Submarine cable insulation aging test method and test system

Abstract

The embodiment of the invention provides a submarine cable insulation aging test method and test system, and relates to the field of cable aging test. The test method comprises the following steps: manufacturing a test sample, wherein the test sample has a water-tree-resistant insulating material; pretreating the test sample; placing the pretreated test sample in saline water, applying a matched voltage U0 to the test sample according to the test electric field intensity E, and continuously testing within a preset time T; performing a stepping breakdown test on the test sample after the continuous test to obtain the residual dielectric strength of the test sample; and comparing the residual dielectric strength with an acceptance standard to obtain a test result of accelerated aging of the test sample. Through the testing method, the aging process of the water-tree-resistant insulating material can be accelerated, an accurate and real aging result can be obtained through simulation, and whether the water-tree-resistant insulating material meets the requirements for manufacturing submarine cables under the action of seawater and voltage or not is verified. The embodiment of the invention further provides a test system.

Description

Technical Field

[0001] The present invention relates to the field of cable aging testing, and in particular to a submarine cable insulation aging testing method and a testing system. Background Art

[0002] In order to ensure long-term operational reliability, conventional submarine cables will continuously extrude a layer of "lead alloy" sheath outside the insulation layer to prevent seawater molecules from entering the insulation layer and causing "water trees" and eventually leading to insulation failure. With the development of submarine cable technology, a new type of "wet design" submarine cable has been invented. This type of submarine cable does not have a "lead alloy" sheath. Therefore, as the use time increases, seawater molecules will gradually enter the insulation layer and gradually grow "water trees". In order to prevent or slow down the growth of this "water tree", relevant researchers have developed "anti-water tree" insulation materials.

[0003] The design life of a submarine cable is generally more than 20 years. When "water tree resistant" insulation materials are used as the insulation layer of the submarine cable, there is currently a lack of a test method to quickly verify that the "water tree resistant" insulation materials can inhibit the formation of "water trees" during the service life of the submarine cable or ensure that "water trees" will not affect the normal use of the submarine cable. In other words, there is a lack of a test method for accelerated aging of "water tree resistant" insulation materials. Summary of the invention

[0004] The present invention provides a submarine cable insulation aging test method and a test system, which can simulate the aging process of a submarine cable made of "anti-water tree" insulation material under actual working conditions, and can quickly verify whether the "anti-water tree" insulation material meets the requirements for being used as the insulation layer of a submarine cable through an accelerated aging test.

[0005] The embodiments of the present invention can be implemented as follows:

[0006] An embodiment of the present invention provides a method for testing insulation aging of a submarine cable, which comprises:

[0007] Making a test sample, wherein the test sample has a "water tree resistant" insulation material, and the test sample is used to replace a submarine cable;

[0008] Pre-treating the test sample to keep the test sample in a stable state;

[0009] Place the pre-treated test sample in salt water, apply a matching voltage U0 to the test sample according to the test electric field strength E, and continue the test within a preset time T;

[0010] Performing a step breakdown test on the test sample after the continuous test to obtain the residual dielectric strength of the test sample;

[0011] Based on the comparison of the residual dielectric strength with the acceptance criteria, the test results of the accelerated aging of the test samples are obtained, and the test results include whether the test samples meet the requirements for manufacturing submarine cables.

[0012] Optionally, the test sample includes, from inside to outside, a conductor, a first water-blocking tape, a conductor shielding layer, an "anti-water tree" insulating layer, and an insulating shielding layer.

[0013] Optionally, the step of pre-treating the prepared test sample to stabilize the test sample comprises:

[0014] The test sample is immersed in salt water while applying pressure to the salt water to change the hydrostatic pressure of the salt water.

[0015] Optionally, the step of pre-treating the prepared test sample to stabilize the test sample comprises:

[0016] In cases where it is desired to shorten the pretreatment period, the brine is heated to a temperature above the normal temperature of seawater.

[0017] Optionally, the frequency range of the voltage U0 applied to the test sample is 50-500 Hz.

[0018] Optionally, the step of the step breakdown test includes: setting a maximum starting voltage U of the test sample to be less than or equal to a voltage U0 corresponding to three times the test electric field strength E.

[0019] Optionally, acceptance criteria include:

[0020] When the design electric field strength E of the test sample b When the voltage is ≤4 kV / mm, the electric field strength achieved at the conductor shield in the step breakdown test is at least 18 kV / mm;

[0021] When the design electric field strength E of the test sample b > 4 kV / mm, the electric field strength achieved at the conductor shield in the step breakdown test is at least E b *(29 / 5.5) kV / mm.

[0022] Optionally, the effective length of the test sample is ≥ 10 meters.

[0023] Optionally, the concentration of the brine is in the range of 3% to 6%.

[0024] An embodiment of the present invention further provides a test system, which is used to implement the above test method. The test system includes:

[0025] A sealed tank, the sealed tank is used to contain salt water, the salt water is used to submerge the middle section of the test sample, and the two ends of the test sample are extended out of the sealed tank;

[0026] A voltage device is used to electrically connect the two ends of the test sample.

[0027] Beneficial effects of the embodiments of the present invention:

[0028] The submarine cable insulation aging test method includes: making a test sample, wherein the test sample has a "water tree resistant" insulation material, and the test sample is used to replace the submarine cable; pre-treating the test sample to make the test sample in a stable state; placing the pre-treated test sample in salt water, applying a matching voltage U0 to the test sample according to the test electric field strength E, and continuously testing within a preset time T; performing a step breakdown test on the test sample after the continuous test to obtain the residual dielectric strength of the test sample; based on the residual dielectric strength and the acceptance standard, the test result of the accelerated aging of the test sample is obtained, and the test result includes whether the test sample meets the requirements for making submarine cables. This test method can accelerate the aging process of the "water tree resistant" insulation material, and simulate more accurate and true aging results to verify whether the "water tree resistant" insulation material meets the requirements for making submarine cables under the action of seawater and voltage.

[0029] The test system for submarine cable insulation aging includes a sealed tank and a voltage device. The sealed tank is filled with salt water, which submerges the middle section of the test sample. Both ends of the test sample extend out of the sealed tank. The voltage device is electrically connected to the two ends of the test sample. The above-mentioned test method can be implemented through this test system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 A schematic flow chart of a submarine cable insulation aging test method provided in an embodiment of the present invention;

[0032] Figure 2 A schematic diagram of the structure of a test sample provided in an embodiment of the present invention;

[0033] Figure 3 A schematic diagram of the structure of a submarine cable provided in an embodiment of the present invention;

[0034] Figure 4 It is a schematic diagram of a test system provided in an embodiment of the present invention.

[0035] Icons: 1-conductor; 2-first water-blocking tape; 3-conductor shielding layer; 4-"anti-water tree" insulation layer; 5-insulating shielding layer; 6-second water-blocking tape; 7-metal shielding layer; 9-third water-blocking tape; 10-inner sheath; 11-filling body; 12-binding tape; 13-lining layer; 14-armor layer; 15-outer layer; 16-optical cable; 20-test sample; 21-sealing tank; 22-pressurizing device; 23-heating device; 24-voltage device; 25-sealing flange; 26-salt water. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0039] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear to indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0040] In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

[0041] The terms "comprises," "comprising," or any other variation thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0042] Unless otherwise clearly specified and limited, the terms "disposed", "connected" and the like should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] It should be noted that, for the aforementioned various method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described order of actions, because according to the present application, some steps can be performed in other orders or simultaneously. The steps in the method of the embodiment of the present application can be adjusted in order, combined, and deleted according to actual needs.

[0044] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0045] As described in the background technology, the design life of a submarine cable is usually 20 to 40 years. When "water tree resistant" insulating materials are used as the insulating layer of a submarine cable, how to ensure that the "water tree resistant" insulating materials can effectively inhibit the growth of "water tree branches" to ensure that the manufactured submarine cable can be used for the design life? However, there is currently a lack of aging test methods for "water tree resistant" insulating materials, especially test methods under accelerated aging conditions.

[0046] Based on this, the embodiments of the present invention provide a submarine cable insulation aging test method and test system, which can simulate the aging process of a submarine cable made of "anti-water tree" insulation material under actual working conditions, and can quickly verify whether the "anti-water tree" insulation material meets the requirements as the submarine cable insulation layer through accelerated aging test. The submarine cable insulation aging test method and test system will be described in detail below.

[0047] refer to Figure 1 , an embodiment of the present invention provides a method for testing the insulation aging of a submarine cable, comprising the following steps:

[0048] Step S10: manufacturing a test sample 20, wherein the test sample 20 has a "water tree resistant" insulating material, and the test sample 20 is used to replace a submarine cable;

[0049] Step S20: pre-treating the test sample 20 to make the test sample 20 in a stable state;

[0050] Step S30: placing the pre-treated test sample 20 in salt water 26, applying a matching voltage U0 to the test sample 20 according to the test electric field strength E, and continuing the test within a preset time T;

[0051] Step S40: performing a step breakdown test on the test sample 20 after the continuous test to obtain the residual dielectric strength of the test sample 20;

[0052] Step S50: Based on the comparison between the residual dielectric strength and the acceptance standard, the test result of the accelerated aging of the test sample 20 is obtained, wherein the test result includes whether the test sample 20 meets the requirements for manufacturing submarine cables or does not meet the requirements for manufacturing submarine cables.

[0053] In an embodiment of the present invention, salt water 26 is used to simulate seawater, and a test electric field strength E is applied to a test sample 20 made of an "anti-water tree" insulating material to simulate the normal working condition of a submarine cable. At the same time, the test electric field strength E is changed to simulate the accelerated aging process of the submarine cable, so as to realize a rapid verification under a relatively accurate and realistic condition whether the "anti-water tree" insulating material meets the requirements for manufacturing a submarine cable under the action of seawater and voltage. In an embodiment of the present invention, salt water 26 is used to simulate seawater, and a test electric field strength E is applied to the test sample 20 to simulate the actual working condition of the submarine cable. The obtained test results have high reliability and accuracy.

[0054] refer to Figure 2 In the embodiment of the present invention, the test sample 20 manufactured includes, from the inside to the outside, a conductor 1, a first water blocking tape 2, a conductor shielding layer 3, an "anti-water tree" insulating layer 4, and an insulating shielding layer 5. The interlayer structure and preparation process of the test sample 20 are the same as those of the actual submarine cable.

[0055] In an embodiment of the present invention, the conductor 1 material of the test sample 20 in step S10 can be copper or aluminum, and can be made into a single solid conductor wire, or multiple copper wires or aluminum wires can be twisted into a solid wire bundle by compacting. During the test, the cross-sectional size of the conductor wire or solid wire bundle can be selected within the range of 10 to 1600 square millimeters. In this embodiment, the cross-sectional size of the selected conductor wire or solid wire bundle is greater than or equal to 50 square millimeters. The conductor shielding layer 3 and the insulating shielding layer 5 are both formed by three-layer co-extrusion using the same material as that used to make the submarine cable. The "anti-water tree" insulating layer 4 is also formed by three-layer co-extrusion. The thickness of the "anti-water tree" insulating layer 4 after forming is generally 2.5 to 15 mm. The thickness of the "anti-water tree" insulating layer 4 during the test in this embodiment is greater than or equal to 4.5 mm.

[0056] In the embodiment of the present invention, the effective length of each test sample 20 is greater than 10 meters.

[0057] In another preferred embodiment, during the pretreatment in step S20, the test sample 20 is immersed in the salt water 26, and pressure is applied to the salt water 26 to change the hydrostatic pressure of the salt water 26; the salt water 26 being outside the insulating shielding layer 5 can accelerate the formation of "water trees" by the salt water 26 on the "anti-water tree" insulating layer 4, thereby accelerating the aging process of the "anti-water tree" insulating layer 4, and pressurizing the salt water 26 is used to simulate the water pressure that the submarine cable is subjected to in seawater, so that the test results are more realistic. In this embodiment, the salt water 26 is pressurized to a hydrostatic pressure in the range of 900 to 1500 millibars.

[0058] Of course, the duration of the pretreatment is related to the thickness of the "anti-water tree" insulating layer 4. The thicker the "anti-water tree" insulating layer 4 is, the longer the pretreatment time is. If the thickness of the "anti-water tree" insulating layer 4 is greater than 8.8 mm, the duration is (100+46*the thickness of the anti-water tree insulating layer, in hours). When the thickness of the "anti-water tree" insulating layer 4 is less than or equal to 8.8 mm, the duration is not less than 500 hours.

[0059] In another preferred embodiment, when the pretreatment time of step S20 needs to be shortened, the brine 26 may be heated up. This is because the diffusion coefficient of the insulating material is generally significantly affected by temperature, and the pretreatment time may be shortened by heating up. In this embodiment, the temperature of the brine 26 may be heated up to a range of 50 to 60 degrees Celsius.

[0060] In step S30, in addition to placing the test sample 20 in salt water 26, the test sample 20 also needs to be placed under a test electric field strength E to simulate the actual scenario of the submarine cable being energized. The test electric field strength E refers to the electric field strength at the conductor shielding layer 3. The test electric field strength E is generated by applying a voltage U0 that can reach the test electric field strength E to the test sample 20. The frequency range of the voltage U0 applied to the test sample 20 is usually 50 to 500 Hz. The higher the voltage frequency, the faster the aging rate of the "anti-water tree" insulation layer 4 and the shorter the test duration. Of course, the voltage U0 applied to the test sample 20 should also be determined according to the cross-sectional dimensions of the conductor to generate a test electric field strength E that meets the requirements.

[0061] For example, in the first accelerated aging test example of this embodiment, 12 test samples 20 are selected for the test, of which 6 test samples 20 have a test duration of not less than 8750 hours, and the test duration of the other 6 test samples 20 is not less than 17500 hours. The frequency of the voltage U0 applied to the 12 test samples 20 is 50 Hz, and the temperature of the salt water 26 is controlled within the range of 40±5°C. b When the electric field strength is less than or equal to 5.5 kV / mm, the test electric field strength E≥9 kV / mm; when the design electric field strength E of the test sample 20 is b If the electric field strength is greater than 5.5 kV / mm, the test electric field strength E ≥ E b *9 / 5.5 kV / mm.

[0062] For example, in the second accelerated aging test example of this embodiment, six test samples 20 are selected for the test, and the test duration of the six test samples 20 is not less than 3000 hours. The frequency of the voltage U0 applied to the test samples 20 is 500 Hz, and the temperature of the salt water 26 is controlled within the range of 40±5°C. b When the electric field strength is less than or equal to 5.5 kV / mm, the test electric field strength E≥9 kV / mm; when the design electric field strength E of the test sample 20 is b >5.5 kV / mm, the test electric field strength E≥E b *9 / 5.5 kV / mm.

[0063] Of course, other test parameters may also be selected and set to perform accelerated aging tests.

[0064] It should be noted that, in the embodiment of the present invention, in the pretreatment test and the accelerated aging process of applying voltage U0, the test sample 20 is in the salt water 26, and the concentration range of the salt water 26 in the two tests is 3% to 6%, such as 4%, 5%, and 5.5%.

[0065] After the test sample 20 undergoes the accelerated aging test, a step breakdown test may be performed on the test sample 20 to obtain the residual dielectric strength of the test sample 20 .

[0066] In the embodiment of the present invention, when performing the step breakdown test, the maximum starting voltage U set for the test sample 20 is less than or equal to the voltage U0 corresponding to three times the test electric field strength E.

[0067] During the step breakdown test, the breakdown voltage can be gradually increased by voltage regulation, and the voltage step length of the voltage regulation depends on the design electric field strength. When the test electric field strength E≤4 kV / mm, the voltage step length ≤ voltage U0, when the test electric field strength E>4 kV / mm, the voltage step length ≤ half of voltage U0.

[0068] For example, in step S40, when the design electric field strength E of the test sample 20 is b ≤4 kV / mm, the electric field strength achieved at the conductor shielding layer 3 of the test sample 20 in the step breakdown test is at least 18 kV / mm, and 18 kV / mm is used as the acceptance standard for the breakdown electric field strength; when the design electric field strength E of the test sample 20 is b When the electric field strength at the conductor shielding layer 3 of the test sample 20 in the step breakdown test is greater than 4 kV / mm, the electric field strength reached at the conductor shielding layer 3 of the test sample 20 is at least E b *(29 / 5.5) kV / mm, E b *(29 / 5.5) kV / mm is used as the acceptance criterion for breakdown electric field strength.

[0069] Of course, the acceptance criteria for the breakdown electric field strength can also be other values, which are related to the thickness of the "anti-water tree" insulation layer 4 and the design electric field strength E b And so on.

[0070] In the embodiment of the present invention, the duration of the step breakdown test is 300 seconds.

[0071] refer to Figure 3 When the test sample 20 meets the acceptance criteria for a submarine cable, a second water-blocking tape 6, a metal shielding layer 7, a third water-blocking tape 9, an inner sheath 10, a lining layer 13, an armor layer 14 and an outer layer 15 are arranged outside the test sample 20. The second water-blocking tape 6 is connected to the insulating shielding layer 5. The second water-blocking tape 6, the metal shielding layer 7, the third water-blocking tape 9, the inner sheath 10, the lining layer 13, the armor layer 14 and the outer layer 15 are arranged in sequence from the inside to the outside, thereby forming a submarine cable that meets the requirements.

[0072] When a plurality of mutually independent and parallel conductor lines are arranged in the lining layer 13 , a filler 11 may be filled in the outer space of the adjacent inner sheath 10 , and the filler 11 and the plurality of conductors 1 are bundled and fixed by a bundling belt 12 .

[0073] An optical cable 16 may also be arranged in the filling body 11 to achieve signal and information transmission.

[0074] The testing method of the embodiment of the present invention has high reliability and accuracy, can accelerate the aging process of the "anti-water tree" insulating material, and quickly verify whether the "anti-water tree" insulating material meets the requirements for manufacturing submarine cables under the action of seawater and voltage.

[0075] refer to Figure 4 , an embodiment of the present invention further provides a submarine cable insulation aging test system, which is used to implement the above-mentioned test method.

[0076] The test system includes: a sealed tank 21 and a voltage device 24. The sealed tank 21 contains salt water 26. The middle section of the test sample 20 is immersed in the salt water 26. Both ends of the test sample 20 extend out of the sealed tank 21. Both ends of the test sample 20 extending out of the sealed tank 21 are electrically connected to the voltage device 24. The voltage device 24 can apply voltages of different values ​​to the test sample 20 to simulate the normal aging process of the submarine cable, accelerate the aging process, and perform a step breakdown test; for example, the test sample 20 is passed through a voltage U0 corresponding to the test electric field strength E, and the test electric field strength E is much higher than the design electric field strength E. b , which is used to simulate the accelerated aging of submarine cables. The electric field strength achieved in the step breakdown test can be the same as the test electric field strength E, or it can be much higher than the test electric field strength E.

[0077] The voltage device 24 used in the embodiment of the present invention is a common AC voltage output device.

[0078] When both ends of the test sample 20 pass through the sealed can 21, they are sealed with the sealed can 21; for example, a sealing flange 25 is installed on the sealed can 21, and both ends of the test sample 20 pass through the sealing flange 25 and extend to the outside of the sealed can 21, so that the test sample 20 is sealed with the tank wall of the sealed can 21.

[0079] The test system of the embodiment of the present invention may further include a pressurizing device 22, which is used to pressurize the salt water 26 in the sealed tank 21, to increase the hydrostatic pressure of the salt water 26, and to simulate the pressure that the submarine cable bears in the seawater. The pressurizing device 22 may be a gas pressure pump, which is connected to the sealed tank 21 through a hard pressurizing pipeline, and pressurizes the salt water 26 by injecting gas, thereby increasing the hydrostatic pressure of the salt water 26, and the connection between the pressurizing pipeline and the sealed tank 21 needs to be sealed.

[0080] The test system of the embodiment of the present invention may also include a heating device 23, which is used to heat the salt water 26 in the sealed tank 21, so that the salt water 26 is heated. On the one hand, the pretreatment time of the test sample 20 can be shortened, and on the other hand, the temperature of the salt water 26 can be changed to simulate the situation of the submarine cable in seawater of different temperatures. The heating device 23 can use electric heating to heat the salt water 26, such as setting an electric heating plate on the inner side of the tank wall of the sealed tank 21 or placing the sealed tank 21 as a whole in a heat source for heating. If it is necessary to accurately monitor the temperature of the salt water 26 in the sealed tank 21, a temperature sensor can be set to monitor the temperature change in real time. Of course, in addition to heating, the salt water 26 can also be cooled; when the salt water 26 is heated, the test sample 20 can be aged faster, and when the salt water 26 is cooled, the test sample 20 can also be aged faster. The accelerated aging test method under the cooling condition is consistent with that under the heating condition, and only the temperature of the salt water 26 needs to be changed.

[0081] The test system of the embodiment of the present invention can implement testing of test samples 20 made of different "anti-water tree" insulating materials under different working conditions. The test is convenient and fast, and the test results are highly accurate and reliable.

[0082] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for testing the insulation aging of a submarine cable, characterized in that: include: Making a test sample (20), wherein the test sample (20) has a "water tree resistant" insulation material, and the test sample (20) is used to replace a submarine cable; Pre-treating the test sample (20) to keep the test sample (20) in a stable state; Placing the pre-treated test sample (20) in salt water (26), applying a matching voltage U0 to the test sample (20) according to the test electric field strength E, and continuing the test within a preset time T; Performing a step breakdown test on the test sample (20) after the continuous test to obtain the residual dielectric strength of the test sample (20); Based on the comparison between the residual dielectric strength and the acceptance standard, a test result of accelerated aging of the test sample (20) is obtained, and the test result includes whether the test sample (20) meets the requirements for manufacturing submarine cables.

2. The method for testing the insulation aging of a submarine cable according to claim 1, characterized in that: The test sample (20) comprises, from the inside to the outside, a conductor (1), a first water-blocking tape (2), a conductor shielding layer (3), an "anti-water tree" insulating layer (4), and an insulating shielding layer (5).

3. The method for testing the insulation aging of a submarine cable according to claim 2, characterized in that: The step of pre-treating the prepared test sample (20) to stabilize the test sample (20) comprises: The test sample (20) is immersed in the salt water (26) while applying pressure to the salt water (26) to change the hydrostatic pressure of the salt water (26).

4. The method for testing the insulation aging of a submarine cable according to claim 1, characterized in that: The step of pre-treating the prepared test sample (20) to stabilize the test sample (20) comprises: When the pretreatment time needs to be shortened, the salt water (26) is heated to make the salt water (26) higher than the normal temperature of seawater.

5. The method for testing the insulation aging of a submarine cable according to claim 2, characterized in that: The frequency range of the voltage U0 applied to the test sample (20) is 50 to 500 Hz.

6. The method for testing submarine cable insulation aging according to claim 1, characterized in that: The steps of the step breakdown test include: The maximum starting voltage U set for the test sample (20) is less than or equal to three times the voltage U0 corresponding to the test electric field strength E.

7. The method for testing the insulation aging of a submarine cable according to claim 2, characterized in that: The acceptance criteria include: When the designed electric field strength E of the test sample (20) b ≤4 kV / mm, the electric field strength achieved at the conductor shielding layer (3) in the step breakdown test is at least 18 kV / mm; When the designed electric field strength E of the test sample (20) b When the voltage is greater than 4 kV / mm, the electric field strength achieved at the conductor shielding layer (3) in the step breakdown test is at least E b *(29 / 5.5) kV / mm.

8. The method for testing submarine cable insulation aging according to claim 1, characterized in that: The effective length of the test sample (20) is ≥10 meters.

9. The method for testing the insulation aging of a submarine cable according to any one of claims 1 to 8, characterized in that: The concentration of the salt water (26) is in the range of 3% to 6%.

10. A test system, the test system being used to implement the test method according to any one of claims 1 to 9, characterized in that: The test system comprises: A sealed can (21), the sealed can (21) is used to contain salt water (26), the salt water (26) is used to submerge the middle section of the test sample (20), and allow both ends of the test sample (20) to extend out of the sealed can (21); A voltage device (24), the voltage device (24) is used to be electrically connected to two ends of the test sample (20).

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