RU2693879C1 - Repaired cable and cable repair method - Google Patents

Abstract

FIELD: cable repair method.

SUBSTANCE: method of repairing a cable having a damaged cable sheath involves removing a damaged portion of the shell to expose the inner portion of the cable, coating the exposed inner portion of the cable with a first material to form a first repair layer, wherein the first material is a flexible material with open cells, coating the first repair layer with a second material which is flexible and impermeable to liquid, to form a second repair layer such that a space exists between the first and second repair layers, which can be filled with a curable resin or a composition with a curable resin, introduction of a curable non-conductive resin between the first and second repair layers, curing said curable resin, coating at least the entire section of the remote shell to form a third repair layer, the third repair layer comprising a second or a third material. Also disclosed is a repaired cable produced by this method.

EFFECT: invention provides repair of damaged cable section without increasing section diameter.

19 cl, 1 dwg

Description

The level of technology

The present invention relates to a method of repairing a cable having a damaged cable sheath and to cables with repaired cable sheaths.

Electrical cables, also called power cables, are used to transmit electrical energy. They are usually classified by voltage class in accordance with the requirements of the IEC 60038 standard, depending on the electrical energy they transmit. Cables used for voltages below 1 kV are called low voltage cables; cables used for voltages between 1 kV and 35 kV are medium voltage cables; and cables for voltages above 35 kV are high voltage cables. As a rule, the higher the voltage, the greater the thickness (diameter) of this cable. A conventional electrical cable contains inside one or more electrical wires (cores) or sets of wires (cores). The veins can be individually or complete surrounded by insulating materials, usually rubber or a thermoplastic polymer. The cable has an outer waterproof sheath that surrounds and protects the inside of the cable from water ingress and mechanical damage, for example, through abrasion, and provides additional electrical insulation.

Electrical cables can be laid over long distances and can be up to several hundred meters long. For transportation, cables are wound on a cable drum. Such cable reels, depending on the length of the cables to be transported, may have several meters in diameter. Cables can be fed from the drum using guide rollers to their temporary or final location, for example, when used in underground mining, mining or construction. When mobile works, portable cables are wound on drums after use and reused elsewhere.

When using and reusing cables, the surrounding cable sheath can be damaged, for example, from abrasion or mechanical stress, in particular, when cables are used under adverse environmental conditions, for example, when working in the mining industry or on construction sites. Such damage contains cracks in the sheath or partial removal of the sheath in one or more places on this cable. The higher the voltage, the greater the need to repair such damage to the cable sheath in order to prevent water from entering, reducing power supply disruptions and exposing a person to high voltage. There is a need to repair the cable sheath in place, i.e. "in the field", without the need for splicing the cable, i.e. without the need to separate the entire cable or its lived.

There are various ways to repair damaged cable sheaths. For example, a heat shrinkable tape or sleeve can be applied over the damaged area of the shell, which subsequently thermally shrinks into place to provide a waterproof shell. However, the application of heat-shrinkable tapes may result in the repaired section having a substantially larger diameter than the adjacent section of the original cable, i.e. to the fact that the cable contains a significant bulge. This can be a disadvantage when winding a cable onto a cable drum, for example for storage or transportation, or when feeding a cable through a guide roller.

Another method of repair uses the so-called cold shrink tubing. Such tubes are placed on top of the damaged section and set down in a cold position. However, to put a tube of cold shrinkage on the cable, the damaged area must either be near the end of this cable, or it must be spliced, which is undesirable. Since electric cables can be very long (hundreds of meters), placing a cold tube on one end of the cable and moving it to the damaged section can be difficult and time consuming, especially when the cable is placed in the final position, connected to power consuming equipment and does not have to be moved .

Other methods apply coating to a damaged section with a curable resin. Usually, a removable plastic mold is placed around the cable at the damaged section and a curable resin is poured into this mold. After curing is completed, the mold is removed, and the cured resin covers the damaged section. This method leaves the cured resin open to the environment, and the repaired section may be vulnerable to abrasion and other damage. When the repaired section is covered with protective materials, for example, insulating and reinforcing tapes, to ensure, for example, better abrasion resistance, the diameter of the damaged cable section can increase significantly, leading to a significant bulge on the cable. Sections repaired in this way tend to be less flexible than unrepaired cable sections.

Therefore, there is a need for alternative or improved repair methods.

Disclosure of the invention

In one aspect, a method for repairing a cable having a damaged cable sheath is proposed, comprising:

(i) if necessary, removing the damaged part of the sheath to expose the inside of the cable;

(ii) coating the exposed inside of the cable with a first material to form a first repair layer, the first material being flexible and containing material with open cells;

(iii) coating the first repair layer with a second material, which is flexible and impermeable to liquid, with the formation of the second repair layer so that between the first and second repair layers there is a space that can be filled with a composition containing a curable resin,

(iv) introducing a composition containing a curable resin between the first and second repair layers;

(v) curing said curable resin;

(vi) coating at least the entire section of the removed shell to form a third repair layer, the third repair layer comprising a second or third material or a combination thereof.

In another aspect of the proposed power cable containing the inner part, covered with outer cable sheath, and the specified cable contains at least one section of the repaired cable sheath containing in the following order from the inner part of the cable to its outer part:

(i) a first repair layer containing a flexible first material containing an open-cell material;

(ii) a second repair layer covering the first repair layer and containing a second material that is flexible and impermeable to liquid;

(iii) a layer of cured resin between the first and second repair layers, filling at least most of the open cells of the first material;

(iv) a third repair layer covering at least the repaired section and containing either the second or third material.

In yet another additional aspect, a cable drum is provided comprising a repaired cable wound on it.

The advantage of the method in accordance with the present invention is that it requires only a small number of components and is easy to use. Repair can be performed "in the field" and without the need for splicing the cable, and can also be performed on a continuous cable. To carry out repairs, the position of the cable must not be changed. The method can additionally lead to the fact that the repaired cable section has essentially the same diameter as the adjacent section of the original (intact) cable. In addition, repaired sections may have flexibility similar to an intact cable.

Brief Description of the Drawings

In FIG. 1 is a schematic representation of a repaired cable in accordance with an embodiment of the present invention in a side view in partial cross-section during repair.

Detailed description

Power cables contain a core or multiple cores. The veins may be individually or complete surrounded by one or more layers of insulating material, usually rubber, for example EPDM rubber, or a flexible thermoplastic and insulating polymer. The conductors and their insulation usually form the inside of the cable. The inner part of the cable is protected by the surrounding sheath, which forms the outer part of the cable. This shell protects the inside from water ingress, physical damage and can additionally provide electrical insulation. The shell is usually made of flexible, durable and moisture-proof material, for example, rubber or other polymeric materials, for example, flexible thermoplastics, and it may contain additional functional ingredients, for example, flame retardants, etc. The shell may also contain reinforcing elements, like fibers, to provide additional protection against physical damage.

Cable diameter and sheath thickness may increase with increasing voltage ranges within which these cables are used. Usually, cables can have a diameter of approximately 20 mm to 95 mm. Typically, the thickness of the cable sheath can be from about 1 mm to 10 mm, preferably from about 2 mm to 5 mm.

Preferably, the cable in accordance with the present invention is a medium voltage cable, i.e. cable used for voltages between 1 kV and 35 kV.

For further illustration, we will now make a link to FIG. 1 without intending to limit the present invention to its embodiment shown in FIG. 1. In FIG. 1 shows an image of an electric cable (10) having a damaged shell. When the sheath is damaged, a damaged sheath section may expose the inside of the cable. In the event that only a damaged area is very small or not deep, or both, it may be advantageous to remove a larger shell section, for example, by using a proper knife or cutter in such a way that the inside of the cable becomes bare and more accessible. This case is illustrated in FIG. 1, which shows the section of the cable (10), which has been completely removed shell in such a way that exposed the inner part of the cable. In the cable shown in FIG. 1, its interior contains three insulated conductors (12). When removing the damaged shell and, optionally, surrounding the intact sections of the shell, care should be taken to ensure that the conductors and their insulating material are not damaged.

As a rule, it is considered that sections up to approximately 1000 mm long are conveniently repaired using methods in accordance with the present invention. Therefore, it is preferable to remove shell sections with a length of less than 1000 mm.

The first material (20) containing the open-cell structure (also referred to herein as the open-cell material) is applied to the exposed inside of the cable. Preferably, the material (20) with open cells is wound around the exposed inside, as shown in FIG. 1. Preferably, the material with open cells is applied on the exposed inside in such a way that it completely covers it. The open cell structure contains cells that can be filled with a curable resin. Open cells of an open cell structure can be at least partially, preferably, completely filled with a curable resin used in the repair method, i.e. open cells of an open-cell structure are large enough to receive a curable resin. Curable resins of different viscosities can be used and the size of the open cells can be adjusted accordingly. As a rule, the cells of an open-cell structure have a length or diameter in the range of approximately 0.1 mm to 20 mm. Open cells of a structure with open cells may be correct or incorrect.

The open-cell structure may be made of woven or non-woven material such that open cells are formed between the fibers of this woven or non-woven material. A structure with open cells may also consist of pores. A material with open cells may also be a foam material having an open cell structure. The underside of this material is with open cells, i.e. the side facing the exposed inside of the cable may or may not have open cells. For example, in cases where it is undesirable for a curable resin to cover the exposed inside, the bottom surface of the open-cell material does not have open cells, but may have an undisturbed continuous surface separating the exposed inside of the cable from the curable resin. Alternatively, a barrier material, for example, a solid liquid-tight tape, is placed over the exposed inside of the cable prior to the application of the material with open cells. In addition, alternatively, open-mesh material may be wound around the exposed inside several times, or this material may have a substantial thickness so that the curable resin cannot penetrate or only partially penetrates it and reaches only part of the inside of the cable, but not fills it completely. However, as a rule, it may be necessary that the curable resin penetrates into the material with open cells and can come into contact with the exposed inside.

A material with open cells typically has a thickness of from about 0.5 mm to 10 mm, preferably from about 1.5 mm to 3 mm. Material with open cells is preferably sufficiently flexible so that it can be wound around the exposed inside of the cable, preferably with your hands. The material with open cells is preferably also adapted to be stretched by the hands in the longitudinal direction, i.e. cable direction (i.e. parallel to the cable length). The material with open cells is preferably a tape of non-woven or woven material of polymer fibers, preferably fibers containing polypropylene, polyester, polyamide, or a combination or mixture thereof. Preferred fibers contain polypropylene, and consist entirely of polypropylene. In accordance with another embodiment of the invention, the open-cell material is a foam material having an open-cell structure at least on its upper surface, configured to receive a curable resin. This foam material may contain, for example, polyurethane foams.

The material with open cells covers at least part of the exposed inside, preferably the completely exposed inside, and forms the first repair layer. The first repair layer may contain overlapping turns of the tape, as shown in FIG. 1. In fact, the first repair layer may contain overlapping turns in the horizontal direction (along the cable length), as shown in FIG. 1, but also in the vertical direction, for example, by winding material (20) with open cells around the inside of the cable several times. Preferably, the open-cell material (20) is a tape, and is wound around the insulated cores (12) to form a continuous coating on the exposed inside of the cable.

Then a second material (40) is applied to the material (20) with open cells. The second material (40) is applied in such a way that between the material (20) with open cells and the second material (40) there remains a space into which a curable resin can be introduced to form a layer (30) of cured resin, as shown in FIG. 1. Typically, said space is designed in such a way that a layer of cured resin can be formed, having a thickness of approximately 0.5 mm to 20 mm. Such a space can be created, for example, by using the second material in the form of a tape or sheet and weakly winding it around the first repair layer formed by the material (20) with open cells. If necessary, for example, depending on the length of the exposed section, the second material can be fastened at one or more locations on the material with open cells, for example, using (removable) clamps or tapes or other suitable means.

The second material (40) is preferably liquid impermeable and has an unbroken continuous surface in such a way that a curable resin does not penetrate it. In accordance with a preferred embodiment of the invention, the second material (40) is transparent. This provides the ability to monitor the distribution and distribution of curable resin through open-cell material, as well as the ability to facilitate the distribution and distribution of this resin if necessary, for example, by manually applying pressure. The composition and thickness of the second material (40) may depend on whether the second material is intended to form the outer layer of the repaired section, or it forms an intermediate layer. If the second material forms the outer layer of the repaired jacket, it must be of substantial thickness and strength to provide insulation, abrasion resistance and water resistance, as required for the outer layers of power cables.

If the second material used is one or more intermediate layers, its thickness must include the application of one or more outer layers that provide the necessary protection and / or insulating properties, and therefore the second material may be rather thin. Usually, the second material is a PVC tape or PVC sheet, which means that the second material is provided in the form of a tape or a sheet and contains PVC (polyvinyl chloride) or consists entirely of PVC and optional additives. In the art, such materials are also called vinyl tapes or vinyl sheets.

In accordance with a preferred embodiment of the invention, the second material is a transparent PVC tape. Preferably, the second material (40), preferably a transparent PVC tape, has a thickness of from approximately 0.05 mm to 15 mm, more preferably from approximately 0.1 mm to 0.5 mm.

The second material is wound around the first repair layer to form a second repair layer. Like the first repair layer, the second repair layer can also be a layer formed by sequentially winding a tape around the inside of the cable in such a way that one turn partially overlaps the previous turn. Accordingly, the second repair layer may comprise a sequence of overlapping turns in the horizontal direction (along the cable length). The second repair layer may also contain more than one layer, for example, the second repair layer may be created by winding the tape around the inside of the tape many times, and may also contain overlapping turns in the vertical direction as well.

The composition containing the curable resin is introduced into the space between the first protective layer containing the material with open cells and the second protective layer containing the second material. This composition can be introduced through one or more holes in the second repair layer, which were either intentionally created when the second material was applied to the first repair layer, or were created in the second repair layer by cutting through one or more holes in it. This composition can be introduced into the space between the first and second repair layers using a suitable device, for example, a nozzle, for example, a cartridge nozzle or other container.

The curable resin can be any resin suitable for sealing cables or sheaths in splicing operations. Preferably, the curable resin is cured to form a flexible resin, for example a resin layer that can be bent by hand. Such electrically insulating resins are known in the art and contain, for example, a curable polyurethane resin. Such curable polyurethane resins are typically offered in the form of reactive two-component compositions that are combined or mixed together before use. These reactive components react with each other in a curing reaction to form a cured polyurethane resin. Other types of curable resins may also be used, for example, heat-curing resins or resins that harden when exposed to suitable radiation. Examples include acrylic resins and epoxy resins.

The curable resin composition is introduced into the space between the first and second repair layers and allows it to enter or penetrate into the material (20) with open cells. Preferably, this composition is colored, and the second repair layer is transparent so that the distribution of the resin over the material with open cells can be observed and maintained, for example, by applying manual pressure if necessary. In accordance with a preferred embodiment of the invention, the third material (50) is used, preferably also in the form of a tape, and is wound tightly around the second repair layer, thus facilitating the distribution of the resin over the interface between the first and second repair layers and its entrance into the open cells of the material with open cells or even penetration into it. The third material is optional, but its use is preferred. It can form the outer layer of the repaired cable section. For this purpose, any suitable material can be used. Preferably, this material is electrically insulating and impermeable to water and other liquids. It contains a continuous undisturbed material and surface. Preferably, the third material contains PVC, and, more preferably, the third material is a PVC tape. Preferably, the third material, when used to form the outer layer, is thicker than the second material. Preferably, the thickness of the second material is less than the thickness of the first material. Preferably, the third material contains on its lower surface one or more adhesive layers for attaching the third material to the second repair layer and to itself when winding around itself one or more times.

The dimensions of the first, second, and optional third or optional additional layers may be chosen in such a way that the thickness of the repaired section is essentially the same as the diameter of the adjacent whole, i.e. intact part of the cable. “Essentially the same” as used herein means that the diameter of the repaired section is the same as the diameter of the adjacent section of the original (intact) cable, or its diameters are up to 50% larger than the diameter of the adjacent original (intact) cable, preferably no more than 25%.

The present invention will now be illustrated by way of examples without the intent to limit the present disclosure to those examples.

Example 1

The 360 mm long section of the KGES-type cable casing (KGES) was cut using a cable cutter to expose the inside of the cable containing several twisted insulated conductors. The KHPP cable has a diameter of approximately 32 mm, and its sheath has a thickness of approximately 3 mm. For the formation of the first repair layer around the entire length of the exposed inside of the cable, one layer of polypropylene mesh tape (SW10 GAASBAND from 3M Company, MN / USA) was wound with a thickness of approximately 0.65 cm. Then, to create a continuous second repair layer covering and surrounding the entire the first layer, around the first repair layer was freely wound a transparent PVC tape (3M EZ wrap 2183 from 3M Company, MN / USA, thickness about 0.2 mm). Due to the free winding of the tape around the first repair layer, a space remains between the first and second repair layers, which can be filled with resin. If necessary, the second repair layer can be fixed in several places with removable clamps or tapes. Then, in order to provide several holes through which resin can be introduced into the space between the first and second repair layers, this repair layer was cut with a sharp knife in several places. Through the holes in the space between the first and second repair layers, a curable two-component reactive mixture was introduced for the production of polyurethane resin (3M SCOTHCAST ELECTRICAL INSULATING RESIN 2131 from 3M Company, MN / USA), and it was allowed to enter the material with open cells in first repair layer. Since this resin was colored 2131, its distribution was observed and introduced until approximately 70-80% of the space was covered with this resin, which was enough to produce a layer of cured resin having a thickness of approximately 3-4 mm. To seal the holes around the second repair layer, 3M EZ wrap 2183 material was wound. To create a protective outer layer (third protective layer) with high abrasion resistance around the repaired section, elastic PVC insulation tape was wound 4 times (3M SCOTH HEAVY DUTY VINYL ELECTRICAL TAPE 22 from 3M Company, MN, USA, thickness approximately 0.3 mm). The total thickness of all repair layers was approximately 4-5 mm, which corresponds essentially to the thickness of the removed shell, and the repaired section had essentially the same diameter as the remaining part of the cable. 20 minutes after putting the resin in, it essentially hardened and the cable was ready for commissioning. The repaired section was flexible and could be bent by hand. The flexibility of the repaired section was comparable to the flexibility of the original cable (as was tested by bending the cable with your hands).

Comparative Example 1

Example 1 was repeated, but with the exception that the first material was not used. The repaired cable was tested for flexibility by bending it around the repaired section, using physical force. The force required for cable bending in comparative example 1 was greater than the force required for cable bending in example 1 in the same way.

Claims (29)

1. The method of repairing a cable having a damaged cable sheath, comprising: (i) if necessary, removing the damaged part of the sheath to expose the inside of the cable; (ii) coating the exposed inside of the cable with a first material to form a first repair layer, the first material being flexible and containing a structure with open cells; (iii) coating the first repair layer with a second material, which is flexible and impermeable to liquid, with the formation of the second repair layer so that between the first and second repair layers there is a space that can be filled with a composition containing a curable resin, (iv) introducing a composition containing a curable resin between the first and second repair layers; (v) curing said curable resin; (vi) coating at least the entire section of the removed shell to form the third repair layer, the third repair layer comprising the second or third material or a combination thereof. 2. The method according to p. 1, in which the second or third repair layer or both layers contain polyvinyl chloride (PVC). 3. The method according to any one of paragraphs. 1 or 2, in which the material with open cells contains a polymer selected from: polypropylene, polyethylene, polybutadiene, polyester, polyamide, or a combination or mixture thereof. 4. A method according to any one of the preceding claims, wherein the open-cell structure comprises polymeric fibers of a woven or non-woven material, the polymeric fibers containing polypropylene, polyester, polyamide, or a combination or mixture thereof. 5. A method according to any one of the preceding claims, wherein the first material is a polypropylene mesh. 6. A method according to claim 1, wherein the open cell structure is an open cell foam material. 7. The method according to any one of the preceding claims, wherein the curable resin is included in at least most of the open cells of the open cell structure. 8. The method according to any one of the preceding claims, wherein the curable resin is cured to form polyurethane. 9. A method according to any one of the preceding claims, wherein the thickness of the first, second, and optional third repair layers is chosen such that the repaired cable section has essentially the same diameter as the adjacent original cable section. 10. A method according to any one of the preceding claims, wherein a composition comprising a curable resin is introduced through at least one hole slotted in the second repair layer. 11. A method according to any one of the preceding claims, wherein the second and optional third material is tapes. 12. The method according to any one of the preceding claims, wherein the second and optional third material are tapes containing polyvinyl chloride. 13. The method according to any of the preceding paragraphs, in which the second material is transparent. 14. The method according to any of the preceding paragraphs, in which the cable is a power cable for use at voltages in the range from approximately 1 to 35 kV. 15. Power cable containing the inner part, covered with outer cable sheath, moreover, the specified cable contains at least one section of the repaired cable sheath containing in the following order from the inner part of the cable to its outer part: (i) a first repair layer containing a flexible first material containing an open cell structure; ii) a second repair layer covering the first repair layer and containing a liquid-impermeable second material; (iii) a layer of cured resin between the first and second repair layers, filling at least most of the open cells of the open cell structure of the first material; (iv) a third repair layer covering at least the repaired section and containing either the second or third material. 16. The cable of claim 15, wherein the diameter of the repaired cable section is substantially the same as the diameter of the adjacent section of the original cable. 17. Cable according to any one of paragraphs. 15 or 16, in which the cable is a power cable for voltages in the range of approximately 1 to 35 kV. 18. Cable according to any one of paragraphs. 15-17, in which at least one section of the repaired cable jacket obtained by the method according to claim 1. 19. Cable drum containing wound on him cable according to any one of paragraphs. 15-18.

Images