Area of the invention

The present invention relates to a cable or pulling arrangement for pulling cables through a borehole and also a method for the pulling of cables through a borehole.

Background of the invention.

High voltage cables are normally held in stretches in the air over a land formation or in ditches in the ground. However, there has been a growing need to lay such cables in boreholes in rock formations or in the ground and soil. How to drill holes for laying cables is known, but the equipment presently available does not allow for pulling cables through long boreholes. For example, it is desirable to be able to pull such cables through boreholes which are several hundred metres long and also several kilometres long.

In order to pull such cables through long boreholes, it is important that the friction between the cable bundle and the interior of the borehole is low. Furthermore, in many cases it will also be important that the cables are in an ordered cable bundle.

It is further preferred that the pulling forces can be transferred uniformly to the cable. Purpose of the present invention.

Thus, it is an aim of the present invention to provide an arrangement and a method for pulling heavy elongated cables, such as high-voltage cables, through a long borehole. It is an aim of the present invention to uniformly transfer the forces arising with the pulling of the cable over the entire length of the cable. It is a further aim of the invention that the cables do not rub against the surface (such as the inner surfaces of the borehole) when being pulled.

It is a further aim of the invention to provide a stable cable arrangement which prevents damage to the cable, and which permits extraction in elongated boreholes.

When pulling cables through long boreholes, including horizontal, inclined, arched or vertical boreholes, friction forces arise between the cable bundle and the inside of the borehole. To date, these frictional forces have made it impossible to be able to pull cables through long boreholes without incurring damage to the cables.

Furthermore, there may also be a need to lay the cables in ordered bundle, for example, when one-wire high voltage cables are laid in a three foil arrangement. Therefore, it is an aim of the invention to provide a pulling arrangement which connects a number of clamps via coupling elements, and where the clamps bundle together a number of cables. It is a further aim of the invention that the coupling elements or clamps are directly or indirectly equipped with friction reducing means. When pulling cables through long boreholes or through boreholes with a steep incline, the forces can be so large in the cables that they are overloaded if the pull is directly on the cable. Therefore, clamps are described which can directly or indirectly be attached to the cable so that parts of the pulling forces will pass through the clamps, i.e. so that in practice one exerts forces at several points along the elongated length of the cables. Preferably the clamps are evenly distributed along the longitudinal direction of the cable bundle and connected via a number of coupling elements.

It is an aim of the invention to provide a pulling arrangement which enables pulling cables through long boreholes. The system must therefore; 1 . Include friction reducing means (such as wheels) between clamps and/or coupling elements and the borehole inner surface, for transport of the cables into (and out of) the borehole

2. To avoid damaging the cable outer sheath when pulling.

3. Bundling of cable, such as three-foil. E.g. for a one-wire voltage cable it is important that they are in a three-foil arrangement to reduce the power loss.

4. Securing the cable set in the event of short circuiting. The system keeps the cables in position in the event of a short circuit in the cable set.

5. Be able to withdraw the cable set in the event of a system fault or

renewal/upgrade of the installation.

6. Coupling element, preferably consisting of rails (mechanical reinforcement) used when the forces during pulling or the operational phase become too large for the cables to be exclusively present in the clamps. Wheels are mounted on the rails to reduce friction during pulling. When using rails (coupling element) the clamps will be anchored to the rail.

Summary of the Invention Thus, the present invention relates in a first aspect to a pulling arrangement or cable arrangement for the pulling of a cable or cable bundle through a borehole, characterised in that the pulling arrangement is comprised of;

- a number of clamp devices attached to the cable bundle in several positions in the longitudinal direction of the cable bundle,

- one or more coupling elements that connect two or more clamp devices in the longitudinal direction of the cable bundle,

- and that the pulling forces that are used for the pulling of the cable arrangement through the borehole are applied by at least one of said coupling elements, and transferred via said clamps to the cable bundle. In one embodiment, the arrangement also comprises a pulling head for pulling of the cable bundle, where the pulling head is comprised of a number of fasteners which can be attached to, and engage with, said coupling elements. In one embodiment the number of fastening means correspond with the number of coupling elements arranged radially on the clamps.

In one embodiment, radially arranged on the exterior of the said coupling elements and/or clamps, there is a number of friction-reducing means to reduce the friction between the pulling arrangement and the inner surface of the borehole when pulling through the borehole.

In one embodiment, said clamps comprise the means for fastening to the cable bundle and fastening means for attachment to the coupling elements.

In one embodiment, said clamps comprise openings or grooves for the uptake of the coupling elements that are placed crossways in relation to the clamps.

In one embodiment, as the coupling element is being secured to the clamps and cable bundle, the coupling elements width stretches mainly radially outwards from the longitudinal axis of the cable bundle.

In one embodiment, said friction reducing means comprises a number of wheels, and where the centre axis of said wheel is embedded in the coupling element.

In one embodiment, the arrangement comprises three cables and the clamps are adapted for receiving three cables, and that the arrangement comprises three coupling elements.

In one embodiment, said clamps have a triangular shape and comprise three contact surfaces which, with by the constriction of the clamp, engage the three cables of the cable bundle, and that said clamp comprises three fastening means for attachment to the three coupling elements of each clamp.

In one embodiment, the arrangement includes a load cell, set up for measuring forces which the cable bundle is subjected to when pulling through the borehole.

In one embodiment, the arrangement includes one or more accelerometers measuring acceleration in three planes, adapted to determine the position of the arrangement.

In one embodiment, the position of the cable arrangement is measured continually when pulling through the borehole so information from the accelerometers will provide coordinates of the elongated length of the borehole. In one embodiment, the arrangement includes image recording means such as a camera, and lighting equipment such as a headlight adapted to take photographs and/or video of the inner surface of the borehole.

In one embodiment, the arrangement includes one or more fibre cables, and that this/these are used for transmitting signals from the arrangement in the borehole to a data processing unit outside the borehole.

In one embodiment, said fibre cable signals are transferred from the load unit, accelerometers, and/or image recording means.

In one embodiment, said load unit, accelerometers, and/or image recording means are arranged in said pulling head.

In a second aspect, the present invention relates to a method for pulling a cable bundle through an elongated borehole, characterised in that a number of cables are bundled together to form a cable bundle with a number of clamps, and that a number of coupling elements are attached to said clamps in the longitudinal length of the cable bundle, and that pulling forces are applied on the one end part of the cable arrangement when pulling the cable bundle through a borehole.

In one embodiment, the arrangement includes a pulling head that attaches to the coupling elements for pulling the cable bundle through the borehole.

In one embodiment, pulling forces are applied via coupling elements to the clamps and to the cable bundle for the pulling of the cable bundle through the borehole. In one embodiment, pulling forces are also applied directly to the cable bundle.

In one embodiment, pulling forces are transferred via coupling elements and clamps to a number of contact points along the elongated length of the cable bundle. In one embodiment, a pulling head is applied and this is attached to the coupling elements.

In one embodiment, friction between the arrangement and the borehole inner surface is reduced by a number of friction-reducing means.

In one embodiment, the arrangement includes a load cell and the forces which the cable bundles are subjected to by pulling through borehole are measured.

In one embodiment, the arrangement includes one or more accelerometers and acceleration is measured in three planes, arranged to determine the location of the arrangement.

In one embodiment, the arrangement includes image recording means such as a camera, and lighting equipment such as a headlight and that images and/or videos of the inner surface of the borehole are recorded. In one embodiment, the arrangement includes one or more fibre cables, and that these are used for transmitting signals from the arrangement in the borehole to a data processing unit outside the borehole. Description of the figures

Preferred embodiments of the invention shall be described in more detail here with reference to the accompanying figures, where:

Figure 1 shows schematically in perspective a cable arrangement according to the invention comprising of a number of cables, clamps for fastening to the cables and coupling elements to connect the clamps.

Figure 2 shows schematically in perspective an alternative embodiment of a cable arrangement.

Figure 3 shows schematically in perspective a pulling head and how this is adapted to be attached to the coupling elements in a cable arrangement.

Figure 4 shows in perspective an embodiment of a clamp which can be used in the invention.

Figure 5 shows a cross section of another embodiment of a clamp, and how a number of coupling elements is fastened to this. Description of preferred embodiments of the invention.

Figure 1 shows a pulling arrangement 10 for pulling one or more cables through a borehole 1 1 . There are major challenges with the pulling of heavy and very long cables through boreholes that may be many kilometres long. A huge amount of friction arises between the cable arrangement and the inner surface of the borehole, and it takes extremely great forces to pull the cable through. The aim of the invention is therefore to reduce the friction between the cable arrangement and the borehole, and also to apply pulling forces to the cable such that these have a more uniform distribution throughout the length of the cable.

The pulling arrangement or cable arrangement 10 shown in figure 1 comprises a number of cables 12,14,16, bundled together in a cable bundle 15. The cable bundle 15 is held together by a number of clamps 20, which can be functionally designed in different ways. It is essential that they hold the cables 12, 14, 16 in place and that they are sufficiently secured to the cables so that the pulling forces can be

transferred via the clamps 20 to the cable bundle 15.

It is preferred that the clamps 20 consist of a clamping device 22 and one or more insertion elements 24, but it is not a prerequisite. Moreover, any insertion elements 24 have a shape such that they can form a good engagement with the cable bundle 15. Often this insertion element is made of a more flexible material than the clamping device 22, and it is preferred that the insertion material is plastic or silicone rubber. The clamping device 22 is equipped with fasteners 26, preferably adjustable, for clamping together.

In the radial circumference of the clamps 20 there are fasteners 20c suitable for attachment to a number of coupling elements 30. In a preferred embodiment to each clamp 20 there are attached three coupling elements 30 (as shown in Figure 2). In other embodiments there is only one coupling element 30 attached to the clamps 20 and further embodiments have clamps 20 attached to two or four coupling elements 30, and in further embodiments there are five or more coupling elements 30 fastened to each clamp 20.

Preferably, each of the coupling elements 30 extend along the length of the whole of the cable bundle 15, but in some embodiments the cable bundle 15 is fitted in the longitudinal direction with several coupling elements 30. If the clamp 20 is adapted for attaching multiple coupling elements 30, then at least one of these may extend throughout the length of the whole of the cable bundle 15, while one or more of the remaining coupling elements 30 can be applied in only parts of the length, and also so that additional coupling elements in total cover the whole or large parts of the cable bundle 15, in the longitudinal direction.

The clamps 20 can be of any type that is fastened well to the cable bundle 15, so one in the pulling of the cable bundle 1 5 through a borehole 1 1 can apply pull forces to the coupling elements 30 and that these, via a number of clamps 20, transfer the pulling forces to the cable bundle 15 in anchor points of all the clamps 20 to the cable bundle 15. As mentioned, in the clamps 20 there are attachment ears 20c equipped for connecting a coupling element 30 to clamps 20. In a preferred embodiment, a clamp 20 is equipped with recesses 20e for receiving the

corresponding longitudinal coupling elements 30. By such a joining of the coupling elements 30 in recesses 22e in the clamps 20, the stability of the cable arrangement 10 is improved. The clamps 20 and coupling elements 30, with the attachment of the clamps 20 to the cable bundle 15 provides a very stable cable arrangement 10, i.e. an arrangement 10 which is sufficiently stable such that very long cable bundles 15 can be pulled through an elongated borehole 1 1 . The considerable forces that are used for pulling the cable bundle 15 through the borehole 1 1 can be applied directly to the cable bundle 15, or indirectly to the cable bundle 15 and the cables 12,14,16 via coupling elements 30 and clamps 20.

A sufficient number of clamps 20 across the length of the cable bundle 15 will prevent the cable bundle 15 from rubbing against the inner surfaces 1 1 a of the borehole 1 1 when pulling through the borehole 1 1 . Although the purpose of the invention is to enable a pulling of heavy cable bundles 15 in a borehole 1 1 , the arrangement 10 can, with an attachment of clamps 20 and coupling elements 30 also be used on lighter cable bundles 15 and also for solutions which will not be pulled through boreholes 1 1 . The coupling elements 30 can, for example, be provided with means for attachment to other constructions, for instance, for suspension in pipelines, tunnels, etc. In a particularly preferred embodiment the width of the coupling element 30 extends radially, with respect to the centre axis of the cable arrangement 10. Hence, the coupling element 30 is in the form of a rail with a length, width and height. The width is substantially larger, perhaps 1 -10 multiples of the height. The rail-shaped coupling element 30 is arranged as edged (width extending radially outwards), and not flat on the circumference of the cable arrangement 10. This causes a significant stiffening in the cable arrangement 10.

It is preferable that the friction reducing means is in the form of wheels. When the width of the coupling elements is of a certain extension, the centre of the wheels 28 can be embedded in the coupling element 30. Thus, one can use the wheels 28 with a relatively large diameter as the centre of the wheels 28 are embedded in the rail, i.e. at a considerable distance from the radial outer periphery of the coupling element 30.

Furthermore, figure 1 shows a number of coupling elements 30 which couples together a number of clamps 20 in the longitudinal direction.

Essential to the arrangement 10 according to the invention is that the clamps 20, which are attached to the cable bundle 15 are held together by coupling elements 30 so that one pulls the cable bundle 15 by pulling the coupling elements 30.

Figure 2 shows schematically in perspective an alternative pulling arrangement 10 comprising a number of coupling elements 30 attached to clamps 20. In this embodiment there are coupling elements 30 that are equipped with friction reducing means 28. Moreover, this figure shows one embodiment of the clamp 20 composed of a clamp arrangement 22 and insertion elements 24.

It is also evident that the arrangement may include a fibre cable 29, preferably provided in the insertion element 24 and within the clamp element 22. Figure 3 illustrates a pulling head 40 and how this is adapted to be able to pull the cable bundle 15 via the coupling elements 30. The coupling elements 30 are attached via clamps 20 to the cable bundle 15. Figure 4 shows an example of an individual clamp 20. The clamp 20 which is shown in figure 4 has a triangular shape and is well suited for bundling together three cables 12, 14, 16. However, one can by the same principle create clamps 20 which are adapted to more or fewer cables. In order to establish a good grip/fastening for the cables (not shown in the figure), the clamp in the figure consists of two parts; an outer clamping arrangement 22 which adjustably can be clamped together about the cables, and insertion elements 24 which forms the very frictional engagement against the cables. It further appears that the clamp 20 of figure 4 is equipped with friction reducing means 28 for reducing friction between the arrangement 10 and the borehole 1 1 . The securing means 20g for attaching one clamp 20 to multiple coupling elements 30 is also shown in figure 4. This clamp 20 corresponds to the clamps 20 which are also shown schematically in figure 1 .

Figure 5 shows an embodiment of the clamp 20, equivalent to the embodiment also shown in figure 1 . The cross-section shows a number of cables 12, 14, 16, held together by clamps 20. The clamps 20 are comprised of two elements in this embodiment, namely the clamp arrangement 22 and insertion element 24. The clamping arrangement 22 is attached to the coupling elements 30.

As indicated above, the pulling arrangement 10 is designed to be able to pull a cable bundle 15 through an elongated borehole 1 1 . The pulling forces which are necessary to be able to pull the cables through the borehole 1 1 are uniformly distributed throughout the length of the cable as they are taken up by the longitudinal coupling elements 30 and the transverse clamps 20. By pulling through an elongated borehole the front part of the cable arrangement 10 will move through the hole of the borehole from the entrance at the one end and out of the bore hole at the other end. It is therefore preferred to equip this front part, preferably in the form of a pulling head 40, with the means to measure different parameters and conditions.

In one embodiment, the pulling arrangement 10, preferably the cable head 40, provided with a load cell capable of measuring forces the cable bundle 15 is exposed to at any time when being pulled through the borehole 1 1 . This will provide information about which forces the cable is subjected to, and also if these were to become large enough so that there is a risk of causing damage the cable. In one embodiment, the pulling arrangement 10, preferably the cable head 40, is provided with one or more accelerometers and one can thus measure the

acceleration in three planes. In this way one can easily determine the location of the arrangement, and would thus also determine how the borehole 1 1 extends through the rock formation.

In one embodiment, the pulling arrangement 10, preferably the cable head 40, is equipped with image recording means such as cameras, and lighting equipment such as a headlight to take images and/or videos of the inner surface (1 1 a) of the borehole (1 1 ).