Special filling resin for submarine cable hard joint and method for repairing armoring

Abstract

The application discloses a filling resin special for submarine cable hard joint, which comprises modified epoxy resin, 0.1-0.4 parts of curing agent, 0.01-0.1 parts of accelerator and 0.05-0.29 parts of superconducting carbon black by mass of the modified epoxy resin, wherein the curing agent is an aliphatic or aromatic amine compound, and the accelerator is an organic peroxide. The filling resin has simple components, excellent mechanical properties and electric conductivity. The resin can be used as a filler between the hard joint and the submarine cable armor layer, and can be applied to various materials, shapes and multi-layer armor layer recovery, so as to ensure the connection strength of the armor layer recovery and reliable electrical connection, and can save additional grounding device and greatly shorten the connection time between the armor layer and the hard joint shell.

Description

Technical Field

[0001] This invention relates to a special filling resin for submarine cable rigid joints, and also to a method for repairing the armor of submarine cable rigid joints, belonging to the technical field of cable connection devices. Background Technology

[0002] Flexible and rigid joints in power cables refer to joints with flexible and rigid physical structures, respectively. Flexible joints have a certain degree of flexibility, allowing for moderate bending, while the rigid outer shell of rigid joints provides additional mechanical strength and tensile resistance. Rigid joints in submarine cables, also known as emergency repair joints, are commonly used for emergency repairs after submarine cables are put into operation. Due to the complex structure of submarine cables, the jointing process is intricate and time-consuming. To protect the submarine cable and facilitate its laying, it has an outer layer of metal armor. For long-distance deep-sea laying or special-purpose submarine cables, there are two or even more layers of armor. When making a submarine cable joint, the armor layer needs to be repaired.

[0003] During the repair process, it is necessary to consider both the armor circulation current and the firmness of the connection between the armor and the shell. The existing solution is to install an anchoring device around the outside of the armor, which connects the shell and the outer metal shell to ground the armor to avoid circulation current. The surrounding anchoring device also ensures a firm connection between the armor and the rigid joint (Ma Yuqing. Research and application of anchoring grounding device for armor of 220kV single-core submarine cross-linked cable for offshore wind power [J]. Enterprise Management, 2022, (S2)). However, this rigid grounding device is prone to poor contact between the clamp and the cable. When the anchoring device is installed on the armor layer, the metal wires of each layer of armor need to be turned outward along the inner circle of the fitting, so that the ends of the metal wires are evenly wrapped around the outer circle of the fitting. Then, the split pressure plate fitting is installed, and finally, the metal wires are pressed tightly onto the tail fitting with bolts, and the clamp fitting is installed to reliably connect with the split pressure plate. Armored metal wires are generally galvanized steel wires. For 220kV and above submarine cables, the wire diameter is 6-8mm. The large diameter and large quantity of wires (up to 100) mean that almost all work is done manually, making the repair process complex, especially the fitting of hardware, which is entirely manual and physically demanding. Furthermore, this installation method is only suitable for single-layer armored installations. Patent application CN 107134703 A discloses a submarine cable repair joint protector applicable to various submarine cable diameters. This method connects the armored metal wires to the joint protective shell using inner and outer conical sleeves, reducing the wire folding angle. Patent application CN 108933423 A discloses a cable joint, which also discloses a technique for filling and fixing the armor layer. Both of these methods reduce workload to some extent, but neither is suitable for fixing double or multi-layer armored cables, nor do they consider armor grounding. The invention patent application with publication number CN 110380376 A discloses a fixing device for a submarine cable with four layers of armored steel wires. Fixing rings are set on the armored steel wires respectively. This solution is suitable for multi-layer armored installation, but the workload of bending the metal wires is large, and the armor grounding is not considered. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a filling resin specifically designed for repairing submarine cable joints that balances connection strength and grounding; another purpose of this invention is to provide a method for repairing armored layers of submarine cable hard joints that is applicable to various materials, shapes, and multiple layers, and can reduce the amount of repair work and time.

[0005] Technical Solution: The filler resin for submarine cable rigid joints of the present invention is characterized by comprising epoxy resin and, by weight of epoxy resin, 0.1-0.4 parts curing agent, 0.01-0.1 parts accelerator, and 0.05-0.29 parts superconducting carbon black, wherein the curing agent is an aliphatic or aromatic amine compound, and the accelerator is an organic peroxide. This filler resin has a simple composition, good uniformity, and combines compressive strength and electrical conductivity.

[0006] Preferably, the curing agent is 0.2 to 0.3 parts and the accelerator is 0.07 to 0.09 parts, based on the mass of epoxy resin.

[0007] Preferably, the modified epoxy resin is one or a mixture of polyether, polyurethane, and isocyanate modified epoxy resin, the curing agent is diethyltoluene diamine, and the accelerator is tert-butyl peroxide. More preferably, the modified epoxy resin is one or a mixture of two of EPU-300A and triglycidyl-p-aminophenol (CAS: 5026-74-4).

[0008] Preferably, the superconducting carbon black DBP is ≥200mL / 100g, and the amount of superconducting carbon black is 0.05~0.2 parts. The superconducting carbon black must be added within a suitable range. The resistivity of the filled resin will not decrease significantly with the increase of the amount of superconducting carbon black added. Excessive superconducting carbon black will result in uneven dispersion in the epoxy resin matrix, which will also make the performance of the filled resin unstable. High superconducting carbon black content will also affect the strength of the filled resin.

[0009] Preferably, the compressive strength of the filled resin after curing is ≥100 MPa, and the volume resistivity at 20℃ is ≤100Ω•cm.

[0010] The method for repairing the armored rigid joint of a submarine cable according to the present invention is characterized by comprising the following steps:

[0011] (1) Peel off the armor layer, restore the filling shell size according to the connector protective shell and armor, and leave 5~50cm of armor wire;

[0012] (2) Secure the armor wires by wrapping around the break point, and bend the reserved armor wires outward one by one. The armor layer after bending is conical. Remove the covering material on the surface of the bent armor wires to expose the metal wires.

[0013] (3) A conical armor restoration filling shell is attached to the peeling break point of the armor layer, and pre-mixed filling resin is injected into the armor restoration filling shell and cured. The filling resin is prepared by thoroughly mixing epoxy resin, curing agent, accelerator, and superconducting carbon black in a mass ratio of 1:0.1~0.4:0.01~0.1:0.05~0.29. There is no obvious black agglomeration in the mixed filling resin. The addition of semi-conductive material to the filling resin allows a reliable electrical connection to be established between the armor layer and the rigid connector metal shell through the filling resin. No grounding fixing device is required between the armor layer and the metal shell. Compared with rigid grounding, filling can reduce some waterproof layers. The filling resin fixes the armor layer, reduces the bending angle of the armor wire, greatly reduces the workload, and reduces the assembly time from 6-12 hours to 2-4 hours. This assembly method expands the scope of application, making it suitable for armored metal wires of various materials, as well as single-layer, double-layer, or multi-layer armored structures. The liquid filling material provides a more comprehensive and uniform coating of the metal wires, effectively preventing poor contact during armor grounding.

[0014] Preferably, in step (1), at least one armor layer is peeled off, and the angle between the outermost armor wire and the core axis is ≤60°. If the angle is greater than 60°, the end of the armor metal wire will be too close to the armor restoration filling cavity, or even in contact, resulting in a mismatch between the armor restoration filling cavity and the armor restoration strength.

[0015] Preferably, when there are at least two armor layers stripped, in step (1), the reserved length of each armor wire increases by 1 to 20 cm as the distance between the armor layer and the wire core decreases.

[0016] Preferably, when at least two armor layers are peeled off, in step (2), the folding angle of each armor wire decreases as the distance between the armor layer and the wire core decreases, and the bending angle error of the same layer of armor wire is no greater than 3°. An error exceeding 3° will affect the uniformity of the armor wire distribution. More preferably, the angle between the outermost armor wire and the wire core axis is 15°~35°.

[0017] Preferably, in step (2), an organic solvent is used to dissolve and remove the coating on the surface of the metal wire. More preferably, the organic solvent is one or a mixture of stearic acid, acetone, turpentine, trichloroethylene, chloroform, and ethanol.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. Adding an appropriate amount of superconducting carbon black to the filling resin results in a filling resin with strong uniformity, conductivity, and good compressive strength; 2. The filling resin composition is simple and waterproof; 3. After repair, the filling resin evenly wraps around each armor wire, its conductivity ensures electrical connection, and its tensile strength ensures the connection strength between the filling resin and the metal wire, eliminating the need for anchoring devices and improving assembly speed; 4. The bending angle of the armor wire is within a suitable range, which, together with the filling resin, strengthens the connection strength, reduces workload, and the assembly time is only 2-4 hours; 5. It is suitable for multi-layer armor repair. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the armored metal wire after bending according to the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0021] Example 1: Preparation of Filler Resin

[0022] In this embodiment, the modified epoxy resin used has an epoxy equivalent of 150~350 g / eq and a purity of ≥99%. Unless otherwise specified, all other reagents are commercially available analytical grade reagents and are used directly without purification.

[0023] By mass, weigh out the modified epoxy resin of model EPU-300A, diethyltoluene diamine, tert-butyl peroxide, and superconducting carbon black, and stir until there is no obvious black agglomeration or uneven dispersion to obtain the premixed filler resin.

[0024] Table 1: Filler Resins with Different Formulations and Performance Tests

[0025]

[0026] According to GB / T 2567, GB / T 7124-2008 and GB / T 3048.3 standards, the performance of the prepared filling resin was tested. The proportion of each component of the prepared filling resin and the test data are shown in Table 1.

[0027] Example 2: Repair Method for Double-Layer Submarine Cable Rigid Joint Armor

[0028] like Figure 1 As shown, repair the armor according to steps one through five, among which, Figure 1 The structures corresponding to the various reference numerals in the attached figures are: 1. Submarine cable; 2. Inner armor; 3. Outer armor; 4. Armor recovery filling shell; 5. Inner cavity of armor recovery filling shell; 6. Stripping break point.

[0029] Step 1: After confirming that the submarine cable 1 is de-energized, strip the PP rope outside the outer armor 3 to expose the armor steel wires 2 and 3 wrapped in asphalt. The outer armor steel wire 3 has a reserved length of 13cm, and the inner armor 2 has a reserved length of 25cm.

[0030] Step 2: At the peeling break point 6, wrap the armor layer tightly around it, and bend the peeled outer and inner armor steel wires 3 and 2 outward one by one. The bending angle of the outer armor steel wire 3 is 50±3°, and the bending angle of the inner armor steel wire 2 is 35±3°. After bending, the inner and outer armor steel wires 2 and 3 form conical armor layers respectively. The bending angle error of the steel wires in the same armor layer is within 3°, and the steel wires in the same layer are kept at equal distances.

[0031] Step 3: Spray asphalt cleaner onto the surface of the steel wire to thoroughly clean the asphalt covering on the surface of the armored steel wire, ensuring that the original color of the steel wire is completely exposed. During the cleaning process, a flame gun can be used to heat the wire to accelerate the removal of asphalt. The flame gun should not be used for more than 30 seconds, and the flame core of the flame gun should be at least 50mm away from the steel wire.

[0032] Step 4: Prepare the filling resin according to "Formula 1 or Formula 2" in Example 1, and premix it;

[0033] Step 5: After folding the armor layer, attach a conical armor restoration filling shell 4. The top of the armor restoration filling shell 4 should surround the peeling break point 6 of the armor layer. Then, inject the pre-mixed filling resin into the inner cavity 5 of the armor restoration filling shell 4. Tap the outer wall of the armor restoration filling shell 4 to expel the air in the filling resin. Let it stand at room temperature for no less than 30 minutes until it is completely cured, thus completing the connection restoration between the armor steel wire and the rigid joint shell.

[0034] According to GB / T 7124-2008 standard, the obtained armor wire and filling resin bonding structure were tested, and their tensile strength was 150~240MPa, which meets the strength requirements for submarine cable armor repair.

Claims

1. A method for repairing the armored rigid joint of a submarine cable, characterized in that, Includes the following steps: (1) Peel off the armor layer, restore the filling shell size according to the connector protective shell and armor, and leave 5~50cm of armor wire; (2) Fix the armor wire around the break point, bend the reserved armor wire outward one by one, and the bent armor wire forms a conical armor layer. Remove the surface covering of the bent armor wire to expose the metal wire. (3) A protective refill shell is attached to the peeling break point, and a premixed filling resin is injected into the inner cavity of the protective refill shell and cured. The filling resin is prepared by fully mixing EPU-300A epoxy resin, curing agent, accelerator and superconducting carbon black in a mass ratio of 1: 0.1~0.4: 0.01~0.1: 0.05~0.

2. The curing agent is an aliphatic or aromatic amine compound, the accelerator is an organic peroxide, and the superconducting carbon black has a DBP ≥ 200 mL / 100 g.

2. The method for repairing the armored rigid joint of a submarine cable according to claim 1, characterized in that, In step (1), at least one armor layer is peeled off. In step (2), the angle between the outermost armor wire and the core axis is ≤60°.

3. The method for repairing the armored rigid joint of a submarine cable according to claim 2, characterized in that, When there are at least two armor layers stripped, in step (1), the reserved length of each armor wire increases by 1 to 20 cm as the distance between the armor layer and the wire core decreases.

4. The method for repairing the armored rigid joint of a submarine cable according to claim 1 or 2, characterized in that, When at least two armor layers are peeled off, in step (2), the angle between the outermost armor wire and the core axis is 15°~35°, the folding angle of each armor wire decreases as the distance between the armor layer and the core decreases, and the bending angle error of the same armor wire is no more than 3°.

5. The method for repairing the armored rigid joint of a submarine cable according to any one of claims 1 to 3, characterized in that, In step (2), an organic solvent is used to dissolve and remove the coating material on the surface of the armoring filament. The organic solvent is one or a mixture of acetone, stearic acid, turpentine, trichloroethylene, chloroform, and ethanol.

6. The method for repairing the armored rigid joint of a submarine cable according to claim 1, characterized in that, The curing agent is 0.2 to 0.3 parts, and the accelerator is 0.07 to 0.09 parts.

7. The method for repairing the armored rigid joint of a submarine cable according to claim 1, characterized in that, The curing agent is diethyltoluenediamine, and the accelerator is tert-butyl peroxide.

8. The method for repairing the armored rigid joint of a submarine cable according to claim 1, characterized in that, The compressive strength of the filled resin after curing is ≥100 MPa, and the volume resistivity at 20℃ is ≤100Ω•cm.

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