JPS637407B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-high voltage power cable with a layer of water.

FIG. 1 shows a cross section of an example of a conventional ultra-high voltage plastic power cable with a water layer. 1 is a conductor, and 2 is an insulating layer including inner and outer semiconductive layers formed on the conductor 1 by extruding crosslinked polyethylene. During extrusion, the outer surface of the insulating layer 2 is formed as a layer having a gear-shaped cross section and having uneven grooves 3 in the longitudinal direction. A corrugated aluminum sheath 5 is placed over the core formed in this way.
is covered, and a PVC coating 6 is applied thereon. In the above structure, thermal expansion caused by the insulating layer 2 is absorbed by the hollow portion 4 formed by the insulating layer 2 and the corrugated aluminum sheath 5, and the corrugated aluminum sheath 5 functions as a conductor for ground fault current.

By the way, since such a power cable has many hollow parts, the thermal resistance is large and the current capacity is therefore small. Furthermore, since a corrugated aluminum sheath (made by extrusion) is used, eddy current loss is large and current capacity is small. Furthermore, a large aluminum extruder is required, which increases the cost, and corrugating increases the outer diameter, and since the corrugated aluminum sheath has low cyclic fatigue strength, the shipping drum becomes larger and the offset dimension becomes larger. Become.

In view of the above-mentioned drawbacks of the conventional ultra-high-voltage power cable with a water layer, the present invention is characterized by eliminating the use of corrugated aluminum sheaths and skillfully arranging metal wires and adhesive-type metal laminate sheaths. However, the present invention will be explained below with reference to embodiments shown in the drawings.

In the embodiment shown in cross section in FIG.
is a conductor, and the conductor 1 is selected from stranded wires, divided conductors, hollow conductors (internal cooling conductors), and the like. An insulating layer 2 made of cross-linked plastic and comprising inner and outer semiconducting layers is extruded thereon to form the core.

On this core, a metal wire layer 7 made of a good electrical conductor such as copper or aluminum is formed by twisting (including SZ twisting). This requires a size that allows ground fault current to flow.

This ground fault current value and duration vary depending on the cable line, but for example, in the case of a 3KA ground fault current of 2 seconds, 40 steel wires with a diameter of 1.2 mm are required.

Twisting the metal wires creates unevenness on the surface, so make sure the outer surface is uniform.
The smooth layer 8 is formed by extrusion, tape winding, or a combination of both. In the case of tape winding, it is preferable to use a combination of a highly rigid tape such as a stainless steel tape and a good cushioning property such as a cotton tape. This smooth layer 8 is an electrically insulating layer or a semiconducting layer, and cannot be a completely good conductor layer in the thickness direction. Further, this smooth layer 8 may contain a moisture absorbent depending on the case.

On the outside of the smooth layer 8 provided in this way, a heat-adhesive metal laminate tape made by pasting together a metal tape with not very low electrical resistance, such as a lead tape, and a plastic tape is vertically attached or wrapped, and further this vertical attachment is applied. Or in a wrapped state,
When the plastic sheath 10 is extruded, the heat-adhesive metal laminate tapes adhere to each other due to the heat generated during extrusion, and a persimmon water layer 9 is formed. The plastic sheath 10 is made of a material such as PVC or polyethylene.

An example of the ultra-high voltage power cable with a water layer according to the present invention has been described above, but the metal wire that carries the ground fault current is divided into many wires, the mutual contact resistance is large, and the metal wire is thermally bonded with a metal laminate. A smooth layer 8, which is not a good electrical conductor, is interposed between the water layer 9 made of tape and the metal wire layer 7, and the metal wire layer 7 is twisted (including SZ twist). , eddy current loss is small, and in this respect it is possible to create a low-loss cable, and since there is a smooth layer 8, wrinkles do not form on the metal laminate tape,
Incomplete joints can be avoided.

On the other hand, there are almost no voids in the radial direction,
Even if some voids occur in the metal wire layer 7, the metal wires are good conductors of heat, so these voids are not a problem, and the thermal resistance is reduced, making it possible to increase the current capacity. Further, in the embodiment, the insulating layer 2 was formed by extruding cross-linked plastic, but it may also be wound with plastic tape.

Furthermore, in the embodiment of the present invention described above, if the smooth layer 8 is made of an extruded plastic insulating layer, metal wires are cross-bonded, and the water layer 9 formed by an adhesive metal laminate tape is grounded at both ends. As a large-capacity power cable or a long-distance cable, it is easy to ensure safety even when the sheath voltage becomes high, so it is a so-called double cable. shield. Can be used as a cable.

As described above, according to the present invention, effects not seen in conventional power cables with water and water are achieved, and since no call gate is applied, for example, a 154KV class cable can be used outside the cable. The diameter can be reduced by about 12 to 18 mm, and the metal laminate tape has good fatigue strength and bending resistance, so shipping cables can be made smaller and the offset can be reduced. Furthermore, if the smooth layer is electrically insulating, it is easy to constantly monitor the insulation to detect external injuries, and it is convenient for maintenance, making it extremely practical. It is possible to provide power cables with high density and water layers.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of an example of a conventional ultra-high voltage power cable with a water layer, and FIG. 2 shows a cross-sectional view of an example of the ultra-high voltage power cable with a water layer of the present invention. It is shown with. DESCRIPTION OF SYMBOLS 1... Conductor, 2... Insulating layer containing a semiconducting layer, 3... Uneven groove, 4... Hollow part, 5... Corrugated aluminum sheath, 6... PVC sheath, 7... Metal wire layer, 8... Smooth layer, 9... Shiny Water layer, 10...plastic sheath.

Claims (1)

[Claims] 1 A twisted metal wire layer of a size that allows a ground fault current to flow outside the core, and a smooth layer consisting of an electrically insulating layer, a semiconducting layer, or a combination of a semiconducting layer and an electrically insulating layer in the thickness direction further outside the core. An ultra-high voltage power cable with a shimmering water layer, further comprising a shimmering water layer made of an adhesive metal laminate tape and an extruded plastic sheath formed on the outside.