This patent application discloses a new type of electrical power cables, process for production of power cables, insulating and laying of electric cables on the seabed need n one , as indicated in the preamble of the following claim 1 . The cables are referred to in this patent application as HVDC ( high voltage direct current - c able s ) cables .

Background:

Electric power transport has been carried out in electric cables ever since it was discovered and started to benefit from this form of energy / energy carrier. As a rule, the transmission of large amounts of electrical energy over a certain distance was made in air insulated high voltage wires attached to insulators on posts. The distribution of electrical energy in houses was done in insulated wires, where paper and rubber were used as insulating material. Later, various plastics were also used as insulating materials.

Copper or aluminium wires were used as electrical conductors. In conductors where relatively small amounts of electrical energy were to be transported, a conductor was usually used. In cables where large amounts of energy are to be transported, several (many] wires are twisted together to form a thicker cable. This is done to make the cable flexible and flexible. Gradually, there was a need to transfer ever-increasing amounts of energy in insulated cables. This was both low voltage, that is to say voltage below 1000 volts and high voltage, that is to say over 1000 volts.

In principle, the cables were constructed in the same way as before, in that many relatively thin conductors were twisted together into thicker copper or aluminum wires, which were subsequently insulated with various types of insulating material, such as plastics. The advantage of this is that you get flexible cables that can be easily bent. This makes it easy to roll the cables into large drums for transport and later laying in soil ditches or on the seabed. The disadvantage is that the cables become relatively expensive and they will always have a limited capacity. Cables are about 10 times more expensive than air lines.

The development of renewable energy, and in particular the offshore wind, has made it necessary to be able to transport large amounts of electrical energy over very large distances. In practice, it has been found that with today's conventional power cables, it is not possible to carry as large amounts of energy as needed, regardless of whether AC (DC) or DC (DC) is transformed up to very high voltage level.

New technology:

This patent application, as mentioned earlier, deals with a whole new type of direct current cables designed to transmit huge amounts of HVDC electrical energy over long distances. The cables are so- called "one - conductors", where the two cables with a certain spacing being added simultaneously.

Cable structure:

A single-conductor cable is constructed with a solid core of aluminum. Around the aluminum core is a thin layer of semiconductor. This may be, for example, a mixture of soot and P o yetylene or soot and Polypropylene . On the outside of this layer is laid a current insulating layer of, for example, Polypropylene . Then a new thin layer of semiconductor that can also be a mixture of soot and poly propylene . If the cable is to lie in the sea in relatively shallow water, it will in most cases be necessary to lay a protective layer on top of the current insulating layer with semiconductors. This layer is intended to both protect the other layers and at the same time give the cable buoyancy in the sea. This layer can be, for example, Expanded Polyester (EPS) . At the very bottom , it may be appropriate to add a layer of Polyurea or something similar. This is done to protect the EPS layer from mechanical stress . The polyurea layer will also protect the cable when laying in the sea from a vessel.

Objects of the Invention.

SUM MARY OF THE INVENTION It is an object of the invention to simplify the manufacture of power cables, and laying them on the seabed from the stern deck of a cable laying vessel.

Furthermore, it is desirable to be able to finish the coating of the cable lines with the necessary protection - telecommunications layer , on board the ship and in the same continuous operation as laying.

Inventions.

Method n for producing and laying current-carrying cables is characterized in that on a self- propelling vessel two similar parallel production lines are established for producing respective parallel power lines interconnected with transverse spacers to define the cable, each separate power line comprising a plurality of metal bars comprising fast - continuous friction welded end to end to form the power lines, each of which are applied to different protective layers in a continuous process, before the cable is discharged into the sea in a continuous and controlled manner and submerged to the seabed. Another term for rod may be a bolt.

Preferably, the friction welding by the leading end of a cord fixed - locked / fixed in a rotary unit on board the vessel, after which a new current conductor rod of a rod bearing at one end travels to the rotary bench and against said front rod end, the rotated and is pressed against the forward rod end to create said friction weld so as to add the new conductor rod to the power line

(downstream).

Furthermore applied each power cord layer of semiconductor layer, an electrically insulating layer, a second semiconductor layer and a protective layer to provide cable buoyancy, and applying a thin protective layer, said layers - the application is performed by welding together a feed rod to the power cord.

Besides holding the two parallel wires back with pairs of opposed against cables act - the braking wheel and which partially enclose the conductive bars after they are friction-welded, but before they are applied the first layer of semiconductor, thereby braking the wheels ensures that the cables are held in in a controlled manner and released into the sea as the ship moves forward. The power lines are made of aluminum.

Other features are stated in claims 6 - 10

In consequence a variant, the respective conductive metal rods applied semiconductor layer, current - insulating layer and another semiconductive layer and friction welded to a cable power line on board assembled in advance, and each metal rod end without said layer to engageable for holding terminals in the joint area, said retaining clamps grips and holds the friction-cable in the bare joint region, wherein a retaining clip holds the cable in the bare friction-welded joint area and move together with the cable length backwards, until a new retaining clip grips and retains in the uninsulated friction-welded joint area further forward of the power line while the rear clamp releases the grip on the joint area.

Advantageous ed a ver of this variety of production and laying cables e r is read into the claims 12- 23.

The figure set enclosed shows the following, with numerical reference given below.

Figure 1 shows a cable production ship. The vessel is in the figure shown with up - opens the production room in the deck so that the internal production line emerges.

Figure 2 is a side view of the cable production ship. We also see the cable of the two parallel HVDC power lines that descend on the seabed behind the ship. Figure 3 shows how the connection of two dynamic branch cables to the two large cables takes place. We see the cables, where the connection points are present inside a "box" that are subsequently filled with a power - insulating fabric, such as polypropylene .

Figure 4 shows the two HVDC cables going into the sea. We see the spacers holding the two cables at a constant correct distance between them. We also see the ROV / drone flushing the cables in the bottom sludge.

Figure 5 Shows a close-up of the ROV / drone, while Figure 6 shows a buoyancy fleet.

Figure 7 calls buoyant raft from one other angle than Fig. 6

Figure 8 shows the special cylinder to be used to repair damaged insulation especially at great depths

Explanation of the numbering reference:

1. Cable production ship .

2. Rotary line for friction welding of rod is

3. Aluminum rod storage room is

4. HVDS cables that go into the sea and down to the bottom.

5. Box for connecting point protection for branch cables

6. Branch cables, two pcs.

7. Boxes that are ready for use.

8. Friction welding point

9. Cooling and grinding points as well as holding / braking of the cables for controlled discharge into the sea.

10. Application of first semiconductor layer. A mixture of Polypropylene and soot.

11. Application of insulating layers, such as polypropylene .

12. Application of a new semiconductor layer

13. Applying protective buoyancy layers, such as low pressure EPS

14. Application of a protective layer of polyurea, for example.

15. ROV / drone for down flushing the cables in the bottom sludge.

16. Mounting point / winch for ROV / drone

17. Buoyancy cylinders of, for example, plastic or steel

18. Underlying cross brace

19. Lines made of plastic, for example

20. Drum / winch

21. Special Cylinder

22. Semiconductor connector sleeve 23. Exterior layer of semiconductor material

24. Sealing sleeve

25. HVDC cable

26. Electric heating wires

27. Pipes that go to the surface

The production and laying of the cables according to the invention can be done in several different ways. In this patent application we will show 4 different examples. The invention will be explained with reference to the figures.

Example 1

In this example, two parallel cables are produced continuously and laid out in the sea and flushed into the bottom sediment. Fences are also posted for later connection to cable. In order to carry out such an operation, a large ship is required, that is, a cable production ship with a lot of technical equipment. Aluminum - leaders e , which will be round rod is of aluminum, the produced aluminum plant and continuously shipped to cable production ship and loaded on the and stored at a suitable place in the vessel . In this example we use the aluminum rod which has a diameter of 400 mm and a length of 25 000 mm. When starting to manufacture and lay such a cable, it will in most cases be most convenient to start at land. The cable production ship backs as close to land as is practically possible before production starts. Production can take place as follows:

An internal crane, often a traverse crane, grabs an aluminum bar and places it in a rotary bench. Where after it is taken a new aluminum rod and disposed in the second rotation - counter. There are two completely parallel production lines. The two rods are then pulled a length backwards in the ship. In our example, that is 25,000 mm. The rods are then tightened so that they cannot rotate around their own axis. Two new aluminum bars are then picked up in the bearing and placed in the rotary bench. They are then pressed with great force and rotated against the two aluminum bars which are fixed. What happens then is that the aluminum rods become friction very quickly - welded together into a rod . The rods are then pulled further back 250 0 0 mm. At the same time, the friction weld is cooled down quickly . This can be done, for example, by gas or strong undercooled liquid. The friction weld is also sharpened so that it forms a completely smooth surface and the joint is not visible. Several powerful brake e- wheels also grip around the aluminum bar one. These reels should hold the cables when the ship comes out into deep water. At startup, they will not use their braking power. New e aluminum rod is being fetched from memory and placed in rotation benches as aluminum wires are pulled backwards. On the next 25 meters backwards is aluminum bolt one sprayed with a thin layer of semiconductor material. This may, for example, consist of Polypropylene mixed with soot. After that, the cables are applied to a layer of insulating material. The most appropriate would be to use Polypropylene which is applied at a thickness of 50 mm. This is extruded on a continuous basis . Poly propylene is then cooled very quickly to give it its natural hardness and then it is re-sprayed on a thin layer of semiconductor. The next process , if laying on relatively shallow water, is to apply a protective layer to the cables, which also gives the cables buoyancy in the sea. This layer can consist of Expander Polyester (EPS). The thickness of this layer will have to vary according to the depth at which the cables are to be laid. The deeper the sea is, the thicker this layer must be. The cables will be very heavy and at great depths, their weight become unmanageable during deployment , if they are not flash 1 1 given buoyancy.

The disadvantage of applying such a layer to the cables is that this layer will have very good thermal insulation, which could reduce the conductivity of the aluminum rods . This can be solved by layering this layer in layers, for example 50 cm with EPS and 50 cm without EPS. It is also conceivable to use EPS with low compressive strength, so that seawater due to the high pressure on the seabed will penetrate into and through the EPS layer relatively quickly, thus cooling down the aluminum rods .

At the end of this process, it may be appropriate to apply a thin protective layer to the EPS layer, for example Polyurea which will protect the underside of the EPS layer . However, where an EPS layer with low tensile strength is used and where water penetration into the EPS layer is desirable due to the cooling effect of the seawater, it will not be appropriate to use, for example, polyurea at the extreme .

When the aluminum cables have been applied to the desired number of insulating and protective layers, the rods are finally mounted between the two cables, to keep the distance between them constant. These braces, for example, can be mounted at intervals of 25 meters. The stays can consist of, for example, aluminum or various forms of plastic. When all this has been done, the two insulated and protected aluminum cables are carefully released into the sea behind the ship. The powerful brake wheels ensure that the two cables are released into the sea in a controlled manner.

Behind the cable production ship is an underwater drone (ROV) in tow. This drone is located above the two cables, when the cables are in place at the bottom. The drone is equipped with powerful electric nozzles, which with great force flush water down the two cables, with the result that the cables are flushed into the bottom sediment and covered with mud / sludge. They will not risk being caught by, for example, bottom trawls.

When cables with this capacity are laid, it will be desirable to have a connection point on the cables for future use. Use places that are often not kept track of when the cables are laid. This must be simple and can be done quickly. It can be solved as follows :

When you apply the protective buoyancy layer of, for example, EPS, you leave a short portion of the two cables without this protective layer. One then removes a small piece of the electrically isulating in - the polypropylene layers, and the semiconductor layer, so that but arrive on aluminum rods . After that, an aluminum clamp is screwed onto each rod. Two conventional dynamic DC cables are then attached to these terminals. A protective case is then placed over the two large cables. That is, the cables pass through the box and the two conventional dynamic cables are routed in two holes between the large cables in the forward direction of the ship. The insulating Polypropylene layer and the semiconductor layers are then repaired around the two clamps. Finally, the whole box is filled with Polypropylene . The box then follows the two cables down into the sea and down to the bottom.

The two dynamic cables are fed out and at certain intervals attached between the two large cables. The length of the dynamic cables is adapted to the sea - the depth at which they are laid out. These cables are then securely insulated at the ends before being discharged into the sea. In this way, we can make a number of connection points on the large main cables that will be easy to connect later. One can easily go down with for example an ROV, grasp the two ends of the conventional dynamic cab - lean and take them up to the sea surface and on a flying or fixed transducer platform. The capacity of these cables will typically be 3 GW.

When a cable is laid out as described in this patent application, with a capacity of many tens of GW, it will be challenging and very undesirable to shut down the current on such a cable. A cable that could in theory supply almost half of Europe with electrical energy. It is therefore important to develop systems and solutions that enable you to connect new connection points without having to interrupt the power in the main cable.

This can be done as follows:

The two insulated ends being taken up on a platform designed as follows: In hv is t end - piece it creeps on an aluminum tube of each conductor before these are applied to an insulating layer of polypropylene . When the insulated ends are picked up on a platform, they are placed in a bench and screwed into place. Heat is then applied so that the Polypropylene on the two aluminum pipes melts.

On the platform there are two similar cables as those that were picked up by the sea. These cables are connected separately. The switches are open, that is, the two cables are disconnected / isolated. On the other two ends of these cables are two aluminum tubes. The inside diameter of these pipes is slightly smaller than the outside diameter of the pipes attached to the dynamic cables picked up by the sea. What also happens is that the pipes attached to the cable e on the platform are heated, so that they expand. They are then connected to the pipes from the dynamic cables from the sea and cooled down. The pipes will now be shrunk together and a very good electrical contact / connection will be obtained . When now closes the switch, the platform with surrounding wind power plants, to supply current to the system - the cable without having had to shut down this.

Example 2

In this example, the cables are prefabricated ashore before being shipped to that cable laying vessel . Prefabrication means that each aluminum rod , which in this example also has a diameter of 400mm and a length of 25,000 mm, is first applied to a thin layer of semiconductor, which may be Polypropylene mixed with soot. The r for a 50 mm electrically insulating layer of polypropylene and then a new thin semiconductor - layer comprising for example polypropylene and carbon black (finely divided coal dust (carbon)) . The rods are then applied to a protective buoyancy layer, for example EPS, and finally the cables are sprayed with a thin layer of polyurea.

At each end of each aluminum rod , no layers are applied at all. For example, these ends may have a length of 1500 mm. Each aluminum rod is thus covered with semiconductor, insulating layers, protective layers having a length of 23,000 mm. The prefabricated aluminum - - the rods are then sequentially transported to a cable laying ship . Cable - laying vessel is now aluminum rods consecutively friction welded to the two long wires in the same manner as in Example 1. The insulated joints between aluminum rods , where they were friction welded together are then sanded and applied semiconductors and polypropylene as electrically insulating layer. In this case it will be appropriate to have a protective case covering the entire uninsulated area, which in our case has a length of 300 0 mm and where polypropylene is injected / - extruded from the bottom of the protective cage and finally pushed out in holes on the upper side of the box, so you are guaranteed that no air bubbles occur in the insulation.

In this case, the brake wheels or, more precisely, the holding system which prevents the cables from sliding uncontrollably into the sea, must be designed in a different way than in Example 1. The holding system, ie a strong clamp, must clamp into the uninsulated area of the cable and follow it a length, that is 25,000 mm backwards and then a new holding system, ie a new clamp, has to take hold further forward and hold while the first clamp releases the roof. The other operations in this example will be done in the same way as in Example 1.

Example 3

In this example, the cables are completely prefabricated on land in a manner similar to gas pipes today. That is, the aluminum rods are friction welded , applied to the conductor layer, electrically insulating Polypropylene layer and any protective EPS coating. This work is done in an area similar to the coil bases we have today. The prefabricated cables are then made to a length of, say, 1000 meters. When sufficient cables are made, they are picked up by coil vessels, which can be traditional coil vessels, built to lay gas pipes. These ships coils reach the prefabricated cables onboard their coils while the cables continuous friction welded by a short piece of aluminum - rod rapidly rotated while the two non-insulated ends of the long cables are pressed against it. When this is done, the joints are plastered and the uninsulated area is applied to semiconductor layers and current in the soldering layer. It is an advantage that these coil vessels have two drums so that they can lay out the two cables in parallel . The coil ship then goes out to the area in question and quickly puts out its cable load. But it will have to wait for a new coil-ship to arrive with a new cargo of ready-made cables before leaving the area, so that the long boilers can be welded together. Example 4

This example concerns the laying of cables discussed in this patent application on land. Cables of this size and with this capacity will necessarily have a relatively high weight. It is therefore challenging to do this when laying such cables on land. This can be done as follows:

One must first make a specially designed vehicle, preferably belted. If an aluminum rod is used that has a bearing similar to those used in this patent application, ie 25,000 mm, this vehicle must have a length of just over 50 meters. It is advantageous to use prefabricated aluminum rod is similar to those described in Example 2. The prefabricated aluminum rods are passed friction welded together. The tracked vehicle then drives a short distance forward, so that the cables are pulled slightly backwards on the vehicle. This may be as far as 25 meters so that there is room for two new prefabricated aluminum rod for friction - welding. Then it will be possible to immediately brush and insulate the uninsulated area, so that the process runs continuously . The application of

Polypropylene , semiconductors and possibly a protective layer at the very end of the uninsulated joints between the rods can be done by tank trucks running on the side of the porch continuously supply these substances which will be necessary for the extrusion processes.

Test station on land

Before a full-scale cable production ship as described in Example 1 can be built , it will be necessary to build a full-scale ala test station on land. This test drive must be equal to one of the production - the lines that should be on cable production vessel and the end of it must culminate in the sea. When a test cable is produced, it is pulled into the sea by a vessel or, for example, a winch. But the cable must be given artificial buoyancy by, for example, buoys. By varying the effort of the vessel / winch, it will also be possible to simulate different depths at which the cable is to be laid. It will also be possible to test the technology with different voltages on the cable.

Practical example

An intended HVDC cable will be laid as described in this patent application, from Germany and up to the area outside Lofoten. The cable remains on the west side of the Norskerenna and it is approximately 2000 km long. Aluminum core of the cable 's conductors are 400 mm in diameter and there is a strpmisoler - layer of Pol propylen having a thickness of 50 mm. As a protective layer on the outside of the current insulating layer, a layer of Expanded Polyester with low compressive strength should be applied. This layer has a thickness of approx. 100 mm, which makes the cables next weightless as they descend into the seawater.

It is further planned that for every 50 km branch cables should be laid out for later connection. It is here utilize dynamic cables, where the end pieces are isolated when they be posted and technology will allow these wires can be connected power sources without having to power down the main cable. The dynamic branch cables have the potential to carry 3 GW per cable pair. That is, they can transport power from 300 10 MW wind turbines when all these are fully produced. The branch cables will also be able to be connected to offshore oil installations and electrified , such as in the North Sea and the Norwegian Sea.

The main cable is designed for a UHVDC voltage of 1200 KV and it will be able to carry continuously 63.4 GW. For shorter periods, for example up to 7 days, it will be able to transport up to 200 GW. At a load of 100 GW, the transmission loss will be approx. 0.4%

It is possible to connect the cable to 6300 wind turbines with a capacity of 10 MW, when all of them run at maximum load. In reality, it will be easy to connect the cable to 10,000 wind turbines with a capacity of 10 MW without the cable being overloaded.

Cable laying starts in Germany. The cable production ship starts production and laying of the two parallel cables means that it backs as close to the shore as possible and the cables are first pulled out of the ship with winches on land and extra floating buoys that keep the cables afloat. On land is connected to a for - sharing facility that also can convert direct current to alternating current, or completely or partially send it on as DC.

The cable production ship then starts regular production and laying of the cables. The cables are kept - running friction welded to the long cables and where after in a continuous manufacturing applied semiconductor layer, electrically insulating layers and protective buoyancy kind. The ship has a large stock of aluminum rod stored between the production lines and the bus part of the ship. This storage can accommodate approx. 4000 aluminum - rod is which has a length of 25m. These rods are produced at an aluminum plant in Norway and continuously ship out to the cable production ship with cargo boats. It is stipulated that the ship will produce and lay in excess of 2 km of cable per day and the warehouse will then last for 30 days of production. Raw materials for the production of Polypropylene , semiconductors and Expander Polyester are stored in large tanks below the production line and replenished when required by chemical tankers.

As the cables are laid, they are flushed into the mud on the seabed by an underwater drone being towed after the cable production ship. The work of adding the 2000 km is stipulated to take 3 years.

Cable routing on large e profound:

Earlier in this patent application it is disclosed to use Foamed polyester (EPS ) as buoyancy - means on the cable during laying. This will work well on shallow water. However, if the depth becomes greater than 70 meters, it will be problematic to use EPS as a buoyancy agent because the cell structure of the expanded Polyester will collapse due to the high water pressure. The cells will be filled with water. The EPS layer loses its buoyancy. In addition, we will get polyester cells that are filled with stagnant water which will thus function as a thermal insulation layer and the cables will then not get optimal cooling from the seawater.

The cables mentioned in this patent application are designed for and intended to be used at really large depths perhaps as far as 3-4,000 meters or deeper. You can then use the following technology:

Cylinders are designed to form a raft and provide buoyancy to the cables during laying. These cylinders are sealed at both ends and must be able to withstand high pressure. The cylinders can be designed from metal / steel, but the most appropriate would be to design them from plastic / carbon fibers.

Before using these buoyancy cylinders, they are pressurized with, for example, air. If the cylinders are used to lay the HVDC cables at a depth of, for example, 3000 meters, the cylinders are pressurized with a pressure of 300 kg / cm2. The cylinders will then withstand the great pressure they are subjected to at a depth of 3000 meters without collapsing.

When HVDC cables are laid out in the sea, as discussed in this patent application, two parallel cables will be laid out. When these cables will be laid in depth for example 2 000 meters in the planned cable route could be used following technology. It produced e t number of buoyancy - cylinders of carbon fibers. The cylinders can have a length of, for example, 20 meters. The diameter must be adjusted to the desired buoyancy that the cylinders should have.

The cables are laid out from the ship as shown in Fig 1 and Fig 2. The buoyancy cylinders, three and three in parallel, are raised from the underside of the cables , so that a buoyancy cylinder comes between the two cables and a buoyancy cylinder on each side of the cables. The buoyancy cylinders are attached to cross bars that remain on the underside of the cables. If the buoyancy cylinders have a length of 20 meters, it will in many cases be suitable with 2 cross bars per cylinder length. That is, three cylinders are attached to two underlying cross bars. The transverse saws must be smooth, often provided with rollers, so that the two HVDC cables can slide relatively frictionally on the transverse rods without damaging the electrical insulation. The transverse rods are also attached to two or more parallel lines, often made of plastic, which are attached to winches / large drums on the ship.

One can now establish a buoyancy fleet of the cylindrical pressurized pontoons which are laid out three and three in parallel to the transverse rods which lie on the cables underside which in turn is attached to the lines attached to the ship. The length of the buoyancy rafts will be adjusted to the maximum depth the cables are to be laid, preferably 2 x the depth. That is if the maximum depth is 2000 meters, the up - operating fleet length be 4000 meters and it will then be necessary with 600 buoyant cylinders each having a length of 20 meters. The buoyancy fleet must be designed so that it has slightly larger buoyancy than the weight of the two HVDC cables.

In practice, this will work as follows : One has a starting point on land where the HVDC cable should begin. The maximum depth of cable to be laid is 2000 meters. The cable ship anchors 4000 meters from the starting point on land in the beach zone and begins to produce two parallel HVDC cables going into the sea. At the same time, three and three parallel buoyancy cylinders are attached to transverse rods and plastic ropes are inserted under the HVDC cables. Due to the buoyancy these provide, the HVDC cables will float in the sea. A line attached to a winch at the take-off point on land goes from the take-off point to the HVDC cables and pulls them ashore as they are produced on board the ship.

Once the end of the HVDC cables has reached the starting point, they will be greased to shore properly. Production on the ship continues and the ship lift ank clean and begin to move forward in sync with the production speed of the two HVDC cables.

The ship also goes with the buoyant raft forward and the cables slide on crossbars , but because some of the cables coming behind buoyant raft cables will therefore take the rearmost end of the buoyant raft almost to the bottom, but there will always be a gap between the bottom and the back the first end of the buoyancy fleet due to the buoyancy of the buoyancy fleet. The angle of buoyancy fleet for - distance to the base will vary with depth. The greater the depth, the greater the angle between the bottom and the buoyancy vessel.

The two HVDC cables can now be safely and safely laid down on the bottom. When you reach the other end point, for example, in the sea, the large HVDC cables are connected to smaller dynamic cables that are brought up to the surface and often up to floating HVDC stations and the ship then continues forward and pulls the entire buoyancy fleet away, from the HVDC cables. The buoyancy fleet can then be dismantled and used for the next mission.

Repair of HVDC cables in deep water.

All cables to be manufactured using this technology must undergo very extensive quality control before being discharged into the sea. However, one must be prepared for mechanical damage to the cables or failure of the electrical insulation . Mechanical damage caused by contact from other vessels will usually occur in relatively shallow water and the cables can then be taken to the surface for repair. This will be a relatively simple operation that will not be discussed in this patent application. We also disregard mechanical damage from other deep water vessels in this patent application because the chance of this is virtually zero. However, one must be prepared for damage to the electrical insulation at really great depths and one can then use the following procedure to repair this damage. You first find the exact location where the damage occurred with the aid of a measuring instrument. In this example, the damage occurred at a depth of 2000 meters.

You then go down with a ROW, find the place and get the cable that is slightly damaged, such as 50 cm. Failure to receive the lifting cable, one can take staying t little mass below it, so that it is free. The semiconductor layer applied to the outside of the current insulating layer is then milled off by the ROW in two places where a special cylinder sleeve sits. Then, a special - cylinder taken down to the site of injury. This special cylinder is made of the same insulation material as the electrical insulation material on the damaged cable. In addition, its surface is applied to a semiconductor layer of the same type applied to the surface of the live cable. Part of the sleeves that enclose the insulating layer of the cable is also applied to a semiconductor layer. The special cylinder is hinged on one side, that is, it can be opened. At each end, as said, the sleeves are so similar that when closed, the sleeves have a diameter corresponding to the diameter of the electrical insulation of the damaged cable. The sleeves are placed over the areas where the semiconductor layer was milled away , but the part of the sleeves applied to the semiconductor layers encloses the semiconductor layers on the cable, so that a semiconductor connection is established over the special cylinder. The special cylinder is run with one half under the damaged cable and then the special cylinder is closed.

In all contact surfaces of the special cylinder, electric heating wires are inserted which are now activated by means of supply from the surface. The two halves of the special cylinder are now fused together. The contact surfaces between the two ends of the special cylinder and the damaged cable are also fused together but not in such a way as to damage the semiconductor contacts. On the one half of the special cylinder, the one on top of the HVDC cable, are attached two pipes that go up to the surface via flexible hoses. A water-soluble liquid is now pumped down to the special cylinder, which is filled with sea water. This bag will preferably be, for example, pure ethanol. As pumping ethanol into the special cylinder, the sea water being displaced through the second pipe because the pipes have different lengths inside special cylinder and pushed up to the ship on the - surface. When you have pumped so much ethanol into the special cylinder that you are absolutely sure that all the seawater is displaced, you can start pumping an insulation material down into the special cylinder. If you have polypropylene as an electrical insulating material in the HVDC cable, this can be pumped down, but it can be challenging to keep it flowing. In this case you have to supply the tube as the polypropylene is pumped through heat and this can be relatively complicated.

A simpler solution would be to use an electrically insulating oil, which usually solidifies to a solid mass after a while . This will be easy to pump down, displace the ethanol contained in the special cylinder and the damage point on the HVDC cable will be repaired.