JPH04190512A - Power cable - Google Patents

Abstract

PURPOSE:To provide an oil impregnated power cable by impregnating with alkyl diphenyl ethane as a low viscosity high density insulation oil. CONSTITUTION:This is a power cable impregnated with alkyl diphenyl ethane as an insulation oil of dynamic viscosity 10cst or less at 40 deg.C. The alkyl diphenyl ethane has been found as an insulation oil for OF cables to satisfy the requirements of a high density as near as possible to that of the sea water and a low viscosity and also superior to conventional OF insulation oil in the resistance against polyolefin such as polyethylene, polypropylene, poly-4-methyl- pentane-1, etc. This maintains oil pressure for a long size.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an oil-immersed electrical cable using a low-viscosity, high-density alkyldiphenylethane as an insulating oil.

[Conventional technology]

In the past, OF cables were proposed as cables with an insulating layer made void-free by impregnating kraft paper with a low-viscosity hydrocarbon insulating oil and applying hydraulic pressure, and it was widely used as a high-voltage cable with excellent voltage stability. (
It is used. As the hydrocarbon-based insulating oil, mineral oil-based insulating oil and alkylhenzene-based insulating oil are generally used in consideration of insulation performance. On the other hand, especially when the OF cable is used as a deep submarine cable, it is necessary to maintain high pressure oil over an extremely long distance (long length). Due to the difference in density between seawater and insulating oil, the minimum hydraulic pressure P (Kg/cm2) required from above ground is P-(d,-d,)X
It is expressed as (D/10). However, d is the density of seawater (g/cm”)
, do is the density of oil (g/cm3), and D is the depth to the seabed (m).

[Problem to be solved by the invention]

However, the density of the above-mentioned general OF insulating oil is do
= 0.86 to 0.90 (g/cm"). For example, taking alkylhenzene oil (d0 = 0.87 g/cm3), at a depth of 2000 m, P = 32 (Kg/cm").
A high hydraulic pressure of more than m2) is required, making it difficult to design an exterior that is resistant to hydraulic pressure. Furthermore, in order to maintain oil pressure over a long period of time, insulating oil with a higher bottom viscosity is currently required. The present invention has been made in view of the conventional circumstances as described above.

[Means for Solving the Problems and Their Effects] The feature of the present invention is that the kinematic viscosity at 40°C is 10cst.
The following electric cable is impregnated with alkyldiphenylethane as an insulating oil. The alkyldiphenylethane used in the present invention was discovered by the present inventors as an oil that satisfies the requirements of having a high density close to that of seawater and a low viscosity as an insulating oil for OF cables. Although it is shown by the formula % formula % (3) 2 and there are three types of structural isomers, its density is about 0.99 (g/cm3)T:
Close to the density of seawater (d,, = 1.03 g/cm3) (
, Moreover, the viscosity shows a value of 2 to 10 csL at 40°C,
It has low viscosity. In addition, in the case of this alkyldiphenylethane, the flash point, pour point, gas absorption, and electrical properties of the oil are comparable to those of conventional insulating oil for OF cables, and it is sufficient when applied to OF cables. It was found that this characteristic was reflected. Furthermore, this alkyldiphenylethane can be used for polyethylene, polypropylene, poly-4-methyl-pentene-1
Regarding oil properties, it is superior to conventional OF insulating oils, and is suitable for use with semi-synthetic papers such as PP laminated paper made of composites of these polyolefins.
It has the advantage that it can also be applied to cables.

【Example】

For a conductor with a cross-sectional area of 1000 mm2, an insulating layer (thickness 1
9mm, 275KV grade) was washed with deionized water in 4 different thicknesses of Kraf I paper (tape thickness, 100μ from the inner layer).
m, 1.25 μm, 15071 m, 200 μm), and after vacuum drying, impregnated with insulating oil,
OF cables (the actual height measurement and the comparative height measurement) were manufactured according to the usual method. In the case of this height measurement, the insulating oil mentioned above has a viscosity of 2.6 cst at 40'C and a density of 1.0 g/cm3 (1,5'C).
Alkyldiphenylethane (manufactured by Nippon Petrochemical Co., Ltd., trade name, 5AS-40) was used. Further, in the comparative height measurement, alkyl Hensen oil (viscosity at 40°C: 9 cst, density at 15°C: 0.87 g/cm 3 ) was used. For each of these OF cables (actual height measurements and comparative height measurements), the AC and impulse (Imp) breakdown voltages, dielectric properties (tan δ), and expected pressure at 2000 m seabed P['', double series P-(d, -d,)X (D/I O)
The results shown in Table 1 were obtained. = 4- From Table 1, it can be seen that the actual height measurement of the present invention is no inferior to the conventional comparative inversion, and requires only an extremely small hydraulic pressure.

【Effect of the invention】

As is clear from the above description, the electric capule according to the present invention is impregnated with alkyldiphenylethane having a kinematic viscosity of 10 cst or less at 40°C as an insulating oil, and therefore has characteristics different from conventional products. Comparable characteristics are obtained, and the pressure required to maintain hydraulic pressure over a long length is significantly lower than that of conventional cables, making it extremely easy to design cable hydraulic pressure-resistant exteriors and manage cable lines after installation. , and other advantages can be obtained. In addition, the above-mentioned alkyldiphenylethanes have better oil resistance to polyolefins than conventional OF insulating oils, so they can also be applied to OF cables made of semi-synthetic paper such as PP laminated paper made of composites of these polyolefins. You can also get the benefits of 71

Claims (1)

[Claims] A power cable characterized in that it is impregnated with alkyldiphenylethane having a kinematic viscosity of 10 cst or less at 40°C as an insulating oil.