JP3417590B2 - DC submarine power cable line - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC underwater power cable line. 2. Description of the Related Art FIGS. 5 to 8 are block diagrams of a conventional DC submarine power cable line. FIG. 5 shows a unipolar operation type line in which both ends of one DC underwater power cable 21 are grounded in water or seawater, and water or seawater is used as a return circuit. In the drawing, reference numeral 3 denotes an AC / DC converter. FIG. 6 shows a single underwater DC power cable 21,
A total of two lines of extremely low-insulation DC underwater power cable 22 that only insulate the lightning surge and the resistance voltage drop of the cable are separately laid, one end of the low-voltage cable 22 is grounded, and this low-voltage cable 22 is used as a return circuit. This is a single-pole operation type track. [0004] FIG. 7 shows a high insulation DC submarine power cable 2.
This is a DC bipolar operation type line in which Articles 21A and 21B are laid, and the neutral point is underwater or seawater grounded with (+) pole and (-) pole respectively. FIG. 8 shows a DC bipolar operation type line in which the grounding points of the DC underwater power cables 21A and 21B of FIG. 7 are connected by the low voltage cable 22 and one end is grounded. [0006] Among the above-mentioned conventional DC submarine power cable lines, the line shown in FIG. 5 has a return current equal to the forward current flowing in the seawater, so that the compass error of the navigating ship and fishes However, in recent years, in the case of single-pole operation, a low-voltage cable 22 constituting a return circuit is often separately laid as shown in FIG. In the bipolar operation system, a return circuit is unnecessary in principle if the (+) and (-) currents are balanced, but (a) a return path for a delicate unbalanced current (b) either high-voltage cable In the event of an accident, the operation is immediately returned to the unipolar operation. However, in order to solve the above-mentioned problem, the adoption of the bipolar operation system shown in FIG. 7 is decreasing, and as shown in FIG. The adoption of a system in which the underwater power cable 22 is laid between ground points to form a return circuit (neutral wire) is increasing. However, in addition to the DC underwater power cable 21 which truly contributes to the DC transmission power in each of the unipolar operation type line shown in FIG. 6 and the bipolar operation type line shown in FIG. A DC submarine power cable for the circuit (neutral line) is required. (A) The cable laying space for securing the route increases, and problems such as compensation for fisheries are involved. (B) The material, processing cost and installation cost for one cable are increased by the return circuit, which is uneconomical and the installation period is long. And so on. In particular, in the case of the bipolar operation system shown in FIG. 8, almost no current flows in the return circuit (neutral line) during normal operation, which is a so-called emergency operation.
It is uneconomical and inefficient. [0009] The present invention SUMMARY OF] is to solve the above-ku things used DC underwater power cable return circuit (neutral), the DC underwater power cable shown in FIG. 8 The present invention provides a DC underwater power cable line capable of exhibiting an effect equivalent to that of a line, and is characterized in that the above-mentioned outer line of the DC underwater power cable provided with an outer wire is formed of a copper wire or a copper alloy wire, and the outer wire is provided. Wire adopting DC bipolar operation method
The return current circuit on the ground side of the road is used as a neutral wire . The total cross-sectional area of the outer cable of the DC submarine power cable is
It is equal to or much larger than the cross-sectional area of the cable conductor through which the internal transmission current flows. Therefore, if this is made of a copper wire or a copper alloy wire, it can be an external conductor smaller than the DC resistance of the internal cable conductor. Therefore, if this copper or copper alloy sheath wire is used as a return circuit (neutral wire) in FIGS. 6 and 8,
Originally, the potential of the return circuit (neutral wire) can be understood from the fact that one end is grounded. The potential is almost close to the ground potential and can perform basic functions without insulation, so large conductor size, An armored wire with high conductivity and low resistance can be a return current circuit (neutral wire). As specific numerical examples, DC 500 kV, 1
× 1600mm ² class DC underwater power cable, 3mm thickness ×
If the outer wire is composed of two layers of 12 mm wide rectangular copper wire,
100 sheets is required, the total cross-sectional area becomes 3600 mm ² next ,, internal twice or more cable conductors 1600 mm ^2. [0013] If an outer wire is composed of one layer of a round hard copper wire having a diameter of 8 mmφ in a DC 500 kV, 1 × 3000 mm ² class DC underwater power cable, approximately 60 wires are required, and the total cross-sectional area thereof is required. comprising the 3016Mm ^2, and the equivalent to the inner cable conductor. Furthermore, a round hard copper wire having a diameter of 8 mmφ is connected to a DC 250 kV, 1 × 600 mm ² class DC underwater power cable.
If layers are used to form an exterior wire, approximately 38 wires are required, and the total cross-sectional area is 1910 mm ² , which is slightly more than three times the internal cable conductor. In general, the easiness of the flow of the direct current is proportional to the conductivity of the conductor (inversely proportional to the resistance), and the conductivity is proportional to the cross-sectional area of the conductor. The DC current is much easier to flow than the DC current flowing through the internal cable conductor. Although it has been described above that the sheath wire basically does not need to be insulated, there is a possibility that a DC voltage corresponding to the return current × the resistance of the outer conductor (sheath wire) = voltage drop may be generated even if it is slight. There is. Since this is preferably as small as possible, it is preferable that the total cross-sectional area of the sheath wire is large as described above.
Applying such a small amount of insulation for the DC voltage to the sheathing line with, for example, polyethylene coating, can further completely prevent the flow of the DC return current into seawater, and for environmental protection and the sheathing line. It is also preferable from the viewpoint of preventing electrical corrosion of the steel. In view of the above, in the case of the bipolar operation system shown in FIG. 8, it is most effective to use the cable line of the present invention. Because (+) (-)
Since only a small amount of current corresponding to the pole imbalance flows through the return circuit (neutral wire), there is little voltage drop, little leakage current into seawater, environmental disturbance, and almost no fear of electrical corrosion of the outer cable. Because it is not. Further, when the DC submarine power cable is buried in the submarine soil, (a) a serving layer such as a jute or a polypropylene string outside the sheathing line for protecting the sheathing line remains without being corroded, The electric resistance of the sheathing line against seawater leakage is high. (B) The electric resistance itself of the buried soil at the bottom of the water is also
Much higher than the electrical resistance of non-buried cables to water. Therefore, it can be said that there is almost no leakage current leaking into the water from the armoring wire, and that it is extremely favorable both in terms of environment and electrical corrosion. In the case of the single-pole operation system with one DC underwater power cable, the outer wire as the return circuit (neutral wire) is a single cable outer wire and two DC underwater power cables. In the case of the bipolar operation system, if the outer wire of the two cables is made of copper wire or copper alloy wire and the two outer wires are combined and used as a return circuit (neutral wire), the conductor of the return circuit can be used. This is preferable because the cross-sectional area is further increased and the electric resistance is significantly reduced. FIG. 4 (a) is a cross-sectional view of an example of a DC underwater power cable constituting a cable line according to the present invention. In the drawing, 11 is a cable conductor, 12 is a cable insulator, 13
Is a metal sheath such as a lead sheath, 14 is a seat for jute, polypropylene string, etc., 15 is an exterior wire, 16 is a serving layer of jute, polypropylene string, etc., and the above-mentioned exterior wire 15 is a large number of copper wires, copper alloy wires, etc. It is configured by this twisting and is used as a return circuit (neutral wire). FIG. 4B is a cross-sectional view of another example of the DC submarine power cable constituting the cable line of the present invention.
The same reference numerals denote the same parts. The cable shown in FIG. 5 has the same overall configuration as the cable shown in FIG. 4, except that each element wire of the armoring line 15 is provided with a corrosion-resistant insulating layer 17 made of polyethylene, vinyl chloride or the like. FIGS. 1 to 3 are explanatory diagrams of specific examples of the DC submarine power cable line of the present invention. FIG. 1 shows a single-pole operation system using one of the submerged DC power cables shown in FIG. 4 or FIG. It is a railroad track. In the drawings, reference numeral 3 denotes an AC / DC converter. FIG. 2 shows the use of the two underwater DC power cables shown in FIG. 4 or FIG. 5, the respective cable conductors 1A and 1B for the (+) and (-) poles of the DC transmission current, and This is a bipolar operation type line used as a current circuit (neutral wire). FIG. 3 is a diagram of a two-phase single-phase 1A, 1B bipolar operation line using four submersible DC power cables, which are totally cut off by using the outer wire 2 of these cables as a return circuit (neutral wire). The area is much larger and the electrical resistance is significantly reduced. Also, even if two lines of the DC submarine power cable are damaged, the remaining two cables can be operated in a bipolar manner, thereby increasing the reliability of the line. Ensuring this reliability is extremely important for DC submarine power cables. As described above, since the DC submarine power cable line of the present invention uses the outer wire of the cable as a return current circuit, the total cross-sectional area is much larger than the cross-sectional area of the cable conductor. There is almost no outflow of return current into water or seawater, which is preferable from the viewpoint of environmental protection and electrical corrosion of the exterior wire. Further, unlike the related art, since the neutral cable is not laid, the space for laying the cable can be reduced, the cost for one cable and the cost required for laying can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a specific example of a single-pole operation type DC underwater power cable line of the present invention. FIG. 2 is an explanatory diagram of a specific example of a DC submarine power cable line of a bipolar operation type according to the present invention. FIG. 3 is an explanatory view of another specific example of the DC submarine power cable line of the bipolar operation type according to the present invention. FIGS. 4A and 4B are cross-sectional views of a structure example of a DC submarine power cable. FIG. 5 is an explanatory diagram of a conventional single-pole operation type DC underwater power cable line. FIG. 6 is an explanatory diagram of another example of a conventional single-pole operation type DC submarine power cable line. FIG. 7 is an explanatory diagram of a conventional DC submarine power cable line of a bipolar operation type. FIG. 8 is an explanatory diagram of another example of the conventional DC submarine power cable line of the bipolar operation type. [Explanation of Signs] 1, 1A, 1B Conductor of DC underwater power cable 2 Armoring line of DC underwater power cable 3 AC / DC converter

Claims (1)

(57) [Claims 1] A line in which a DC submarine power cable provided with a sheathing line is constituted by a copper wire or a copper alloy wire, and the sheathing line adopts a DC bipolar operation system. A submarine power cable line for use as a neutral line on the ground-side return current circuit of the present invention.