Withstand voltage test method and device for mineral substance magnesium oxide insulation copper sheath cable

Abstract

The invention belongs to the technical field of cable voltage withstanding tests, and particularly relates to a mineral magnesium oxide insulation copper sheath cable voltage withstanding test method and device, the device comprises a far-end oil cup, a near-end oil cylinder and a sealing gasket, the far-end oil cup is provided with a fixing groove and an oil injection groove which are communicated, and the inner diameter of the fixing groove is smaller than that of the oil injection groove; the near-end oil cylinder is provided with an oil injection cavity and a fixed cavity which are communicated, and the inner diameter of the fixed cavity is smaller than that of the oil injection cavity; the sealing gasket is arranged at the bottom of the oil injection cavity; the far-end oil cup and the near-end oil cylinder are provided with at least two inner threaded holes in the fixing groove and the fixing cavity respectively, and hexagon socket screws are in threaded connection with the inner threaded holes.

Description

Technical Field

[0001] The present invention belongs to the technical field of cable withstand voltage testing, and particularly relates to a method and device for withstanding voltage testing of a mineral magnesium oxide insulated copper sheathed cable. Background Art

[0002] Due to its excellent fire resistance and high temperature resistance, mineral magnesium oxide insulated copper sheathed cables are widely used in special working condition environments. However, in the prior art, there are the following problems when such cables are subjected to withstand voltage testing:

[0003] Moisture absorption problem: The magnesium oxide insulation layer is extremely prone to moisture absorption in the air, resulting in a decrease in insulation performance and easy breakdown or excessive leakage current during withstand voltage testing;

[0004] Structural defect: After the copper sheath is peeled, an arc transition cannot be achieved, and the magnesium oxide powder between the conductor and the copper sheath is loose, resulting in insufficient spacing between the conductor and the copper sheath and unable to meet the test voltage requirements;

[0005] Vague test results: The existing test methods cannot distinguish between end defects and cable body defects, resulting in difficult determination of test results. Summary of the Invention

[0006] Based on the problems mentioned in the above background art, the present invention provides a method and device for withstanding voltage testing of a mineral magnesium oxide insulated copper sheathed cable.

[0007] The technical solution adopted by the present invention is as follows:

[0008] In the first aspect, the present invention provides a device for withstanding voltage testing of a mineral magnesium oxide insulated copper sheathed cable, including a distal oil cup, a proximal oil cylinder, and a gasket. The distal oil cup is provided with a communicating fixing groove and an oil injection groove, and the inner diameter of the fixing groove is smaller than that of the oil injection groove; the proximal oil cylinder is provided with a communicating oil injection cavity and a fixing cavity, and the inner diameter of the fixing cavity is smaller than that of the oil injection cavity; the gasket is arranged at the bottom of the oil injection cavity; at least two internal thread holes are provided at the fixing groove and the fixing cavity of the distal oil cup and the proximal oil cylinder respectively, and an internal hexagonal bolt is threadedly connected in the internal thread hole.

[0009] Further, the inner hole size of the gasket is 1.0 - 1.5 mm smaller than the outer diameter of the cable.

[0010] Further, the outer ring slope of the gasket is 1 - 2°, and the size of the largest part of the outer ring is 0.5 - 1.0 mm larger than the inner diameter of the oil injection cavity.

[0011] Second aspect, the present invention provides a method for voltage withstand test of a mineral magnesium oxide insulated copper sheath cable, comprising the following steps: S1: Strip the copper sheath at the non-high voltage end of the cable, insert the copper conductor at the non-high voltage end into the distal oil cup, and fix the cable with an inner hexagon bolt; S2: Inject dimethyl silicone oil into the oil injection tank, and the height of the added dimethyl silicone oil is 2 - 2.5 cm to submerge the bottom of the copper sheath at the non-high voltage end; S3: Strip the copper sheath at the high voltage end of the cable, expose 4 - 5 cm of the copper conductor, and insert the high voltage end copper conductor upward into the proximal oil cylinder; S4: Put the vulcanized gasket on one side of the high voltage end of the cable and place it at the bottom of the oil injection cavity, inject dimethyl silicone oil into the oil injection cavity, and the height of the added dimethyl silicone oil in the oil injection cavity is 2 - 2.5 cm to submerge the bottom of the copper sheath at the high voltage end; S5: Connect one of the copper conductors exposed at the connection between the test high voltage end and the proximal oil cylinder; S6: Connect the test grounding end: including all copper conductors at the proximal oil cylinder that are not connected to the test high voltage end, the copper sheath at the proximal oil cylinder, the copper sheath at the distal oil cup, the inner hexagon bolts at the proximal oil cylinder, and the inner hexagon bolts at the distal oil cup.

[0012] Further, in step S4, the copper conductor exposed at the high voltage end is 3 - 4 cm higher than the upper part of the proximal oil cylinder, which is convenient for connecting the test high voltage end, and the top of the copper sheath is 3 - 4 cm lower than the upper part of the proximal oil cylinder.

[0013] Further, the method for manufacturing and vulcanizing the gasket in step S4 includes the following steps: S41: Use RTV silicone material for gasket manufacturing; S42: Before vulcanization, evenly apply a layer of silicone oil-based release agent on the inner surface of the mold; S43: Use alkoxysilane as the curing agent, where the weight ratio of the RTV silicone material to the curing agent is 100:2 - 3, and the curing time is 2 - 2.5 hours.

[0014] Advantages of the present invention:

[0015] 1. Through the filling of silicone gaskets and dimethyl silicone oil, the magnesium oxide insulation layer is completely isolated from air contact, avoiding the decline of insulation performance caused by moisture absorption, and fundamentally solving the problem of voltage withstand breakdown.

[0016] 2. The stepped design of the distal oil cup and the proximal oil cylinder, combined with the fixation of inner hexagon bolts, ensures uniform spacing between the copper sheath and the conductor, meets the spacing requirements of high voltage tests, and avoids abnormal leakage current caused by loose structure.

[0017] 3. The voltage withstand test can be completed with one-time installation, without repeated disassembly and oil injection, significantly shortening the test cycle; the height of the silicone oil liquid level is standardized, ensuring the consistency of test conditions and more reliable result judgment.

[0018] 4. Through reusable nylon oil cups / cylinders and standardized gasket molds, material loss is reduced; the operation steps are simple, reducing the dependence on professional personnel. Description of the Drawings

[0019] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings;

[0020] Figure 1 It is a schematic diagram of the assembly of the distal oil cup of the present invention;

[0021] Figure 2 It is a schematic diagram of the assembly of the proximal oil cylinder of the present invention;

[0022] The accompanying drawings are labeled as follows:

[0023] Distal oil cup 1, fixing groove 11, oil injection groove 12, proximal oil cylinder 2, oil injection cavity 21, fixing cavity 22, gasket 23, hexagon socket head bolt 24, internal thread hole 25, cable 3, copper sheath 31, copper conductor 32, dimethyl silicone oil 4. Specific embodiments

[0024] As Figures 1 to 2 shown, in the first aspect: a voltage withstand test device for a mineral magnesium oxide insulated copper sheath cable, comprising a distal oil cup 1, a proximal oil cylinder 2 and a gasket 23. The distal oil cup 1 is provided with a communicating fixing groove 11 and an oil injection groove 12, and the inner diameter of the fixing groove 11 is smaller than that of the oil injection groove 12; the proximal oil cylinder 2 is provided with a communicating oil injection cavity 21 and a fixing cavity 22, and the inner diameter of the fixing cavity 22 is smaller than that of the oil injection cavity 21; the gasket 23 is arranged at the bottom of the oil injection cavity 21; at least two internal thread holes 25 are provided at the positions of the distal oil cup 1 and the proximal oil cylinder 2 corresponding to the fixing groove 11 and the fixing cavity 22 respectively, and the internal thread holes 25 are internally threaded with hexagon socket head bolts 24.

[0025] By adopting the above technical solution, by setting the fixing groove 11 (small inner diameter) and the oil injection groove 12 (large inner diameter) of the distal oil cup 1, and the fixing cavity 22 (small inner diameter) and the oil injection cavity 21 (large inner diameter) of the proximal oil cylinder 2, and combining the internal thread holes 25 and the hexagon socket head bolts 24 to fix the copper sheath 31 of the cable 3, a stepped sealing structure is formed; the stepped design ensures that the distance between the copper sheath 31 and the conductor is uniform, avoiding the problem of insufficient distance caused by the looseness of magnesium oxide powder after peeling, and meeting the distance requirements of high-voltage tests; the bolt fixes the copper sheath 31, and in cooperation with the filling of dimethyl silicone oil 4, it effectively isolates the air from contacting with magnesium oxide, preventing the decrease of insulation performance caused by moisture absorption.

[0026] As a preferred solution, the inner hole size of the gasket 23 is 1.0 - 1.5 mm smaller than the outer diameter of the cable 3. The inner hole of the gasket 23 forms an interference fit with the outer wall of the cable 3. The interference fit completely isolates the air from entering the magnesium oxide layer, avoiding the breakdown risk caused by moisture absorption, and the tight fit reduces the shaking of the cable 3, ensuring the stable position of the conductor during the test.

[0027] As a preferred solution, the outer ring of the gasket 23 has a slope of 1-2°, and the size at the largest part of the outer ring is 0.5-1.0 mm larger than the inner diameter of the oil injection cavity 21. The outer ring of the gasket 23 forms a wedge-shaped fit with the inner wall of the oil cylinder. The slope design causes the gasket 23 to expand outwards when pressed, tightly filling the gap between the inner wall of the oil cylinder, preventing the leakage of dimethyl silicone oil 4. At the same time, due to the slope setting, the size at the smallest part of the outer ring is slightly smaller than the inner diameter of the oil cylinder, ensuring that the gasket 23 can be easily pressed in and self-locked, simplifying the operation steps.

[0028] Second aspect: A method for the withstand voltage test of a mineral magnesium oxide insulated copper sheathed cable, comprising the following steps: S1: Peel the copper sheath 31 at the non-high-voltage end of the cable 3, insert the copper conductor 32 at the non-high-voltage end into the distal oil cup 1, and fix the cable 3 with the hexagon socket head cap screw 24; S2: Inject dimethyl silicone oil 4 into the oil injection groove 12, and the height of the injected dimethyl silicone oil 4 is 2-2.5 cm to submerge the bottom of the copper sheath 31 at the non-high-voltage end; S3: Peel the copper sheath 31 at the high-voltage end of the cable 3, expose 4-5 cm of the copper conductor 32, and insert the high-voltage end copper conductor 32 upwards into the proximal oil cylinder 2; S4: Put the vulcanized gasket 23 on one side of the high-voltage end of the cable 3 and place it at the bottom of the oil injection cavity 21. Inject dimethyl silicone oil 4 into the oil injection cavity 21, and the height of the injected dimethyl silicone oil 4 into the oil injection cavity 21 is 2-2.5 cm to submerge the bottom of the copper sheath 31 at the high-voltage end; S5: Connect one of the copper conductors 32 exposed at the connection between the test high-voltage end and the proximal oil cylinder 2; S6: Test the grounding end connection: including all the copper conductors 32 at the proximal oil cylinder 2 that are not connected to the test high-voltage end, the copper sheath 31 at the proximal oil cylinder 2, the copper sheath 31 at the distal oil cup 1, the hexagon socket head cap screw 24 at the proximal oil cylinder 2, and the hexagon socket head cap screw 24 at the distal oil cup 1.

[0029] As a preferred solution, in S4, the copper conductor 32 exposed at the high-voltage end is 3-4 cm higher than the upper part of the proximal oil cylinder 2, which is convenient for connecting the test high-voltage end, and the top of the copper sheath 31 is 3-4 cm lower than the upper part of the proximal oil cylinder 2.

[0030] By peeling the copper sheath 31 at the non-high-voltage end and fixing it to the distal oil cup 1, extending the copper conductor 32 at the high-voltage end and inserting it into the proximal oil cylinder 2, the problem of fuzzy test results is solved: through standardized end treatment (such as controlling the length of the copper conductor 32), the defects of the end and the cable 3 body are clearly distinguished, improving the accuracy of result determination; and the copper conductor 32 at the high-voltage end is extended by 4-5 cm to ensure a safe distance when connecting the high-voltage test end and avoid arc discharge.

[0031] Secondly, the injection height of the dimethyl silicone oil 4 is standardized. Inject the dimethyl silicone oil 4 to submerge the bottom of the copper sheath 31 by 2-2.5 cm. The silicone oil completely covers the bottom of the copper sheath 31, blocking the contact path between the magnesium oxide and the air, ensuring the stable performance of the insulating layer. Standardizing the liquid level height eliminates the differences in manual operations and improves the repeatability and credibility of the test results.

[0032] Since the top end of the exposed copper conductor 32 is 3 - 4 cm higher than the proximal oil cylinder 2 and the bottom end is 3 - 4 cm lower than the proximal oil cylinder 2, the length of the copper conductor 32 not only meets the connection requirements of the high - voltage end but also avoids the risk of accidental short - circuit caused by being too long; and the end of the copper conductor 32 is located in the silicone oil in the oil cylinder, reducing the electric - field distortion and the possibility of partial discharge.

[0033] As a preferred solution, the manufacturing and vulcanization method of the gasket 23 in S4 includes the following steps: S41: The gasket 23 is made of RTV silicone material; S42: Before vulcanization, a layer of silicone - oil - based mold release agent is evenly applied to the inner surface of the mold; S43: An alkoxysilane is used as the curing agent, and the weight - part ratio of the RTV silicone material to the curing agent is 100:2 - 3, and the curing time is 2 - 2.5 hours.

[0034] The precise ratio and curing time ensure the elasticity and durability of the silicone gasket, making it not easy to age and crack during long - term use. The rapid vulcanization process shortens the production cycle, adapts to the needs of batch tests, and reduces the comprehensive cost.

[0035] The above has introduced the present invention in detail. The description of the specific embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A voltage withstand test device for a mineral magnesium oxide insulated copper sheathed cable, characterized in that: Comprising A distal oil cup (1), the distal oil cup (1) being provided with a communicating fixing groove (11) and an oil injection groove (12), the inner diameter of the fixing groove (11) being smaller than the inner diameter of the oil injection groove (12); A proximal oil cylinder (2), the proximal oil cylinder (2) being provided with a communicating oil injection cavity (21) and a fixing cavity (22), the inner diameter of the fixing cavity (22) being smaller than the inner diameter of the oil injection cavity (21); A gasket (23), the gasket (23) being arranged at the bottom of the oil injection cavity (21); At least two internal threaded holes (25) are provided at the fixing groove (11) and the fixing cavity (22) of the distal oil cup (1) and the proximal oil cylinder (2) respectively, and an internal hexagonal bolt (24) is threadedly connected in the internal threaded hole (25).

2. The voltage withstand test method and device for a mineral magnesium oxide insulated copper sheathed cable according to claim 1, characterized in that: The inner hole size of the gasket (23) is 1.0 - 1.5 mm smaller than the outer diameter of the cable (3).

3. The voltage withstand test method and device for a mineral magnesium oxide insulated copper sheathed cable according to claim 1, characterized in that: The outer ring slope of the gasket (23) is 1 - 2°, and the size of the largest part of the outer ring is 0.5 - 1.0 mm larger than the inner diameter of the oil injection cavity (21).

4. Method for voltage withstand test of mineral magnesium oxide insulated copper sheathed cable, based on the device according to any one of claims 1-2, characterized in that: Comprising the following steps: S1: Strip the copper sheath (31) at the non-high-voltage end of the cable (3), insert the non-high-voltage end copper conductor (32) into the distal oil cup (1), and fix the cable (3) through the internal hexagonal bolt (24); S2: Inject dimethyl silicone oil (4) into the oil injection groove (12), and the height of the added dimethyl silicone oil (4) is 2 - 2.5 cm to submerge the bottom of the non-high-voltage end copper sheath (31); S3: Strip the copper sheath (31) at the high-voltage end of the cable (3), expose the copper conductor (32) for 4 - 5 cm, and insert the high-voltage end copper conductor (32) upward into the proximal oil cylinder (2); S4: Put the vulcanized gasket (23) on one side of the high-voltage end of the cable (3) and place it at the bottom of the oil injection cavity (21), inject dimethyl silicone oil (4) into the oil injection cavity (21), and the height of the added dimethyl silicone oil (4) in the oil injection cavity (21) is 2 - 2.5 cm to submerge the bottom of the high-voltage end copper sheath (31); S5: Test one of the copper conductors (32) exposed at the connection of the high-voltage end to the proximal oil cylinder (2); S6: Test the grounding end connection: including all copper conductors (32) of the proximal oil cylinder (2) not connected to the test high-voltage end, the copper sheath (31) at the proximal oil cylinder (2), the copper sheath (31) at the distal oil cup (1), the internal hexagonal bolts (24) at the proximal oil cylinder (2) and the internal hexagonal bolts (24) at the distal oil cup (1).

5. The method for the withstand voltage test of the mineral magnesium oxide insulated copper sheathed cable according to claim 3, characterized in that: In S4, the copper conductor (32) exposed at the high-voltage end is 3 - 4 cm higher than the upper part of the proximal oil cylinder (2), which is convenient for connecting the test high-voltage end, and the top of the copper sheath (31) is 3 - 4 cm lower than the upper part of the proximal oil cylinder (2).

6. The method for the withstand voltage test of the mineral magnesium oxide insulated copper sheathed cable according to claim 3, wherein: The manufacturing and vulcanization method of the gasket (23) in S4 includes the following steps: S41: The gasket (23) is made of RTV silicone material; S42: Before vulcanization, evenly apply a layer of silicone oil-based release agent on the inner surface of the mold; S43: Use alkoxysilane as the curing agent, and the weight ratio of the RTV silicone material to the curing agent is 100:2 - 3, and the curing time is 2 - 2.5 hours.

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