Power cables with impregnated paper insulation. Paper insulated cables
Power cables with impregnated paper insulation BPI have found application in the transmission and distribution circuits of electricity in stationary installations for a rated alternating voltage of 1 kV, 6 kV, 10 kV, 20 kV and 35 kV with a frequency of 50 Hz.
Cables with BPI are designed for operation in areas with cold, temperate and tropical climates. Cables can be laid both directly into the ground or underground cable channels, and laid indoors and outdoors.
Cables with impregnated paper insulation can be used in difficult operating conditions: in hazardous areas, on car overpasses, bridges, in rooms with high temperature and humidity. Special types Such material can be used for the installation of electrical networks in soil with high chemical and corrosive activity, as well as in rivers, lakes and swampy soils. And thanks to the non-drip impregnation, cables can be laid on steeply inclined and vertical routes. An additional advantage of three- and four-core cables with impregnated paper insulation for voltages up to 10 kV is that, due to the sector shape of the cores, the cable has a smaller diameter than a cable of the same cross section with round cores with polymer insulation. This fact saves space during installation. cable lines.
General design wires with paper insulation.- aluminum core (less often copper), consisting of one (several) wires; lived can be from 1 to 5;
- impregnated paper insulation (for each core);
- impregnated paper insulation (common);
- lead sheath.
B - Armor made of flat steel tapes (after the shell material symbol).
AB - Aluminum armor.
SB - (first or second (after A) letter) lead armor.
C - Sheath material lead.
A - Separately leaded core.
P - Armor made of flat galvanized steel wires.
K - Armor made of round galvanized steel wires.
B - Paper insulation with depleted impregnation (at the end of the designation) through a dash.
b - No pillow.
l - As part of the pillow, an additional 1 lavsan ribbon.
2l - The pillow contains an additional double lavsan ribbon.
G - Lack of a protective layer ("naked").
n - Non-combustible outer layer. Placed after the armor symbol.
Shv - The outer layer in the form of a pressed-out hose (sheath) made of polyvinyl chloride.
Shp - The outer layer in the form of a pressed-out hose (sheath) made of polyethylene.
Shvpg - Outer layer of extruded PVC hose with low flammability.
(ozh) - Cables with single-wire conductors (at the end of the designation).
U - Paper insulation with an increased heating temperature (at the end of the designation).
C - Paper insulation impregnated with a non-draining compound. Placed in front of the designation.
Examples: CSB decoding Aluminum cable insulated with paper impregnated with a special composition. It can be both stranded (mp) and single-core (og). Each core and common belt insulation is covered with a layer of paper insulation.
A
WITH- lead sheath;
B
Decoding ASBL
A- aluminum conductor;
WITH- lead sheath;
B
l- in the pillow under the armor there is a layer of plastic tapes.
ASB2l decoding
A- aluminum conductor;
WITH- lead sheath;
B- armor made of two steel bands;
2l- in the pillow under the armor there is a double layer of plastic tapes.
SB decoding
WITH- lead sheath;
B- armor made of two steel bands.
Decoding ASSHv
A- aluminum conductor;
WITH- lead sheath;
Shv
SShv decoding there are no other letters before the letter “C”, which means the conductor is copper;
WITH- lead sheath;
Shv- a protective cover in the form of a hose made of PVC;
TsAShv, TsSShv, TsASB, TsSB, SBl, TsASBl, TsSBl, SB2l, TsASB2l, TsSB2l, ASB2lG, SB2lG, ASBG, SBG, TsASBG, TsSBG, ASBSHv, ASBlShv, ASB2lShv, SBShv, SblShv, SB2lShv, TsAS BShv, TsASBLShv, TsSBshv, TsSBlShv, ASP, ASPl, ASP2l, ASPG, SP, Spl, SP2l, SPG, TsASP, TsASpl, TsASPG, TsSP, TsSPl, TsSPG, ASKl, SKl, TsSKl, TsASKl
It is convenient to classify power cables according to the rated voltage for which they are designed, the type of insulation and design features cables.
All power cables according to the rated operating voltage can be divided into two groups. The group of low voltage cables includes cables intended for operation in electrical networks with an isolated neutral of alternating voltage 1,3,6,10,20 and 35 kV with a frequency of 50 Hz. The same cables can be used in AC voltage networks with grounded neutral and in DC voltage networks. Such cables are produced in Russia with impregnated paper, plastic and rubber insulation, and the most promising type of insulation is plastic. Cables with plastic insulation are easier to manufacture, easy to install and operate. The production of plastic insulated power cables is currently expanding significantly. Power cables with rubber insulation are produced in limited quantities.
Single-core and three-core cables are designed for operation in networks with a voltage of 1-35 kV, two- and four-core cables are used in networks with voltage up to 1 kV.
The four-core cable is designed for four-wire AC networks. The fourth core in it is grounding or grounding, therefore its cross section is usually less than the cross section of the main cores. However, when laying cables in explosive rooms and in some other cases, the cross section of the fourth core is chosen equal to the cross section of the main cores.
Cables with a radial electric field for voltages of 20 and 35 kV.
With an increase in the operating voltage, the electric field strengths in the cable insulation increase, and at voltages greater than 20 kV, the values of the tangential component of the field strength in cables with belt insulation are close to the values at which insulation breakdown is possible. In this regard, cables for voltages of 20 and 35 kV are made either in a single-core version with round aluminum or copper conductors in a lead and aluminum sheath, or in a three-core version, while the cable is twisted from three round insulated cores, each of which has a lead sheath. In the insulation of these cables electric field radial, while the longitudinal component of the field strength is practically absent, which makes it possible to manufacture cables with paper insulation impregnated with a viscous oil-rosin composition for voltages of 20 and 35 kV.
Three-core cables with a radial electric field produced in Russia (the so-called cables with separately lead-coated cores) have the OSB, AOSB brands. These cables were developed by Doctors of Technical Sciences, prof. S.M. Bragin and S.A. Yakovlev.
Abroad, the so-called H-cables are widely used, which were named after their inventor, the German engineer M. Hochstaedter.
In an H-cable, three insulated and shielded cores are twisted together and placed in a common lead or corrugated aluminum sheath. The radial field in the insulation is ensured by the presence of screens made of copper tapes on the surface of each insulated core. IN Lately H-cables with sector conductors have found distribution. H-cables have slightly smaller dimensions, while reducing the consumption of materials for their manufacture. However, OSB cables are more flexible, contain less impregnating composition and have Better conditions for heat sink.
Cables with separately lead-coated conductors are produced only with round copper or aluminum conductors with a cross section of 25 ... 185 mm 2 for a voltage of 20 kV and a cross section of 120 ... 150 mm 2 for a voltage of 35 kV. For cables of the OSB type, mainly stranded conductors are used, and best performance have cables with sealed conductors. When compacting the cores, their diameter decreases and the surface of the core is smoothed. To equalize the electric field, screens made of semi-conductive paper are placed on the surface of the core. A shield of semi-conductive paper, either metallized semi-conductive paper, or semi-conductive paper, over which aluminum or copper foil is placed, is also applied over the insulation. The thickness of the cable insulation for a voltage of 20 kV for cross sections of 25 ... 95 mm 2 is 7 mm, for sections of 120 ... 150 mm 2 - 6 mm, cables for a voltage of 35 kV - for all sections of 9 mm.
The thickness of the lead sheath, depending on the cross section of the core, is within 1.4 ... 2.8 mm. Aluminum sheaths for such cables have not yet been used because of their rigidity. Separately leaded conductors are twisted with filling the gaps between them with impregnated cable yarn or glass yarn. In cross section, a cable with filling can have both a round shape and a triangle shape with rounded tops. Outside, twisted cores with filling are wrapped with fabric tape or cable yarn, and then protective covers are applied to them. Example symbol: cable OSBU 3x50-20 GOST 18410-73 - cable brand OSB with conductors with a cross section of 50 mmg for a voltage of 20 kV.
General requirements for cables with impregnated paper insulation for 1-35 kV.
The specified cables are designed for operation at temperatures environment±50 °С. When laying cables, the minimum bending radius should not exceed 15 times the outer diameter of the cable for stranded lead-sheathed cables and 25 times for other cables.
The electrical insulation resistance at a temperature of 20 ° C is usually not less than 200 kOhm / m for cables with a voltage of 6 kV and above. The value of the dielectric loss tangent (tg 8), measured at the building length at a voltage equal to half the nominal, does not exceed 0.008. The guaranteed service life of the cable is at least 25 years.
for a long time allowable temperature conductors of cables for a voltage of 1-35 kV, the so-called operating temperature, must correspond to
Long-term permissible temperature of cores of cables with impregnated paper insulation for voltage 1-35 kV
Rated cable voltage |
Insulation impregnation |
Permissible operating temperature, °C |
depleted |
||
depleted |
||
Correction factors for air temperature
Normal |
Correction factors |
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temperature |
at actual air temperature, С |
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* For gas-filled cable lines 10-35 kV.
Comparative characteristics of the electrical strength of paper, penetrating oil and cable insulation
Insulation |
One-minute dielectric strength at 20 "C, kV/mm |
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variable tension |
constant tension |
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dried paper |
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Penetrating oil |
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Cable insulation (paper + oil) |
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Classification and marking of power cables
Essential elements
Power cable design
Power cables consist of the following main elements: current-carrying conductors (TPZh), insulation, sheaths and protective covers. In addition to the main elements, the design of power cables may include screens, neutral conductors, protective earth conductors and fillers.
Conductors designed to pass electric current, they are basic and zero. The main cores are used to perform the main function of the cable - the transmission of electricity through them. Zero cores are designed for the flow of the phase current difference (poles) with their uneven load. They are connected to the neutral of the current source.
Protective earth conductors are auxiliary conductors of the cable and are designed to connect metal parts of the electrical installation that are not under operating voltage, to which the cable is connected, with the protective earth loop of the current source.
Insulation is a layer of dielectric (impregnated paper, plastic, rubber, etc.) superimposed on a conductive core. Serves to ensure the necessary electrical strength of the current-carrying conductors of the cable in relation to each other and to the grounded sheath (ground).
Screens are used to protect external circuits from the influence of electromagnetic fields of currents flowing through the cable, and to ensure the symmetry of the electric field around the cable cores.
Placeholders designed to eliminate free gaps between the structural elements of the cable in order to seal, give the necessary shape and mechanical stability of the cable structure.
Shells protect the internal elements of the cable from moisture and other external influences.
Protective covers designed to protect the cable sheath from external influences. Depending on the design of the cable, the protective covers include a pillow, an armor cover and an outer cover.
Power cables are conveniently classified according to the rated voltage for which they are designed; classification features can also serve as the type of insulation and design features of cables (see Fig. 1.1).
All power cables according to the rated operating voltage can be divided into two groups. The group of low voltage cables includes cables intended for operation in electric networks with an isolated neutral of alternating voltage 1, 3, 6, 10, 20 and 35 kV with a frequency of 50 Hz. The same cables can be used in AC voltage networks with grounded neutral and in DC voltage networks. Such cables are produced in Russia with impregnated paper, plastic and rubber insulation, and the most promising type of insulation is plastic.
Rice. 1.1. Power cable classification
Cables with plastic insulation are easier to manufacture, easy to install and operate. The production of plastic insulated power cables is currently expanding significantly. Power cables with rubber insulation are available in limited quantities. Low voltage cables, depending on the purpose, are available in single-core, two-core, three-core and four-core versions (Fig. 1.2–1.4).
Rice. 1.2. Two-core cables with round (a) and segmented (b) cores
Single-core and three-core cables are designed for operation in networks with a voltage of 1–35 kV, two- and four-core cables are used in networks with voltage up to 1 kV.
Rice. 1.3. Three-core cables with round (a) and sector (b) cores
The four-core cable is designed for four-wire AC networks. The fourth core in it is grounding or grounding, so its cross section is usually less than the cross section of the main cores. However, when laying cables in hazardous areas and in some other cases, the cross section of the fourth core is chosen equal to the cross section of the main cores.
Rice. 1.4. Four-core cables
To a cable group high voltage cables intended for operation in AC voltage networks of 110, 220, 330, 380, 500, 750 kV and higher, as well as direct voltage cables of kV and higher are included. The bulk of high voltage cables in Russia are currently manufactured with oil-impregnated paper insulation - these are oil-filled cables of low and high pressure. The high dielectric strength of the insulation of these cables is provided by the excess oil pressure in them. However, gas-filled cables have also become widespread abroad, in which gas is used, both in the form of an insulating medium and to create excess pressure in the insulation. Plastic-insulated high-voltage cables are the most promising, but the problem of creating such cables for voltages of 110 kV and higher has not yet been completely resolved.
The marking of power cables usually includes letters indicating the material from which the core is made, insulation, sheath, and type of protective cover. The marking of high voltage cables also reflects the features of its design.
Copper conductors in the marking of cables are not marked with a special letter, the aluminum conductor is indicated by the letter A, which is at the beginning of the marking. The next letter of the cable brand indicates the insulation material, and impregnated paper insulation does not have a letter designation, polyethylene insulation is denoted by the letter P, polyvinyl chloride insulation is denoted by the letter B, and rubber insulation- the letter P. This is followed by a letter corresponding to the type of protective sheath: A - aluminum, C - lead, P - polyethylene hose, B - polyvinyl chloride sheath, P - rubber shell. The last letters indicate the type of protective cover.
For example, an SG brand cable has a copper core, impregnated paper insulation, a lead sheath, and there are no protective covers. The APASHv brand cable has an aluminum core, polyethylene insulation, an aluminum sheath and a PVC hose. Oil-filled cables contain the letter M in their designation (unlike gas-filled cables - the letter G), as well as a letter indicating the characteristics of the oil pressure in the cable and related design features. For example, a cable of the MNS brand is an oil-filled, low-pressure cable in a lead sheath with a reinforcing and protective cover or a cable of the MVDT brand is an oil-filled high-pressure cable in a steel pipeline.
for voltage 1–35kV
Power cables with belt insulation. The bulk of power cables for voltages up to 10 kV are produced as three-core with sector cores, the so-called cables with belt insulation (Fig. 1.5). Such cables are produced with copper and aluminum conductors with a cross section from 6 to 240 mm 2.
Rice. 1.5. Three-core cable with belt insulation:
1 - vein; 2 - phase insulation; 3 - belt insulation;
4 - metal shell; 5.6 - protective and strengthening covers
IN last years copper has become extremely scarce, therefore aluminum is most widely used in the cable industry, both for conductive conductors and for sheaths.
The electrical conductivity of aluminum is 1.65 times less than that of copper, however, its density is 3.3 times less than the density of copper, which makes it possible to obtain aluminum conductors with the same electrical resistance 2 times lighter than copper ones. Currently, 85% of power cables with impregnated paper and plastic insulation for voltages of 1 kV and above are made with aluminum conductors. The production of single-wire aluminum conductors in the form of a solid sector gives a great economic effect in the cable industry. The use of such conductors makes it possible to reduce the diameter of the cable, in addition, in the manufacture of such conductors, labor productivity increases, since, in comparison with the manufacture of multi-wire conductors, the volume of drawing operations is reduced and the operation of twisting the conductors is eliminated. Solid sector conductors have greater rigidity than twisted ones, in addition, the complexity of installing cables with such conductors is somewhat increased. However, studies have shown that the rigidity of the cable is mainly determined not by current-carrying cores, but, first of all, by the material and design of the sheath.
Cable insulation consists of tapes of cable paper impregnated with oil-rosin composition. In cables for voltages of 1–10 kV, each phase is insulated separately, and then a common insulation is applied over the twisted insulated cores - belt insulation. The gaps between the insulated cores are filled with sulphate paper bundles. The electric field in cables with belt insulation has a complex form. The field lines of force in some areas of the cable section are not perpendicular to the layers of paper, so a tangential component of the electric field appears in the insulation.
Cables produced in Russia are designed for operation in networks with isolated neutral. In this case, in emergency mode, the voltage between adjacent undamaged phases will be equal to the voltage between these phases and the shell and equal to the linear voltage of the network. Indeed, when one of the phases is closed to the shell with an isolated neutral, the latter acquires the potential of the damaged phase. Therefore, in order to ensure an approximate equality of the average electric field strengths in phase and belt insulation in emergency mode, it is necessary to choose them of equal thickness. However, taking into account the fact that the emergency modes of operation of cables are of a short-term nature, a slight increase in the field strength in the cable insulation is allowed during short-term voltage increases.
The main disadvantage of impregnated paper insulation is its high hygroscopicity, therefore, to protect the insulation from moisture during storage, laying and operation, the cables are enclosed in a metal sheath. In Russia, power cables are produced in lead and aluminum sheaths.
Cables with aluminum sheaths are much lighter than cables with lead sheaths (the density of aluminum is 4.2 times less than that of lead).
The high electrical conductivity of aluminum makes it possible to use aluminum sheaths as the fourth core of the cable, which provides significant savings in aluminum, insulating and protective covers. However, cables with aluminum sheaths cannot be used under conditions of exposure to aggressive environments (alkali vapors, concentrated alkaline solutions). In such conditions it is necessary to use cables in lead sheaths.
Experience in the manufacture and installation of cables with an aluminum sheath with a diameter of more than 40 mm revealed their excessive rigidity. The use of a corrugated sheath increases the flexibility of the cables, however, when such cables are laid on inclined routes, the impregnating composition may run off along the corrugations and the formation of air inclusions in the cable insulation. In this regard, corrugated sheaths can only be used in cables, the insulation of which is impregnated with non-draining compounds.
Cables with a radial electric field for voltages of 20 and 35 kV. With an increase in the operating voltage, the electric field strengths in the cable insulation increase, and at voltages greater than 20 kV, the values of the tangential component of the field strength in cables with belt insulation are close to the values at which insulation breakdown is possible. In this regard, cables for voltages of 20 and 35 kV are made either in a single-core version with round aluminum or copper conductors in a lead and aluminum sheath, or in a three-core version, while the cable is twisted from three round insulated cores, each of which has a lead sheath. In the insulation of these cables, the electric field is radial, while the longitudinal component of the field strength is practically absent, which makes it possible to manufacture cables with paper insulation impregnated with a viscous oil-rosin composition for voltages of 20 and 35 kV.
Three-core cables with a radial electric field produced in Russia (the so-called cables with separately lead-coated cores) have the OSB, AOSB brands (Fig. 1.6).
Rice. 1.6. Three-core cable with individually lead-coated cores:
1 - vein; 2 - isolation; 3 - lead sheath; 4 - filling;
5 - wire armor
Cables with separately lead-coated conductors are produced only with round copper or aluminum conductors with a cross section of 25 - 185 mm 2 for a voltage of 20 kV and 120 - 150 mm 2 for a voltage of 35 kV. For OSB cables, mainly stranded conductors are used, and cables with compacted conductors have the best characteristics.
Aluminum sheaths for such cables have not yet been used because of their rigidity.
Cables for vertical laying. When laying cables with impregnated paper insulation on routes with a large level difference, there is a danger of the impregnating composition draining to the lower part of the route. In the upper sections of the route, therefore, the dielectric strength of the cable decreases due to the occurrence of air gaps in the insulation. In the lower parts of the route, due to high blood pressure impregnating composition, depressurization of the cable is possible. Reducing the effect of impregnating composition runoff can be achieved by the following measures: the use of locking sleeves when connecting the construction lengths of the cable; a decrease in the volume of the impregnating composition in the cable; an increase in the viscosity of the impregnating composition.
Some General requirements to cables with impregnated paper insulation by 1–35 kV. These cables are designed for operation at an ambient temperature of ±50 °C. When laying cables, the minimum bending radius should not exceed 15 times the outer diameter of the cable for stranded lead-sheathed cables and 25 times for other cables. The long-term permissible temperature of cable cores for a voltage of 1–35 kV, the so-called operating temperature, is set equal to 50 ° C for 35 kV and 80 ° C for 1–3 kV.
The guaranteed service life of the cable is at least 25 years.
Advantages: high electrical parameters; greater operational reliability.
Flaws: the manufacturing process is complex and inefficient; cables are made only in a metal sheath, since the impregnated paper is not moisture resistant, which significantly increases the cost and makes their design heavier; due to the runoff of the impregnating composition in the cables, there are restrictions for vertical laying.
1.4. Power cables with plastic insulation for voltage 1–35kV
The use of plastics for insulating power cables can significantly simplify the technology of their manufacture. Plastic insulation can be applied to conductive conductors by extrusion (extrusion) on worm presses. This process is much more productive than taping insulation. In addition, this eliminates the need for drying and impregnation of the insulation. The use of plastics also makes it possible to facilitate the construction of cables, to simplify laying and installation, and also to lay on routes with a large level difference.
The main materials used to replace oil impregnated paper insulation are polyethylene, polyvinyl chloride and ethylene propylene rubber.
One of the most promising materials for cable insulation is polyethylene. This material has a number of advantages over other materials: high electrical strength; small values of density, e r and tgδ; good flexibility; moisture resistance. It should also be noted that, of all known polymeric materials, only polyethylene can currently be obtained very pure, containing a minimum amount of impurities, which makes it possible to use it in products designed to operate at high electric field strengths.
The most suitable material for cable insulation is cross-linked polyethylene, i.e. polyethylene with spatial structure molecules. Its electrical properties are at the level of properties of thermoplastic polyethylene, and the heat resistance is higher.
In Russia, power cables with plastic insulation for a voltage of 0.66-6 kV, designed for the transmission and distribution of electricity in stationary installations, are produced with aluminum and copper conductors with a cross section of 1.5 to 240 mm 2. The cores of these cables can be round and sector. PVC and vulcanized polyethylene can be used as insulation.
To protect against moisture and mechanical damage, the cables have a plastic or aluminum sheath.
Cables of this type are designed for operation at ambient temperatures from -50 to +50°C. Permissible heating of cable cores in emergency mode, not exceeding 8 hours per day and not more than 1000 hours during the service life, should not exceed 80 ° C for PVC and polyethylene insulation and 130 ° C for vulcanized polyethylene insulation.
Power cables for a voltage of 10-35 kV are produced, as a rule, with vulcanized polyethylene insulation, both single-core and three-core. The most commonly used single-core cables, which are supplied in large building lengths, are easier to install and operate (in terms of repair work).
Domestic single-core cables with vulcanized polyethylene insulation for a voltage of 10 kV are produced with aluminum conductors with a cross section of 120–240 mm 2. The sheath with a thickness of 1.9–2.1 mm can be made, for example, from PVC or low-flammability PVC. Nominal insulation thickness 4 mm. Electrically conductive screens along the core and along the insulation have a nominal thickness of 0.7 mm. Continuous operating temperature should not exceed 90 °C.
Domestic cables for a voltage of 35 kV have a similar design. As insulation, vulcanized polyethylene is used, as a sheath - polyethylene or polyvinyl chloride plastic compound. In the presence of significant tensile forces in operation, armor made of round galvanized steel wires is used. Cross-sections of cable conductors - from 95 to 240 mm 2, current-carrying conductors - copper or aluminum. Insulation thickness - 7 mm; the thickness of the electrically conductive screen along the core is 1.0 mm, along the insulation - 0.4 mm. The nominal thickness of the sheath shall be 2.3-2.5 mm.
The catalog of our site presents various cable and wire products.
One of the types of power cables - paper insulated cable. The laying of such a cable can be permanently carried out in the ground, under water, in the air. Such cables are used for distribution and transmission of electricity up to 35 kV.
A cable belonging to this class may have copper or aluminum conductors. Also paper insulated cables can have a different shape: monolithic, sector or multi-wire.
Any of these types of cables is designed for operating temperatures from -50 to +500C and for alternating voltage 10-50 Hz.
Paper cable tapes impregnated with oil rosin or non-drip composition are applied over the cores. Cores insulated in this way are twisted.
The gaps between the cores are filled with special bundles made of sulphate paper. Then the belt insulation is applied. Phase and belt insulation can be of different thickness, depending on the working conditions.
The disadvantage of such paper insulation, even impregnated with a special composition, is that it is highly hygroscopic. To protect the cable from moisture during installation and operation, it is placed in a metal sheath.
Power cable with paper insulation may have different skins. It all depends on the environment and climate zone it is used in. The shell can be made of aluminum, lead or armored PVC.
Mechanical damage is not terrible for an aluminum sheathed cable (unlike lead sheathed cables), and besides, it is more hermetic.
The electrical conductivity of aluminum is high, which makes it possible to use the aluminum sheath as the fourth cable core. This saves aluminum, protective and insulating cover.
However, if paper insulated power cable is operated in an aggressive environment (for example, alkaline fumes or concentrated alkaline solutions), then only a lead-sheathed cable can be used in such a situation.
If the cable has a diameter of more than 40 mm, then it becomes excessively rigid. In this case paper insulated cable manufactured with corrugated aluminum shell. But even in this case, there are drawbacks.
If the cable is laid at an angle, the impregnating composition may run off along the corrugations. Therefore, a corrugated sheath is used only if the paper cable tapes are impregnated with a viscous, non-flowing compound.
In our catalog you can choose the brand power cable with paper insulation, which is most suitable for solving the task assigned to you. Our consultants will help you in choosing the right cable.
Power cables with impregnated paper insulation(with viscous impregnation) have significant restrictions on the rated voltage due to intense ionization processes at AC voltage, and therefore are used in distribution networks in Russia at voltages up to 35 kV inclusive (abroad at voltages up to 60 kV).
In Russia, power cables with impregnated paper insulation for voltages up to 35 kV inclusive are produced in accordance with GOST 18410-73 (manufacturers are Kamkabel, Sevkabel, Irkutskkabel, Moskabel, etc.). As already noted, these cables are the most mass-produced type of product. Their share is about 95% of all types of cables used in distribution networks.
Cables with viscous impregnation up to 10 kV inclusive (see Fig. 1) are most often made of three-core with belt insulation and sector copper or aluminum conductors with a cross section of 6 to 240 mm2 or more (cables of the AAG, AASHv, ASB, ASShv, SB, SBShv and others). Aluminum conductors can be single-wire in the entire range of cross-sections or multi-wire compacted in the cross-section range from 70 to 240 mm2. Copper conductors are made mainly of multi-wire.
AAShv cable 
7 - Sublayer of bitumen and PET film; 8 - PVC outer cover.
SBShv cable 
7 - Pillow made of bitumen and crepe paper; 8 - Armor from steel tapes;
9 - Sublayer of bitumen and PET film; 10 - Outer cover made of PVC compound.
Rice. 1. Structural elements of cables with belt insulation up to 10 kV:
1 - Single-wire or multi-wire conductor, aluminum or copper;
2 - Phase paper insulation impregnated with a viscous or non-flowing compound;
3 - Filling from paper bundles;
4 - Belt paper insulation impregnated with a viscous or non-draining compound;
5 - Screen made of electrically conductive paper for cables of 6 kV and more;
6 - Aluminum or lead sheath.
Cable insulation consists of tapes of cable paper based on sulphate cellulose with a thickness of 80, 120 and 170 microns impregnated with an oil rosin composition. For the manufacture of the impregnating composition, cable oil or a mixture of petroleum oils is used. As a thickener, rosin, polyethylene wax or polyisobutylene is used. Each phase of the cables is isolated separately, and then a common, so-called belt insulation is applied over the twisted insulated cores. In cables of 6 kV and above, a shield of semi-conductive paper is applied to the belt insulation. The gaps between the insulated cores in the cable are filled with sulphate paper bundles.
In cables for 1 and 3 kV, the insulation thickness is selected mainly from the condition of its mechanical strength. For 1 kV cables, the thickness of the phase insulation is 0.75–0.95 mm, and the thickness of the belt insulation is 0.5–0.6 mm, for 3 kV cables, 1.35 and 0.7 mm, respectively. In 6 and 10 kV cables, the insulation thickness is selected taking into account the electric field strengths in the insulation in operating and emergency modes (for example, the short circuit of one phase to the sheath). For 6 kV cables, the thickness of the phase and belt insulation is 2.0 and 0.95 mm, and for 10 kV cables - 2.75 and 1.25 mm, respectively.
The main disadvantage of impregnated paper insulation is its high hygroscopicity. To protect the insulation from moisture during storage, laying and operation, the cables are enclosed in a lead or aluminum sheath. Recently, most cables are made in an aluminum sheath, because. aluminum shells are quite hermetic, mechanically stronger and more resistant to vibration loads compared to lead shells. However, cables with aluminum sheaths cannot be used in corrosive environments.
Metal shells, as a rule, are protected from corrosion and mechanical damage by protective covers. The protective cover of the cables consists of a cushion, armor and an outer cover. The pillow protects the metal shell from corrosion, and also plays the role of protection against mechanical damage when armor is applied. Armor can be made of steel tapes and steel galvanized round or flat wires. The simplest cover construction is alternating layers of bituminous compound or bitumen, impregnated cable yarn or glass yarn, bituminous compound, and a coating to keep the coils of cables from sticking to the drum (eg, chalk coating). The most reliable are the Shv and Shp type outer covers, which have the following construction: a bitumen-based adhesive, plastic tape and an extruded PVC or plastic hose. For laying cables in rooms or places with increased fire hazard, bitumen layers are replaced with a special non-combustible composition (such outer covers are indicated by the “ng” index in the cable brand, for example, AASHng brand cable). Low flammability outer covers with reduced smoke and gas emission are also used (indicated by the “ng-LS” index in the cable brand). The choice of the type of protective cover is determined by the material of the cable sheath, as well as the conditions of its laying.
Cables for 20 and 35 kV are made either in a single-core version with round aluminum and copper conductors in a lead and aluminum sheath (cables of the AAG, ASG, SG, AASHv brands), or in a three-core version (see Fig. 2), while the cable is twisted from three round insulated cores, each of which is enclosed in a lead sheath (cables of the AOSB, OSB brands, etc.).
Cables with separately leaded conductors are produced with round copper and aluminum conductors with a cross section of 25 to 400 mm2 for 20 kV cables and a cross section of 120 to 400 mm2 for 35 kV cables. For cables of this type, mainly multi-wire compacted cores are used. To equalize the electric field, screens made of semi-conductive paper are placed on the surface of the core. A shield of semi-conductive paper, either metallized semi-conductive paper, or semi-conductive paper and aluminum or copper foil, is also applied over the insulation.
AOSB cable
Rice. 2. Structural elements of cables with separately lead-coated conductors for 20 and 35 kV:
1 - Stranded conductor, aluminum or copper;
2 - Screen made of electrically conductive paper;
3 - Phase paper insulation impregnated with a viscous or non-flowing composition;
4 - Screen made of electrically conductive paper;
5 - Lead sheath.
6 - Protective layer of crepe paper and polyethylene terephthalate film;
7 - Filling from cable yarn;
8 - Cable yarn pillow;
9 - Armor from steel tapes;
10 - Outer cover made of fibrous materials.
In 20 kV cables, the insulation thickness is 7.0 mm for conductors with a cross section of 25–95 mm2 and 6.0 mm for conductors with a cross section of 120–400 mm2. In 35 kV cables, the insulation thickness is 9.0 mm.
The thickness of the lead sheath, depending on the cross section of the core, is in the range of 1.4–2.8 mm. Separately leaded strands are twisted and the gaps between them are filled with impregnated cable yarn or glass yarn. Outside, twisted cores with filling are wrapped with cable yarn, and then protective covers are applied to them.
Abroad, the so-called H-cables (according to the first letter of the German inventor Hochstaedter) have also become widespread. In an H-cable, three insulated and shielded cores are twisted together and placed in a common lead and corrugated aluminum sheath. H-cables have slightly smaller dimensions and, accordingly, the consumption of materials for their manufacture is reduced. However, compared to them, cables with separately leaded conductors are more flexible and have better conditions for heat dissipation.
For laying on vertical and steep routes with a large level difference (more than 15-25 m), where there is a danger of impregnating composition flowing into the lower part of the route, cables with paper insulation impregnated with a non-draining composition are used (cables of the TsAABSHv, TsAABl, TsSB, TsAOSBG brands and etc.). The non-draining impregnating composition has a high viscosity, which practically excludes its movement along the cable. Cables with paper insulation impregnated with a non-drip composition are produced for 6, 10 and 35 kV in single-core and three-core versions. Their designs do not fundamentally differ from the design of conventional cables with viscous impregnation, but the thickness of the insulation of these cables is somewhat larger. In addition, to increase the electrical strength of the cable insulation by 35 kV, it is graded in thickness.
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