JPS5936492B2 - Power cable installation method from single-point moored offshore power plant to mooring tower - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an offshore power plant, and particularly to a method for laying an electric cable between a power generation vessel and a stabilization tower that employs a single-point mooring method.

Due to land shortages, a proposal has recently been made to construct a power plant on a ship floating in the ocean, and the method described below is being considered as a highly practical method.

This method, for example, as shown in FIG.
A power generation vessel 4 is attached to a mooring tower 1 consisting of a rotating outer cylinder 1d having a heavy cylindrical mooring body 1c at the upper end, which can freely rotate around the outer periphery of a base pillar 1a using a mooring arm 3.
and cable pen 5 on the power generation ship side and mooring tower 1.
An electric power cable 7 is installed between the rotating contactors 6 on the side, and the generated electric power is transmitted to a consumption point on land via a submarine cable 8.

This one-point mooring method allows the power generation vessel 4 to rotate freely around the mooring tower 1 in response to ocean currents, wind, etc.
Further, at the connection point between the mooring arm 3, the power generation vessel 4, and the mooring tower 1, there is a first. The second hinge parts 9 and 10 are provided so that when the sea surface 11 repeatedly rises and falls due to waves, the power generation vessel 4 is moored so that it rises and falls accordingly.

In other words, since this method allows mooring without going against natural forces such as ocean currents and wind, it has the advantage of being able to achieve the objective economically compared to, for example, a method that attempts to securely secure the power generation vessel at two or more points. .

However, in this method, when the power generation vessel 4 moves up and down due to waves as shown in Fig. 2, the power generation vessel 4 and the mooring tower 1
At the same time as the distance between them changes, the angles θ1 and θ2 formed by the mooring arm 3, the power generation vessel 4, and the mooring tower 1 change.

For this reason, the less flexible electric cable 7 that hangs down due to its own weight repeatedly deforms as shown by the dotted line in FIG.

Therefore, large bending forces are repeatedly applied to the electric cable, especially near the zero point, which often causes cracks in the metal sheath, displacement of the insulating paper, and even deformation, leading to dielectric breakdown.

Therefore, in order to prevent this, as shown by the dashed line in FIG.
A method has been proposed in which the length of the cable is shortened by tucking it in to prevent it from bending, and in the opposite case, the cable is fed out.

However, this method has drawbacks such as the equipment for cable retraction being large, complex, and expensive, and moreover, is prone to failures, so there are concerns about its adoption.

The present invention provides a method for laying a power cable in the one-point locking method, which is less likely to cause dielectric breakdown of the power cable as described above.

Next, the details will be explained using the drawings.

The present invention is a partial diagram of an embodiment shown in FIG. 3 (the same reference numerals as in FIG. 1 indicate equivalent parts).

), a circular arc-shaped flexible arch 15 (for example, an elastic A metal strip (made of steel or other material having a
The power cable 5 is selected so that it does not deform following the bending of the power cable pull 7, and on the contrary, the power cable I deforms following the deformation of the flexible arch 15.

In this way, the flexible arch 15 changes the angles θ□, θ2 formed by the firing arm 3, the power generation vessel 4, and the firing tower 1, and the distance between the power generation vessel 4 and the firing tower 1. is always deformed into a circular arc shape having the maximum curvature in that state, and the electric cable 7 held along this arc is also deformed into the same shape.

Therefore, the bending force is distributed over the entire cable without strain, and it is less likely that the power cable will be repeatedly subjected to large bending forces, as would be the case in the conventional system, i.e., without a flexible arch.

Therefore, the risk of dielectric breakdown due to cracks in the metal sheath is significantly reduced.

At the same time, if it is fixed along the flexible arch as in the present invention, it will prevent the movable power capeple of the power generation vessel from swinging from side to side around the tidal current or the stopping tower. This can also avoid damage to the cable attachment bases of the power generation vessel and the arresting tower.

Although one flexible arch is used in the above, points 13, 14, and 12a are used as shown in FIG.

two flexible arches 15a fixed by 12b,
It goes without saying that this can be carried out using 15b.

As is clear from the above explanation, according to the present invention, it is possible to prevent damage to the installed cable between the power generation vessel and the detention tower, which are pinned at one point, by the simple method of providing a flexible arch. This is extremely useful in practice.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the locking method of a single-point locking offshore power plant, Fig. 2 is an explanatory diagram of the cause of damage to the power cable, Fig. 3 is a partial diagram of an embodiment of the present invention, and Fig. 4 is a partial diagram of another embodiment.

Claims (1)

[Claims] 1. In a single-point fixed offshore power plant in which a power generation vessel and a mooring tower are connected by a mooring arm via a hinge, an arc-shaped mooring vessel is fixed at three points: the power generation vessel, the mooring tower, and the mooring arm. By providing a flexible arch and fixing the power cable connecting the power generation vessel and the mooring tower along the flexible arch, the bending force on the power cable due to the movement of the power generation vessel is absorbed by the flexible arm. A method for installing electric power cables from a single-point holding type offshore power plant to a mooring tower, which is characterized by protecting the electric power cables by dispersing them throughout the entire cable.