Insulation testing device and method

Abstract

The present invention discloses an insulation test device and method, the insulation test device includes a material layer with liquid holding ability, and the two sides of the material layer are covered with a liquid permeable surface and a liquid blocking surface; before the insulation test of the stator lead-out cable joint is performed, the material layer is preliminarily placed in a liquid holding state; during the test, the above-mentioned test device is positioned and wrapped around the outer periphery of the cable joint, and after installation, the liquid permeable surface faces the tested cable joint and wraps the cable joint, and the liquid blocking surface isolates the material layer from the external environment, so that the liquid in the material layer can evaporate from the liquid permeable surface toward the environment where the cable joint is located, thereby creating a closed humid space, and the relative humidity of the environment where the cable joint is located is relatively high, meeting the insulation test requirements. In addition, the test device is small in size, occupies a small space, and has good conformability to the cable joint, is not limited by the test space, can be placed arbitrarily with the product storage, has high flexibility in use, and is highly versatile.

Description

Technical Field

[0001] The present invention relates to the technical field of stator insulation testing, and in particular to an insulation testing device and method. Background Art

[0002] Stator insulation is the core processing step of stator winding, and insulation is also called the heart of the generator. Stator insulation generally has test methods such as inter-turn, withstand voltage, and partial discharge. Some stators with high requirements also have harsh tests such as immersion and water spraying. It is not easy to use test methods to evaluate the stator cable connector position. Usually, the external connector position only needs to examine its insulation protection, that is, it only needs to measure the insulation resistance value to examine the environmental resistance and sealing performance.

[0003] Specifically, after the generator stator is manufactured, it is required to insulate the stator lead cable and the end ring joint. The insulation treatment of this position is carried out after the stator assembly has completed insulation treatment and testing, so the sealing during insulation treatment will be weaker than that of the stator assembly. Especially for stators produced in some humid areas, moisture may be introduced into this position during insulation treatment, resulting in lower insulation resistance values ​​in the final product test, factory test, and test after arriving at the wind farm. It is easy to be misjudged as an insulation problem of the stator assembly, resulting in unnecessary trouble and freight losses when returning from the wind farm to the motor factory. In addition, if the insulation treatment of this position is poor, it will lead to penetrating moisture. It happens that this position is close to the grounding metal such as the stator bracket. In severe cases, it may cause insulation failure of the lead cable to the ground, which is manifested as local burning. Therefore, if this position is not sealed well, it will bury quality risks and risks; therefore, it is necessary to verify the insulation reliability of this position.

[0004] The most direct way to simulate moisture exposure is to conduct a water immersion test on this type of outsourced insulation. However, this position is generally close to the end ring of the stator. The surrounding structure of this position is complex, and according to the rule of stator placement, this position is generally on the upper part of the stator. Therefore, the feasibility of immersing this position in water after filling a container with water is almost zero. If a special container tooling is designed, the sealing requirements for the container tooling at the position where the cable enters and exits are too high, which is difficult. Therefore, the reliability verification method currently used for this position is to conduct a 2-hour water spray test.

[0005] However, the water spraying method consumes a lot of water, and the stator has limited operating positions, so the stator has to be transported back and forth, which increases the difficulty of the test, especially in an environment with limited transportation space, which greatly limits the feasibility of the test. Therefore, the insulation test of the stator lead wire joint has become a bottleneck process in the stator assembly production process.

[0006] Therefore, how to improve the flexibility of the application environment of the stator lead wire connector insulation test and save the consumption of water resources is a problem that technical personnel in this field need to solve urgently. Summary of the invention

[0007] The present invention provides an insulation testing device for insulation testing of a stator lead-out cable joint, comprising a material layer capable of holding liquid, wherein both sides of the material layer are covered with a liquid-permeable surface and a liquid-blocking surface, wherein the liquid-permeable surface is formed by a liquid-permeable material capable of allowing liquid to pass through, and the liquid-blocking surface is formed by a liquid-blocking material that blocks liquid from passing through. When the device is used for insulation testing, it is installed at the cable joint position, the liquid-permeable surface faces the cable joint to be tested, and the liquid-blocking surface isolates the material layer from the external environment.

[0008] Before conducting insulation testing on the stator lead-out cable connector, the material layer is placed in a liquid-holding state in advance; during testing, the above insulation test device is positioned and wrapped around the outer periphery of the cable connector, and after installation, the liquid-permeable surface faces the tested cable connector and wraps the cable connector, and the liquid-blocking surface isolates the material layer from the external environment, so that the liquid in the material layer can evaporate from the liquid-permeable surface toward the environment where the cable connector is located, thereby creating a closed humid space, and the relative humidity of the environment where the cable connector is located is relatively high, meeting the insulation test requirements. In addition, the test device is small in size, occupies little space, and has good conformability to the cable connector. It is not limited by the test space and can be placed anywhere with the product storage. It has high flexibility in use and strong versatility.

[0009] After the test device wraps the cable joint for a predetermined time, the tester measures the insulation resistance value at the cable joint position and determines the insulation performance of the cable joint based on the measured insulation resistance value.

[0010] Optionally, the material layer includes a super absorbent resin material, the super absorbent resin material is laid on the inner surface of an attachment substrate, the attachment substrate forms the liquid-permeable surface, and the liquid-blocking surface is circumferentially connected to the attachment substrate.

[0011] Optionally, the attachment substrate is a liquid-permeable structure formed by gauze, cotton cloth or linen cloth.

[0012] Optionally, the material layer has a thickness of 5 mm-20 mm.

[0013] Optionally, the thickness of the material layer is 7mm-12mm.

[0014] Optionally, the material layer has a water absorption capacity of at least 2 kg.

[0015] Optionally, the liquid-blocking surface includes a substrate, and an inner surface of the substrate facing the material layer is further provided with a waterproof coating.

[0016] Optionally, it further comprises a first positioning component and a second positioning component disposed on the base, wherein the first positioning component and the second positioning component cooperate to position the device in a test state of wrapping a cable connector.

[0017] Optionally, the first positioning component is a Velcro tape, and the second positioning component is a fluffy fabric layer arranged on the outer surface of the base; or,

[0018] The first positioning component and the second positioning component are a male buckle and a female buckle that snap together.

[0019] Optionally, the material of the area of ​​the base where the Velcro is installed is an elastic material.

[0020] Optionally, the base body has folded sections folded under the material layer at both ends along the length direction of the cable, the folded sections are engaged with the liquid-permeable surface, and at least the material of the folded sections in the base body is elastic material and / or the folded sections are retractable.

[0021] Optionally, the liquid-permeable surface is further provided with a conductor and a lead wire having one end connected to the conductor, and after the device is installed, the other end of the lead wire is located outside the liquid-blocking surface; or,

[0022] The liquid-permeable surface is a liquid-permeable structure formed by a conductor wire. The device also includes a lead wire with one end connected to the liquid-permeable surface. After the device is installed, the other end of the lead wire is located outside the liquid-blocking surface.

[0023] Furthermore, the present invention provides an insulation test method for insulation testing of a stator lead-out cable connector, the method comprising the following steps:

[0024] The insulation test device described in any one of the above items is fully contacted with the liquid in advance so that the material layer is in a liquid-holding state; and the conductor is pre-wound around the cable joint position to be tested;

[0025] The insulation test device is positioned on the outer periphery of the cable connector wrapped with the conductor. After installation, the liquid-permeable surface faces the tested cable connector and wraps the cable connector, the liquid-blocking surface isolates the material layer from the external environment, and the lead wire of the conductor is exposed outside the device;

[0026] The insulation testing device is kept wrapped around the cable joint for a predetermined time, and the insulation resistance value is measured, and the insulation performance of the cable joint is judged according to the measured insulation resistance value.

[0027] In addition, the present invention also provides an insulation test method for insulation testing of a stator lead-out cable connector, the method comprising the following steps: fully contacting the insulation test device with liquid in advance so that the material layer is in a liquid-holding state;

[0028] Position the insulation test device at the periphery of the cable connector. After installation, the liquid-permeable surface faces the tested cable connector and wraps the cable connector. The liquid-blocking surface isolates the material layer from the external environment, and the lead wire of the conductor is exposed outside the device.

[0029] The insulation testing device is kept wrapped around the cable joint for a predetermined time, and the insulation resistance value is measured, and the insulation performance of the cable joint is judged according to the measured insulation resistance value.

[0030] Since the above method is implemented on the basis of the above insulation testing device, the method also has the above technical effects of the insulation testing device. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A partial cross-sectional view of an insulation testing device in one embodiment of the present invention;

[0032] Figure 2 for Figure 1 A schematic diagram of the structure of the device shown in a flat state;

[0033] Figure 3 for Figure 1 The device is shown in a schematic diagram of wrapping a cable connector;

[0034] Figure 4 This is a flowchart of an insulation testing method provided by the present invention.

[0035] in, Figures 1 to 3 The corresponding relationship between the reference numerals and the component names is as follows:

[0036] 1-insulation test device; 11-liquid permeable surface; 12-material layer; 20-liquid blocking surface; 21-base; 211-folding section; 22-waterproof coating; 23-flannel fabric layer; 30-velcro;

[0037] 2- Cable connector. DETAILED DESCRIPTION

[0038] This paper conducts an in-depth study on the technical problems of the limitations of the water spray test on the insulation performance of the stator joint in the existing technology. The study found that the water spray test or immersion test is to provide an environment with a high humidity to measure the insulation resistance value of the stator joint. When the insulation resistance value meets a certain value, it is considered that the insulation of the stator joint meets the use requirements.

[0039] Based on the above research findings, this paper conducted exploration and a large number of experiments and proposed a test device that can provide an insulation test environment with a simple structure and high versatility.

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0041] Please refer to Figure 1 , Figure 2 and Figure 3 , Figure 1 A partial cross-sectional view of an insulation testing device in one embodiment of the present invention; Figure 2 for Figure 1 A schematic diagram of the structure of the device shown in a flat state; Figure 3 for Figure 1 The device is shown in a schematic diagram wrapped around a cable connector.

[0042] The present invention provides an insulation test device 1, comprising a material layer 12 with a liquid holding capacity, wherein the material layer 12 comprises a material with a liquid holding capacity, so that the material layer can hold a large amount of liquid during the test, and the liquid holding capacity of the material can be several times, dozens of times, hundreds of times, or even thousands of times its own weight. The preferred material herein is a highly absorbent resin material, which can be a polyacrylic acid polymer, or a starch-based or cellulose-based material, and its liquid holding capacity is thousands of times its own weight.

[0043] Usually the preferred liquid in the test is water, but it can be other liquids as long as it can provide the humid environment required for the insulation test of the cable connector 2.

[0044] The material layer 12 in the present invention is covered with a liquid-permeable surface 11 and a liquid-blocking surface 20 on both sides. The liquid-permeable surface 11 is formed by a liquid-permeable material that allows liquid to pass through, that is, the liquid-permeable surface 11 formed by the liquid-permeable material can allow the liquid held in the material layer 12 to pass through, and the liquid-blocking surface 20 is formed by a liquid-blocking material that blocks the liquid from passing through. When the insulation test device 1 is installed at the position of the cable connector 2, the liquid-permeable surface faces the cable connector 2 to be tested, and the liquid-blocking surface isolates the material layer 12 from the external environment. The main function of the liquid-blocking material is to prevent the liquid in the material layer 12 from volatilizing to the outside world, and to try to volatilize the liquid held in the material layer 12 from the liquid-permeable surface to the environment where the cable connector 2 is located to provide a humid test environment.

[0045] Before conducting an insulation test on the stator lead-out cable connector 2, the material layer 12 is placed in a liquid-holding state in advance; during the test, the insulation test device 1 is positioned and wrapped around the outer periphery of the cable connector 2. After installation, the liquid-permeable surface faces the tested cable connector 2 and wraps the cable connector 2. The liquid-blocking surface 20 isolates the material layer 12 from the external environment, so that the liquid in the material layer 12 can evaporate from the liquid-permeable surface 11 toward the environment where the cable connector 2 is located, thereby creating a closed humid space. The relative humidity of the environment where the cable connector 2 is located is relatively high, meeting the insulation test requirements. In addition, the insulation test device 1 is small in size, occupies little space, and has good conformability to the cable connector 2. It is not limited by the test space and can be placed anywhere with the product storage. It has high flexibility in use and strong versatility.

[0046] After the insulation testing device 1 wraps the cable joint 2 for a predetermined time, the tester measures the insulation resistance value at the position of the cable joint 2 and determines the insulation performance of the cable joint 2 according to the measured insulation resistance value.

[0047] Under the same material conditions, the thicker the material layer 12 is, the greater the amount of liquid it holds, and the longer it can create a humid space. Therefore, according to the test time of the tested cable joint 2, the thickness of the material layer 12 is appropriately selected; according to the insulation test time and the specific insulation performance requirements of the generator insulation (reflected in the amount of water absorbed by the material layer), when the insulation test time needs to be maintained for more than 2 hours, the thickness of the material layer 12 can be set to 5mm-20mm, preferably 7mm-12mm; when the water absorption needs to be maintained at 1.5kg to 2kg, the thickness of the material layer is selected to be 10mm. The thickness can also be set directly according to the water absorption required by the test, and the water absorption is set to more than 2kg.

[0048] In a specific embodiment, the material layer 12 includes an attachment substrate superabsorbent resin material, the superabsorbent resin material is laid on the inner surface of the attachment substrate, the liquid-permeable surface is directly formed by the attachment substrate, the liquid-blocking surface 20 is circumferentially joined to the attachment substrate to encapsulate the superabsorbent resin material in the liquid-blocking surface 20 and the attachment substrate, and the liquid-blocking surface 20 encapsulates the attachment substrate at the edge to prevent the superabsorbent resin material from evaporating liquid to the external environment when the attachment substrate surrounds the test connector.

[0049] In the above embodiment, the super absorbent resin material is laid on the inner surface of the attachment substrate, and the attachment substrate directly forms a liquid-permeable surface. The attachment substrate provides a support basis for the installation of the super absorbent resin material, and can directly form a liquid-permeable surface, and no other material layer is required on the inner surface of the attachment substrate.

[0050] The super absorbent resin material is laid on the inner surface of the attachment substrate, so that the super absorbent resin material fully absorbs liquid and is conducive to the rapid evaporation of liquid from the liquid-permeable surface.

[0051] Practice has proved that under the conditions of an ambient temperature of 25°C and a relative humidity of less than 40%, the device can ensure a stable humidity of 90% within 120 hours, which can fully meet the expected requirements of the water spray test.

[0052] The attachment substrate in the above embodiment is preferably a mesh structure formed by gauze, cotton or linen. Of course, the attachment substrate can also be other materials as long as it can meet the purpose of allowing liquid to pass through, which will not be described in detail herein.

[0053] In the above embodiments, the liquid blocking surface 20 includes a substrate 21, and the inner surface of the substrate 21 facing the super absorbent resin material is further provided with a waterproof coating 22. The waterproof coating 22 is mainly used to prevent water from volatilizing. The specific material can refer to the prior art.

[0054] The device 1 of the present invention may further include a first positioning component and a second positioning component disposed on the base 21 , and the first positioning component and the second positioning component cooperate to position the insulation test device 1 in a test state of wrapping the cable joint 2 .

[0055] That is to say, after the tooling is installed in cooperation with the cable connector 2, the tooling can be directly positioned by using the first positioning component and the second positioning component provided on the tooling, so the installation is convenient and fast.

[0056] There are many specific forms and structures of the first positioning component and the second positioning component, such as the Velcro 30 in an adhesive form, or a snap buckle form, or a tether form, etc.

[0057] In the present invention, Velcro 30 and snap fasteners are preferred. For example, the first positioning component is Velcro 30, and the second positioning component is a fluffy fabric layer 23 arranged on the outer surface of the base. The fluffy fabric layer 23 can be partially arranged on the outer surface of the base, and of course the fluffy fabric layer 23 can also be arranged on the entire outer surface of the base.

[0058] The first positioning component and the second positioning component are a male buckle and a female buckle that are snap-fitted. The specific forms of the male buckle and the female buckle are not limited.

[0059] The material of the area of ​​the base where the Velcro 30 is installed is an elastic material, so that the Velcro 30 can fit more closely to the fluffy fabric layer 23 after being attached.

[0060] In order to make the space where the cable connector 2 is located more airtight, the following settings are further made in this article.

[0061] In a specific embodiment, the base body has folded sections 211 folded under the material layer 12 at both ends along the length direction of the cable, the folded sections 211 are joined to the liquid-permeable surface 11, and at least the material of the folded sections 211 in the base body 21 is an elastic material, or the folded sections 211 are a retractable structure; because the folded sections 211 located in the length direction of the cable connector 2 are elastic, after the insulation testing device 1 is installed, the folded sections 211 can be circumferentially elastically attached to the cable, which is beneficial to the sealing of the space where the cable connector 2 is located and is beneficial to extending the holding time of the insulation test.

[0062] The insulation test of cable joint 2 is usually measured by instruments such as resistance meters. In order to facilitate the measurement of insulation resistance, this article can also make the following settings.

[0063] In a specific embodiment, a conductor and a lead wire connected to the conductor at one end may also be positioned on the liquid-permeable surface. After the insulation test device 1 is installed, the other end of the lead wire is located outside the liquid-blocking surface 20. In the above embodiment, the conductor and the lead wire are directly positioned on the liquid-permeable surface. When the insulation test device 1 is installed, the conductor is also positioned with the cable connector 2 at the same time, which reduces the installation process and improves the installation efficiency.

[0064] In another specific embodiment, the liquid-permeable surface is a liquid-permeable structure formed by a conductor wire, and the insulation testing device 1 also includes a lead wire with one end connected to the liquid-permeable surface. After the insulation testing device 1 is installed, the other end of the lead wire is located outside the liquid-blocking surface 20.

[0065] In this embodiment, the conductor and the liquid-permeable surface are integrated, and the structure is further simplified, which is conducive to full contact between the conductor and the cable connector 2.

[0066] Please refer to Figure 4 , Figure 4 The present invention provides a flowchart of a method for testing the insulation of a stator lead-out cable connector 2.

[0067] Based on the insulation test device 1 for the insulation test of the stator lead-out cable joint 2, the present invention also provides a method for the position insulation test of the stator lead-out cable joint 2. For the case where the conductor is combined with the liquid-permeable surface, the method comprises the following steps:

[0068] S11, fully contacting the insulation test device 1 with liquid in advance, so that the material layer is in a liquid holding state with a predetermined water absorption amount;

[0069] S12, positioning the insulation test device 1 on the periphery of the cable connector 2, after installation, the liquid permeable surface faces the tested cable connector 2 and wraps the cable connector 2, the liquid blocking surface 20 isolates the material layer 12 from the external environment, and the lead wire of the conductor is exposed outside the test device;

[0070] S13, keeping the insulation testing device 1 wrapped around the cable joint 2 for a predetermined time, and measuring the insulation resistance value, and judging the insulation performance of the cable joint 2 according to the measured insulation resistance value.

[0071] In addition, the conductor can also be set separately from the insulation testing device 1, so that the method for insulation testing of the stator lead-out cable connector 2 provided by the present invention includes the following steps:

[0072] S21, the insulation test device 1 is fully contacted with liquid in advance, so that the material layer is in a liquid holding state with a predetermined water absorption amount; and the conductor is pre-wound around the position of the cable connector 2 to be tested;

[0073] S22, positioning the insulation test device 1 on the outer periphery of the cable connector 2 wrapped with the conductor, after installation, the liquid permeable surface faces the tested cable connector 2 and wraps the cable connector 2, the liquid blocking surface isolates the material layer from the external environment, and the lead wire of the conductor is exposed outside the insulation test device 1;

[0074] S23, keeping the insulation testing device 1 wrapped around the cable joint 2 for a predetermined time, and measuring the insulation resistance value, and judging the insulation performance of the cable joint 2 according to the measured insulation resistance value.

[0075] Since the above method is implemented on the basis of the above insulation testing device 1 , the method also has the above technical effects of the testing device 1 .

[0076] The above is a detailed introduction to an insulation testing device and method provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. An insulation testing device, characterized in that: The invention is used for insulation testing of stator lead-out cable joints, comprising a material layer (12) capable of holding liquid, wherein both sides of the material layer (12) are covered with a liquid-permeable surface (11) and a liquid-blocking surface (20), wherein the liquid-permeable surface (11) is formed of a liquid-permeable material capable of allowing liquid to pass through, and the liquid-blocking surface (20) is formed of a liquid-blocking material capable of blocking liquid from passing through. When the device is used for insulation testing, it is installed at the cable joint position, the liquid-permeable surface (11) faces the cable joint to be tested, and the liquid-blocking surface (20) isolates the material layer (12) from the external environment.

2. The insulation testing device according to claim 1, characterized in that: The material layer (12) comprises a high water absorbent resin material, the high water absorbent resin material is laid on the inner surface of an attachment substrate, the attachment substrate forms the liquid permeable surface (11), and the liquid blocking surface (20) is circumferentially connected to the attachment substrate.

3. The insulation testing device according to claim 2, characterized in that: The attachment substrate is a liquid-permeable structure formed by gauze, cotton cloth or linen cloth.

4. The insulation testing device according to claim 1, characterized in that: The thickness of the material layer (12) is 5 mm-20 mm.

5. The insulation testing device according to claim 4, characterized in that: The thickness of the material layer (12) is 7 mm-12 mm.

6. The insulation testing device according to claim 1, characterized in that: The water absorption capacity of the material layer (12) is at least 2 kg.

7. The insulation testing device according to claim 1, characterized in that: The liquid-blocking surface (20) comprises a substrate (21), and the inner surface of the substrate (21) facing the material layer (12) is further provided with a waterproof coating (22).

8. The insulation testing device according to claim 7, characterized in that: It also comprises a first positioning component and a second positioning component which are arranged on the base (21), and the first positioning component and the second positioning component cooperate to position the device in a test state of wrapping a cable joint.

9. The insulation testing device according to claim 8, characterized in that: The first positioning component is a Velcro (30), and the second positioning component is a fluffy fabric layer arranged on the outer surface of the base (21); or, The first positioning component and the second positioning component are respectively a male buckle and a female buckle that snap together.

10. The insulation testing device according to claim 9, characterized in that: The material of the area of ​​the base (21) where the Velcro (30) is installed is an elastic material.

11. The insulation testing device according to claim 7, characterized in that: The base body (21) has folded sections (211) folded under the material layer (12) at both ends along the length direction of the cable, the folded sections (211) are connected to the liquid-permeable surface (11), and at least the material of the folded sections (211) in the base body (21) is elastic material and / or the folded sections are retractable.

12. The insulation testing device according to any one of claims 1 to 11, characterized in that: The liquid-permeable surface (11) is also provided with a conductor and a lead wire having one end connected to the conductor, and after the device is installed, the other end of the lead wire is located outside the liquid-blocking surface (20); or, The liquid-permeable surface (11) is a liquid-permeable structure formed by a conductor wire. The device also includes a lead wire with one end connected to the liquid-permeable surface (11). After the device is installed, the other end of the lead wire is located outside the liquid-blocking surface (20).

13. A method for insulation testing, characterized in that: Used for insulation testing of stator lead-out cable joints, the method comprises the following steps: The insulation test device (1) according to any one of claims 1 to 12 is fully contacted with liquid in advance so that the material layer (12) is in a liquid-retaining state; and the conductor is pre-wound around the cable joint position to be tested; The insulation test device (1) is positioned on the periphery of a cable joint wound with a conductor, and after installation, the liquid-permeable surface (11) faces the cable joint to be tested and wraps the cable joint, the liquid-blocking surface (20) isolates the material layer (12) from the external environment, and the lead wire of the conductor is exposed outside the insulation test device (1); The insulation testing device (1) is kept wrapped around the cable joint for a predetermined time, and the insulation resistance value is measured, and the insulation performance of the cable joint is judged based on the measured insulation resistance value.

14. A method for insulation testing, characterized in that: Used for insulation testing of stator lead-out cable joints, the method comprises the following steps: preliminarily bringing the insulation testing device (1) according to claim 12 into full contact with liquid so that the material layer (12) is in a liquid-retaining state; The insulation test device (1) is positioned on the periphery of a cable connector. After installation, the liquid-permeable surface (11) faces the tested cable connector and wraps the cable connector, the liquid-blocking surface (20) isolates the material layer (12) from the external environment, and the lead wire of the conductor is exposed outside the device; The insulation testing device (1) is kept wrapped around the cable joint for a predetermined time, and the insulation resistance value is measured, and the insulation performance of the cable joint is judged based on the measured insulation resistance value.

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