RU66592U1 - ELECTRIC POWER CABLE - Google Patents

Abstract

The design of an electric power cable with insulated conductive cores and filling the gaps between them, used to transmit electrical energy, is proposed. In order to improve the operational characteristics of the cable as fillers for the gaps between insulated cores, it contains bundles of microcreated paper with a specific gravity of (60-80) g / m ² , a density of (0.65-0.75) g / cm ³ and a burst energy in a machine direction (150-350) J / m ² made from sulphate coniferous unbleached pulp. The new cable is high-tech and has high quality and reliability, especially when using filler tows from base paper of the BKM cable microcreated brand glued with rosin glue.

Description

The utility model relates to cable technology, namely, to the designs of high voltage power cables used to transmit electrical energy.

Power cable designs are known - analogues (Barnes S. Power cables. Moscow, Energia, 1971), used for transmission and distribution of electricity, consisting of conductive wires twisted from smooth soft copper or aluminum wires, oil-insulated paper insulation tapes and a waterproof metal sheath overlaid on one or more insulated cores. The metal sheath, if necessary (determined by the conditions of cable laying) is protected by steel armor.

Also known are the designs of multicore cables (Fig.): “Power cables with impregnated paper insulation” according to GOST 18410-73, year of commissioning 1975, Russia, and “Power cables with plastic insulation” according to GOST 16442-80, year of commissioning 1982, Russia.

The insulation of these cables consists of insulation 2 around each core (phase insulation) and insulation 4 around twisted insulated conductors (belt insulation). Insulated conductors of multicore analog cables are twisted to fill 3 gaps between the conductors.

Filling the gaps between insulated cores is necessary to eliminate air cavities leading to premature

failure of the power cable (breakdown), to give the cable a round shape and ensure uniformity of the electric field, increase the electric strength of the insulation.

In power cables with impregnated paper insulation in accordance with GOST 18410-73, phase and zone insulation are made of cable paper of brand K and KM in accordance with GOST 23436-83, commissioned 1985, Russia, 120 or 140 microns thick. As fillers for the gaps between insulated conductive cores, cable bundles of K and KM grade paper are used with a thickness of not more than 80 microns.

In power cables with plastic insulation in accordance with GOST 16442-80, cords or bundles made of PVC plastic, polyethylene, unvulcanized rubber, jute yarn or other equivalent material, for example, cable paper, are used as gap fillers between insulated conductive wires.

The use of cables with paper filling the gaps between insulated cores is due to the fact that the paper is chemically stable, resistant to electric fields, can work for a long time at elevated temperatures (70-85 ° C), is more technological and economical in comparison with other types of insulating materials (plastic , rubber) used in cables for electric power transmission.

Closest in its parameters to the utility model is the "Electric power cable" according to the patent of the Russian Federation No. 50039, published on December 10, 2005 (prototype).

The phase and zone insulation of the cable according to the prototype is made of microcreated paper tapes, which differs from ordinary cable paper in the increased break energy in the machine direction. Therefore, the paper insulation of the cable according to the prototype based on microcreated paper has greater resistance to tearing and cracking when bending the cable in comparison with analogues.

In the cable according to the prototype, as fillers for the gaps between insulated conductive cores, cable bundles of K-080 and KM-080 grade 80 mm thick paper are used in accordance with GOST 23436-83, the characteristics of which are shown in Table 1. The cable paper is made from the color of natural fiber from unbleached sulfate softwood pulp or softwood pulp with the addition of hardwood pulp according to normative and technical documentation. The addition of hardwood pulp reduces the cost of cable paper, but at the same time, the strength characteristics of the paper, its heat resistance and moisture resistance are reduced. Paper is made of machine smoothness (using a machine calender). K-grade cable paper is two-layer, and KM is three-layer. The main drawback of cable paper is the low values of elongation in the machine direction (≤2.5%), which significantly reduces the manufacturability and quality of bundles of this paper and cable.

The electric power cable according to the prototype (Fig.) Is made according to the following technology. On copper or aluminum conductive conductors 1, phase insulation 2 is applied on insulating tape winding machines.

The number of paper tapes and the thickness of the phase insulation depend on the brand of cable (rated voltage) and the thickness of the paper. In phase isolation, micro-creased paper base paper of the BKM-120 or BKM-140 brands according to TU 5433-004-50289046-2005, year of entry 2005, Russia is used. Insulated and marked cores enter a general twist with filling the gaps between the cores with paper tows 3. The paper tow is made of cable paper K-080 or KM-080. Cable paper is cut on a paper-cutting machine into rollers with a width of (40 ÷ 60) mm, depending on the brand of the bundle: Ж-2; G-3; G-4. When cutting, the paper is wetted with water to facilitate the process of twisting the bundles. The bundles of paper moistened in water have a more circular cross section and do not unwind during their manufacture and laying on the cable. The wetted paper rollers are fed to paper spinning machines, where paper tows are obtained, wound into bobbins.

Before using in electric cables, paper tows in bobbins are dried on racks at a temperature of (20 ÷ 30) ° С for several days. Then the bundles fall on the general twist of the cable, where they are laid in the gaps between the twisted insulated cores in a taut state. With a slight tension, the bundles can be displaced from the gaps between the cores during twisting and the cable is rejected. Belt insulation is applied over twisted insulated cores and paper harnesses 4

from paper tapes of a certain width. In belt insulation, microcreated paper BKM-120 or BKM-140 is used.

In cables for voltage of 6 and 10 kV over the belt insulation and in cables for voltage of 20 and 35 kV, a screen 5 of conductive paper is superimposed on the cores and on top of the insulation. After that, the cable is subjected to drying and impregnation to remove moisture and air from paper insulation, filler and screen and impregnating them with dielectric composition, for example, MP-2 oil-rosin compound (75% KM-22 cable oil and 25% KNMK cable rosin by weight) .

The processes of drying and impregnation of paper insulation, aggregate and screen are interrelated processes, since moisture from the atmosphere is quickly absorbed by dry paper, and therefore these two processes are performed simultaneously, or they are impregnated immediately after drying without exposure to atmospheric air. The sequence of operations of drying and impregnation of cables:

- loading the cable into a vacuum boiler with a steam jacket;

- heating the cable under vacuum to a temperature of (120 ± 3) ° С by passing current through the core and steam in the boiler jacket;

- preliminary drying under vacuum at a temperature of (125 ± 5) ° С;

- drying under vacuum at a temperature of (125 ± 5) ° С;

- inlet to the boiler with a cable of degassed impregnating composition MP-2 under vacuum at a temperature of (130 ± 10) ° С;

- impregnation of the cable under vacuum at a temperature of (130 ± 10) ° С;

- cable impregnation at atmospheric pressure and temperature (130 ± 10) ° С;

- unloading the cable from the vacuum boiler;

- cooling the cable to a temperature of (60-70) ° C.

The paper impregnated with an oil-rosin compound is a hygroscopic material, and therefore, after drying-impregnation, a moisture- and air-tight protective metal sheath 6 (lead or aluminum) is applied to the cable over the screen.

Protective coatings are applied over the metal sheath of the cable:

- a pillow 7, consisting of alternating layers of bitumen, polyethylene terephthalate film and creped paper or non-woven fabric;

- armor 8 of steel tapes or wire;

- outer cover 9 of bitumen with chalk or alternating layers of bitumen, polyethylene terephthalate film, fibrous materials (glass yarn or impregnated cable yarn or impregnated fabric jute tape), chalk or plastic sheath (plasticized polyvinyl chloride or polyethylene).

The disadvantages of the prototype include:

- reduced mechanical strength and elasticity of paper filling the gaps between the cores;

- increased uneven filling of the gaps between the cores;

- the presence of breaks, omissions, displacements of the filler (paper tows);

- increased unevenness of the electric field of the cable, leading to its premature breakdown;

- low manufacturability of the cable when applying paper tows due to their increased stiffness and breakage.

All these disadvantages of the prototype significantly reduce the quality, reliability and manufacturability of cables.

The technical task of the utility model is the development of power electric cables that are not inferior to the prototype in basic characteristics, but more technological, high-quality and highly reliable.

The technical result is achieved by the fact that, as fillers for the gaps between the insulated conductive cores, the cable contains bundles of microcreated paper with a specific gravity of (60-80) g / m ² , a density of (0.65-0.75) g / cm ³ and a burst energy of machine direction (150-350) J / m ² , made from soft sulfate coniferous unbleached pulp.

A common feature of the prototype and the proposed technical solution is the presence of paper tows used to fill the gaps between insulated conductive cores. At the same time, the proposed cable differs from the known one by the use of paper tows from microcreated paper with a specific gravity (60-80) g / m ² , a density (0.65-0.75) g / cm ³ and a burst energy in the machine direction (150- 350) J / m ² made from 100% sulphate unbleached softwood pulp.

Advantages of the new cable:

- high mechanical strength and elasticity of paper filling gaps between insulated cores;

- uniform filling and round cross-sectional shape of the cable;

- the absence of breaks, offsets and omissions of paper filling;

- high adaptability when applying paper tows and stranding;

- high quality;

- reducing the cost of cable.

Restrictions on the choice of paper for the manufacture of bundles impose conditions for the manufacture of bundles and cables:

- mechanical load on the paper when cutting it into tapes with a width of (40 ÷ 60) mm;

- mechanical load on paper tapes when they are twisted into bundles in a wet state;

- drying of paper tows;

- mechanical load on the paper tow (stretching) in the wet state when it is applied to the cable in the gap between the cores.

Limitations are also affected by paper characteristics: thickness, density, porosity, destructive force and elongation in the machine direction, moisture resistance, durability, cost; and paper tow: diameter, specific gravity meters, wet strength, elasticity, round cross-sectional shape.

The thickness of the paper within (90-110) microns is determined by the design and diameter of the bundle, the required mechanical characteristics of the paper and bundle, the technology of making paper and bundle. The lower limit on the thickness of the paper is limited by its strength characteristics and manufacturing technology. In the manufacture of paper with a thickness of less than 90 microns, marriage takes up more than 50%. The upper limit on the thickness of the paper is limited by the technology of manufacturing bundles. With a paper thickness of more than 110 microns, the tow is obtained of poor quality.

The density of the paper characterizes the total content of cellulose fibers and should be in the range (0.65-0.75) g / cm ³ . The lower limit on the density of paper is limited by its strength characteristics, and the upper limit is permeable to dielectric compositions. The higher the density of the paper, the more difficult the process of drying and impregnating it. Harnesses made of thicker paper are less flexible and less technological.

A complex criterion for the mechanical strength of cable paper for bundles is the burst energy (TU 5433-004-50289046-2005, year of entry 2005, Russia), determined by calculation by the formula:

E = K × P × L, J / m ² , where

K = 0.41 - coefficient for machine direction;

K = 0.48 - coefficient for the transverse direction;

P - destructive force, N;

L is the elongation,%.

The higher the burst energy, the stronger the paper. Of all cable papers with a thickness of 80 μm, the three-layer cable has the maximum burst energy

KM-080 grade paper (table 1) with a nominal thickness of 80 microns and a density of 0.78 g / cm ³ . Nevertheless, KM-080 paper tows have low strength, especially when wet (table 2).

Due to the increased density (0.76-0.78) g / cm ³ and reduced air permeability, K and KM cable papers are not well impregnated with high viscosity dielectric compounds. For high-quality drying and impregnation of a cable with KM-080 paper tows, increased values of temperature and operation time are required. The most qualitative cable papers are impregnated only with oil-rosin composition MP-2. When using more viscous non-leaking impregnating compounds such as MP-5 and Napelik (France), there may be incomplete impregnation of paper tows based on cable paper.

KM-080 thick cable paper tows are stiff and non-circular.

In order to eliminate the above drawbacks, the authors of the utility model proposed to use BKM grade microcreated paper for bundles according to TU 5433-004-50289046-2005 with a thickness of (90-110) microns and a density of (0.65-0.75) g / cm ³ made from 100% coniferous sulfate unbleached pulp (table 1).

Microcreated paper differs from ordinary crepe paper with a very small crepe, almost invisible to the naked eye, so its thickness is almost equal to the thickness of uncreated base paper. This paper, unlike crepe paper, cannot be stretched by hand. Microcreping of paper is carried out in the drying part of the paper

machines using "endless" rubber tape or rubberized shaft. The humidity of the paper web is (30-40)%. Micro folds on a paper web are formed due to the speed difference between the metal and rubberized shafts between which the web passes, their clamping and due to the elastic properties of the rubber.

The advantages in the properties possessed by microcreated paper are explained by giving the fibers increased elastoplastic properties and high flexibility due to their preliminary deformation during creping without breaking the structure of the paper, as with macrocreping. One of the main distinguishing features of microcreated paper is its increased extensibility (elongation) in the machine direction, which is 4-5 times higher than that of cable paper. Microcreated paper in comparison with cable uncreated paper has a lower tensile strength in the machine direction (1.2-1.5 times). However, due to the high degree of elongation, in practice it turns out to be better than the more tensile, but less tensile cable paper. This is due to the high dynamic strength (burst energy) of microcreated paper. The bursting energy of microcreated BKM grade paper in the machine direction is two times higher than that of KM grade cable paper of the same thickness, therefore BKM paper and bundles made of it are able to withstand much greater tensile and dynamic loads.

The dynamic strength and elasticity of paper tows are their most important performance properties. Microcreated Harnesses

papers provide even and high-quality filling of gaps between the isolated veins of a cable without formation of air cavities in isolation. This helps increase the electrical strength and reliability of paper insulation. At the same time, tears and breakage of paper tapes during the manufacture of bundles, as well as breakage of bundles and their displacement when applied to the cable, are eliminated.

Microcreated paper of the BKM brand has high resistance to mechanical damage (tears, cuts, punctures, tears), is moisture-proof and heat-resistant, has a low cost, therefore it meets the requirements listed above to the greatest extent.

BKM paper tows remain flexible and elastic after impregnation with dielectric compounds.

In order to improve the conditions for impregnation with dielectric compositions, microcreated paper is made of reduced density (0.65-0.75) g / cm ³ . With a decrease in the density of the paper or an increase in its porosity, the temperature of the impregnation decreases by (10-15) ° C, and the paper filling is completely and qualitatively impregnated with more viscous non-leaky compositions. With a decrease in the temperature of impregnation, paper filling and dielectric composition are less susceptible to oxidative destructive processes, increasing the cable service life. When using less thick paper, paper tows absorb a larger amount of impregnating composition, whose dielectric properties are significantly higher than paper, so the cable is filled with microcreped

reduced density paper has higher dielectric insulation characteristics.

To increase the mechanical strength, especially in the wet state, microcreated paper can be produced with glue rosin glue up to (0.5-1.0)% by mass, which does not impair the dielectric properties of the paper. Rosin glue is made on the basis of gum peeled rosin used in the dielectric impregnating composition MP-2.

The microcreped highly porous surface of the paper helps to keep the viscous dielectric composition of MP-2 from flowing along the cable on inclined sections of the track.

The manufacturing technology of bundles of microcreated paper and cable based on them does not significantly differ from the manufacturing technology of bundles and cable according to the prototype.

The essence of the proposed utility model is illustrated by the following examples.

Table 1 shows the options for samples of cable and microcreped paper and their main characteristics, in table 2 - options for samples of a bundle of grade Zh-2 (RD 16.14.507-86, year of entry 1986, Russia) from cable and microcreated paper and their main characteristics, and in table 3 - comparative quality indicators of samples of the AAShv electric cable of 10 kV filled with microcreated paper and AAShv cable of 10 kV according to the prototype with the filling of KM-080 cable paper.

The harness for the new cable design was made of microcreated paper of different thickness and density, for the cable according to the prototype — from cable paper of the KM-080 brand. An MP-2 oil-rosin compound was used as a dielectric impregnating composition.

Technological conditions for the manufacture of paper tow and electric cable in the above examples were similar.

From tables 2 and 3 it is seen that the bundles of microcreated paper are more durable and elastic, therefore, the number of breaks and defects associated with the displacement of the bundles per 1 km of cable is much less than that of the prototype.

In this case, the optimal parameters of the microcreped paper used for the manufacture of bundles for filling the gaps between the insulated conductive cores of the cable should be within:

Specific gravity, g / m ² 60-80 Density, g / cm ³ 0.65-0.75 The energy of the gap in the machine direction, J / m ² 150-350

A decrease in the specific gravity and density of the paper leads to a decrease in the breaking force and, accordingly, the burst energy, as well as to the appearance of breaks in the paper tow when applied to the cable. With a decrease in paper density, its heat resistance decreases.

An increase in the specific gravity and density of the paper leads to an increase in the stiffness of the tow. A hard tourniquet easily unwinds and loses its round shape, unevenly fills the gaps between isolated

cores of a cable and moves when superimposed on a cable, which is a defective sign. The manufacturability and quality of a thick and thick paper tow is low.

Thus, the claimed utility model of an electric cable surpasses the prototype in the quality and manufacturability of filling the gaps between the conductive conductors, as well as in the electric strength and reliability of the cable.

The highest quality and manufacturability of paper harnesses and electric cables is achieved when using the base paper of the cable microcreated brand BKM-100 according to TU 5433-004-50289046-2003, developed by the authors of the utility model, which differs from the microcreated paper used according to the prototype for phase and zone insulation cable, reduced thickness and stiffness, increased water absorption and increased wet strength. Before folding into bundles, the paper should be well moistened with water. With insufficient wetting of the paper with water, the tows are obtained poor-quality or not at all. Increased absorbency of paper BKM-100 is achieved by reducing the content of rosin glue to (0.2 ÷ 0.3)% instead of (0.5 ÷ 1.0)% for microcreated paper according to the prototype. From microcreated paper according to the prototype, the tows are of poor quality, therefore this paper is not used for the production of tows.

When using BKM-100 paper for bundles, the cost of manufacturing an electric cable is reduced.

Power electric cables for voltage from 1 to 10 kV with filling the gaps between insulated conductive conductors based on BKM-100 microcreated paper passed comprehensive tests at cable plants in the Russian Federation with positive results. Production of these cables has been established.

Table 1 Name of characteristic Cable paper Microcreated Paper Options K-080 KM-080 one 2 3 (BKM-100) four 5 Fiber composition: - cellulose sulf. not white.,% according to GOST 7500-85 one hundred one hundred 100 Coniferous 100 Coniferous 100 Coniferous 100 Coniferous 100 Coniferous Paper design Two-layer machine smoothness Three-layer machine smoothness Microcreated Microcreped Microcreated Microcreated Microcreated Thickness, microns in accordance with GOST 12769-85 80 80 80 90 one hundred 110 120 Weight 1 m ² , g according to GOST 27015-86 62 61 fifty 60 70 80 90

Continuation of table 1 Name of characteristic Cable paper Microcreated Paper Options K-080 KM-080 one 2 3 (BKM-100) four 5 Density, g / cm ³ according to GOST 27015-86 0.78 0.76 0.62 0.65 0.70 0.75 0.78 Breaking force, N: - in a machine e.g. 78 83 fifty 56 80 one hundred 109 - across. e.g. 35 39 35 40 61 65 70 according to GOST ISO 1924-1-96 Relative extension, %: - in a machine e.g. 2.0 2.2 6.0 6.5 7.0 8.5 8.5 - across. e.g. 6.6 7.0 7.0 6.5 6.5 8.0 8.0 according to GOST ISO 1924-1-96

Continuation of table 1 Name of characteristic Cable paper Microcreated Paper Options K-080 KM-080 one 2 3 (BKM-100) four 5 The energy of the gap, J / m ² : - in a machine e.g. 64 75 123 150 230 350 380 - across. e.g. 111 131 118 125 190 250 270 Tear resistance in the transverse direction, N according to GOST 13525.3-97 0.6 0.8 1,0 2.2 2.6 2.9 3.2 Breathability, cm ³ / min according to GOST 13525.14-77 40 60 210 180 170 140 80

table 2 Paper tow quality indicators Cable harness KM -080 Options microcreated paper tow according to table 1 one 2 3 (BKM-100) four 5 Breaking load of paper tow, kgf - outside the reel: (humidity up to 10%) 10.6 10.8 11.2 11.9 12.1 12.5 - inside the reel: (humidity up to 20%) 5,0 5.2 6.4 6.9 7.0 7.5

Continuation of table 2 Paper tow quality indicators Cable harness KM-80 Options microcreated paper tow according to table 1 one 2 3 (BKM-100) four 5 Cross-sectional shape of the harness Flat Round Round Round Round Flat Manufacturability and quality of the harness The harness is hard, low-tech, high wet breakage Elastic tourniquet The tow is elastic, the workability and quality of the tow are high The tow is elastic, the workability and quality of the tow are high The tow is elastic, the workability and quality of the tow are high The harness is tough, low-tech, easily unwinds and loses its shape

Table 3 Power cable quality indicators Prototype (AAShv cable 3 × 150 exp - 10 kV with filling from cable paper KM-080) Options for AAShv cable 3 × 150 exp - 10 kV with filling from microcreated paper according to Table 1 one 2 3 (BKM-100) four 5 The number of defects associated with the displacement of bundles per 1 km of cable 5 ÷ 20 0 0 0 0 1 ÷ 5 The number of wire breaks per 1 km of cable 20 ÷ 30 1 ÷ 2 0 0 0 0

Continuation of table 3 Power cable quality indicators Prototype (AAShv cable 3 × 150 exp - 10 kV with filling from cable paper KM-080) Options for AAShv cable 3 × 150 exp - 10 kV with filling from microcreated paper according to Table 1 one 2 3 (BKM-100) four 5 Manufacturability and quality Cable manufacturability and paper filling quality are low High quality paper filling Cable manufacturability and paper filling quality are high Low cable technology

Claims (2)

1. Electric power cable with insulated conductive conductors and filling the gaps between them, characterized in that, as gap fillers between the insulated conductive conductors, it contains bundles of microcreated paper with a specific gravity (60-80) g / m ² , density (0.65 -0.75) g / cm ³ and an energy gap in the machine direction (150-350) J / m ² made from softwood unbleached softwood pulp. 2. The electric power cable according to claim 1, characterized in that as a gap filler between insulated conductive cores, it contains bundles of base paper of a cable microcreated brand BKM-100 glued with rosin glue.