Testing method for waterproof sealing performance of cable connector protection box

Abstract

The present application provides a method for testing the waterproof sealing performance of a cable joint protection box. By placing a cable joint with a protection box installed in a constant temperature water bath test device for alternating hot and cold cycles, the present application fully simulates the actual on-site immersion and humid environment of the cable joint and the protection box, the high temperature state when running at full load, and the high and low cycle changes of the cable temperature when the load fluctuates. The present application also combines the insulation resistance value before and after the test and the DC withstand voltage test results for comprehensive evaluation, thereby being able to objectively and effectively assess the sealing performance of the cable joint protection box. The present application's method can be used specifically for the detection method of the cable joint outer protection box to detect the sealing performance of the protection box, and can be promoted for sampling inspection by testing agencies, manufacturers, and users.

Description

Technical Field

[0001] The invention belongs to the field of cable test and detection, and in particular relates to a detection method specially used for assessing the waterproof sealing performance of a cable intermediate joint protection box. Background Art

[0002] With the continuous advancement of "cableization" in power grid construction, the mileage of cables of various voltage levels has increased year by year. Due to the space and environmental limitations of cable laying channels, typical urban cable laying scenarios include drainage pipes and cable trenches, and a considerable number of cable lines have cable bodies and cable intermediate joints that are in a state of submersion; in addition, with the large-scale construction and operation of photovoltaic power stations and wind farms, cable lines that serve as channels for collecting and transmitting electric energy are often directly buried in the soil in the field, and it is common for the operating environment of cable joints to be humid or even flooded all year round. Therefore, failures caused by water ingress to cable joints are a common cause of cable line failures.

[0003] In order to avoid failures caused by water ingress into the cable joints, more and more cable line users install a special protection box on the outside of the cable joints. The inside of the protection box is filled with waterproof sealant to prevent moisture in the external environment of the cable from penetrating into the cable joints and causing cable joint failures.

[0004] At present, due to the lack of unified national or industry standards for cable joint protection boxes, various types of explosion-proof box products emerge in an endless stream, with varying quality, and users have no reliable evaluation basis when choosing products. In particular, there is no clear assessment method for the waterproof sealing performance of cable joint protection boxes, resulting in many manufacturers on the market falsely exaggerating the waterproof sealing effect of their protection boxes. Summary of the invention

[0005] In view of this, an object of the present invention is to provide a method for detecting the waterproof sealing performance of a cable joint protection box, so as to solve or overcome at least one technical problem existing in the prior art.

[0006] The present application provides a method for testing the waterproof sealing performance of a cable joint protection box, comprising:

[0007] Step 1: Obtain a protection box and a cable, wherein the length of the cable is at least one meter greater than the length of the protection box, and cut the cable in the middle to form two cables;

[0008] Step 2: Use a cable connector to connect the two cut sub-cables, so that at least 0.5 m of the length of the two sub-cables is reserved relative to each other;

[0009] Step 3: Install the protection box outside the cable connector, inject sealant into the protection box, and wait for the sealant in the protection box to solidify;

[0010] Step 4: Wrap a copper shielding mesh and a wet cloth around the outside of the protection box, apply a voltage between the conductor in the cable and the wet cloth outside the protection box, and measure the insulation resistance between the conductor and the wet cloth outside the protection box;

[0011] Step 5: Remove the copper shielding mesh and the wet cloth from the protection box, and seal both ends of the cable;

[0012] Step 6: Place the cable connector with the protection box installed in a constant temperature water bath test device, so that the water surface is at least one meter above the protection box, and perform at least 20 cycles of heating and cooling;

[0013] Step 7, taking out the cable from the constant temperature water bath test device, and removing the seals at both ends of the cable;

[0014] Step 8, placing the copper shielding mesh and wet cloth outside the protection box again, applying voltage again, and measuring the insulation resistance between the conductor in the cable and the wet cloth outside the protection box;

[0015] Step 9. Ground the wet cloth and apply 25kV voltage between the conductor inside the cable and the wet cloth outside the protection box for a preset time.

[0016] Furthermore, in step 2, after the cable connector is installed, it is left to stand for at least 4 hours to allow the armor belt to dry.

[0017] Furthermore, in step 3, the method of injecting sealant into the protection box is:

[0018] Pour the sealant into the energy-draining hole of the protection box until the protection box is filled;

[0019] Cover the energy vent hole cover, wrap it with tape to tie it up, and set the energy vent hole upward.

[0020] Furthermore, in step 4 and step 8, the applied voltage value is 1000V.

[0021] Furthermore, in step 5, the method of sealing both ends of the cable is:

[0022] Strip-shaped waterproof sealant is used to wrap the two ends of the cable;

[0023] Wrap waterproof tape around the outside of the strip waterproof sealant;

[0024] Install cable sealing caps at both ends of the cable, and perform heat shrink molding operations on each of the cable sealing caps;

[0025] After the cable sealing caps are cooled, a heat shrink tube is placed on each cable sealing cap, and each heat shrink tube is heat-shrink molded;

[0026] A waterproof tape is used to seal and wrap around each of the heat shrink tubes.

[0027] Furthermore, when the strip-shaped waterproof sealant and the waterproof tape are used for winding, at least 3 turns are performed.

[0028] Further, the method for performing the heat shrink molding operation is:

[0029] Use an open flame or an electric heating gun to bake the cable sealing cap or the heat shrink tube, so that the cable sealing cap is attached to the outside of the waterproof tape, or the heat shrink tube is attached to the cable sealing cap.

[0030] Further, in step six, the cable connector with the protection box installed is placed in a constant temperature water bath test device for heating at a temperature of 70° C. to 75° C., and the heating is continued for at least 5 hours;

[0031] The cable connector with the protection box installed is cooled to a temperature within 10°C above room temperature.

[0032] Furthermore, in step 4 and step 8, the insulation resistance of each phase is measured according to the actual number of cores of the cable.

[0033] Furthermore, in step nine, the voltage is a DC voltage, and the preset setting time is at least 1 minute.

[0034] Further, when the difference between the insulation resistance measured in step 4 and the insulation resistance measured in step 8 is not greater than 5 times;

[0035] And, in step nine, after applying a voltage of 25 kV for a preset time, the protection box is not broken down;

[0036] It is determined that the protection box meets the waterproof sealing performance.

[0037] The beneficial effects of this application are:

[0038] The cable joint protection box waterproof sealing performance detection method provided by the present application fully simulates the actual on-site water-immersed and humid environment of the cable joint and protection box, the high temperature state when running at full load, and the high and low cycle changes of the cable temperature when the load fluctuates, and combines the insulation resistance value before and after the test and the DC withstand voltage test results for comprehensive evaluation, so as to objectively and effectively evaluate the sealing performance of the cable joint protection box. The method of the present application can be used specifically for the detection method of the cable joint outer protection box to detect the sealing performance of the protection box, and can be promoted for sampling detection by testing institutions, manufacturers and users. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0040] Figure 1 It is a schematic flow chart of a method for detecting the waterproof sealing performance of a cable joint protection box provided in accordance with an embodiment of the present invention;

[0041] Figure 2 It is a schematic diagram of a structure in which a protection box is installed outside a cable connector according to an embodiment of the present invention;

[0042] Figure 3 It is a schematic diagram of the effect of placing a cable connector equipped with a protection box provided by an embodiment of the present invention in a constant temperature water bath test device.

[0043] Among them, 1-cable, 2-protection box, 3-constant temperature water bath test device. DETAILED DESCRIPTION

[0044] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by the same or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0045] refer to Figures 1 to 3 The present application provides a method for detecting the waterproof sealing performance of a cable joint protection box, comprising the following steps:

[0046] Step 1: obtain a protection box 2 and a cable 1, wherein the length of the cable 1 is at least one meter greater than the length of the protection box 2, and cut the cable 1 in the middle to form two cables; it should be understood that the protection box 2 used for the test should be a good protection box 2, or a protection box 2 selected by sampling.

[0047] Step 2: Use a cable connector to connect the two cut sub-cables, so that the two ends of the two sub-cables that are relatively separated are at least 0.5m long, and the surface of the reserved end is not treated; after the cable connector is installed, let it stand for at least 4 hours to allow the armor belt to dry. Specifically, the cable connector can be cold shrink type, heat shrink type or prefabricated type.

[0048] Step three, install the protection box 2 outside the cable connector, inject sealant into the protection box 2, and wait for the sealant in the protection box 2 to solidify; the sealant here is a matching device of the protection box 2, which ensures the sealing of the protection box 2. The sealant is configured on site and is fully stirred.

[0049] Specifically, the method of injecting the sealant into the protection box 2 is as follows: inject the sealant into the energy release hole of the protection box 2 until the protection box 2 is full; cover the energy release hole cover, wrap it with tape for binding, and set the energy release hole upward. Finally, wait for the sealant in the protection box 2 to solidify completely.

[0050] Step 4: Wrap a copper shielding mesh and wet cloth around the outside of the protection box 2, apply a voltage of 1000 V between the conductor in the cable 1 and the wet cloth outside the protection box 2, and measure the insulation resistance between the conductor and the wet cloth outside the protection box 2; technicians in this field should understand that one end is connected to the conductor in the cable 1 and the other end is connected to the wet cloth outside the protection box 2.

[0051] Step 5: Remove the copper shielding mesh and the wet cloth from the protection box 2, and seal both ends of the cable 1.

[0052] Specifically, the method for sealing the two ends of the cable 1 is: wrapping the two ends of the cable 1 with strips of waterproof sealant; wrapping the outside of the strips of waterproof sealant with waterproof tape; installing cable caps at both ends of the cable 1, and heat shrinking each of the cable caps; after each of the cable caps cools down, a heat shrink tube is installed on each of the cable caps, and heat shrinking each of the heat shrink tubes is performed; and sealing and wrapping the outside of each of the heat shrink tubes with waterproof tape. Through the above operations, the sealing of the two ends of the cable 1 (cable 1 connected by a cable connector) is achieved, providing waterproof protection for subsequent tests.

[0053] When using the strip waterproof sealant and the waterproof tape for winding, wrap at least 3 times, preferably 4-6 times, and the cable cap and heat shrink tube are selected with appropriate sizes to avoid the diameter being too large, which will cause a large air gap at the end of the cable 1 after heat shrink molding, and avoid the problem of too small diameter leading to inability to install.

[0054] The method for heat shrinking the cable cap and the heat shrinkable tube is: use an open flame or an electric heating gun to bake the cable cap or the heat shrinkable tube so that the cable cap fits on the outside of the waterproof tape, or the heat shrinkable tube fits on the cable cap.

[0055] Step 6: Place the cable connector with the protection box 2 installed in the constant temperature water bath test device 3 (it should be understood that the entire cable 1 is placed in the constant temperature water bath test device), so that the water surface is at least one meter higher than the protection box 2, that is, Figure 3 The water level in the protective box 2 is higher than that in the protective box 2, and at least 20 cycles of heating and cooling (alternating hot and cold cycles) are performed.

[0056] Specifically, in this step, the cable connector equipped with the protection box 2 is placed in the constant temperature water bath test device 3 and heated to a temperature of 70°C to 75°C, and the heating is continued for at least 5 hours; then cooled, and the cable connector equipped with the protection box 2 is cooled to a temperature within 10°C above the room temperature.

[0057] It should be understood that by placing the cable connector equipped with the protection box 2 in the constant temperature water bath test device 3 for alternating hot and cold cycles, the cable connector and the protection are simulated as being immersed in water in an actual environment, as well as the high and low temperature cycles of the cable 1 when subjected to load fluctuations at high temperatures during full load operation.

[0058] Step 7: After the hot and cold alternating cycle is completed, the cable 1 is taken out from the constant temperature water bath test device 3, the seals at both ends of the cable 1 are removed, and the conductors at both ends of the cable 1 are exposed to facilitate voltage loading in subsequent tests.

[0059] Step 8. Place the copper shielding mesh and wet cloth outside the protection box 2 again, and apply voltage again. The voltage is the same as the voltage value in step 4, both are 1000V. In addition, one end is connected to the conductor and the other end is connected to the wet cloth. Then measure the insulation resistance between the conductor in the cable 1 and the wet cloth outside the protection box 2.

[0060] Step 9: Ground the wet cloth, and apply a 25 kV voltage between the conductor in the cable 1 and the wet cloth outside the protection box 2 for a preset time. Specifically, the applied 25 kV voltage is a DC voltage, and the preset time is 1 minute.

[0061] In this embodiment, in step 4 and step 8, the insulation resistance of each phase is measured according to the actual number of cores of the cable 1. Specifically, the insulation resistance of each phase is measured by connecting one end of the voltage to the conductor of each phase.

[0062] In this embodiment, steps one to nine are the specific operation process of the method for detecting the waterproof sealing performance of the cable joint protection box. As those skilled in the art should understand, it also includes the step of determining the waterproof sealing performance of the cable joint protection box 2. Specifically, the determination step includes: comparing the insulation resistance measured in step four with the insulation resistance measured in step eight, and observing whether the protection box 2 is broken down after step nine. When the difference between the insulation resistance measured in step four and the insulation resistance measured in step eight is not greater than 5 times (condition one); and in step nine, after applying a voltage of 25kV for a preset time, there is no breakdown (condition two); when both of the above conditions are met, it is determined that the protection box 2 meets the waterproof sealing performance. When any of the above conditions is not met, it is considered unqualified, and it is determined that the cable joint protection and product cannot meet the waterproof sealing requirements.

[0063] The cable joint protection box waterproof sealing performance detection method provided by the present application fully simulates the actual on-site water-immersed and humid environment of the cable joint and the protection box 2, the high temperature state when running at full load, and the high and low cycle changes of the temperature of the cable 1 when the load fluctuates, and combines the insulation resistance value before and after the test and the DC withstand voltage test results for comprehensive evaluation, so as to objectively and effectively evaluate the sealing performance of the cable joint protection box 2. The method of the present application can be used specifically for the detection method of the cable joint outer protection box 2 to detect the sealing performance of the protection box 2, and can be promoted for sampling detection by detection institutions, manufacturers and users.

[0064] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0065] Finally, it should be noted that: Obviously, the above embodiments are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the present invention.

Claims

1. A method for testing the waterproof sealing performance of a cable joint protection box, characterized in that: include: Step 1: Obtain a protection box and a cable, wherein the length of the cable is at least one meter greater than the length of the protection box, and cut the cable in the middle to form two cables; Step 2: Use a cable connector to connect the two sub-cables into the cable, so that at least 0.5 m of length is reserved at the two opposite ends of the two sub-cables; Step 3: Install the protection box outside the cable connector, inject sealant into the protection box, and wait for the sealant in the protection box to solidify; Step 4: Wrap a copper shielding mesh and a wet cloth around the outside of the protection box, apply a voltage between the conductor in the cable and the wet cloth outside the protection box, and measure the insulation resistance between the conductor and the wet cloth outside the protection box; Step 5: Remove the copper shielding mesh and the wet cloth from the protection box, and seal both ends of the cable; Step 6: Place the cable connector with the protection box installed in a constant temperature water bath test device, so that the water surface is at least one meter higher than the protection box, and perform at least 20 cycles of heating and cooling; Step 7, taking out the cable from the constant temperature water bath test device, and removing the seals at both ends of the cable; Step 8, placing the copper shielding mesh and wet cloth outside the protection box again, applying voltage again, and measuring the insulation resistance between the conductor in the cable and the wet cloth outside the protection box; Step 9. Ground the wet cloth and apply 25kV voltage between the conductor inside the cable and the wet cloth outside the protection box for a preset time.

2. The method for detecting the waterproof sealing performance of a cable joint protection box according to claim 1, characterized in that: In step 2, after the cable connector is installed, it is left to stand for at least 4 hours to allow the armor belt to dry.

3. The method for detecting the waterproof sealing performance of a cable joint protection box according to claim 1, characterized in that: In step 3, the method of injecting sealant into the protection box is: Pour the sealant into the energy-draining hole of the protection box until the protection box is filled; Cover the energy vent hole cover, wrap it with tape to tie it up, and set the energy vent hole upward.

4. The method for detecting the waterproof sealing performance of a cable joint protection box according to claim 1, characterized in that: In step 4 and step 8, the applied voltage value is 1000V.

5. The method for detecting the waterproof sealing performance of a cable joint protection box according to claim 1, characterized in that: In step 5, the method of sealing both ends of the cable is: Strip-shaped waterproof sealant is used to wrap the two ends of the cable; Wrap waterproof tape around the outside of the strip waterproof sealant; Install cable sealing caps at both ends of the cable, and perform heat shrink molding operations on each of the cable sealing caps; After the cable sealing caps are cooled, a heat shrink tube is placed on each cable sealing cap, and each heat shrink tube is heat-shrink molded; A waterproof tape is used to seal and wrap around each of the heat shrink tubes.

6. The method for testing the waterproof sealing performance of a cable joint protection box according to claim 5, characterized in that: When the strip-shaped waterproof sealant and the waterproof tape are used for winding, at least three turns are performed.

7. The method for testing the waterproof sealing performance of a cable joint protection box according to claim 5, characterized in that: The method of heat shrink molding is: Use an open flame or an electric heating gun to bake the cable sealing cap or the heat shrink tube, so that the cable sealing cap is attached to the outside of the waterproof tape, or the heat shrink tube is attached to the cable sealing cap.

8. The method for testing the waterproof sealing performance of a cable joint protection box according to claim 1, characterized in that: In step 6, the cable connector with the protection box installed is placed in a constant temperature water bath test device for heating at a temperature of 70° C. to 75° C., and the heating is continued for at least 5 hours; The cable connector with the protection box installed is cooled to a temperature within 10°C above room temperature.

9. The method for testing the waterproof sealing performance of a cable joint protection box according to claim 1, characterized in that: In step 4 and step 8, the insulation resistance of each phase is measured according to the actual number of cores of the cable.

10. The method for testing the waterproof sealing performance of a cable joint protection box according to claim 1, characterized in that: In step nine, the voltage is a DC voltage, and the preset time is at least 1 minute.

11. The method for testing the waterproof sealing performance of a cable joint protection box according to claim 1, characterized in that: When the difference between the insulation resistance measured in step 4 and the insulation resistance measured in step 8 is not greater than 5 times; And, in step nine, after applying a voltage of 25 kV for a preset time, the protection box is not broken down; It is determined that the protection box meets the waterproof sealing performance.

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