RU2631421C1 - Wire for overhead power transmission lines - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: non-insulated wire for overhead power transmission lines comprises a steel core (1) made of one or more rods (2) having the form of interconnected complex profiles, and several concentric inner lays, and an external lay made of power rods of trapezoidal cross-section made of aluminium or aluminium-zirconium alloy (3). The external wire lay is formed by rods with a cross-section in form of an equilateral trapezium, on the larger base of which the teeth with a radius of curvature r and depressions with a radius of curvature r are made, in this case the height of the tooth 3 is determined taking into account the distance of separation of the circumferences centers of the tooth and depression.

EFFECT: design of the wire makes it possible to increase the long-term permissible current of the wire without increasing the cross-sectional area and operating temperature.

3 cl, 7 dwg, 6 tbl

Description

The invention relates to the field of electrical engineering, and in particular to the design of uninsulated stranded wires for overhead power lines.

Known design of steel-aluminum wire brand AC [GOST 839-80. Uninsulated wires for overhead power lines. Approved and enacted by resolution of the USSR State Committee for Standards dated June 23, 80 No. 2987], consisting of a steel core providing mechanical strength of the wire, and one or more concentric coils of round aluminum wires (active material) that transmit electrical energy. The core of the wire is twisted from galvanized steel round wires.

The disadvantage of this design are: low fill factor of the cross section of the current-carrying part of the wire with active material, which increases the outer diameter of the wire; low long-term permissible current at operating temperature of the wire.

The closest in technical essence is the design of a compact bare cable for overhead power lines [RU 96442 U1, IPC Н01В 5/00 (2006.01), publ. 07/27/2010], consisting of a steel plastically pressed core made of steel wires with a corrosion-protective metal coating of the POS grade, providing mechanical strength of the wire, and one or more concentric coils of wires from ABE aluminum alloy according to GOST 20967-75 or TAL aluminum-zirconium alloy or ZTAL trapezoidal section (active material) that transmit electrical energy. The core of the wire is twisted from galvanized steel wires, the shape of which is set by crimping and has the form of interconnected shaped profiles.

The disadvantages of the known uninsulated wire are as follows: long-term allowable current is increased by increasing the temperature of recrystallization of aluminum; the wires are made of a special high-tech heat-resistant aluminum-zirconium alloy; For the suspension of wires on supports, special linear reinforcement is required, due to the high temperature of the conductor, which is more than 200 ° C.

Other constructions of conductors are also known, for example, cables, which can increase the long-term allowable current due to its forced cooling, i.e. improving the conditions of heat removal from the cable.

Distinguish between internal, external and indirect cooling systems.

The main features of the internal cooling system are: the conductive core is cooled by pumping oil through the internal channel; for circulation of oil in a closed cycle, a return pipe and a heat exchanger are necessary for its cooling; cable line lengths are limited due to small volumes of cooling oil. Cables with an internal cooling system are manufactured in accordance with GOST 16441-78.

Systems with external (surface) cooling of the cable line have the following features: air, water, oil under high pressure can be used as a cooling medium; the cooling medium is in direct contact with the outer surface of the cable; as a constructive solution, a cable line is laid in the pipe (combined or with phase separation), along which air is blown, water or oil is pumped [SU 150142 A1, 1962]. This system includes surface cooling of a cable line by a cryogenic system, where a cryogen acts as a cooling medium [RU 2491671 C2, 2013].

The main features of the indirect cooling system are: there is no direct cooling of the cable with water, oil or air; pipes with running water installed near the cable line are used as a heat sink; heat transfer from the cable line occurs due to lower ambient temperature.

The main disadvantages of its forced cooling are: the creation and operation of complex additional conductor cooling systems.

The task to which the claimed technical solution is directed is to develop a design of bare wire for an overhead power line, without creating additional cooling systems having improved performance characteristics.

The problem is solved by achieving a technical result, which consists in increasing the throughput of power lines by increasing the long-term allowable current of the wire without increasing the cross-sectional area.

The technical result is achieved by the fact that in the known uninsulated wire for overhead power lines containing a steel core made of one or more wires having the form of interconnected shaped profiles, and several concentric inner wires and external wire made of trapezoidal conductive wires of aluminum or aluminum-zirconium alloy, a feature is that the specified external winding is formed by wires with a cross section in the form of isos ary trapezoid at a greater basis of which the teeth are made with a radius of curvature r and depressions with a radius of curvature r, the height of the tooth Η determined considering the distance razdvizheniya tooth centers of circles and troughs. It is possible that TAL or ZTAL alloy is used as an aluminum-zirconium alloy, and the interwire space of the wire is filled with grease.

The inventive design of non-insulated wire allows you to increase the long-term allowable current of the wire, without increasing the cross-sectional area, operating temperature of the conductor, as well as the creation of forced cooling systems. The increase in the long-term permissible current is carried out by increasing the amount of heat transferred by the wire to the environment from the side surface, by increasing the perimeter of the cross section.

An increase in conductor throughput by increasing the long-term allowable current is known. For this, a special conductive material is used - a heat-resistant alloy or special systems to improve the conditions of heat removal from the conductor. Also known is the design of the wire with improved conditions for heat removal from the conductor, by increasing the area of the side surface of the conductor, and thereby increases the long-term allowable current [RU 156801 U1, 2015, RU 156715 U1, 2015]. In known wire structures, the tooth height Η is not more than two radii of curvature of the tooth - 2 r (n). But the construction of the wire is not known where, to increase the perimeter of the cross section of the wire, the height of the tooth increases due to the extension of the centers of the circle - the tooth, with a radius of curvature r (n) and a cavity with a radius of curvature r (n) by a distance h. Moreover, the height of the tooth зуб = 2r (n) + h (n).

When using wires in the form of an isoside trapezoid on the larger base of which the teeth are made on the wire in the outer layer, faster cooling of the wire occurs than when using wires with a smooth surface in the wire (prototype). Consequently, more electricity can be transmitted through the wire, while the temperature of the wire does not exceed the permissible temperature of recrystallization of the active material.

In FIG. 1 shows a cross section of a wire consisting of wires.

In FIG. 2 shows a cross section of an outer coil wire.

In FIG. 3 shows an uninsulated twisted wire.

In FIG. 4 shows the dependences: a change in the radius of curvature r of a tooth versus the number of teeth; change in the perimeter of the cross section of the wire from the number of teeth at the height of the tooth Η = 2r; the change in the perimeter of the cross section of the wire from the number of teeth with an increased tooth height H = 2r + h.

In FIG. 5 depicts: temperature of a wire with a cross-section of 300/37 mm ² of aluminum-zirconium alloy on the length of the perimeter of the cross section at currents of 900 A, 1300 A, 1700 A, 2100 A.

In FIG. 6 shows a conductor consisting of three sections. The first section is a circle in cross section, the second section is a gear wheel in cross section with the number of teeth 12 pcs., And the third section is in cross section a gear wheel with 24 teeth in number.

In FIG. 7 shows the distribution of heat flux vectors (W / mm ² ) from the surface of the conductor.

In FIG. 1 shows: 1 - the core of the wire with the form of interconnected shaped profiles of steel wires; 2 - conductive aluminum wire or wire of aluminum-zirconium alloy with a cross section in the form of an isosceles trapezoid; 3 - conductive aluminum wire or wire of aluminum-zirconium alloy with a cross section in the form of an equilateral trapezoid, on the larger base of which the teeth are made; 4 - inner wire coil; 5 - external wire coil; 6 - the teeth made on the outer surface of the conductive wire 3 of the external winding.

In FIG. 2 shows: 3 - aluminum conductive wire or aluminum-zirconium alloy wire with a cross section in the form of an isosceles trapezoid, on the larger base of which teeth are made; 6 - a tooth with a radius of curvature r; 7 - cavity with a radius of curvature r, 8 - Η - tooth height; 9 - h is the distance of the separation of the centers of the circumferences of the tooth and the cavity (the distance between the axes of the radius of curvature of the tooth 6 and the cavity 7); 10 - outer radius R of the wire with a cross section in the form of a circle.

In FIG. 3 shows: 1 - the core of the wire with the form of interconnected shaped profiles of steel wires; 2 - conductive aluminum wire or wire of aluminum-zirconium alloy with a cross section in the form of an isosceles trapezoid; 3 - conductive aluminum wire or wire of aluminum-zirconium alloy with a cross section in the form of an isosceles trapezoid, on a larger base of which teeth 6 are made; 4 - inner wire coil; 5 - external wire coil.

In FIG. 4 shows: 11 - curve of the radius of curvature r (n) of the tooth versus the number of teeth; 12 is a change curve of the perimeter of the cross section P1 (n) in the form of a gear from the number of teeth; 13 - change curve of the perimeter of the cross-section P2 (n) in the form of a gear from the number of teeth with an increased height H = 2r + h; 14 - line of the perimeter of the wire with a cross section of P (n) in the form of a circle.

In FIG. 5 shows: 15 - curve of the temperature change of the conductor from the length of the perimeter of the cross section of the wire at a current of 900 A; 16 - curve of temperature change from the length of the perimeter of the cross section of the wire at a current of 1300 A; 17 - curve of temperature change from the length of the perimeter of the cross section of the wire at a current of 1700 A; 18 is a curve of temperature change from the length of the perimeter of the cross section of the wire at a current of 2100 A; 19 - line - the perimeter of the cross section of the wire (prototype); 20 - line - the perimeter of the cross section of the wire (the claimed solution); point A - the point of intersection of the line 19 of the perimeter of the cross section of the wire (prototype) with the temperature change curve at a current of 1700 A; point B - the point of intersection of the line 20 of the perimeter of the cross section of the wire (the claimed technical solution) with the temperature change curve at a current of 1700 A.

In FIG. 6 shows: 21 - conductor; 22 - the first section of the conductor with a cross section of a circle; 23 - the second section of the conductor with a cross section of the gear wheel with the number of teeth 12 pcs .; 24 - the third section of the conductor with a cross section of a circle, a gear wheel with the number of teeth 24 pcs.

In FIG. 7 shows: 21 - conductor; 25 is the heat flux vector from the surface of the conductor.

The main provisions of the physical essence of the design of the wire with an increased continuous allowable current are as follows:

1. The presence of current in the wire causes it to heat.

2. Cooling the wire faster with a larger lateral surface area.

3. The perimeter of geometric shapes (triangle, circle, hexagon) is different for the same area.

4. The fill factor of the full cross section of a multiwire wire with an active material is higher for trapezoidal wires compared to a circular cross section.

5. The current density in a wire with a radius of 11.95 mm (9.554 mm) of active aluminum (copper) material with a cross section at 50 Hz is evenly distributed in the cross section.

6. Wires, when transmitting electricity at voltages of 6-35 kV, create an uneven electric field around its surface that does not ionize the air (electricity losses to the crown are negligible).

7. Loss of electricity in the wire decreases with decreasing heating temperature of the wire.

Let us show the possibility of using a wire consisting of wires in an external layer with a cross section in the form of an isosceles trapezoid, on a larger base of which teeth are made with an increased tooth height Η due to the separation of the tooth circumference centers, with a radius of curvature r (n) and - depressions with a radius of curvature r (n) over a distance h.

Design rationale

1. The amount of heat generated by the flow of current

When a long-term permissible current flows, the wire heats up in accordance with the Joule-Lenz law. The maximum amount of heat without violating the mechanical strength of the wire released in the conductor per unit time is determined [G. Alexandrov Transmission of electrical energy / G.N. Alexandrov. - 2nd ed. -SPb .: Publishing house of the Polytechnic University, University, 2009. - 412 p. (Energy at the Polytechnic University). - S. 16]:

where I _dl.dop is the current heating the wire under specified climatic conditions to an acceptable temperature according to the conditions of the mechanical strength of the wire, A [STO 56947007-29.240.55.143-2013 Methods for calculating the maximum current loads according to the conditions of maintaining the mechanical strength of the wires and the permissible dimensions of overhead lines. M .: JSC FGC UES, 2013];

R _E - specific resistance of the conductor, Ohm / m;

ρ _t is the electrical resistivity of the wires at a wire temperature of 25 ° C, Ohm⋅m;

F is the cross-sectional area, mm ² .

The heating temperature of the wire largely depends on the resistance and environmental conditions.

2. Wire cooling

The wire is cooled by radiation and convection. The amount of heat given off by the wire (unit length) to the environment per unit time is determined by the following dependence [G. Alexandrov Transmission of electrical energy / G.N. Alexandrov. - 2nd ed. - SPb .: Publishing house of the Polytechnic University, University, 2009. - 412 p. (Energy at the Polytechnic University). - S. 16]:

where α _T is the heat transfer coefficient, depending on the temperature of the wire and its size, W / (m ² ⋅K);

S _bp - the area of the side surface of the wire per 1 m of the length of the wire, m ² ;

Τ is the absolute temperature of the wire, K;

T ₀ - absolute ambient temperature (in Russia it is recommended to take t ₀ = 25 ° C), K.

The area of the side surface of a unit length of wire is expressed by the formula:

S _bp = P⋅L, (3)

where L is the length of the conductor, mm;

Ρ - perimeter of the cross-sectional area of the conductor, m

An analysis of relations (3), (4) shows that increasing the perimeter of the cross section of the wire increases the lateral surface area of a unit length of the wire and, therefore, the amount of heat removed from its surface.

3. The perimeter of geometric shapes

From geometry it is known that with the same area (for example, 300 mm ² ) in different figures, their perimeter is different. Table 1 shows the values of the perimeters of various geometric shapes.

Thus, of the geometric figures considered in table 1, the largest perimeter of the star. When performing an external wire winding 5 of conductive wires 3 with a cross section in the form of an equal-sided trapezoid on the larger base of which teeth 6 are made, the perimeter will be the largest.

To increase the filling density of the active material in the cross section of the wire, the conductive wire 2 is adopted with a cross section in the form of an isosceles trapezoid.

4. Long-term allowable wire current

We find the long-term allowable current of the wire by equating the right-hand sides of expressions (1) and (2) taking into account expression (3):

where χ _s - fill factor of the wire with the active material.

Relation (4) shows the dependence of the long-term allowable current on the perimeter of the cross section of the wire.

5. Heat transfer coefficient

The heat transfer coefficient of a heated wire flowing around air whose temperature is less than the temperature of the wire is:

α _T = α _I + α _K , (5)

where α _K is the heat transfer coefficient of convection, W / (m ² ⋅K);

α _And - heat transfer coefficient by radiation, W / (m ² ⋅K).

The heat transfer coefficient by radiation depends on the temperature of the outer surface of the wire and is found according to the Stefan-Boltzmann law:

where ε is the black factor of the wire surface;

С ₀ = 5.7⋅10 ^-8 W / (m ² K ⁴ ) is the radiation constant of a completely black body;

Τ is the absolute temperature of the wire, K;

₀ T - absolute temperature of the surrounding environment, K.

The heat transfer coefficient of convection, which depends on the perimeter of the cross section of the wire [RU 2417905 C1], is determined by the ratio:

where a, b are constant coefficients;

λ = 0.026 W / (m⋅K) - thermal conductivity of air;

v = 1,51⋅10 ^-5 m ² / s - kinetic viscosity of air;

=0,6 м/с - скорость ветра;

= 0.6 m / s - wind speed;

Ρ - perimeter of the cross section of the wire, m

The values of the coefficients a and b are taken from the following conditions:

, то а=0,44; b=0,813;- if

then a = 0.44; b = 0.813;

, то а=0,59; b=0,288.- if

then a = 0.59; b = 0.288.

принимается из следующих условий:Relationship value

accepted from the following conditions:

, то

=2,73;- if

then

= 2.73;

, то

=5.19.- if

then

= 5.19.

Relation (7) shows that increasing the perimeter of the wire cross-section Ρ reduces the heat transfer coefficient of convection.

In FIG. 6 shows a conductor consisting of three sections with different lateral surface areas.

In the ANSYS 16.0 program, a physical model of the conductor is constructed, consisting of three sections with different lateral surface areas (Fig. 6).

In FIG. 7 shows the density of the heat flux vectors 25 from the surface of the conductor. In FIG. 7 shows that the density of the heat flux vectors 25 is higher in the third section 24 with a cross-section of a gear with the number of teeth 24 pcs.

Thus, a conductor with a cross section of a gear wheel cools better than a conductor with a cross section of a circle.

6. Skin effect

The direct current density is evenly distributed over the cross section of the wire.

With alternating current, current is displaced from its volume of the conductor to the surface, the depth of which is called the thickness of the skin layer [Bogachkov I.V. Electromagnetic fields and waves. Part 1 / I.V. Bogachkov. - study benefits for universities - Omsk: Publishing House of OmSTU, 2014].

The thickness of the skin layer in the conductor is determined by the formula:

where f is the frequency, Hz;

σ is the specific conductivity, S / m;

μ ₀ = 4π⋅10 ^-7 - magnetic permeability, GN / m;

μ - relative magnetic permeability (for aluminum - 1,00026; for copper - 0,9999904).

An analysis of relation (8) shows that the thickness of the skin layer depends on the frequency of the electromagnetic field and the material of the conductor, so at a frequency of 50 Hz, the thickness of the skin layer for aluminum is 11.95 mm, and for copper - 9.554 mm.

The radius of the wire according to [GOST 839-80] AC-120/27 is - 7.7 mm, the wire AC-300/39 - 12 mm.

Thus, the skin effect of an aluminum wire with a radius of up to 12 mm can be ignored.

7. The condition of the corona wire

Around the wire there is a discharge in the form of a corona at the maximum value of the initial critical electric field strength [L. Rozhkova Electrical equipment of stations and substations / L.D. Rozhkova, V.S. Kozulin. - A textbook for technical schools. - M .: Publishing house "Energy", 1975. S. 281-283]:

where m is a coefficient taking into account the unevenness of the surface of the wire (for stranded wires m = 0.82);

r ₀ is the radius of the wire, see

The electric field strength near the surface of an unbroken wire is determined by the expression:

where U is the linear voltage, kV;

D _cp is the geometric mean distance between the phase wires, see

Wires are not corona if the highest field strength at the surface of any wire is not more than 0.9⋅E ₀ . Thus, the condition for checking for the crown can be written as:

1.07Ε≤0.9E ₀ (11)

An analysis of expressions (9) ... (11) shows that with an increase in the perimeter of the wire cross-section Ρ or line voltage, the condition of corona wire increases.

Table 2 compares for the voltage classes 6-35 kV the condition of corona wire, with an external coil 5 of conductive wires 3 with a cross section in the form of an equal-sided trapezoid, on the larger base of which teeth 6 are made.

Based on table 2, a wire with teeth on an external winding can be used in voltage classes up to 35 kV.

According to the above provisions of the physical nature, the design of the wire, consisting of an outer coil of wires with a cross section in the form of an isosceles trapezoid, on a larger base of which teeth with increased height are made, allows to increase the long-term allowable current. At the same time, the cross-sectional area Ρ of the wire is not increased and the amount of active material (aluminum, copper, etc.) in the wire remains unchanged. Such a wire can be used in the national economy for overhead power lines up to a voltage class of 35 kV.

8. The calculation of the design of the proposed wire

We perform the calculation of the design of the wire with a cross section of 300/37 (the claimed technical), consisting of a heat-resistant aluminum-zirconium alloy.

The perimeter of the cross section of a smooth wire 300/37 (prototype) is determined by the formula:

Ρ = 2⋅R⋅π. (12)

where R is the outer radius of the smooth wire, mm

To calculate the size of the teeth, we find the radius of curvature, which depends on the number of teeth of the wire and on the outer radius of the wire.

The radius of curvature of the tooth is found by the formula:

where R is the outer radius of the smooth wire, mm; n is the number of teeth, pcs.

The perimeter of the cross section of the wire with n teeth is found by the formula:

P1 (n) = 2⋅r (n) ⋅n⋅π. (fourteen)

By the formulas (12) ... (15) in FIG. 4, curve 11 is plotted - the change in the radius of curvature of the tooth r from the number of teeth n, and curve 12 is the change in the length of the perimeter of the cross section Ρ of the wire with teeth from the number of teeth n, straight line 13 of the perimeter of the wire with a cross section in the form of a circle (prototype).

The analysis of FIG. 4 shows that an increase in the number of teeth leads to an increase in the perimeter of the cross section of the wire (curve 12) is not linear, i.e. the more teeth, the smaller their radius (curve 11), and subsequently the perimeter P1 (n) increases slightly. Therefore, there is no need to create a large number of teeth on the wire.

To increase the perimeter of the cross-section P1 (n) of the wire, it is proposed to increase the tooth height Η due to the extension of the centers of the circle - tooth 6, with a radius of curvature r (n) and a cavity 7 with a radius of curvature r (n) by a distance h, which is determined by the expression:

h (n) = k⋅r (n), (15)

where k is the coefficient of increase in tooth height Η, k = 2.

The perimeter of the cross section of the wire with n teeth with a coefficient k of increasing the height Η of the tooth is determined by the formula:

P2 (n) = 2⋅r (n) ⋅n⋅ (π + k-2) (16)

In FIG. 4, according to formula (16), curve 13 is constructed — the change in the perimeter of the cross section of the wire with teeth P2 (n) versus the number of teeth n, taking into account the coefficient of increase k (multiplicity) of the tooth height Η.

The number of teeth on the wire of the external winding depends on the required perimeter of the cross-section P2 of the wire, and on the number of wires of the external winding and is determined by the ratio:

where n1 is the number of teeth of the wire, N is the number of wires in the outer coil of the wire.

The calculation results of the main dimensions of the wire 300/37 (the claimed technical solution) are presented in table 3.

As can be seen from FIG. 4 and table 3, with an increase in the number of teeth n at the wire 300/37 (the claimed solution), the perimeter P2 (n) significantly increases with the number of teeth n from 3 to 50 pcs. We accept a wire with the number of teeth n, a multiple of the number of wires in the outer layer, n = 48 pcs. At the same time, the cross-sectional perimeter of the wire is 115.19, increased by 176%.

Additionally, to increase the perimeter of the cross-section P2 (n) is possible by increasing the height of the tooth Η (Fig. 2) by increasing the distance of the extension of the centers of the circumferences of the tooth 6 and the cavity 7.

The height of the tooth is determined from the expression taking into account (16):

Η = 2r (n) + h (n) = r (n) (2 + k) (18)

As an example of the claimed technical solution, a calculation was performed for a wire 300/37 with an increased tooth height при with different k tooth heights. The results of calculating the perimeter of the wire with an increased tooth height Η are shown in table 4.

Thus, increasing the height Η of the tooth by increasing the distance between the centers of the tooth and the cavity, the perimeter increases even more. The size of the tooth height Η, depending on the distance h of the separation of the centers of the circumferences of the tooth and the cavity (multiplicity), is limited only by the mechanical strength and dimensions of the wire of the external winding, as well as by the conditions of external cooling of the wire.

9. Calculation of wire temperature

As stated above, an electric current (for example, a load current) in a wire leads to heat generation in accordance with the Joule-Lenz law, according to relation (1). In this case, taking into account the cooling of the environment, the wire is heated to a temperature that is found from expression (4):

Now we analyze how increasing the length of the perimeter of the cross section of the wire changes the conditions for cooling the wire at different currents.

For this, in FIG. 5 according to expression (19), four dependencies are constructed: curve 15 — change in the temperature of the conductor versus the length of the perimeter of the wire’s cross section at a current of 900 A; curve 16 - temperature change from the length of the perimeter of the cross section of the wire at a current of 1300 A; curve 17 - temperature change from the length of the perimeter of the cross section of the wire at a current of 1700 A; curve 18 - temperature change from the length of the perimeter of the cross section of the wire at a current of 2100 A.

In the graph of FIG. 5 shows the perimeter of the cross section of the wire (prototype) - straight line 19 and the perimeter of the cross section of the wire (the claimed solution) - straight line 20.

The intersection points of straight line 19 with curves 15, 16, 17, 18 show the temperature of the wire (prototype) at currents of 900 A, 1300 A, 1700 A, 2100 A, respectively. Similarly, the points of intersection of straight line 20 with curves 15, 16, 17, 18 show the temperature of the wire (the claimed solution) at the same currents.

For example, point A is the intersection of the straight line 19 of the perimeter of the wire cross section (prototype) with curve 17 of the temperature change at a current of 1700 A; point B - the intersection of the straight line 20 of the perimeter of the wire cross section (patent) with curve 17 of the temperature change at a current of 1700 A.

Consider what temperature the wire 300/37 (prototype) heats up at currents of 900 A, 1300 A, 1700 A, 2100 A.

The calculation results are presented in table 5.

Thus, a wire with a large perimeter of the cross section cools better, therefore, the conductor can withstand more current, thereby the long-term allowable current of the wire 300/37 (the claimed solution) is higher than that of the wire 300/37 (prototype).

At a current of 1700 A, the wire (the claimed solution) with an increased perimeter P2 is colder compared to the wire (prototype) by ΔΤ. Therefore, with the same section of the wire 300/37, but with an increased perimeter of the cross section, you can transfer more electricity. The effect of cooling the wire is manifested more at currents close to long-term acceptable.

10. Comparison of wire parameters (analogue, prototype, claimed solution)

The parameters of the known bare wires (analogue, prototype) and the proposed wire for calculating the long-term allowable current are shown in table 6.

A comparative analysis of the calculated parameters in table 6 shows:

1. A wire with an increased lateral surface has a large area, therefore, this wire is cooled more intensively, while the long-term allowable current for a wire manufactured without using a heat-resistant alloy increases by 11.4% compared to the analogue, and for a wire with a heat-resistant alloy the increase in the long-term allowable current is 22.4% compared with the prototype.

2. The use of trapezoidal cross-section wires allows to increase the fill factor of the active material and, therefore, reduce the wire diameter compared to the analog by 10%, while the outer diameter of the proposed wire corresponds to the diameter of the prototype, also made from trapezoidal cross-section wires only without corrugation of the teeth in the outer in the midst of the surface.

3. Reducing the temperature of the wire by increasing its lateral surface allows you to reduce the resistance and thereby reduce energy loss during power transmission. The loss of electricity in the proposed wire is less by 1.2% and 6.2% compared with the loss in the wires of the analogue and prototype, respectively.

4. The cost of the proposed wire is lower, because with a higher intensity of cooling the wire, its long-term allowable current increases, so you can use a wire with a smaller cross section in comparison with the analog and prototype, thereby saving on conductive material (aluminum, aluminum, copper, etc. .P.).

5. The mechanical strength of the proposed wire is 5-10% higher (similar to the prototype) compared to the analogue by increasing the contact area of the steel wires of the core, and thereby increases the structural stability of the core.

Thus, the inventive wire has improved technical characteristics, which allows more to transmit electricity through power lines.

Information confirming the possibility of carrying out the invention.

Uninsulated wire for overhead power lines is made using a cord (bundle) twisting system.

The core wire 1 with a cross section of a regular hexagon (inner layer) and a trapezoidal cross section (outer layer), having the form of interconnected shaped profiles, is made by drawing a wire rod from carbon structural steel, while a zinc coating of a certain thickness is applied to the steel wire.

Conducting wires 2, 3 with a cross-sectional shape in the form of a regular trapezoid are made by drawing a wire rod having an appropriate profile from aluminum or its heat-resistant alloy.

The core 1 of the wire and wire 2, 3 (Fig. 1) is laid in the shape of a circle and twisted together in one direction on a twisting machine in a spiral with a certain twisting pitch. The twist can be right or left. The twisted core is then plastically crimped by cold rolling using special carbide rollers. As a result of such compression, the cross-sections of the wires accept mutually conjugate shaped profiles. Linear contact between the wires develops in strip. The contact area increases and contact pressures decrease, the gaps between the wires are filled, and the structural stability of the core increases. The core becomes smoother and the shape rounded.

The interwire space of the wire is filled with grease during the application of the internal coils of wires.

Also, non-insulated wire can be made of modern materials, metals and their alloys on the basis of existing technologies using drawing equipment and tooling for the manufacture of profile wire, and twisting equipment containing units for twisting profile wires.

The basic provisions of the present invention are also applicable for the manufacture of cable products such as insulated wires, busbars and cables.

Claims (3)

1. Non-insulated wire for overhead power lines, containing a steel core made of one or more wires having the form of interconnected shaped profiles, and several concentric internal wires and external wires made of trapezoidal conductive wires of aluminum or aluminum-zirconium alloy, characterized the fact that the specified outer winding is formed by wires with a cross section in the form of an isosceles trapezoid, on a larger base of which teeth are made with the radius of curvature r and the cavity with the radius of curvature r, while the height of the tooth H is determined taking into account the distance of the separation of the centers of the circumferences of the tooth and the cavity. 2. Uninsulated wire according to claim 1, characterized in that the TAL or ZTAL alloy is used as an aluminum-zirconium alloy. 3. Uninsulated wire according to claim 1, characterized in that the interwire space of the wire is filled with grease.

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