A method for repairing submarine cables in offshore wind farms under severe sea conditions

Abstract

The present invention discloses a submarine cable repair method for an offshore wind farm under severe sea conditions, comprising: a cable break; first and second submarine cables are salvaged, tested, and their ends sealed with lead before being sunk; a first small self-elevating platform vessel approaches the first submarine cable, and a PSV vessel and the first small self-elevating platform vessel sequentially salvage the end of the first submarine cable onto their own decks; the PSV vessel releases a new submarine cable, and the first small self-elevating platform vessel hoists the lead-out end of the new submarine cable onto its own deck and makes a first joint; the PSV vessel lays the new submarine cable, and a second small self-elevating platform vessel approaches the second submarine cable; the PSV vessel cuts the new submarine cable and transfers the cut end of the new submarine cable to the second small self-elevating platform vessel; the PSV vessel and the second small self-elevating platform vessel sequentially salvage the end of the second submarine cable onto their own decks and make a second joint; and the first and second small self-elevating platforms lower the first and second joints into the water. The present invention has high maintenance and construction efficiency and is not sensitive to sea conditions.

Description

Technical Field

[0001] The invention relates to a method for repairing submarine cables of an offshore wind farm under severe sea conditions. Background Art

[0002] The explosive growth of offshore wind power has also led to a surge in submarine cable business, and the application of submarine cables is becoming more and more extensive. As the number of submarine cables increases, the maintenance work of submarine cables has also increased.

[0003] Damage to submarine cables can be sudden, rendering them unable to transmit electricity and halting offshore wind power generation, resulting in significant economic losses. Patent application publication number CN115395442A discloses a submarine cable repair method. This patent application utilizes conventional vessels for submarine cable repairs, requiring strict sea conditions, including wind speeds no greater than level 5 and wave heights no higher than 0.5 meters. These conditions are rarely met during the winter off-season, leading to delayed repairs and significant power generation losses. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a method for repairing submarine cables of offshore wind farms under severe sea conditions, which not only has low requirements on sea conditions, but also can effectively improve the efficiency of repair construction.

[0005] The object of the present invention is achieved as follows: A method for repairing submarine cables of an offshore wind farm under severe sea conditions is characterized by comprising the following steps:

[0006] Step 1: First, determine the submarine cable fault area through seabed topography scanning and cable fault distance measurement. Then, operate the PSV vessel to the submarine cable fault area and clean the surface sediment in the submarine cable fault area. After entering the water, divers first determine the actual damage location of the submarine cable, and then use underwater hydraulic cutting tools to cut the submarine cable at the actual damage location. The two submarine cable sections formed after the cut are marked as the first submarine cable and the second submarine cable respectively.

[0007] In step 2, the PSV vessel salvages the ends of the first and second submarine cables onto the deck for fault detection and dehumidification. The damaged and flooded sections of the submarine cables are removed. After the detection is complete, the ends of the first and second submarine cables are sealed with lead. Annular slings are then tied to the heads of the first and second submarine cables, respectively. The steel wire rope, the sling, and the buoy are connected to the slings via shackles. The ends of the first and second submarine cables are then placed on the seabed, with the buoys on the first and second submarine cables floating on the sea surface.

[0008] Step 3: The first small self-elevating platform vessel approaches the end of the first submarine cable and inserts a pile leg to secure it; the PSV vessel first uses a salvage buoy to salvage the end of the first submarine cable to the top of its own deck. The PSV then docks next to the first small self-elevating platform vessel, and the first small self-elevating platform vessel's crane hoists the end of the first submarine cable on the PSV vessel onto its own deck;

[0009] Step 4: The PSV unleashes the new submarine cable from the cable reel fixed on its deck. The first small jack-up platform hoists the lead-out end of the new submarine cable onto its deck and makes a first joint between the end of the first submarine cable and the lead-out end of the new submarine cable.

[0010] Step 5: The PSV activates its DP positioning system and, based on the location of the faulty cable indicated by the seabed scan, lays a new cable along the original cable route. The new cable and the second cable are spliced ​​to a set length. Meanwhile, a second small jack-up platform approaches the end of the second cable and inserts a stake to secure it.

[0011] Step 6: After the PSV completes laying the new submarine cable, it cuts the new submarine cable from the outlet of the cable reel. The PSV then pulls over to the side of the second small jack-up platform and transfers the cut end of the new submarine cable to the second small jack-up platform.

[0012] Step 7: The PSV first uses the salvage buoy to salvage the end of the second submarine cable to the top of its own deck. The PSV then docks next to the second small jack-up platform. The second small jack-up platform's crane then lowers the end of the second submarine cable on the PSV onto its own deck and makes a second joint between the cut end of the new submarine cable and the end of the second submarine cable.

[0013] Step 8. After the second joint is made, the crane on the second small self-elevating platform uses a multi-point lifting device to lift the second joint and the bend limiter, and moves them to the lying arm perpendicular to the new submarine cable. At the same time, the crane on the first small self-elevating platform uses a multi-point lifting device to lift the first joint and the bend limiter, and moves them to the lying arm perpendicular to the new submarine cable. When the crane wire ropes on the first small self-elevating platform and the crane wire ropes on the second small self-elevating platform are stressed, they are slowly released; then the first joint and the second joint are slowly lifted into the water until they are smoothly placed on the seabed.

[0014] In the above-mentioned method for repairing submarine cables of offshore wind farms under severe sea conditions, in step 2, surface mud and sand in the faulty area of ​​the submarine cable are cleaned by manual or mechanical mud removal.

[0015] In the above-mentioned method for repairing submarine cables of offshore wind farms under severe sea conditions, during step five, the first joint is manufactured in a joint manufacturing room set up on the deck of the first small jack-up platform vessel.

[0016] In the above-mentioned method for repairing submarine cables of offshore wind farms under severe sea conditions, during step seven, the second joint is manufactured in a joint manufacturing room set up on the deck of the second small jack-up platform vessel.

[0017] In the above-mentioned method for repairing submarine cables for offshore wind farms under severe sea conditions, during step eight, after the first and second connectors are lowered to the seabed, an AC withstand voltage test and an optical fiber test are performed on the submarine cable. After the tests are qualified, the offshore booster station and the submarine cable terminals are reset.

[0018] The submarine cable maintenance method for offshore wind farms under severe sea conditions of the present invention has the following characteristics:

[0019] 1. The present invention mainly adopts PSV (Platform Supply Vessel) for submarine cable repair. PSV has the advantages of full rotation propulsion, good seakeeping, strong berthing ability, and strong resistance to wind and waves. The deck is equipped with a 40t folding arm marine crane, a marine cable reel and a cable repair operation platform. The cable reel has an outer diameter of 10m and an inner diameter of 5m, and can carry about 200t of cable. It also has a DP2 dynamic positioning system and an anchor positioning system, which can accurately locate and shift on site. In the construction sea area, the significant wave height is 2.5m and the wind speed is within level 7. It can operate normally.

[0020] 2. This invention uses a small jack-up platform vessel as the platform for submarine cable joint production, creating a stable work platform that is unaffected by wind and waves. Furthermore, in the event of force majeure, workers can be arranged to suspend on-site operations and evacuate the site, thereby ensuring the reliability and personal safety of offshore joint production.

[0021] 3. The present invention adopts a small self-elevating platform vessel + PSV vessel to carry out submarine cable repair operations. After the small self-elevating platform vessel enters the site, normal submarine cable repair operations can be carried out in wave heights of 2.5m or less and wind speeds of level 7 or less. The repair period of a 35kv submarine cable does not exceed 5 days, and the repair period of a 220kv submarine cable does not exceed 10 days, which effectively improves the efficiency of repair construction, shortens the emergency repair time, and reduces the power generation loss of offshore wind farms.

[0022] 4. The present invention reduces the workload of divers, improves the safety of divers, and reduces the labor intensity of divers. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a state diagram when performing step 1 of the submarine cable repair method of the present invention;

[0024] Figure 2a This is a state diagram when performing step 2 of the submarine cable maintenance method of the present invention;

[0025] Figure 2b This is a state diagram when performing step 2 of the submarine cable maintenance method of the present invention;

[0026] Figure 2c This is a state diagram when performing step 2 of the submarine cable maintenance method of the present invention;

[0027] Figure 3a is a state diagram when performing step three of the submarine cable repair method of the present invention;

[0028] Figure 3b is a state diagram when performing step three of the submarine cable repair method of the present invention;

[0029] Figure 4 is a state diagram when performing step 4 of the submarine cable maintenance method of the present invention;

[0030] Figure 5a is a state diagram when performing step 5 of the submarine cable maintenance method of the present invention;

[0031] Figure 5b is a state diagram when performing step 5 of the submarine cable maintenance method of the present invention;

[0032] Figure 6 is a state diagram when performing step 6 of the submarine cable maintenance method of the present invention;

[0033] Figure 7a is a state diagram when performing step seven of the submarine cable repair method of the present invention;

[0034] Figure 7b is a state diagram when performing step seven of the submarine cable repair method of the present invention;

[0035] Figure 8a is a state diagram when performing step eight of the submarine cable repair method of the present invention;

[0036] Figure 8b FIG. 1 is a state diagram when performing step eight of the submarine cable repair method of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings.

[0038] See also Figures 1 to 8b The method for repairing submarine cables of an offshore wind farm under severe sea conditions of the present invention comprises the following steps:

[0039] Step 1: First, the submarine cable fault area is determined by seabed topography scanning and cable fault distance measurement. Then, the PSV vessel 100 is operated to the submarine cable fault area, and the surface mud and sand in the submarine cable fault area are cleared by manual or mechanical mud removal. After entering the water, the divers first determine the actual damaged location of the submarine cable, and then use underwater hydraulic cutting tools to cut the submarine cable at the actual damaged location. The two submarine cable sections formed after the cut are marked as the first submarine cable 10 and the second submarine cable 20 respectively.

[0040] Step 2: The PSV vessel 100 salvages the ends of the first submarine cable and the second submarine cable onto the deck (see Figure 2a and Figure 2b ), perform fault detection and dehumidification on the deck of the PSV vessel 100, and remove the damaged section and the water-influent section of the submarine cable (after the submarine cable is cut underwater, seawater will enter the submarine cable from the broken end during the period until it is salvaged from the sea surface. The specific extent of water ingress should be determined by inspecting the water-blocking tape inside the submarine cable while cutting, and continue cutting until the water-blocking tape is dry). After the inspection is completed, the ends of the first submarine cable and the second submarine cable are first sealed with lead, and then annular slings are tied to the heads of the first submarine cable and the second submarine cable respectively, and the steel wire rope, the sling and the buoy are connected to the annular sling in sequence through the shackle. Finally, the ends of the first submarine cable 10 and the second submarine cable 20 are placed on the seabed, so that the buoy on the first submarine cable 10 and the buoy on the second submarine cable 20 both float on the sea surface (see FIG. Figure 2c );

[0041] Step 3: The first small self-elevating platform vessel 200 approaches the end of the first submarine cable 10 and then inserts the pile legs to fix it. Since the crane radius of the first small self-elevating platform vessel 200 is insufficient to lift the end of the first submarine cable, the PSV vessel 100 needs to first use the salvage buoy to salvage the end of the first submarine cable 10 to the top of its own deck. The PSV vessel 100 then docks next to the first small self-elevating platform vessel 200, and then the crane of the first small self-elevating platform vessel 200 hoists the end of the first submarine cable 10 on the PSV vessel 100 to its own deck (see Figure 3a and Figure 3b );

[0042] Step 4: The PSV 100 unwinds the new submarine cable 30 from the cable reel fixed on its deck. The first small jack-up platform 200 hoists the lead-out end of the new submarine cable 30 onto its deck. On the deck of the first small jack-up platform 200, the positions of the lead-out end of the new submarine cable 30 and the end of the first submarine cable 10 are adjusted. The new submarine cable 30 and the first submarine cable 10 are overlapped to a set length. Then, a first joint 10A is made between the end of the first submarine cable 10 and the lead-out end of the new submarine cable 30 (see FIG. 1 ). Figure 4); The first joint 10A is produced in a joint production room set up on the deck of the first small jack-up platform vessel 200;

[0043] Step 5: The PSV 100 starts the DP positioning system and, based on the route location of the faulty submarine cable indicated by the seabed scanning, lays the new submarine cable 30 along the original submarine cable route (see Figure 5a ), the new submarine cable 30 and the second submarine cable 20 are overlapped to set a length, so as to facilitate the subsequent production of the second joint 20A between the cut end of the new submarine cable 30 and the end of the second submarine cable 20; at the same time, the second small self-elevating platform vessel 300 advances to the side of the end of the second submarine cable 20 and then inserts the pile legs for fixing (see Figure 5b );

[0044] Step 6: After the PSV 100 has completed the laying of the new submarine cable 30, it cuts the new submarine cable 30 from the outlet of the cable reel. Then, the PSV 100 moves to the side of the second small self-elevating platform vessel 300 and transfers the cut end of the new submarine cable 30 to the second small self-elevating platform vessel 300 (see FIG. Figure 6 );

[0045] Step 7: Since the crane radius of the second small self-elevating platform vessel 300 is insufficient to lift the end of the second submarine cable 20, the PSV vessel 100 needs to first salvage the end of the second submarine cable 20 to the top of its own deck through the salvage buoy. The PSV vessel 100 then docks next to the second small self-elevating platform vessel 300, and then the crane of the second small self-elevating platform vessel 300 hoists the end of the second submarine cable 20 on the PSV vessel 100 to its own deck (see FIG. Figure 7a ), adjust the position of the cut end of the new submarine cable 30 and the end of the second submarine cable 20 on the deck of the second small self-elevating platform ship 300, and make a second joint 20A between the cut end of the new submarine cable 30 and the end of the second submarine cable 20 (see Figure 7b ); the second joint 20A is produced in a joint production room set up on the deck of the second small jack-up platform vessel 300;

[0046] Step 8: After the second joint 20A is completed, the crane on the second small self-elevating platform vessel 300 uses a multi-point lifting device to lift the second joint 20A and the bend limiter, and moves them to the arm perpendicular to the new submarine cable 30. At the same time, the crane on the first small self-elevating platform vessel 200 uses a multi-point lifting device to lift the first joint 10A and the bend limiter, and moves them to the arm perpendicular to the new submarine cable 30 (see FIG. Figure 8a ), when the crane wire rope on the first small self-elevating platform ship 200 and the crane wire rope on the second small self-elevating platform ship 300 are slowly released after being stressed, the first joint 10A and the second joint 20A are slowly lowered into the water until they are smoothly placed on the seabed (see Figure 8b); After the first connector 10A and the second connector 20A are sunk to the seabed, the submarine cable AC withstand voltage test and optical fiber test are carried out. After the test and the test are qualified, the offshore booster station and the submarine cable terminal are reset.

[0047] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Those skilled in the art may make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also fall within the scope of the present invention and should be defined by the claims.

Claims

1. A method for repairing submarine cables of an offshore wind farm under severe sea conditions, characterized in that: The following steps are involved: Step 1: First, determine the submarine cable fault area through seabed topography scanning and cable fault distance measurement. Then, operate the PSV vessel to the submarine cable fault area and clean the surface sediment in the submarine cable fault area. After entering the water, divers first determine the actual damage location of the submarine cable, and then use underwater hydraulic cutting tools to cut the submarine cable at the actual damage location. The two submarine cable sections formed after the cut are marked as the first submarine cable and the second submarine cable respectively. In step 2, the PSV vessel salvages the ends of the first and second submarine cables onto the deck for fault detection and dehumidification. The damaged and flooded sections of the submarine cables are removed. After the detection is complete, the ends of the first and second submarine cables are sealed with lead. Annular slings are then tied to the heads of the first and second submarine cables, respectively. The steel wire rope, the sling, and the buoy are connected to the slings via shackles. The ends of the first and second submarine cables are then placed on the seabed, with the buoys on the first and second submarine cables floating on the sea surface. Step 3: The first small self-elevating platform vessel approaches the end of the first submarine cable and inserts a pile leg to secure it; the PSV vessel first uses a salvage buoy to salvage the end of the first submarine cable to the top of its own deck. The PSV then docks next to the first small self-elevating platform vessel, and the first small self-elevating platform vessel's crane hoists the end of the first submarine cable on the PSV vessel onto its own deck; Step 4: The PSV unleashes the new submarine cable from the cable reel fixed on its deck. The first small jack-up platform hoists the lead-out end of the new submarine cable onto its deck and makes a first joint between the end of the first submarine cable and the lead-out end of the new submarine cable. Step 5: The PSV activates its DP positioning system and, based on the location of the faulty cable indicated by the seabed scan, lays a new cable along the original cable route. The new cable and the second cable are spliced ​​to a set length. Meanwhile, a second small jack-up platform approaches the end of the second cable and inserts a stake to secure it. Step 6: After the PSV completes laying the new submarine cable, it cuts the new submarine cable from the outlet of the cable reel. The PSV then pulls over to the side of the second small jack-up platform and transfers the cut end of the new submarine cable to the second small jack-up platform. Step 7: The PSV first uses the salvage buoy to salvage the end of the second submarine cable to the top of its own deck. The PSV then docks next to the second small jack-up platform. The second small jack-up platform's crane then lowers the end of the second submarine cable on the PSV onto its own deck and makes a second joint between the cut end of the new submarine cable and the end of the second submarine cable. Step 8. After the second joint is made, the crane on the second small self-elevating platform uses a multi-point lifting device to lift the second joint and the bend limiter, and moves them to the lying arm perpendicular to the new submarine cable. At the same time, the crane on the first small self-elevating platform uses a multi-point lifting device to lift the first joint and the bend limiter, and moves them to the lying arm perpendicular to the new submarine cable. When the crane wire ropes on the first small self-elevating platform and the crane wire ropes on the second small self-elevating platform are stressed, they are slowly released; then the first joint and the second joint are slowly lifted into the water until they are smoothly placed on the seabed.

2. The method for repairing submarine cables of an offshore wind farm under severe sea conditions according to claim 1, characterized in that: During step 2, the surface mud and sand in the fault area of ​​the submarine cable is cleaned by manual or mechanical mud removal.

3. The method for repairing submarine cables of an offshore wind farm under severe sea conditions according to claim 1, characterized in that: During step five, the first joint is manufactured in a joint manufacturing room set up on the deck of the first small jack-up platform vessel.

4. The method for repairing submarine cables of an offshore wind farm under severe sea conditions according to claim 1, characterized in that: During step seven, the second joint is manufactured in a joint manufacturing room set up on the deck of the second small jack-up platform vessel.

5. The method for repairing submarine cables of an offshore wind farm under severe sea conditions according to claim 1, characterized in that: During step eight, after the first and second connectors are lowered to the seabed, an AC withstand voltage test and an optical fiber test of the submarine cable are performed. After the test is passed, the terminals of the offshore booster station and the submarine cable are reset.

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