trees. The detection of cable water tree resistance requires accelerated aging of cable samples, and the existing water tree accelerated aging methods generally take more than 7 days. A water tree aging test obtains fewer samples, and the water tree aging process has poor repeatability, and the effect cannot be guaranteed. The existing water tree accelerated aging method is not suitable for rapid detection of cable water tree resistance. Therefore, how to obtain a considerable number of cable water tree samples and conduct tests in a relatively short period of time is of great significance for the rapid evaluation of cable water tree resistance, which helps to grasp the quality of the incoming cables from the source and improve the reliability of power grid operation. Summary of the invention

[0004] The present invention overcomes the shortcomings of the prior art and provides a detection method for a rapid detection device for the water tree resistance of a cross-linked polyethylene cable, which can quickly detect and evaluate the water tree resistance of the cross-linked polyethylene cable and solve the technical problem that the quality of the incoming cable cannot be controlled.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a rapid detection device for the water tree resistance of a cross-linked polyethylene cable, comprising: a high-frequency high-voltage power supply, a constant temperature box, a high-voltage fuse, a cable sample, an organic glass cylinder, an organic glass cover, a copper electrode, an insulating base and a NaCl solution, wherein the organic glass cylinder is arranged above the insulating base, the organic glass cylinder and the insulating base are fixed inside the constant temperature box, the interior of the organic glass cylinder is filled with the NaCl solution, the upper port of the organic glass cylinder is covered with the openable organic glass cover, the copper electrode passes through the organic glass cover, and the The lower end of the copper electrode is submerged in the NaCl solution, and the upper end of the copper electrode is grounded. There are multiple cable samples arranged axially and horizontally, and the multiple cable samples all penetrate the cylinder walls on opposite sides of the organic glass cylinder, and the cable samples are sealed and connected to the cylinder wall of the organic glass cylinder. The multiple cable samples are evenly arranged on the same horizontal plane, and the NaCl solution submerges the cable samples located inside the organic glass cylinder. One end of each of the cable samples is connected to a high-voltage fuse through a wire, and the multiple high-voltage fuses are connected to the high-frequency high-voltage power supply fixed outside the constant temperature box through a wire.

[0006] The cable sample is formed by stripping, and the cable sample includes: La segment, Lb segment and Lc segment, the Lb segment and Lc segment are two segments, the La segment is located in the middle of the cable sample, one end of the La segment is Lb segment and Lc segment in sequence, the other end of the La segment is Lb segment and Lc segment in sequence, the two Lb segments are symmetrically arranged, the two Lc segments are symmetrically arranged, the outermost layer of the La segment is an outer semi-conductive layer, the outermost layer of the segment is an insulating layer, the outermost layer of the Lc segment is a cable core, the La segment is arranged inside the organic glass cylinder, two rows of pinholes are evenly arranged on the La segment, the deepest point of the pinholes is 2 to 2.5 mm from the inner semi-conductive layer of the cable sample, the two Lb segments penetrate the opposite sides of the organic glass cylinder and are sealed and connected to the cylinder wall of the organic glass cylinder. One of the Lc segments of the cable sample is connected to the high-voltage fuse through a wire.

[0007] A high-voltage bushing is also connected to the wires connecting the plurality of high-voltage fuses and the high-frequency high-voltage power supply, and the high-voltage bushing passes through the wall of the thermostatic box.

[0008] The length ratio of the La segment, the Lb segment and the Lc segment is: La segment: Lb segment: Lc segment = 20:14:1.

[0009] Two rows of through holes are arranged on the two opposite sides of the organic glass cylinder, and the Lb section of the cable sample passes through the corresponding through holes and is sealed and connected by glass glue. The diameter of the through hole is 2mm larger than the diameter of the Lb section of the cable sample, and the distance between each two adjacent through holes in the same row is greater than or equal to 10cm.

[0010] The organic glass cover is provided with a through hole through which the copper electrode passes.

[0011] The distance between every two adjacent pinholes on the cable sample La segment is 1 cm.

[0012] A method for detecting a rapid detection device for anti-water tree capability of a cross-linked polyethylene cable, comprising the following steps:

[0013] 1) Cable sample production:

[0014] Remove the cable outer sheath, steel armor, filler and copper tape to expose the single-phase cable and cut it into small cable samples. Strip the outer semi-conductive layer at both ends of the cable sample to expose the insulation layer, and then strip the insulation layer at the end to expose the cable core. Use a steel needle to reserve two symmetrical rows of pinholes in the middle part of the cable sample where the outer conductive layer is left, with a spacing of about 1 cm between the pinholes.

[0015] 2) Cable sample installation:

[0016] Insert the cable sample prepared in step 1) into the through hole on the side of the organic glass cylinder. Place the outer semi-conductive layer in the middle of the cable sample in the organic glass cylinder. Use glass glue to fill the gap between the through hole and the cable sample to ensure that the solution in the cylinder does not leak out.

[0017] 3) Add NaCl solution:

[0018] Inject a 20% NaCl solution into the plexiglass cylinder, submerge the cable sample in the NaCl solution, insert the copper electrode into the through hole on the plexiglass cover and fix it, place the plexiglass cover on the plexiglass cylinder, and immerse the lower end of the copper electrode in the NaCl solution;

[0019] 4) Wire connection:

[0020] Place the organic glass cylinder and sample prepared in step 3) on the insulating base of the thermostat, use a wire to connect the cable core at one end of the cable sample to the high-voltage fuse, high-voltage bushing, and high-frequency high-voltage power supply, and ground the copper electrode;

[0021] 5) Water tree accelerates aging:

[0022] Set the temperature of the thermostat to 60°C, turn on the high-frequency high-voltage power supply with a voltage of 5kV for 120 hours;

[0023] 6) Result analysis:

[0024] After continuous pressurization for 120 hours, the cable sample is taken out and the cable core is removed. The cable sample is cut into 0.1mm thick slices along the pinhole. The slice sample is placed under a microscope for observation and measurement. The water tree initiation at the pinhole tip and the length and width of the water tree are recorded. For each cable sample, at least ten pinhole water trees should be counted, and the water tree initiation rate, length and width average values ​​should be calculated. The water tree initiation rate and water tree size are compared with the standard values ​​to evaluate the cable's ability to resist water trees.

[0025] Compared with the prior art, the present invention has the following beneficial effects.

[0026] 1. The present invention adopts the method of parallel pressurization of multiple groups of cable samples to carry out water tree aging test, which can complete the water tree aging test of multiple cable samples at one time. Each cable sample can age dozens of water tree samples. This method can reduce the water tree aging time of cable samples by multiples and improve the efficiency by multiples. After a single cable sample is broken down, the high-voltage fuse of the sample branch is disconnected, which will not affect the water tree aging of other cable samples, and the reliability and safety of the test are greatly improved.

[0027] Second, the method of averaging the water tree initiation and water tree size of multiple samples in the present invention can more accurately evaluate the water tree resistance of cable samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] Figure 1 It is a front view of the device for quickly detecting the water tree resistance of cross-linked polyethylene cable according to the present invention.

[0030] Figure 2 It is a top view of the device for quickly detecting the water tree resistance of cross-linked polyethylene cables according to the present invention.

[0031] Figure 3 Schematic diagram of the structure of the cable sample of the present invention.

[0032] Figure 4 It is a left side view of the organic glass cylinder of the present invention.

[0033] In the figure: 1 is a high-frequency high-voltage power supply, 2 is a high-voltage bushing, 3 is a constant temperature box, 4 is a high-voltage fuse, 5 is a cable sample, 6 is a plexiglass cover, 7 is a copper electrode, 8 is an insulating base, 9 is a NaCl solution, 10 is a cable core, 11 is an insulating layer, 12 is an outer semi-conductive layer, 13 is a pinhole, 14 is a through hole, and 15 is a plexiglass cylinder. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific embodiments.

[0035] A cross-linked polyethylene cable water tree resistance rapid detection device, comprising: a high-frequency high-voltage power supply 1, a thermostat 3, a high-voltage fuse 4, a cable sample 5, an organic glass cylinder 15, an organic glass cover 6, a copper electrode 7, an insulating base 8 and a NaCl solution 9, wherein the organic glass cylinder 15 is arranged above the insulating base 8, the organic glass cylinder 15 and the insulating base 8 are fixed inside the thermostat 3, the interior of the organic glass cylinder 15 is filled with the NaCl solution 9, the upper end of the organic glass cylinder 15 is covered with the openable organic glass cover 6, the copper electrode 7 penetrates the organic glass cover 6, and the lower end of the copper electrode 7 is Submerged in the NaCl solution 9, the upper end of the copper electrode 7 is grounded, there are multiple cable samples 5 arranged axially horizontally, the multiple cable samples 5 all penetrate the cylinder walls on opposite sides of the organic glass cylinder 15, and the cable samples 5 are sealed and connected to the cylinder wall of the organic glass cylinder 15, and the multiple cable samples 5 are evenly arranged on the same horizontal plane, the NaCl solution 9 submerges the cable samples 5 located inside the organic glass cylinder 15, one end of each of the cable samples 5 is connected to a high-voltage fuse 4 through a wire, and the multiple high-voltage fuses 4 are connected to the high-frequency high-voltage power supply 1 fixed to the outside of the constant temperature box 3 through a wire.

[0036] The cable sample 5 is formed by stripping, and the cable sample 5 includes: La segment, Lb segment and Lc segment, the Lb segment and Lc segment are two segments, the La segment is located in the middle of the cable sample 5, one end of the La segment is Lb segment and Lc segment in sequence, the other end of the La segment is Lb segment and Lc segment in sequence, the two Lb segments are symmetrically arranged, the two Lc segments are symmetrically arranged, the outermost layer of the La segment is an outer semi-conductive layer 12, the outermost layer of the Lb segment is an insulating layer 11, and the outermost layer of the Lc segment is a cable core 10, the La segment is arranged inside the organic glass cylinder 15, two rows of pinholes 13 are evenly arranged on the La segment, the deepest part of the pinholes 13 is 2 to 2.5 mm away from the inner semi-conductive layer of the cable sample, and the two Lb segments penetrate the cylinder walls of the organic glass cylinder 15 on both sides opposite to each other and are sealed and connected to the cylinder wall of the organic glass cylinder 15. One of the Lc segments of the cable sample 5 is connected to the high-voltage fuse 4 through a wire.

[0037] A high-voltage bushing 2 is also connected to the wires connecting the plurality of high-voltage fuses 4 and the high-frequency high-voltage power supply 1 , and the high-voltage bushing 2 passes through the wall of the thermostatic box 3 .

[0038] The length ratio of the La segment, the Lb segment and the Lc segment is: La segment: Lb segment: Lc segment = 20: 14: 1. The total length of the cable sample 5 is 50 cm, the length of the La segment is 20 cm, the length of the Lb segment is 14 cm, and the length of the Lc segment is 1 cm.

[0039] Two rows of through holes 14 are arranged on the opposite sides of the organic glass cylinder 15. The Lb section of the cable sample 5 passes through the corresponding through holes 14 and is sealed by glass glue. The diameter of the through hole 14 is 2 mm larger than the diameter of the Lb section of the cable sample 5. The distance between each two adjacent through holes 14 in the same row is greater than or equal to 10 cm.

[0040] The organic glass cover 6 is provided with a through hole through which the copper electrode 7 passes.

[0041] The distance between every two adjacent pinholes 13 on the cable sample 5La section is 1 cm.

[0042] A method for detecting a rapid detection device for anti-water tree capability of a cross-linked polyethylene cable, comprising the following steps:

[0043] 1) Cable sample production:

[0044] Remove the outer sheath, steel armor, filler and copper tape of the cable to expose the single-phase cable and cut it into small sections of cable samples about 50 cm long. Strip the outer semi-conductive layer at both ends of the cable sample to expose the insulation layer, and then strip the insulation layer at the end to expose the cable core. Use a steel needle to reserve two symmetrical rows of pinholes in the middle part of the cable sample where the outer conductive layer is left, with a spacing of about 1 cm between the pinholes.

[0045] 2) Cable sample installation:

[0046] Insert the cable sample prepared in step 1) into the through hole on the side of the organic glass cylinder. Place the outer semi-conductive layer in the middle of the cable sample in the organic glass cylinder. Use glass glue to fill the gap between the through hole and the cable sample to ensure that the solution in the cylinder does not leak out.

[0047] 3) Add NaCl solution:

[0048] Inject a 20% NaCl solution into the plexiglass cylinder. The liquid level of the solution should be at least 1 cm higher than the cable sample. Place the copper electrode into the through hole on the plexiglass cover and fix it. Place the plexiglass cover on the plexiglass cylinder. The lower end of the copper electrode should be at least 2 cm submerged in the NaCl solution.

[0049] 4) Wire connection:

[0050] Place the organic glass cylinder and sample prepared in step 3) on the insulating base of the thermostat, use a wire to connect the cable core at one end of the cable sample to the high-voltage fuse, high-voltage bushing, and high-frequency high-voltage power supply, and ground the copper electrode;

[0051] 5) Water tree accelerates aging:

[0052] Set the temperature of the thermostat to 60°C, turn on the high-frequency high-voltage power supply with a voltage of 5kV for 120 hours;

[0053] 6) Result analysis:

[0054] After continuous pressurization for 120 hours, the cable sample is taken out and the cable core is removed. The cable sample is cut into 0.1mm thick slices along the pinhole. The slice sample is placed under a microscope for observation and measurement. The water tree initiation at the pinhole tip and the length and width of the water tree are recorded. For each cable sample, at least ten pinhole water trees should be counted, and the water tree initiation rate, length and width average values ​​should be calculated. The water tree initiation rate and water tree size are compared with the standard values ​​to evaluate the cable's ability to resist water trees.

[0055] The experimental sample data is as follows:

[0056] Pinhole number 1 2 3 4 5 6 7 8 9 10 average value Water tree length (μm) 162.5 203.3 134.0 110.6 99.5 155.7 178.2 205.1 122.6 156.8 152.8 Water tree width (μm) 42.1 65.9 39.1 25.2 16.9 42.1 50.3 72.3 34.2 50.1 43.8

[0057] Conclusion: The water tree initiation rate of the sample is 100%, the average length of the water tree is 152.8μm, and the average width of the water tree is 43.8μm. After a large number of experiments, it is concluded that the standard values ​​for this type of cable are a water tree initiation rate of less than 56%, an average length of the water tree is less than 53.3μm, and an average width of the water tree is less than 12.3μm. The water tree initiation rate, average length of the water tree, and average width of the water tree of this sample are all greater than the standard values, so the sample test failed.

[0058] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Those familiar with the technology may modify or improve the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for detecting a rapid detection device for the water tree resistance of a cross-linked polyethylene cable, the rapid detection device comprising: A high-frequency high-voltage power supply (1), a thermostat (3), a high-voltage fuse (4), a cable sample (5), an organic glass cylinder (15), an organic glass cover (6), a copper electrode (7), an insulating base (8) and a NaCl solution (9), wherein the organic glass cylinder (15) is arranged above the insulating base (8), the organic glass cylinder (15) and the insulating base (8) are fixed inside the thermostat (3), the interior of the organic glass cylinder (15) is filled with the NaCl solution (9), the upper end of the organic glass cylinder (15) is covered with the openable organic glass cover (6), the copper electrode (7) passes through the organic glass cover (6), and the copper electrode (7) The lower end of the cable sample (5) is submerged in the NaCl solution (9), the upper end of the copper electrode (7) is grounded, a plurality of the cable samples (5) are axially arranged horizontally, the plurality of the cable samples (5) all penetrate the cylinder walls of the organic glass cylinder (15) on opposite sides, and the cable samples (5) are sealed and connected to the cylinder wall of the organic glass cylinder (15), the NaCl solution (9) submerges the cable samples (5) located inside the organic glass cylinder (15), one end of each of the cable samples (5) is connected to a high-voltage fuse (4) through a wire, and the plurality of the high-voltage fuses (4) are connected to the high-frequency high-voltage power supply (1) fixed outside the thermostat (3) through a wire; The cable sample (5) comprises: a La segment, an Lb segment and an Lc segment, wherein the Lb segment and the Lc segment are both two segments, the La segment is located in the middle of the cable sample (5), one end of the La segment is the Lb segment and the Lc segment in sequence, and the other end of the La segment is the Lb segment and the Lc segment in sequence, the outermost layer of the La segment is an outer semi-conductive layer (12), the outermost layer of the Lb segment is an insulating layer (11), and the outermost layer of the Lc segment is a cable core (10), the La segment is arranged inside the organic glass cylinder (15), two rows of pinholes (13) are evenly arranged on the La segment, and the two Lb segments penetrate the cylinder walls of the organic glass cylinder (15) on opposite sides and are sealed to the cylinder walls of the organic glass cylinder (15); A high-voltage bushing (2) is also connected to the wires connecting the plurality of high-voltage fuses (4) and the high-frequency high-voltage power supply (1), and the high-voltage bushing (2) penetrates the wall of the thermostatic box (3); It is characterized by comprising the following steps: 1) Cable sample production: Remove the outer sheath, steel armor, filler and copper tape of the cable to expose the single-phase cable and cut it into small cable samples. Strip the outer semi-conductive layer at both ends of the cable sample to expose the insulation layer, then strip the insulation layer at the end to expose the cable core. Use a steel needle to reserve two symmetrical rows of pinholes in the middle part of the cable sample where the outer conductive layer is left; 2) Cable sample installation: Insert the cable sample prepared in step 1) into the through hole on the side of the organic glass cylinder. Place the outer semi-conductive layer in the middle of the cable sample in the organic glass cylinder. Use glass glue to fill the gap between the through hole and the cable sample. 3) Add NaCl solution: Inject a 20% NaCl solution into the plexiglass cylinder, insert a copper electrode into the through hole on the plexiglass cover and fix it, and place the plexiglass cover on the plexiglass cylinder; 4) Wire connection: Place the organic glass cylinder and sample prepared in step 3) on the insulating base of the thermostat, use a wire to connect the cable core at one end of the cable sample to the high-voltage fuse, high-voltage bushing, and high-frequency high-voltage power supply, and ground the copper electrode; 5) Water tree accelerates aging: Set the temperature of the thermostat to 60°C, turn on the high-frequency high-voltage power supply, the voltage is 5kV, and continue for 120 hours; 6) Result analysis: After continuous pressurization for 120 hours, the cable sample was taken out and the cable core was removed. The cable sample was cut into 0.1 mm thick slices along the pinhole. The slice samples were observed and measured under a microscope. The water tree initiation at the pinhole tip and the length and width of the water tree were recorded. The water tree initiation rate and water tree size were compared with the standard values ​​to evaluate the cable's ability to resist water trees.

2. The detection method of a rapid detection device for anti-water treeing ability of cross-linked polyethylene cable according to claim 1 is characterized in that: The length ratio of the La segment, the Lb segment and the Lc segment is: La segment: Lb segment: Lc segment = 20:14:

1.

3. The detection method of a rapid detection device for anti-water treeing ability of cross-linked polyethylene cable according to claim 2 is characterized in that: Two rows of through holes (14) are arranged on opposite sides of the organic glass cylinder (15), and the Lb section of the cable sample (5) passes through the corresponding through holes (14) and is sealed and connected by glass glue.

4. The detection method of a rapid detection device for anti-water treeing ability of cross-linked polyethylene cable according to claim 3 is characterized in that: The organic glass cover (6) is provided with a through hole through which the copper electrode (7) passes.

5. The detection method of a rapid detection device for anti-water treeing ability of cross-linked polyethylene cable according to claim 4 is characterized in that: The distance between every two adjacent pinholes (13) on the La section of the cable sample (5) is 1 cm.

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