Insulating cable power lines. Power lines Their characteristics and classification. What are the air power lines

The main elements of air lines are wires, insulators, linear fittings, supports and foundations. On the air lines of the variable three-phase current suspend at least three wires constituting one chain; On DC air lines - at least two wires.

According to the number of chains, the WL is divided into one, two and multi. The number of chains is determined by the power supply scheme and the need for its redundancy. If two chains are required under the power supply scheme, these chains can be suspended on two separate single-chain VLs with single-chain supports or on one two-chained VL with two-charts. The distance / between adjacent supports is called the span, and the distance between the supports of the anchor type is an anchor site.

Wires suspended on insulators (A, - Length of garlands) to supports (Fig. 5.1, a), sag on a chain line. The distance from the point of the suspension to the lower point of the wire is called the arrow of the Prior /. It determines the enabarition of the wire approximation to the Earth A, which is equal to the locality: to the surface of the Earth to 35 and a kV - 7 m; 220 kV - 8 m; to buildings or structures up to 35 kV - 3 m; 110 kV - 4 m; 220 kV - 5 m. The length of the span / is determined by economic conditions. The length of the span to 1 kV is usually 30 ... 75 m; By square - 150 ... 200 m; 220 kV - up to 400 m.

Varieties of power supplements

Depending on the method of suspension of wires, supports are:

1. intermediates on which the wires are fixed in supporting clamps;
2. anchor type that serve to tension wires; On these tolls, the wires are fixed in stretch clamps;
3. angular, which are installed at the angles of rotation of WL with suspension of wires in supporting clamps; They can be intermediate, branches and angular, end, anchor corner.

The same support was enlarged above 1 kV are divided into two types of anchor, fully perceiving the tension of wires and cables in adjacent spans; Intermediate, not perceiving wires or partially perceive.

Wooden supports are used on VL (Fig. 5l, b, B), wooden supports of the new generation (Fig. 5.1, d), steel (Fig. 5.1, e) and reinforced concrete supports.

Wooden supports Vl

Wooden supports are still distributed in countries with forest reserves. The advantages of the tree as a material for the supports are: a small proportion, high mechanical strength, good electrical insulating properties, a natural round sorting. The disadvantage of wood is its rotting, to reduce which antiseptics apply.

The effective method of combating rotting is the impregnation of wood with oil antiseptics. In the US, the transition to wooden glued supports.

For a voltage of 20 and 35 kV, which use pins insulators, it is advisable to use single-suitable candle-shaped supports with a triangular location of the wires. On 6 -35 kV air power transmission with tide insulators at any location of the wires between them D, M, should be no less than the values \u200b\u200bdefined by the formula

where u is lines, kV; - the largest arrow of the provice corresponding to the overall span, m; B is the wall thickness of the ice, mm (no more than 20 mm).

For 35 kV and higher with suspended insulators with horizontal location of the wires, the minimum distance between the wires, M is determined by the formula

Rack of supports are performed by composite: the upper part (actual stand) - from the logs of 6.5 ... 8.5 m long, and the lower part (the so-called stepper) - from reinforced concrete cross section 20 x 20 cm, 4.25 and 6.25 m Or from logs with a length of 4.5 ... 6.5 m. Component supports with reinforced concrete stepmother combine the advantages of reinforced concrete and wooden supports: the grossability and resistance to rotting in the touch of the touch with the soil. The compound of the rack with a stepmaker is performed by wire bands from steel wire with a diameter of 4 ... 6 mm, tensioned with a twist or tension bolt.

Anchor and intermediate angular supports for VL 6 - 10 kV are performed as an aumed structure with composite racks.

Steel power supports

Widely used on voltage voltage of 35 kV and higher.

By constructive performance, steel supports can be two types:

1. tower or Single Rooms (see Fig. 5.1, e);
2. portal, which, according to the method of consolidation, are divided into freestanding supports and supports on deheating.

The advantage of steel supports is their high strength, disadvantage - corrosion exposure, which requires during the operation of periodic color or anticorrosion coating.

Supports are made of steel angular rolled (mainly applied an equal corner); High transitional supports can be made of steel pipes. In nodes of the connection of the elements, a steel sheet of various thicknesses is used. Regardless of the constructive performance, steel supports are performed in the form of spatial lattice structures.

Reinforced concrete power supports

Compared to metal more durable and economical in operation, as it requires less care and repair (if you take a life cycle, then reinforced concrete - more energy-price). The main advantage of reinforced concrete supports is a decrease in steel consumption by 40 ... 75%, lack of a large mass. By the method of manufacturing, reinforced concrete supports are divided into concrete on the installation site (mostly such supports are used by abroad) and factory manufacture.

Mounting the traverse to the barrel of the reinforced concrete support is performed using bolts skipped through special holes in the rack, or using steel clamps covering the barrel and having a pin for attaching the ends of the traverse belts. Metallic traverses are pre-exposed hot galvanized, so they do not require some time during the operation of special care and observation.

The air lines are performed by uninsulated, consisting of one or more pigged wire. The wires from one wire, called single-rockers (they are made by section from 1 to 10 mm2), have less strength and apply only on a voltage to 1 kV. Multi-voltage wires, retained from several wires are applied on VL of all stresses.

Materials of wires and cables should have high electrical conductivity, have sufficient strength, withstand atmospheric effects (in this respect, copper and bronze wires have the greatest resistance; aluminum wires are subject to corrosion, especially on sea coasts, where salts are contained; steel wires are destroyed even in normal atmospheric conditions).

For VL, one-robust steel wires with a diameter of 3.5 are used; 4 and 5 mm and copper wires with a diameter of up to 10 mm. The limitation of the lower limit is due to the fact that the wires of smaller diameter have insufficient mechanical strength. The upper limit is limited due to the fact that the bends of the single-rocker wire of larger diameter can cause such residual deformations in its external layers, which will reduce its mechanical strength.

Multi-voltage wires twisted from several wires have great flexibility; Such wires can be performed by any cross section (they are made by cross section of 1.0 to 500 mm2).

The diameters of individual wires and their quantity are selected so that the amount of transverse sections of individual wires gave the required overall cross-section of the wire.

As a rule, the multi-voltage wires are made of round wires, and one or more wires of the same diameter are placed in the center. The length of the twisted wire is slightly larger than the length of the wire measured by its axis. This causes an increase in the actual mass of the wire per 1 ... 2% compared to the theoretical mass, which is obtained by multiplying the cross section of the wire for length and density. In all calculations, the actual mass of the wire specified in the relevant standards is taken.

The brands of uninsulated wires indicate:

• letters m, a, ac, ps - material of the wire;
• the numbers are a cross section in square millimeters.

Aluminum wire and maybe:

• aT brands (solid insertion)
• AM (annealed soft) alloys AN, Already;
• ACS, ASCS - from a steel core and aluminum wire;
• PS - from steel wires;
• PST - from steel galvanized wire.

For example, A50 denotes an aluminum wire, the cross section of which is 50 mm2;

• AC50 / 8 is a steel aluminum wire with a cross section of an aluminum part 50 mm2, a steel core of 8 mm2 (the conductivity of only the aluminum part of the wire is taken into account in electrical calculations);
• PSTZ, 5, PST4, PST5 - single-wire steel wires, where the numbers correspond to the wire diameter in millimeters.

Steel cables applied on VL as light-proof, made from galvanized wire; Their cross section should be at least 25 mm2. On the voltage of 35 kV, the cables with a cross section of 35 mm2 are used; on the lines of kV - 50 mm2; On 220 kV lines and above -70 mm2.

The cross-section of the multi-wiring wires of various grades is determined for the voltage of up to 35 kV under the conditions of the mechanical strength, and for the voltage in the KV and higher - under the conditions of losses on the crown. On VL when crossing various engineering structures (communication lines, iron and highways, etc.), it is necessary to ensure higher reliability, so the minimum cross sections of the wires in the intersection spans should be increased (Table 5.2).

When conducting wires by air flow, aimed across the axis of the VL or at a certain angle to this axis, a curvature occurs from the leeward side of the wire. When the frequency of the formation and movement of the vortices with one of the frequencies of its own oscillations, the wire begins to fluctuate in the vertical plane.

Such oscillations of the wire with amplitude 2 ... 35 mm, wavelength 1 ... 20 m and frequency of 5 ... 60 Hz are called vibration.

Usually, the vibration of the wires is observed at a wind speed of 0.6 ... 12.0 m / s;

Steel wires are not allowed in spans over pipelines and railways.

Vibration, as a rule, takes place in flights longer than 120 m and in open areas. The danger of vibration lies in the cliff of individual wire wires in areas of their exit from the clamps of the increase in mechanical voltage. There are variables from periodic bends of wires as a result of vibration and stored in a suspended key main tensile stresses.

In flights up to 120 m long protection against vibration is not required; The protection and sections of any VL protected from transverse winds are not subject to On large transitions of rivers and water spaces requires protection independently of the wires. On the voltage of 35 ... 220 kV and the above, the protection against vibration is performed by installing vibrations suspended on the steel cable absorbing the energy of vibrating wires with a decrease in vibration amplitude near the clamps.

With ice, the so-called dance of the wires is observed, which, as well as vibration, is excited by the wind, but differs from the vibration of a greater amplitude reaching 12 ... 14 m, and a larger wavelength (with one and two half-waves in the span). In the plane perpendicular to the axis of the VL, the wire on the voltage of 35 - 220 kV wires is isolated from the supports of the garlands of suspended insulators. For isolation of VL 6 -35 kV, pin insulators are used.

Passing through the wires VL, it highlights heat and heats the wire. Under the influence of heating the wires occur:

1. extension of the wire, increasing the arrows of the Provision, the change in the distance to the Earth;
2. changing the tension of the wire and its ability to carry a mechanical load;
3. change the resistance of the wire, i.e., change the loss of electrical power and energy.

All conditions may vary if there are constractions of environmental parameters or change together, affecting the operation of the WL wire. When operating, it is believed that at a rated load current, the wire temperature is 60 ... 70 "s. The temperature of the wire will be determined by the simultaneous impact of heat dissipation and cooling or heat sink. The heat sink of wires of the VL increases with increasing wind speed and decrease in ambient temperature.

With a decrease in air temperature from +40 to 40 ° C and increasing wind speed from 1 to 20 m / s thermal losses change from 50 to 1000 W / m. At positive ambient air temperatures (0 ... 40 ° C) and minor wind speeds (1 ... 5 m / s), thermal losses are 75 ... 200 W / m.

To determine the effect of overloading to increase losses, first determined

where Rq is the resistance of the wire at 02, Ohm; R0] - wire resistance at a temperature corresponding to the estimated load under operating conditions, Ohms; A /. ° C - coefficient of temperature increase of resistance, OM / ° C.

An increase in the resistance of the wire compared with the resistance corresponding to the calculated load, possibly when overloading 30% by 12%, and with overload 50% - by 16%

Increase the loss of the losses of overload up to 30%, you can expect:

1. when calculating Vl on Au \u003d 5% or? / 30 \u003d 5.6%;
2. when calculating Vl on A17 \u003d 10% D? / 30 \u003d 11.2%.

Up to 50% overload, the increase in loss will be equal to 5.8 and 11.6%, respectively. Given the load schedule, it can be noted that when the loss is overloaded up to 50%, the loss briefly exceeds permissible regulatory values \u200b\u200bby 0.8 ... 1.6%, which does not significantly affect the quality of electricity.

Application of SIP wire

Since the beginning of the century, low-voltage air networks are distributed, made as a self-supporting insulated wire system (SIP).

A SIP is used in cities as a mandatory settlement, as a highway in rural areas with a weak population density, branch to consumers. Methods of laying SIP are different: pulling on supports; tensioning by facades of buildings; Laying along the facades.

The design of the SIP (unipolar armored and unarmented, tripolar with an isolated or bare carrier neutral) in general consists of copper or aluminum conductor of a multi-breeding vein, surrounded by an internal semiconductor extruded screen, then insulated with coated polyethylene, polyethylene or PVC. The tightness is provided by a powder and compounded ribbon, on top of which there is a metal screen from copper or aluminum in the form of spirally laid threads or tapes, using extruded lead.

On top of the cable armor, made of paper, PVC, polyethylene, make aluminum armor in the form of a grid of strips and threads. External protection is made of PVC, polyethylene without gelogen. Splings of gaskets, calculated taking into account its temperature and cross-section of wires (at least 25 mm2 for highways and 16 mm2 on branches to inputs for consumers, 10 mm2 for steel aluminum wire) range from 40 to 90 m.

With a slight increase in costs (about 20%) compared to uninsulated wires, the reliability and safety of the line, equipped with a SIP, rises to the level of reliability and safety of cable lines. One of the advantages of air lines with insulated wires was in front of ordinary power transmission lines is to reduce losses and power by reducing reactive resistance. Parameters of direct lines sequence:

• ASB95 - R \u003d 0.31 Ohm / km; X \u003d 0.078 ohm / km;
• SIP495 - respectively 0.33 and 0.078 Ohm / km;
• SIP4120 - 0.26 and 0.078 Ohm / km;
• AC120 - 0.27 and 0.29 Ohm / km.

The effect of loss reduction when using the SIP and the immutability of the load current can be from 9 to 47%, the loss of power is 18%.

Air line power line(VL) - a device intended for transmitting or distribution of electrical energy by wires with a protective insulating shell (VLZ) or uninsulated wires (VL), located outdoors and attached with traverse (brackets), insulators and linear reinforcements to supports or other Engineering facilities (bridges, overpasses). The main elements of the WL are:

• wires;
• protective cables;
• support supporting wires and bulk at a certain height above the level of land or water;
• insulators, insulating wires from the body support;
• linear fittings.

For the beginning and for the end of the air line, linear portals of switchgear are taken. According to the structural device, the WL is divided into monoton and multi-dimensional, usually 2-chain.

It usually consists of three phases, so the supports of the monolayer voltage above 1 kV are designed for the suspension of three phase wires (one chain) (Fig. 1), six wires are suspended (two parallel-running chains). If necessary above phase wires, one or two lightning protection cables are suspended. On the supports of the distribution network voltage voltage of up to 1 kV, it is hampered from 5 to 12 wires for the power supply of various consumers by one VL (external and internal lighting, electrical disposal, household loads). A voltage of up to 1 kV with a deaf-and loaped neutral, in addition to phase, is equipped with a zero wire.

Fig. one. Fragments of 220 sq. M:a - monograph; B - two-chart

The wires of the power lines are mainly made of aluminum and its alloys, in some cases from copper and its alloys, are performed from a cold-made wire with sufficient mechanical strength. However, a multi-wire wire of two metals with good mechanical characteristics and a relatively low cost was obtained the greatest distribution. Wires of this type include steel aluminum wires with the ratio of the cross-sectional area of \u200b\u200bthe aluminum and steel part from 4.0 to 8.0. Examples of the location of phase wires and lightning cables are shown in Fig. 2, and the design parameters of the standard row of stresses are shown in Table. one.

Fig. 2.: a - triangular; b - horizontal; B is a hexagonal "barrel"; M - reverse "christmas tree"

Table 1. Constructive parameters of air lines

Nominal voltage VL, KV	Distance between phase wires, m	Length spanlet, M.	Height	Gabritis
Less than 1.	0,5	40 – 50	8 – 9	6 – 7
6 – 10	1,0	50 – 80	10	6 – 7
35	3	150 – 200	12	6 – 7
110	4 – 5	170 – 250	13 – 14	6 – 7
150	5,5	200 – 280	15 – 16	7 – 8
220	7	250 – 350	25 – 30	7 – 8
330	9	300 – 400	25 – 30	7,5 – 8
500	10 – 12	350 – 450	25 – 30	8
750	14 – 16	450 – 750	30 – 41	10 – 12
1150	12 – 19	–	33 – 54	14,5 – 17,5

For all the above options for the location of the phase wires on the supports, the asymmetrical location of the wires relative to each other is characterized. Accordingly, it leads to the unequal reactive resistance and conductivity of different phases caused by mutual inductance between the wires of the line and as a result of the asymmetry of phase stresses and the voltage drop.

In order to make the capacity and inductance of all three phases of the chain are the same, the transposition of wires is used on the power line, i.e. Mutually change their location relative to each other, with each phase wire passes one third of the paths (Fig. 3). One such triple move is called the transposition cycle.

Fig. 3. Scheme of the total transposition cycle of the power line sections: 1, 2, 3 - phase wires

The transposition of the phase wires of the power line with uninsulated wires is used to the voltage of 110 kV and higher and at the length of the line 100 km and more. One of the options for mounting wires on the transposition support is shown in Fig. 4. It should be noted that the transposition of conductive cores is sometimes used in CL, in addition, modern design and construction technologies are allowed to technically implement the line parameters management (controlled self-compatible lines and super high voltage compact air lines).

Fig. four.

The wires and protective cables of the VL in certain places should be rigidly fixed on the tensioning insulators of the anchor supports (end supports 1 and 7, installed at the beginning and end of VL, as shown in Fig. 5 and stretched to a given population. Between the anchor supports, intermediate supports are installed necessary to maintain wires and cables using supporting insulant garlands with supporting clamps, at a given height (support 2, 3, 6), installed on a direct section of the VL; angular (supports 4 and 5), installed on the rotations of the voltage ll; transitional (Supports 2 and 3), installed in the span of an overhead line of any natural obstacle or engineering structure, such as railway or highway.

Fig. five.

The distance between the anchor supports is called an anchor power line of the power line (Fig. 6). The horizontal distance between the fastening points of the wires on the adjacent supports is called the length of the span L. . Sketch of the span is shown in Fig. 7. The length of the span is chosen mainly for economic considerations, except for transitional spans, taking into account both the height of the supports and the sagging of wires and cables, as well as the number of supports and insulators along the entire length of the VL.

Fig. 6.: 1 - supporting garland of insulators; 2 - tension garland; 3 - intermediate support; 4 - Anchor Support

The smallest distance vertically from the ground to the wire with its largest savage is called the dimension line to the Earth - h. . Dimensional lines should be maintained for all rated voltages, taking into account the risk of overlapping the airbase between the phase wires and the highest point of the area. It is also necessary to take into account the environmental aspects of the impact of high tensions of the electromagnetic field on living organisms and plants.

The greatest deviation of the phase wire f. n or lightning cable f. t from horizontal under the action of a uniformly distributed load from its own mass, the mass of the ice and the wind pressure is called the wire arrow. To prevent the sealing of wires, the cable cable arrow is performed less than the wire of the wire of 0.5 - 1.5 m.

Constructive elements of VL, such as phase wires, cables, the garlands of insulators have a significant mass. Therefore, the forces acting on one support reaches hundreds of thousands of Newton (H). The forces of the tension on the wire from the weight of the wire, the weight of the tensioning garlands of insulators and the ice formations are directed along the normal, and the forces caused by the wind pressure on the normal from the wind stream vector, as shown in Fig. 7.

Fig. 7.

In order to reduce inductive resistance and increasing the bandwidth of long-range gear, various options for compact power transmission lines are used, a characteristic feature of which is a reduced distance between phase wires. Compact power transmission rap have a narrower spatial corridor, a smaller level of electric field strength at the ground level and allow technically implementing the control parameters control (controlled self-compatible lines and lines with unconventional configuration of the split phases).

2. Cable power line

Cable power line (CL) consists of one or more cables and cable fittings for connecting cables and to attach cables to electrical apparatus or switchgear bus.

In contrast, the cables are laid not only in the outdoors, but also indoors (Fig. 8), in the ground and water. Therefore, the CL is subject to moisture, the chemical aggressiveness of water and soil, mechanical damage when carrying out earthworks and soil displacement during storm rains and floods. The design of the cable and structures for the cable laying should provide for protection against the indicated influences.

Fig. eight.

The value of the nominal voltage cables are divided into three groups: cables low voltage(up to 1 kV), cables average voltage(6 ... 35 kV), cables high voltage(110 kV and higher). By the nature of the current distinguish variable and DC cables.

Power cables are executed single-core, dwelling, three-core, four-housing and pentile.Single voltage cables are performed; duct - DC cables; Three-core - medium voltage cables.

Low voltage cables are performed with quantity lived to five. Such cables can have one, two or three phase veins, as well as zero working cowards N. and zero protective custody Re or combined zero working and protective custody Pen. .

On the material of the conductive livers distinguish cables with aluminum and copper veins.Due to copper deficit, cables with aluminum cores received the greatest distribution. Used as insulating material cable paper impregnated with oxicanphole composition, plastic and rubber.There are cables with normal impregnation, impregnated with impregnation and impregnating the unscrewing composition. Cables with depleted or unscrewing impregnation are paved along the highway with a large height difference or vertical sites.

High voltage cables are performed oil-filled or gas-filled.In these cables, paper insulation is filled with oil or gas under pressure.

Protection of isolation from drying and entering air and moisture is ensured by applying a hermetic shell on isolation. Cable protection from possible mechanical damage is provided by armor. To protect against aggressiveness of the external environment, an external protective cover is served.

When studying cable lines, it is advisable to note superconducting Cables for Power Linesthe basis of the design of which is the phenomenon of superconductivity. In a simplified phenomenon superconductivityin metals can be represented as follows. Between electrons, as between the same name of the charged particles, the Coulomb forces are acting. However, with ultra-low temperatures for superconducting materials (and these are 27 pure metals and a large number of special alloys and compounds), the nature of the interaction of electrons among themselves and with an atomic lattice is substantially modified. As a result, the electron attracting and the formation of so-called electronic (Cooper) pairs becomes possible. The emergence of these pairs, their increase, the formation of "condensate" of electronic pairs and explains the appearance of superconductivity. With an increase in temperature, the part of the electrons is thermally excited and goes into a single state. With some so-called critical temperature, all electrons become normal and the state of superconductivity disappears. The same happens when increasing tension magnetic POla. Critical temperatures of superconducting alloys and compounds used in the technique are 10 - 18 K, i.e. from -263 to -255 ° C.

The first projects, experimental models and prototypes of such cables in flexible corrugated cryostal shells were implemented only in the 70s and 1980s of the XX century. As a superconductor, tapes based on an intermetallic niobium compound with tin cooled by liquid helium were used.

In 1986, the phenomenon was opened high temperature superconductivityAlready at the beginning of 1987, conductors of this kind were obtained, which are ceramic materials, the critical temperature of which was increased to 90 K. The exemplary composition of the first high-temperature superconductor YBA 2 Cu 3 O 7-D (D< 0,2). Такой сверхпроводник представляет собой неупорядоченную систему мелких кристаллов, имеющих размер от 1 до 10 мкм, находящихся в слабом электрическом контакте друг с другом. К концу XX века были начаты и к этому времени достаточно продвинуты работы по созданию сверхпроводящих кабелей на основе высокотемпературных сверхпроводников. Такие кабели принципиально отличаются от своих предшественников. Жидкий азот, применяемый для охлаждения, на несколько порядков дешевле гелия, а его запасы практически безграничны. Очень важным является то, что жидкий азот при рабочих давлениях 0,8 - 1 МПа является прекрасным диэлектриком, превосходящим по своим свойствам пропиточные составы, используемые в традиционных кабелях.

Technical and economic studies show that high-temperature superconducting cables will be more efficient compared to other types of power already at the transmitted power of more than 0.4 - 0.6 GW · A, depending on the real object of use. High-temperature superconducting cables are assumed to be used in the future in energy as conductives on power plants with a capacity of over 0.5 GW, as well as deep inputs in megalopolises and large energy-intensive complexes. At the same time, it is necessary to actually evaluate the economic aspects and a full range of works to ensure the reliability of such cables in operation.

However, it should be noted that in the construction of new and reconstructions of old CLs, it is necessary to be guided by the provisions of PJSC Rosseti, according to which it is forbidden to apply :

• power cables that do not meet the current fire safety requirements and excreasing large concentrations of toxic products during combustion;
• cables with paper-oil insulation and oil-filled;
• cables manufactured using synalar crosslinking technology (Silantalized compositions contain grafted organofunctional silane groups, and crosslinking of the molecular chain of polyethylene (PE), leading to the formation of a spatial structure, in this case, due to the communication of silicon-oxygen-silicon (Si-O-Si) rather than carbon-carbon (C - C), as is the case with peroxide stitching).

Cable products depending on the designs are divided into cables , wires and cords .

Cable- Fully ready-to-use factory electrical product, consisting of one or more insulated conductive veins (conductors), prisoners, as a rule, to a metal or non-metallic shell, on top of which, depending on the laying and operation conditions, there may be appropriate protective cover, which May include armor. Power cables depending on the class of the voltage have from one to five aluminum or copper veins with a cross section from 1.5 to 2000 mm 2, of which the cross section of up to 16 mm 2 is single-wire, over - the multi-voltage.

The wire- One uninsulated or one or more isolated lived, on top of which, depending on the conditions of laying and operation, there may be a non-metallic shell, winding and (or) braid with fibrous materials or wire.

Cord- Two or more isolated, or particularly flexible living with a cross section of up to 1.5 mm 2, twisted or laid parallel, on top of which, depending on the conditions of gasket and operation, a non-metallic shell and protective coatings can be applied.

Sophisticated power lines (LPP), serve to deliver electricity over long distances. On the scale of the state, they are strategically important objects that are designed and erected in accordance with SNiP and Pue.

These linear sections are classified on cable and air power transmission lines, installation and gasket of which require compulsory compliance with the calculated conditions and the installation of special designs.

Air lines power lines

Fig.1 Air high-voltage power lines

The most common is the air lines, the laying of which occurs in the open air using high-voltage pillars, to which the wires are fixed using special fittings (insulators and brackets). Most often is the racks of the SC.

The power of power supply includes:

• supports for different stresses;
• bare wires of aluminum or copper;
• traverses that ensure the required distance, eliminating the possibility of contacting wires with elements of support;
• insulators;
• ground contour;
• dischargers and Lightning Course.

The minimum wisp should be: 5 ÷ 7 meters in non-heated terrain and 6 ÷ 8 meters in settlements.

As high-voltage columns are used:

• metal structures that are effectively used in any climatic zones and with different loads. They are distinguished by sufficient strength, reliability and durability. Represent a metal frame, the elements of which are connected using bolted connections that facilitate the delivery and installation of the supports on the installation site;
• reinforced concrete supports, which are the easiest view of the structures that have good strength characteristics, are easy to install and install on them. The disadvantages of the installation of concrete supports include - a certain effect on them of wind loads and the characteristics of the soils;
• wooden supports that are the most low-cost in production and have excellent dielectric characteristics. The small weight of the wood structures allows you to quickly deliver them to the place of installation and easy to install. The disadvantage of these PSP supports are low mechanical strength, which allows them to be installed only with a certain load and exposure to biological destruction processes (material rotting).

The use of one or another design is caused by the voltage of the electrical network. We use the skill to determine the power supply voltage in appearance.

Classified ll:

1. by current - permanent or variable;
2. upon voltage rates - for direct current with a voltage of 400 kilovolts and variable - 0.4 ÷ 1150 kilovolt.

Cable LP.

Fig.2 Cable lines underground type

Unlike air lines, cable are insulated and therefore they are more expensive and reliable. This type of wires are used in places where the installation of air lines is impossible - in cities and settlements with dense development, in the territories of industrial enterprises.

Cable LP Classified:

1. on voltage - just like the air lines;
2. by type of insulation - liquid and solid. The first type is petroleum oil, and the second is a cable braid consisting of polymers, rubber and wash paper.

The distinctive features are the laying method:

• underground;
• underwater;
• for structures that protect cables from atmospheric influences and provide a high degree of safety during operation.

Fig.3 Laying underwater power lines

Unlike the first two ways of laying cable power passes, the option "Construction" provides for the creation:

• cable tunnels in which power cables are placed on special support structures, allowing installation work and maintenance of lines;
• cable channels that are swallowed structures under the floor of the buildings in which the laying of cable lines occurs in the ground;
• cable mines - vertical corridors having a rectangular cross section that provide access to power transmission;
• cable floors, which are dry, technical space with a height of about 1.8 m;
• cable blocks consisting of pipes and wells;
• open type Overap - for horizontal or inclined cable gasket;
• cameras used to lay connective couplings of LPP sites;
• gallery is the same overpass, only a closed type.

Conclusion

Despite the fact that cable and power lines are used everywhere, both options have their own characteristics that must be taken into account in the design documentation defining

Power lines

Power line (LEP) - one of the components electrical network , energy equipment system intended for transmission electricity.

According to MTTEP (intersectoral rules for the technical operation of electrical installations of consumers) Power line - Electrical line leaving the power plant or substation and intended for transmitting electrical energy.

Distinguish air and cable power cable lines.

The LEP also transmits information using high-frequency signals, estimated in Russia about 60 thousand RF channels for LAP are used. They are used for dispatch control, telemetry data transmission, relay protection signals and anti-emergency automation.

Air lines power lines

Air line power line (VL) - a device intended for transmission or distribution electrical Energy on the wires in the open air and attached with the help of traverse (brackets), insulators and fittings to supports or other facilities ( brostam , overpass).

Composition of VL

• Sectioning devices
• Fiber optic communication lines (in the form of separate self-supporting cables, or built into the threat-protective cable, power wire)
• Auxiliary equipment for the needs of the operation (high-frequency communication equipment, capacitive power take-off, etc.)

Documents regulating

Classification VL

By the nature of the current

• VL AC Cone
• DC DC

Basically, the WL serve to transmit AC and only in some cases (for example, to communicate power systems, the power supply of the contact network, etc.) use DC lines.

For VL AC adopted the following voltage classes scale: variable - 0.4, 6, 10, (20), 35, 110, 150, 220, 330, 400 (Vyborg PS - Finland), 500, 750 and 1150 kV; Permanent - 400 square meters.

By destination

• superdalny VL voltage 500 kv. and higher (designed to communicate individual energy Systems)
• trunk voltage 220 and 330 kV (designed to transmit energy from powerful power plants , as well as for communication with power systems and merge power plants inside the power system - for example, connect power plants with distribution points)
• distribution voltage voltage 35, 110 and 150 kV (designed for power supply of enterprises and settlements Large regions - connect distribution points with consumers)
• 20 kV 20 kV and lower, supplying electricity to consumers

By tension

• VL to 1 kV (linked class voltage)
• Ll above 1 kV
  • VL 1-35 kV (voltage class ll)
  • BL 110-220 kV (voltage voltage ll)
  • 330-500 kV 330-500 kV (voltage class voltage)
  • VL 750 kV and higher (voltrawhd voltage class)

These groups differ significantly in the basic requirements in terms of calculated conditions and structures.

By the mode of operation of neutrals in electrical installations

• Three-phase networks with ungrounded (isolated) neutral (neutral is not attached to ground The device or is attached to it through the devices with greater resistance). In Russia, such a neutral regime is used in networks with a voltage of 3-35 kB with small currents of single-phase closures on the ground.
• Three-phase networks with resonant-grounded (compensated) neutrals (neutral bus is attached to grounding through inductance). In Russia, it is used in networks with a voltage of 3-35KV with large currents of single-phase closures on the Earth.
• Three-phase networks with efficiently grounded neutrals (high and ultra-high voltage networks, the neutrals of which are connected to the ground directly or through a small active resistance). In Russia, this is a voltage of 110, 150 and partially 220kV, i.e. Networks in which transformers are used, and not autotransformers that require a mandatory deaf grounding of neutral on operating mode.
• Networks with a deaf-and loaped neutral (neutral of the transformer or generator joins the grounding device directly or through low resistance). These include networks with a voltage of less than 1QV, as well as a 220kV voltage network and higher.

According to the mode of operation depending on the mechanical state

• The normal mode of operation (wires and cables are not trimmed)
• Emergency mode of operation (with full or partial breakage of wires and cables)
• Will mounting mode (during the installation of supports, wires and cables)

The main elements of VL

• Route - The position of the axis of the VL on the earth's surface.
• Pickets (PC) - segments on which the track is broken, the PC length depends on the rated voltage of the VL and the type of terrain.
• Zero pissing sign denotes the beginning of the route.
• Center sign Indicates the center of the layout in nature on the highway under construction.
• Production Picket - Installing picket and centers on the track in accordance with the alignment of the arrangement of the supports.
• Foundation of Support - Design embedded in a soil or resting on it and transmitting loads from support, insulators, wires (cables) and from external influences (ice, wind).
• Foundation base - Soil the bottom of the pit, perceiving the load.
• Splut (The length of the span) is the distance between the centers of the two supports, on which the wires are suspended. Distinguish intermediate (between two adjacent intermediate supports) and anchor (between anchor supports) passages. Transition variet - A span crossing any construction or a natural obstacle (river, ravine).
• Rotate angle line - The angle α between the routes of the VL route in adjacent flights (before and after turn).
• Sag - The vertical distance between the lower point of the wire in the span and the direct connecting point of its attachment on the supports.
• Gabritis wire - Vertical distance from the lowest point of the wire in span to intersected engineering structures, the surface of the earth or water.
• Plume (the loop) - Cut the wire connecting on an anchor support stretched wires of adjacent anchor flaps.

Cable power cable lines

Cable power line (CL) - Names a line for transmitting electricity or individual pulses of it, consisting of one or more parallel cables With connecting, locking and end couplings (seals) and fasteners, and for oil-filled lines, in addition, with feeding devices and the oil pressure alarm system.

By classification Cable lines are similar to airlines

Cable lines divide under the conditions of passage

• Underground
• By structures
• Underwater

cable facilities include

• Cable tunnel - a closed structure (corridor) with supporting structures located in it for placing cables and cable couplings on them, with a free passage along the entire length, allowing the cable laying, repairs and inspections of cable lines.

• Cable canal - Closed and swallowed (partially or completely) in soil, floor, overlap, etc. Disprovable structure, intended for placing cables in it, laying, inspection and repair of which can be performed only when removed.

• Cable mine - Vertical cable construction (as a rule, rectangular section), which has a height of several times more sides of the section, equipped with brackets or a staircase for moving along it, people (passing mines) or removable in full or partially wall (non-projective mines).

• Cable floor - Part of the building bounded by floors and overlapping or coating, with a distance between the floor and protruding parts of the overlap or coating of at least 1.8 m.

• Double floor - the cavity limited by the walls of the room, the inter overlap and floor of the room with removable plates (on all or part of the area).

• Cable block - Cable construction with pipes (channels) for laying cables with shoes related to it.

• Cable camera - Underground cable structure, closed by a deaf removable concrete slab, designed to lay cable couplings or manifold cables into blocks. A camera having a hatch to enter it is called a cable well.

• Cable flight - Overhead or terrestrial open horizontal or inclined extended cable structure. Cable overap can be passing or disadvantaged.

• Cable gallery - Overhead or ground-based closed or partially (for example, without side walls) horizontal or inclined extended passage cable construction.

By type of isolation

The insulation of cable lines is divided into two main types:

• liquid
  • cable oil oil
• solid
  • paper-oil
  • polyvinyl chloride (PVC)
  • rubber-paper (RIP)
  • stitched polyethylene (XLPE)
  • ethylene-propylene rubber (EPR)

There is no insulation of gaseous substances and some types of liquid and solid isolation due to their relatively rare application at the time of writing the article.

Losses in LPP

Electricity loss in wires depend on force tok. , so when transferring it to long distances, voltage increase repeatedly (at the same time reducing current strength) with transformer that when transmitting the same power allows you to significantly reduce the loss. However, with increasing tension, various kinds of discharge phenomena begin to occur.

Another important value affecting the economy of the LEP is COS (F) - the value characterizing the ratio of active and reactive power.

In the super high voltage air lines there are loss of active power on the crown ( crown discharge). These losses depend largely on the weather conditions (in dry weather, less, respectively, in the rain, frost, the snow increases these losses) and splitting the wire in the line phases. The loss on the crown for lines of different stress has its own values \u200b\u200b(for the line 500kv, the average annual losses on the crown are about Δp \u003d 9.0 -11.0 kW / km). Since the crown discharge depends on the tension on the surface of the wire, then the splitting of phases is used to reduce this voltage in air lines. That is, the place of one wire is used from three or more wires in the phase. These wires are located at an equal distance from each other. The equivalent radius of the split phase is obtained, this decreases the tension on a separate wire, which in turn reduces the loss on the crown.

- (VL) - the power line, the wires of which are maintained above the ground using supports, insulators. [GOST 24291 90] Topic Termin: Energy Equipment Headings Encyclopedia: Abrasive Equipment, Abrasives, Highways ... Encyclopedia Terms, Definitions and Explanations of Building Materials

Air line power line - (power line, LEP A construction designed for transmission to the distance of electrical energy from power plants to consumers; placed in the outdoors and is usually made by uninsulated wires, which are suspended with ... ... Large polytechnic encyclopedia

Air line power line - (VL) Device for transmission and distribution of electricity over the wires located in the open air and attached with the help of insulators and reinforcements to supports or brackets, racks on engineering facilities (bridges, overpass, etc.) ... Official terminology

air line power line - 51 electric power line; Power line lines, wires that are supported above the ground using supports, insulators 601 03 04 De Freileitung en overhead line FR LIGNE AÉRIENNE