LS Cable Wins Order For Submarine High Voltage DC Cables in The UK
Vattenfall has taken a major step forward in the delivery of the Norfolk Boreas wind farm, signing a contract with LS Cable & System and the DEME Group for the delivery of export cables connecting the wind farm to the National Grid.
The consortium was also selected as the preferred bidder for the export cable for the remaining part of the Vattenfall Norfolk block.
The contract includes the design, engineering, procurement, manufacture, and testing of approximately 360 km of high-voltage direct current (HVDC) export cable, with fiber optic cable including offshore installation and onshore connections.
The selection of the innovative HVDC cable allowed Vattenfall to reduce the use of the cable route by a third, reducing the local impact and making the project more sustainable.
Catrin Jung, Head of Offshore Wind at Vattenfall, said: “We are looking forward to working closely with LS Cable & System and DEME Group to make this project a success. The Norfolk North Wind Farm is a major project for Vattenfall and an important step towards a fossil-free life in the UK within a generation.”
How was the submarine fiber optic cable laid or repaired?
Submarine fiber optic cables are exceptionally difficult to lay and repair. Submarine cable projects are recognized worldwide as large, complex, and difficult projects. In shallow seas, such as with water depth of fewer than 200 meters the sea cable using buried, while in the deep sea is used to lay. Hydro-jet burial is the main burial method. Buried equipment at the bottom of several rows of water jets, parallel distribution on both sides, operation, each hole at the same time to the seabed jet high-pressure water column, the seabed mud, and sand will be washed away, the formation of the cable trench.
Equipment on the upper part of a guide hole, used to guide the cable (fiber optic cable) to the bottom of the cable trench, by the tide will automatically fill the trench. The buried equipment is towed forward by the construction vessel, and various instructions are made through the working cable. The cable laying machine generally does not have underwater burial equipment, relying on the self-weight of the cable laid on the surface of the sea floor.
Once the cable problems, in the vast ocean, from the depth of hundreds of meters or even thousands of meters to finding less than 10 cm diameter of the sea bed of the cable, it is like a needle in a haystack. Then detecting the fracture point of the cable, salvaging it, re-connected it, and putting it back on the sea floor, its technical difficulty can be imagined.
The specific repair process of submarine fiber optic cable is as follows
1. After the robot dives into the water, it scans and detects the exact location of the broken submarine fiber optic cable.
2. The robot will dig out the submarine fiber optic cable which is shallowly buried in the mud and cut it off with cable scissors. A rope is lowered on the ship and tied by the robot to one end of the fiber optic cable, and then pulled out of the sea. At the same time, the robot places a wireless transmitter transponder at the cut-off point.
3. Using the same method, another section of fiber optic cable is also pulled out of the sea. As with the telephone line, the ship’s instruments were connected to the two ends of the cable, through the two directions of the submarine cable landing station, to detect the part of the cable is blocked in which end. After that, retrieve a longer part of the blocked part of the submarine cable and cut it off. The other section is mounted with buoys and temporarily left to float in the sea.
4. Next, the spare submarine cable will be manually connected to the two broken points of the U.S. and China submarine cable. Connecting cable joints, a “highly technical” work, not ordinary people can do, must be special rigorous training, and get the relevant international organizations after the license to operating personnel. Such a “connector”, Shanghai Telecom currently has only three or four.
5. After the backup submarine cable is connected, after repeated testing, communication is normal, then thrown into the seawater. At this point, the underwater robot again to “on”: the repair of the submarine cable “buried”, that is, with a high-pressure water gun will be the silt of the sea floor out of a trench, the repair of the submarine cable “placed” into it.