JPH11273466A - High-voltage direct current power cable and sea bottom laying method for powder cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new cable and cable laying method which can perform a high-energy, long distance transmission between two places separated by a water area at a reasonable cost with a high reliability. SOLUTION: A conductor 1 is of multi-wire type made from copper, while an insulation 2 may consist of winding of a tape or an extruded shape, and a metal sheath 3 is made of lead alloy as conventional. The first layer 4 covering the metal sheath is made of a polymer such as polyethylene(PE) and may be of semiconductive for avoiding potential difference or decreasing it. A reinforcing material 5 in the crosswise direction consisting of a tape of stainless steel etc., is installed on the surface of the layer 4, and thereon a second layer 6 is installed which consists of a hard copper wire equipped with profile. Thereon the following are installed; an insulating material sheath 7 as PE sheath, a layer 8 consisting of galvanized steel wires, and an outside protection material 9 made from polypropylene lines and asphalt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-voltage direct current (HV)
DC) cables and methods of laying such cables on the sea floor. Such cables and how to lay them,
WO 97/04466 (G Barlog 13).

[0002]

2. Description of the Related Art UK 2295506 describes an HVDC system in which a rectifier and a plurality of converters are connected by a DC link and the firing angle of the rectifier in a closed loop is determined using the extinction angle of the inverter. By controlling, the arc extinguishing angle of the inverter is maintained at a predetermined value or more. Each converter has a closed loop controller that controls the firing angle of the rectifier in response to the DC current, DC voltage, the extinction angle of the converter itself, and the firing angle of the converter itself.

[0003] DE 1 262 425 describes the "Voltage Wise R" of cables in the HVDC laying method.
ELIEF) device, the laying method is such that both ends are connected to the AC network via "smoothing" coils and rectifiers, and the AC network for supplying and receiving power and the associated rectifier are connected on both ends to the AC side. The number of phases does not include the same prime number.

[0004] The usual method of transferring energy from one place to another across water bodies, such as between Norway and Denmark, uses HVDC cables with a central insulated conductor and uses seawater for return current. The method to use. This cable is laid between AC circuits having the same number of phases. One alternative is to lay another HVDC cable parallel to the first cable for the return current. This is an expensive solution.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new cable and a new laying technique, and to provide a reliable high energy long distance between two places separated by water bodies. The purpose is to meet the customer's requirement that the transfer be affordable.

[0006]

The main features of the present invention are as follows.
It is defined in the claims. With these solutions,
Applicant has succeeded in satisfying customer requirements. Applicant's cable operates in unipolar mode without an external magnetic field. This laying method eliminates seawater electrodes, which can be expensive and cause widespread environmental problems.

[0007] The above and other features and objects of the present invention will become apparent from the following detailed description of embodiments of the present invention, taken in conjunction with the drawings.

[0008]

FIG. 1 is a sectional view of a cable.
A center conductor having one or more layers of insulating material 2 encapsulated within a metal sheath is shown. The inner and outer semiconductor layers respectively arranged on the surface of the core wire 1 and below the lead sheath 3 are not shown. In the lead sheath, an insulator sheath 4, a reinforcing material 5, an exterior 6, an insulator 7, an exterior 8,
And the outer protective layer 9 are continuously arranged.

The conductor 1 is a multi-wire type copper conductor. The insulator 2 may be a wound tape or an extruded insulator. The metal sheath 3 is a conventional lead alloy sheath. The first layer 4 covering the metal sheath is a polymer such as polyethylene (PE). This first layer can be a semiconductor to avoid or reduce potential differences. A lateral stiffener 5 such as a stainless steel tape is placed on the surface of layer 4. Next, the two-layer exterior 6 which is a hard copper wire with a profile is arranged. Next, an insulator sheath 7 which is a PE sheath, an exterior 8 made of galvanized steel wire, and an outer protective material 9 made of polypropylene thread and asphalt are arranged.

For cables capable of transmitting 800 MW at 500 KV through the route of submarine cables over 500 km, the center conductor should have a cross-sectional area of 1.600 mm ² and the return conductor should be approximately 1.900 mm
^It should have a cross-sectional area of ² . This cable should preferably be buried in the seabed, from the seabed, preferably at a depth of 2.5 m.

FIG. 2 schematically shows the main components (conductor 1, return conductor 6, and sheath 8) arranged between the two terminal stations A and B. Stations A and B include converters (not shown) for interconnection with an AC network (not shown). The conductor 1 transfers the cable current from A to B,
Are continuously grounded. The coaxial return conductor 6 is connected to ground potential through surge arresters (valves) 10 and 11 located at both ends of the cable.
It is grounded in the middle of between. This grounding is provided by a semiconductor material.

The grounding of the metal return conductor must be such that there is no circulating current. At the same time, the converter must also have true ground. The circulating current is divided according to the resistance in different loops. Because seawater can be considered a very large conductor, only the resistance of the lead to the electrode, the resistance of the electrode, and the final resistance at the ground point define the loop resistance.

In FIG. 3, the laying method is similar to the laying method of FIG. 2, but in this alternative, the return conductor 6 has one end (A
(End) is grounded, and the other end (end B) is connected to the ground through a surge arrester (valve) 12.

For a cable having a metal return conductor, 80
At a load of 0 MW, a DC voltage of about 10 kV is applied for a length of 540 km. A resistor can be used to limit the ground current, but is undesirable if there is a ground current. Another method is to prevent circulating current by a single point connection. This method is possible if one of these valves needs to be grounded directly, but at the other end, the other group of valves is applied with 10 kV to ground.

If the cable system is grounded in the middle (FIG. 2), both valve groups have approximately 5 kV to ground.
DC voltage is applied. In this case, at both ends, the diode can be used as a Zener diode, and the outer insulator can be protected from overvoltage.

The above detailed description of the embodiments of the present invention is to be understood as merely examples and should not be considered as limiting the scope of protection.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a cross section of an HVDC cable.

FIG. 2 is a diagram illustrating an example of a cable laying method.

FIG. 3 is a diagram illustrating an example of a cable laying method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 core wire, conductor 2 insulating material, insulator 3 lead sheath 4 insulator sheath, first layer 5 reinforcing material, layer 6 sheath, return current conductor 7 insulator, insulator sheath 8 exterior 9 outer protective layer, outer protective material

Claims (6)

[Claims] An HVDC power supply including a central conductor (1), an insulating layer (2) covered with a metal sheath (3) such as a lead sheath, an outer sheath (8), and a corrosion protection material (9). A cable, comprising: a coaxial return current conductor (6) disposed between a metal sheath (3) and an outer corrosion protection layer (9). 2. Outside the metal sheath (3), a polymer insulator (or semiconductor) layer (4), a steel tape reinforcement (5), a copper sheath (6) functioning as a return current conductor, at least one layer. Cable according to claim 1, characterized in that it comprises a polymer insulation layer (7), a sheath (8) and an outer sheath (9) in sequence. 3. Cable according to claim 2, wherein the polymer layers (4, 7) are PE layers. 4. The armor (8) is continuously grounded along the cable route between A and B, and the return conductor (6) is grounded in the middle of the end connections (A, B). The method of laying a submarine cable for an HVDC cable according to any one of claims 1 to 3, wherein the method is performed. 5. The method according to claim 4, wherein the return conductor is grounded through surge arresters (10, 11) arranged at both ends (A, B). 6. The sheath (8) is continuously grounded along a cable route between A and B, the return conductor (6) is directly grounded at one end (A side), and the other end ( B
4. The method of laying submarine cables for HVDC cables according to claim 1, wherein the side is grounded through a surge arrester (12).