JPH02126521A - Manufacture of crosslinked polyethylene insulated power cable - Google Patents

Abstract

PURPOSE:To improve the electric characteristics of a crosslinked polyethylene insulated power cable by uniformly winding a semiconductive cloth tape having a specific tensile strength around a cable core through a water barrier layer made up of a metal laminate tape layer or not through the water barrier layer such that a specific bearing is provided to the semiconductor cloth tape, and then, forming a metal shielding layer. CONSTITUTION:A semiconductor cloth tape having a tensile strength of 30kg/15mm width or more is uniformly wound around a cable core through a water barrier tape made up of a metal laminate tape layer or not through it such that the bearing (P) shown in Formula 1 is 1.5kg/cm<2> or more, and then, a metal shielding layer, a pressure wind tape layer and a corrosion resisting layer are formed as necessity arises. In Formula 1, P = bearing (kg/cm<2>), T = wind tensile force of a semiconductive cloth tape (kg) Beta = wind angle (radian), W = width (cm) of the semiconductive cloth tape, D = diameter (cm) of the cable core. Therefore, an expansion of the diameter due to a high temperature heat cycle and a shrinkage in the longitudinal direction hardly occur. Thereby, it is possible to keep stable electric characteristics for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in crosslinked polyethylene insulated power cables.

[Conventional technology]

Conventionally, cross-linked polyethylene insulated power cables use cross-linked polyethylene as an insulator, which has excellent heat resistance, heat deformation resistance, and electrical properties. layer or an external semiconducting layer.

After it became clear that the properties of the interface between the insulator and the inner and outer semiconducting layers, such as smoothness and adhesion, significantly affected the electrical performance of the cable, This has changed to extruded inner and outer semiconductive layers formed by extruding a semiconductive resin composition using an extruder.

These technological advances have greatly improved the electrical properties of cross-linked polyethylene insulated power cables.

[Problem to be solved by the invention]

However, when a crosslinked polyethylene insulated cable is heated to near its melting point, the cable core expands in diameter and contracts in the longitudinal direction due to large volumetric expansion. When a cable is repeatedly subjected to such high-temperature heat cycles, the above-mentioned tendency is exacerbated, causing large conductors to protrude at both ends of the cable, which tends to cause misalignment with the stress cone at the cable termination and joint, resulting in electric field irregularities. , there was a problem that it could easily cause troubles such as the outbreak of corona.

The present invention was achieved as a result of intensive studies from this viewpoint.

[Means to solve the problem]

That is, the present invention provides a cable core formed by successively forming an extruded internal semiconductive layer, an insulator layer, and an extruded external semiconductive layer on the outside of a conductor, through a water spray layer consisting of a metal laminate tape layer, Or without intervention, tensile strength 30kg/15an
After uniformly wrapping a semiconductive cloth tape having a width of + width or more so that the surface pressure (P) expressed by the following formula is 1.5 kg/d or more, apply a metal shielding layer as necessary as usual. This is a method for manufacturing a cross-linked polyethylene insulated power cable, characterized in that a pressing tape layer and an anti-corrosion layer are formed according to the method.

here P is surface pressure (kg/cj) T is tape winding tension (kg) β is the tape wrapping angle (radian) W is tape width (cm) D is cable core diameter (cm) It is.

In the present invention, the tensile strength of the semiconductive cloth tape is 30k.
g/If the width is less than 15mm, depending on the tape winding tension,
Because the semiconductive cloth tape breaks or shows non-uniform elongation, uniform winding cannot obtain force.

Further, if the surface pressure (P) is less than 1.5 kg/c, it is not possible to suppress shrinkage in the longitudinal direction of the cable due to high temperature heat cycles of the cable. Tensile strength 30kg/1
Semi-conductive cloth tape with a width of 5 mm or more, with a surface pressure of 1.5
Even if the cable is subjected to high-temperature heat cycles,
Expansion of the diameter of the cable core is suppressed by this semi-conductive cloth tape, and therefore almost no expansion of the diameter or contraction in the longitudinal direction occurs, and there is no protrusion of the conductor. It has been discovered that stable electrical characteristics can be maintained over a long period of time.

According to the present invention, since a surface pressure of 1.5 kg/c4 or more is always applied to the cable core, even if defects such as voids and foreign objects exist in the cable core insulation, the insulation will No voids are generated at the interface between the cable and the defect, and therefore the high-temperature electrical properties of the cable do not deteriorate rapidly.

In the case of a core water-fed cable in which a metal laminate tape is provided as a water-shielding layer on a cable core, the semiconductive cloth tape of the present invention is applied and manufactured on this water-shielding layer.

(Example〕 Next, examples of the present invention will be shown.

Examples 1 to 3, Comparative Examples 1 to 3 In manufacturing a 35 kV 110 AWG aluminum conductor cable, an inner semiconducting layer, an insulating layer, and an outer semiconducting layer are extruded in this order on an aluminum conductor, and then this outer semiconducting layer is formed by extrusion in this order. For the layer, a semiconductive cloth tape was manufactured under the conditions shown in Table 1.

Table 1 A cable was completed by providing a copper wire (1.6 mmφ) shielding layer and a polyethylene anticorrosion layer on the semiconductive cloth tape layer.

In Comparative Example 3, a copper wire shielding layer and a polyethylene anticorrosion layer were provided on the external semiconductive layer without providing a semiconductive cloth tape.

Using the above cable, a heat cycle test was conducted, followed by a room temperature/high temperature AC breakdown test.

In the heat cycle test, a 3 m finished cable was used, and the conductor was energized and heat cycled 100 times between the conductor temperature of 130'C and room temperature, and the conductor protruded! ! (1iii amount of insulator) was measured.

The room temperature AC destructive test was tested at 25°C, and the high temperature AC destructive test was tested at 90°C. The test results were expressed as high/MAC destruction value/chamber/MAC destruction value.

As a result, in Examples 1 to 3 of the present invention, when the conductor protrusion was 15 mm or less, the high temperature AC breakdown value/room temperature C breakdown value was 0.95 to 1,00, which was good. In Comparative Examples 1 to 3, when the conductor protrusion amount was 10 nu* or more, the high temperature AC breakdown value/room temperature C breakdown value was 0.90 or less.

〔Effect of the invention〕

As shown in the examples above, according to the present invention, even if the cable is repeatedly subjected to high temperature heat cycles, there is no significant shrinkage of the insulator core, and no significant decrease in high temperature AC breakdown characteristics occurs. It has stable electrical performance over a long period of time.

In particular, when the cable core is combined with a water-shielding layer made of metal laminate tape, the water-shielding layer has a tensile strength of 30K.
By uniformly wrapping a semiconductive cloth tape having a width of g/15+nm or more so that the surface pressure is 1.5 kglcr& or more, the effect becomes remarkable and is extremely useful in practice.

Claims (1)

[Claims] A cable core formed by sequentially forming an extruded internal semiconductive layer, an insulating layer, and an extruded external semiconductive layer on the outside of a conductor, through a water-blocking layer consisting of a metal laminate tape layer. Or, without using a semiconductive cloth tape having a tensile strength of 30 kg/15 mm width or more, the surface pressure (P) expressed by the following formula is 1.5 kg/c
Manufacture of a cross-linked polyethylene insulated power cable, characterized in that it is uniformly wound to a thickness of m^2 or more, and then a metal shielding layer, a pressure-wrapping tape layer, and an anti-corrosion layer are formed as required by a conventional method. Method. P=2・T・cos^2β/W・D where P is surface pressure (kg/cm^2) T is wrapping tension of semiconductive cloth tape (kg) β is wrapping of semiconductive cloth tape Angle (radian) W is the tape width (cm) of the semiconductive cloth tape D is the cable core diameter (cm).