Method for evaluating the basic insulation level of a high voltage direct current submarine cable sample

Abstract

The application provides a method for evaluating basic insulation level of a high-voltage direct-current submarine cable sample, comprising the following steps: stripping the non-metal sheath layer, the metal shielding layer and the insulation shielding layer of two end portions of the high-voltage direct-current submarine cable sample in sequence; connecting the metal conductors of the two end portions of the high-voltage direct-current submarine cable sample by using a metal bar and hoisting the metal bar to a preset height by using hoisting equipment; connecting the metal bar and a high-voltage direct-current power supply, grounding the metal shielding layer of one end of the high-voltage direct-current submarine cable sample; disconnecting the metal bar and the high-voltage direct-current power supply; processing the exposed insulation layers of the two end portions of the high-voltage direct-current submarine cable sample to be no longer in the exposed state; hoisting the metal bar to the preset height by using the hoisting equipment, connecting the metal bar and an impulse voltage generator, grounding the metal shielding layer of one end of the high-voltage direct-current submarine cable sample; and gradually increasing the impulse voltage amplitude of the impulse voltage generator. The application can obtain the basic insulation level of a factory joint.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cable test, in particular to a method for evaluating basic insulation level of high-voltage direct-current submarine cable sample. BACKGROUND

[0002] The high-voltage direct-current submarine cable factory joint is used for connecting two sections of extruded length or manufacturing length of direct-current submarine cable under controllable factory conditions. Since the three-layer structure of the factory joint insulation needs to be made layer by layer, compared with the three-layer co-extruded cable body, the factory joint is a weak part of the high-voltage direct-current submarine cable system, and therefore the joint insulation outer diameter may be slightly larger than the cable insulation outer diameter to ensure sufficient electrical strength. At present, the quality evaluation method of the factory joint is mainly direct-current withstand voltage. However, the cable system also needs to withstand impulse overvoltage in the power grid, and therefore the ability of the factory joint to withstand impulse voltage needs to be evaluated, that is, the basic insulation level (BIL) of the factory joint needs to be obtained.

[0003] To obtain the basic insulation level of the cable and cable accessories, lightning impulse voltage resistance test needs to be performed, and for the high-voltage direct-current submarine cable system, to obtain the basic insulation level closer to the actual operation condition, direct-current voltage superimposed impulse voltage test needs to be performed. At present, if impulse voltage test needs to be performed, a finished cable terminal needs to be matched to avoid external flashover, and the finished cable terminal will occur external flashover or even breakdown before the factory joint breakdown. Therefore, to obtain the basic insulation level of the direct-current cable factory joint of a higher voltage grade, a special cable margin test terminal needs to be matched. At present, there are few related products on the market, and large-scale application has not been seen, and the prices of the finished terminal and the margin test terminal are both high.

[0004] At present, there is no method for evaluating the basic insulation level of the high-voltage direct-current submarine cable factory joint. SUMMARY

[0005] In view of the above-mentioned shortcomings of the prior art, the technical problem to be solved by the present application is to provide a method for evaluating the basic insulation level of a high-voltage direct-current submarine cable sample, which can perform impulse voltage test on the high-voltage direct-current submarine cable sample containing a factory joint after direct-current withstand voltage pretreatment without the aid of a finished cable terminal accessory or a special cable margin test terminal, and obtain the basic insulation level of the factory joint.

[0006] To solve the above-mentioned technical problem, the present application provides a method for evaluating the basic insulation level of a high-voltage direct-current submarine cable sample, the high-voltage direct-current submarine cable sample containing a factory joint, the high-voltage direct-current submarine cable sample comprising, in sequence from inside to outside along the radial direction of the cross section thereof, a metal conductor, an insulation layer, an insulation shielding layer, a metal shielding layer, and a non-metal sheath layer, the method comprising a direct-current withstand voltage pretreatment step and an impulse voltage test step, wherein:

[0007] The direct current voltage resistance pretreatment step comprises:

[0008] According to preset stripping length requirements, the non-metal sheath layer, the metal shielding layer and the insulation shielding layer of the two end portions of the high-voltage direct current submarine cable sample are sequentially stripped until the insulation shielding layer and the insulation layer respectively meet the corresponding preset exposure length requirements.

[0009] The metal conductors of the two end portions of the high-voltage direct current submarine cable sample are connected by using a metal bar, and the metal bar is lifted to a preset height by using a lifting device so that the high-voltage direct current submarine cable sample is in a suspended state, and the lifting device and the metal bar are in an insulating state.

[0010] The metal bar is connected to the high-voltage direct current power supply, and the metal shielding layer at one end of the high-voltage direct current submarine cable sample is grounded.

[0011] The voltage polarity and amplitude output by the high-voltage direct current power supply are adjusted according to preset requirements, and the high-voltage direct current submarine cable sample is subjected to direct current voltage resistance pretreatment for a preset time length.

[0012] The step of the impulse voltage test comprises:

[0013] The metal bar is disconnected from the high-voltage direct current power supply, and the high-voltage direct current submarine cable sample is lowered.

[0014] The exposed insulation layer of the two end portions of the high-voltage direct current submarine cable sample is treated so as not to be in an exposed state.

[0015] The metal bar is lifted to a preset height by using a lifting device so that the high-voltage direct current submarine cable sample is in a suspended state, and the lifting device and the metal bar are in an insulating state, the metal bar is connected to the impulse voltage generator, and the metal shielding layer at one end of the high-voltage direct current submarine cable sample is grounded.

[0016] The voltage polarity, waveform and amplitude output by the impulse voltage generator are adjusted according to preset requirements, and the high-voltage direct current submarine cable sample is subjected to step-by-step impulse voltage tests according to a preset step-by-step voltage boosting step and a number of impulse voltage tests at each step.

[0017] The impulse voltage amplitude of the impulse voltage generator is gradually increased according to preset impulse voltage polarity and amplitude requirements at each step until the factory joint in the high-voltage direct current submarine cable sample is broken down, and the last impulse voltage value before breakdown is obtained.

[0018] Preferably, the step of stripping the non-metal sheath layer, the metal shielding layer and the insulation shielding layer of the two end portions of the high-voltage direct current submarine cable sample according to preset stripping length requirements until the insulation shielding layer and the insulation layer respectively meet the corresponding preset exposure length requirements comprises polishing the fracture of the insulation shielding layer.

[0019] Preferably, the hoisting device is an insulating guide pole, and the bottom end of the insulating guide pole is connected to the metal bar.

[0020] Preferably, the step of processing the exposed insulation layer of the two ends of the high-voltage direct-current submarine cable sample into a state of no longer being exposed includes coating a semiconductive material on the outer surface of the insulation layer from which the insulation shield layer has been stripped.

[0021] Preferably, the step of coating a semiconductive material on the outer surface of the insulation layer from which the insulation shield layer has been stripped includes coating a semiconductive paint or tightly wrapping a semiconductive tape on the outer surface of the insulation layer from which the insulation shield layer has been stripped.

[0022] Preferably, the step of processing the exposed insulation layer of the two ends of the high-voltage direct-current submarine cable sample into a state of no longer being exposed includes disconnecting the metal bar from the metal conductor of the two ends of the high-voltage direct-current submarine cable sample, cutting the cable segment containing the exposed insulation layer, and leaving the insulation shield layer in a state of being exposed, and then connecting the metal conductor of the two ends of the high-voltage direct-current submarine cable sample using the metal bar.

[0023] Preferably, the step of adjusting the voltage polarity and amplitude of the output of the high-voltage direct-current power supply according to the preset requirements includes adjusting the output voltage polarity of the high-voltage direct-current power supply (4) to be positive or negative.

[0024] Preferably, the step of adjusting the voltage polarity, waveform, and amplitude of the output of the impulse voltage generator according to the preset requirements includes adjusting the output voltage polarity of each stage of the impulse voltage generator to be positive or negative.

[0025] Preferably, the step of gradually increasing the amplitude of the impulse voltage of the impulse voltage generator according to the preset requirements of the polarity and amplitude of each stage of the impulse voltage until the factory joint in the high-voltage direct-current submarine cable sample is broken down, and obtaining the value of the last impulse voltage before breakdown further includes taking the value of the last impulse voltage before breakdown of the high-voltage direct-current submarine cable sample as the basic insulation level of the factory joint.

[0026] The basic insulation level evaluation method of the high-voltage direct-current submarine cable sample of the application has the following beneficial effects: the implementation steps of the basic insulation level evaluation method of the application are mainly divided into two stages: the first stage realizes the execution of the direct-current voltage withstand pretreatment step on the high-voltage direct-current submarine cable sample containing the factory joint without the help of the finished product cable terminal or the special cable margin test terminal, and the second stage realizes the execution of the impulse voltage test step after the direct-current voltage withstand pretreatment. Specifically, in the above direct-current voltage withstand pretreatment step, first, according to the preset stripping length requirement, the non-metal sheath layer, the metal shielding layer and the insulation shielding layer of the two end portions of the high-voltage direct-current submarine cable sample are sequentially stripped until the insulation shielding layer and the insulation layer respectively meet the corresponding preset exposure length requirement, and the layer structure is generally exposed in steps in a stepped manner; further, the metal conductor of the two end portions of the high-voltage direct-current submarine cable sample is connected by using a metal bar, and the metal bar is hoisted to a preset height by using hoisting equipment to make the high-voltage direct-current submarine cable sample in a suspended state, and the hoisting equipment and the metal bar are in an insulating state, so that the metal bar and the metal conductor of the high-voltage direct-current submarine cable sample form a closed conductive loop; finally, the metal bar is connected with the high-voltage direct-current power supply, and the metal shielding layer at one end of the high-voltage direct-current submarine cable sample is grounded, so that the direct-current voltage withstand pretreatment is completed. In the above impulse voltage test step, first, the metal bar is disconnected from the high-voltage direct-current power supply, and the high-voltage direct-current submarine cable sample is lowered; further, it is more important that the exposed insulation layer of the two end portions of the high-voltage direct-current submarine cable sample is treated to no longer be in an exposed state; the metal bar is hoisted to a preset height by using hoisting equipment to make the high-voltage direct-current submarine cable sample in a suspended state, and the hoisting equipment and the metal bar are in an insulating state, the metal bar is connected with the impulse voltage generator, and the metal shielding layer at one end of the high-voltage direct-current submarine cable sample is grounded; the impulse voltage amplitude of the impulse voltage generator is gradually increased until the high-voltage direct-current submarine cable sample is broken down, and the last impulse voltage value is obtained, that is, the basic insulation level of the factory joint can be obtained. Therefore, the basic insulation level evaluation method of the application can perform the impulse voltage test on the high-voltage direct-current submarine cable sample containing the factory joint after the direct-current voltage withstand pretreatment without the help of the finished product cable terminal accessory or the special cable margin test terminal, and obtain the basic insulation level of the factory joint. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 shows the cross-sectional schematic view of the high-voltage direct-current submarine cable sample of the application;

[0028] Figure 2 shows the implementation schematic view of the basic insulation level evaluation method of the high-voltage direct-current submarine cable sample of the application.

[0029] ELEMENT NUMBER EXPLANATION

[0030] 1 high-voltage direct-current submarine cable sample

[0031] 11 Factory Connector

[0032] 12 Metallic conductors

[0033] 13 Insulation layer

[0034] 14 Insulating shielding layer

[0035] 15 Metal shielding layer

[0036] 16 Non-metallic sheath layer

[0037] 2 Metal strips

[0038] 3. Lifting equipment

[0039] 4. High-voltage DC power supply

[0040] 5. Impulse Voltage Generator Detailed Implementation

[0041] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0042] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the scope of the invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0043] Since the most significant characteristic of submarine power cable production is its long-distance power transmission, factory joints (i.e., joints made on-site in the factory during the submarine power cable production process) must be used for cable splicing during the manufacturing process.

[0044] like Figure 1 and Figure 2 As shown, the high voltage DC submarine cable sample 1 of the present invention includes a factory connector 11. The high voltage DC submarine cable sample 1 includes, from the inside to the outside, a metal conductor 12, an insulation layer 13, an insulation shielding layer 14, a metal shielding layer 15, and a non-metallic sheath layer 16 along its own cross-section radially.

[0045] The application provides a basic insulation level evaluation method for the high-voltage direct-current submarine cable sample 1, and the basic insulation level evaluation method comprises a direct-current voltage resistance pretreatment step and an impulse voltage test step.

[0046] The direct-current voltage resistance pretreatment step comprises the following steps:

[0047] According to the preset stripping length requirement, the non-metal sheath layer 16, the metal shielding layer 15 and the insulation shielding layer 14 of the two end portions of the high-voltage direct-current submarine cable sample 1 are sequentially stripped until the insulation shielding layer 14 and the insulation layer 13 meet the corresponding preset exposure length requirements, respectively.

[0048] The metal conductors 12 of the two end portions of the high-voltage direct-current submarine cable sample 1 are connected by using the metal bar 2, and the metal bar 2 is lifted to a preset height by using the hoisting equipment 3 so that the high-voltage direct-current submarine cable sample 1 is in a suspended state, and the hoisting equipment 3 and the metal bar 2 are in an insulating state.

[0049] The metal bar 2 is connected with the high-voltage direct-current power supply 4, and the metal shielding layer 15 at one end of the high-voltage direct-current submarine cable sample 1 is grounded.

[0050] The voltage polarity and amplitude output by the high-voltage direct-current power supply 4 are adjusted according to the preset requirement, and the high-voltage direct-current submarine cable sample 1 is subjected to direct-current voltage resistance pretreatment for a preset time length.

[0051] The impulse voltage test step comprises the following steps:

[0052] The metal bar 2 is disconnected from the high-voltage direct-current power supply 4, and the high-voltage direct-current submarine cable sample 1 is lowered.

[0053] The exposed insulation layer 13 of the two end portions of the high-voltage direct-current submarine cable sample 1 is processed so as to no longer be in an exposed state.

[0054] The metal bar 2 is lifted to a preset height by using the hoisting equipment 3 so that the high-voltage direct-current submarine cable sample 1 is in a suspended state, and the hoisting equipment 3 and the metal bar 2 are in an insulating state, the metal bar 2 is connected with the impulse voltage generator 5, and the metal shielding layer 15 at one end of the high-voltage direct-current submarine cable sample 1 is grounded.

[0055] The voltage polarity, waveform and amplitude output by the impulse voltage generator 5 are adjusted according to the preset requirement, and the high-voltage direct-current submarine cable sample 1 is subjected to step-by-step impulse voltage test according to a preset step-by-step voltage boosting step and a number of impulse voltage tests at each step.

[0056] The amplitude of the impulse voltage of the impulse voltage generator 5 is gradually increased according to the preset impulse voltage polarity and amplitude requirement at each step until the factory joint 11 in the high-voltage direct-current submarine cable sample 1 is broken down, and the last impulse voltage value before the breakdown is obtained.

[0057] The implementation steps of the basic insulation level evaluation method of the present application mainly include two stages: the first stage implements a DC voltage withstand pretreatment step on the HVDC submarine cable sample 1 containing the factory joint 11 without the aid of a finished cable terminal or a dedicated cable margin test terminal, and the second stage implements an impulse voltage test step after the DC voltage withstand pretreatment. Specifically, in the DC voltage withstand pretreatment step, first, according to the preset stripping length requirement, the non-metallic sheath layer 16, the metal shielding layer 15, and the insulation shielding layer 14 of the two end portions of the HVDC submarine cable sample 1 are sequentially stripped until the insulation shielding layer 14 and the insulation layer 13 respectively meet the corresponding preset exposure length requirement, and each layer structure is generally exposed in steps in a stepped manner; second, the metal conductor 12 of the two end portions of the HVDC submarine cable sample 1 is connected using a metal bar 2, and the metal bar 2 is lifted to a preset height using a hoisting device 3 so that the HVDC submarine cable sample 1 is in a suspended state, and the hoisting device 3 and the metal bar 2 are in an insulating state, so that the metal bar 2 and the metal conductor 12 of the HVDC submarine cable sample 1 form a closed conductive loop; then, the metal bar 2 is connected to a high-voltage DC power supply 4, and the metal shielding layer 15 at one end of the HVDC submarine cable sample 1 is grounded, and finally, the voltage polarity (positive or negative) and amplitude output by the high-voltage DC power supply 4 are adjusted according to the preset requirement, and the HVDC submarine cable sample 1 is subjected to a preset duration of DC voltage withstand pretreatment, thereby completing the DC voltage withstand pretreatment. In the impulse voltage test step, first, the metal bar 2 is disconnected from the high-voltage DC power supply 4, and the HVDC submarine cable sample 1 is lowered; second, and more importantly, the exposed insulation layer 13 of the two end portions of the HVDC submarine cable sample 1 is treated so that it is no longer in an exposed state; then, the metal bar 2 is lifted to a preset height using the hoisting device 3 so that the HVDC submarine cable sample 1 is in a suspended state, and the hoisting device 3 and the metal bar 2 are in an insulating state, the metal bar 2 is connected to an impulse voltage generator 5, and the metal shielding layer 15 at one end of the HVDC submarine cable sample 1 is grounded; then, the voltage polarity (positive or negative), waveform, and amplitude output by the impulse voltage generator 5 are adjusted according to the preset requirement, and the HVDC submarine cable sample 1 is subjected to a step-by-step impulse voltage test according to the preset step-by-step voltage boosting step and the number of impulse voltage tests at each step; finally, the amplitude of the impulse voltage of the impulse voltage generator 5 is gradually increased according to the preset impulse voltage polarity and amplitude requirement at each step, until the factory joint 11 in the HVDC submarine cable sample 1 is broken down, and the last impulse voltage value before the breakdown of the HVDC submarine cable sample 1 is obtained, i.e., the basic insulation level of the factory joint 11 is obtained.

[0058] That is to say: the application not only solves the problem that the high-voltage DC submarine cable sample containing a factory joint cannot be subjected to a DC voltage withstand test without the help of a finished cable terminal accessory or a special cable margin test terminal; but also solves the problem that the high-voltage DC submarine cable sample containing a factory joint cannot be subjected to an impulse voltage test without the help of a finished cable terminal accessory or a special cable margin test terminal.

[0059] Therefore, the basic insulation level evaluation method of the application can be used to perform an impulse voltage test on a high-voltage DC submarine cable sample containing a factory joint after DC voltage withstand pretreatment without the help of a finished cable terminal accessory or a special cable margin test terminal, so as to obtain the basic insulation level of the factory joint.

[0060] In order not to affect the impulse voltage test step, the step of stripping the non-metal sheath layer 16, the metal shielding layer 15 and the insulation shielding layer 14 from the two end portions of the high-voltage DC submarine cable sample 1 in sequence according to the preset stripping length requirement until the insulation shielding layer 14 and the insulation layer 13 meet the corresponding preset exposure length requirement includes: polishing the break of the insulation shielding layer 14.

[0061] In order to simplify the structure of the hoisting device 3 and smoothly hoist the high-voltage DC submarine cable sample 1, the hoisting device 3 is an insulating guide rod, and the bottom end of the insulating guide rod is connected to the metal bar 2, generally at the middle of the metal bar 2.

[0062] Since the insulation shielding layer 14 has a semi-conductive property, as an embodiment, the step of processing the exposed insulation layer 13 of the two end portions of the high-voltage DC submarine cable sample 1 into a state no longer exposed includes: coating a semi-conductive material on the outer surface of the insulation layer 13 from which the insulation shielding layer 14 has been stripped.

[0063] Further, the step of coating a semi-conductive material on the outer surface of the insulation layer 13 from which the insulation shielding layer 14 has been stripped includes: coating a semi-conductive paint or tightly wrapping a semi-conductive adhesive tape on the outer surface of the insulation layer 13 from which the insulation shielding layer 14 has been stripped.

[0064] As another embodiment, the step of processing the exposed insulation layer 13 of the two end portions of the high-voltage DC submarine cable sample 1 into a state no longer exposed includes: disconnecting the metal bar 2 from the metal conductor 12 of the two end portions of the high-voltage DC submarine cable sample 1, cutting off the cable section containing the exposed insulation layer 13, and still exposing the insulation shielding layer 14, and then connecting the metal conductor 12 of the two end portions of the high-voltage DC submarine cable sample 1 using the metal bar 2.

[0065] In summary, the application can perform impulse voltage test on the high-voltage DC submarine cable sample containing factory joints after DC voltage resistance pretreatment without the help of finished cable terminal accessory or special cable margin test terminal, and obtain the basic insulation level of the factory joints. Therefore, the application effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0066] The above embodiments only exemplarily illustrate the principles and effects of the application, and are not used to limit the application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the application should be covered by the claims of the application.

Claims

1. A method for evaluating the basic insulation level of a high-voltage direct current submarine cable sample, characterized in that, The high-voltage DC submarine cable sample (1) contains a factory connector (11). The high-voltage DC submarine cable sample (1) includes, from the inside out, a metal conductor (12), an insulation layer (13), an insulation shielding layer (14), a metal shielding layer (15), and a non-metallic sheath layer (16) along its cross-section. The basic insulation level assessment method includes a DC withstand voltage pretreatment step and an impulse voltage test step, wherein: The DC withstand voltage pretreatment step includes: According to the preset stripping length requirements, the non-metallic sheath layer (16), the metal shielding layer (15) and the insulating shielding layer (14) are stripped from both ends of the high voltage DC submarine cable sample (1) in sequence until the insulating shielding layer (14) and the insulating layer (13) meet the corresponding preset exposure length requirements. The metal conductors (12) at both ends of the high voltage DC submarine cable sample (1) are connected by a metal busbar (2), and the metal busbar (2) is lifted to a preset height by a hoisting device (3) so that the high voltage DC submarine cable sample (1) is in a suspended state, and the hoisting device (3) and the metal busbar (2) are in an insulated state. Connect the metal busbar (2) to the high voltage DC power supply (4), and ground the metal shielding layer (15) at one end of the high voltage DC submarine cable sample (1); Adjust the voltage polarity and amplitude of the high voltage DC power supply (4) according to the preset requirements, and perform DC withstand voltage pretreatment of the high voltage DC submarine cable sample (1) for a preset duration. The impulse voltage test steps include: Disconnect the metal busbar (2) from the high voltage DC power supply (4) and lower the high voltage DC submarine cable sample (1); The exposed insulation layer (13) at both ends of the high voltage DC submarine cable sample (1) is treated to be no longer exposed; Using the hoisting equipment (3), the metal busbar (2) is lifted to a preset height so that the high voltage DC submarine cable sample (1) is in a suspended state. The hoisting equipment (3) and the metal busbar (2) are in an insulated state. The metal busbar (2) is connected to the impulse voltage generator (5). The metal shielding layer (15) at one end of the high voltage DC submarine cable sample (1) is grounded. Adjust the voltage polarity, waveform and amplitude of the impulse voltage generator (5) according to the preset requirements, and conduct a step-by-step impulse voltage test on the high voltage DC submarine cable sample (1) according to the preset step-by-step voltage increase step size and the number of impulse voltage tests per stage. According to the preset polarity and amplitude requirements of each impulse voltage level, the impulse voltage amplitude of the impulse voltage generator (5) is gradually increased until the factory joint (11) in the high voltage DC submarine cable sample (1) is broken down, and the last impulse voltage value before the breakdown is obtained.

2. The method for evaluating the basic insulation level of high-voltage DC submarine cable samples according to claim 1, characterized in that: The step of sequentially stripping the non-metallic sheath layer (16), the metal shielding layer (15), and the insulating shielding layer (14) from both ends of the high-voltage DC submarine cable sample (1) according to the preset stripping length requirements, until the insulating shielding layer (14) and the insulating layer (13) respectively meet the corresponding preset exposure length requirements, includes: grinding the break point of the insulating shielding layer (14).

3. The method for evaluating the basic insulation level of high-voltage DC submarine cable samples according to claim 1, characterized in that: The hoisting equipment (3) is an insulated guide rod, with the bottom end of the insulated guide rod connected to the metal bar (2).

4. The method for evaluating the basic insulation level of high-voltage DC submarine cable samples according to claim 1, characterized in that: The step of processing the exposed insulation layer (13) at both ends of the high voltage DC submarine cable sample (1) to no longer be exposed includes coating the outer surface of the insulation layer (13) after the insulation shield layer (14) has been stripped off with a semiconductor material.

5. The method for evaluating the basic insulation level of high-voltage DC submarine cable samples according to claim 4, characterized in that: The step of coating the outer surface of the insulating layer (13) after the insulating shielding layer (14) has been removed with a semiconducting material includes: applying semiconducting paint or tightly wrapping semiconducting tape on the outer surface of the insulating layer (13) after the insulating shielding layer (14) has been removed.

6. The method for evaluating the basic insulation level of high-voltage DC submarine cable samples according to claim 1, characterized in that: The step of processing the exposed insulation layer (13) at both ends of the high-voltage DC submarine cable sample (1) to no longer be exposed includes: disconnecting the metal busbar (2) from the metal conductors (12) at both ends of the high-voltage DC submarine cable sample (1), cutting off the cable segment containing the exposed insulation layer (13), and still leaving the insulation shielding layer (14) exposed, and then using the metal busbar (2) to connect the metal conductors (12) at both ends of the high-voltage DC submarine cable sample (1).

7. The method for evaluating the basic insulation level of high-voltage DC submarine cable samples according to claim 1, characterized in that: The steps of adjusting the voltage polarity and amplitude of the high voltage DC power supply (4) according to preset requirements include: adjusting the voltage polarity of the high voltage DC power supply (4) to positive or negative polarity.

8. The method for evaluating the basic insulation level of high-voltage DC submarine cable samples according to claim 1, characterized in that: The steps of adjusting the voltage polarity, waveform and amplitude of the impulse voltage generator (5) according to the preset requirements include: adjusting the output voltage polarity of each voltage level of the impulse voltage generator (5) to positive or negative polarity.

9. The method for evaluating the basic insulation level of high-voltage DC submarine cable samples according to claim 1, characterized in that: The step of gradually increasing the impulse voltage amplitude of the impulse voltage generator (5) according to the preset impulse voltage polarity and amplitude requirements for each level until the factory joint (11) in the high voltage DC submarine cable sample (1) is broken down, and obtaining the last impulse voltage value before the breakdown, further includes: taking the last impulse voltage value before the breakdown of the high voltage DC submarine cable sample (1) as the basic insulation level of the factory joint (11).

Images