Section 2. Sewerage of electricity

Overhead power lines with voltage above 1 kV. Climatic conditions and loads

Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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2.5.38. When calculating overhead lines and their elements, climatic conditions should be taken into account - wind pressure, ice wall thickness, air temperature, the degree of aggressive environmental influences, the intensity of thunderstorm activity, the dance of wires and cables, vibration.

The determination of the design conditions for wind and ice should be made on the basis of the relevant maps of the climatic zoning of the territory of the Russian Federation (Fig. 2.5.1, 2.5.2) with the refinement, if necessary, of their parameters in the direction of increasing or decreasing according to regional maps and materials of long-term observations of hydrometeorological stations and meteorological posts wind speed, mass, size and type of ice-frost deposits. In little-studied areas*, special surveys and observations may be organized for this purpose.

In the absence of regional maps, the values ​​of climatic parameters are refined by processing the relevant data of long-term observations in accordance with methodological guidelines (MU) for calculating climatic loads on overhead lines and constructing regional maps with a frequency of 1 time in 25 years.

The basis for wind pressure zoning is the values ​​of maximum wind speeds with a 10-minute interval of averaging speeds at a height of 10 m with a frequency of 1 time in 25 years. Ice zoning is carried out according to the maximum wall thickness of cylindrical ice deposits at a density of 0,9 g/cm3 on a wire with a diameter of 10 mm, located at a height of 10 m above the ground, with a frequency of 1 time in 25 years.

The air temperature is determined on the basis of data from meteorological stations, taking into account the provisions of building codes and regulations and the instructions of these Rules.

The intensity of thunderstorm activity should be determined on the basis of zoning maps of the territory of the Russian Federation according to the number of thunderstorm hours per year (Fig. 2.5.3), regional maps, if necessary, using data from weather stations on the average annual duration of thunderstorms.

The degree of aggressive environmental impact is determined taking into account the provisions of SNiPs and state standards containing requirements for the use of overhead lines, Ch. 1.9 and instructions of this chapter.

The definition of regions by the frequency of repetition and intensity of the dance of wires and cables should be carried out according to the zoning map of the territory of the Russian Federation (Fig. 2.5.4) with clarification according to the operation data.

According to the frequency of repetition and intensity of the dance of wires and cables, the territory of the Russian Federation is divided into areas with moderate dance of wires (the frequency of repetition of dance is 1 time in 5 years or less) and with frequent and intensive dance of wires (the frequency of repetition is more than 1 time in 5 years).

* Little-studied areas include mountainous terrain and areas where there is only one representative meteorological station per 100 km of the overhead line to characterize climatic conditions.

2.5.39. When determining climatic conditions, the influence on the intensity of icing and wind speed of the features of the terrain microrelief (small hills and hollows, high embankments, ravines, beams, etc.) should be taken into account, and in mountainous areas - the features of the micro- and mesorelief of the terrain (ridges , slopes, plateau-like areas, valley bottoms, intermountain valleys, etc.).

2.5.40. The values ​​of maximum wind pressures and ice wall thicknesses for overhead lines are determined at a height of 10 m above the ground with a frequency of 1 time in 25 years (standard values).

Rice. 2.5.1. Map of the zoning of the territory of the Russian Federation by wind pressure

Rice. 2.5.2. Map of the zoning of the territory of the Russian Federation according to the thickness of the ice wall

Rice. 2.5.3. Map of the zoning of the territory of the Russian Federation according to the average annual duration of thunderstorms in hours

Rice. 2.5.4. Map of the zoning of the territory of the Russian Federation according to the dance of wires

2.5.41. Standard wind pressure W0, corresponding to a 10-minute wind speed averaging interval (ν0), at a height of 10 m above the earth's surface is taken from Table. 2.5.1 in accordance with the zoning map of the territory of Russia by wind pressure (Fig. 2.5.1) or according to regional zoning maps.

The normative wind pressure obtained during the processing of weather data should be rounded up to the nearest higher value given in Table. 2.5.1.

Wind pressure W is determined by the formula, Pa

Wind pressures over 1500 Pa should be rounded up to the next higher multiple of 250 Pa.

For 110-750 kV overhead lines, the standard wind pressure should be taken at least 500 Pa.

For overhead lines constructed in hard-to-reach areas, it is recommended to take the wind pressure for the corresponding area one higher than that accepted for the given region according to regional zoning maps or based on the processing of long-term observations.

Table 2.5.1. Standard wind pressure W0 at a height of 10 m above the ground

2.5.42. For sections of overhead lines constructed under conditions conducive to a sharp increase in wind speeds (high bank of a large river, a hill that stands out sharply above the surrounding area, ridge zones of ridges, intermountain valleys open to strong winds, a coastal strip of seas and oceans, large lakes and reservoirs within 3-5 km), in the absence of observational data, the standard wind pressure should be increased by 40% compared to that adopted for the given area. The values ​​obtained should be rounded up to the nearest value indicated in Table. 2.5.1.

2.5.43. The normative wind pressure in ice conditions Wg with a frequency of 1 time in 25 years is determined by formula 2.5.41, according to the wind speed in ice conditions νg.

The wind speed νg is taken according to the regional zoning of wind loads in case of ice or is determined from observational data in accordance with the guidelines for calculating climatic loads. In the absence of regional maps and observational data, Wg = 0,25 W0. For overhead lines up to 20 kV, the standard wind pressure during ice should be taken at least 200 Pa, for overhead lines 330-750 kV - at least 160 Pa.

Standard wind pressures (wind speeds) during ice are rounded up to the nearest following values, Pa (m/s): 80 (11), 120 (14), 160 (16), 200 (18), 240 (20), 280 (21 ), 320 (23), 360 (24).

Values ​​greater than 360 Pa should be rounded to the nearest multiple of 40 Pa.

2.5.44. The wind pressure on the wires of the overhead line is determined by the height of the reduced center of gravity of all wires, on the cables - by the height of the center of gravity of the cables, on the structure of the overhead lines - by the height of the midpoints of the zones, counted from the mark of the earth's surface at the installation site of the support. The height of each zone should be no more than 10 m.

For different heights of the center of gravity of wires, cables, as well as the midpoints of the design zones of the overhead line supports, the wind pressure is determined by multiplying its value by the coefficient Kw, taken from Table. 2.5.2.

The resulting wind pressure values ​​should be rounded up to a whole number.

For intermediate heights, the values ​​of the coefficients Kw are determined by linear interpolation.

The height of the reduced center of gravity of wires or cables hpr for the overall span is determined by the formula, m

hpr \u2d hav - 3/XNUMX f

where hav is the arithmetic mean value of the height of fastening wires to insulators or the arithmetic mean value of the height of fastening the cables to the support, measured from the ground marks at the installation sites of the supports, m;

f - sag of the wire or cable in the middle of the span at the highest temperature, m

Table 2.5.2. Variation of the Kw coefficient in height depending on the type of terrain*

* Terrain types are as defined in 2.5.6.

2.5.45. When calculating wires and cables, the wind should be taken at an angle of 90º to the axis of the overhead line.

When calculating the supports, the wind should be taken as directed at an angle of 0º, 45º and 90º to the axis of the overhead line, while for the corner supports, the direction of the bisector of the external angle of rotation formed by adjacent sections of the line is taken as the axis of the overhead line.

2.5.46. The normative wall thickness of ice be with a density of 0,9 g / cm3 should be taken from Table. 2.5.3 in accordance with the zoning map of the territory of Russia according to the thickness of the ice wall (see Fig. 2.5.2) or according to regional zoning maps.

It is recommended that the normative thicknesses of ice walls obtained during the processing of meteorological data be rounded up to the nearest higher value given in Table. 2.5.3.

In special areas on ice, the thickness of the ice wall obtained by processing weather data, rounded up to 1 mm, should be taken.

For 330-750 kV overhead lines, the standard thickness of the ice wall should be at least 15 mm.

For overhead lines constructed in hard-to-reach areas, it is recommended to take the thickness of the ice wall corresponding to the area one higher than that accepted for the given region according to regional zoning maps or based on the processing of meteorological data.

Table 2.5.3. Normative ice wall thickness be for a height of 10 m above the ground

2.5.47. In the absence of observational data for sections of overhead lines passing through dams and dams of hydraulic structures, near cooling ponds, cooling towers, spray pools in areas with a lower temperature above minus 45 ° C, I standard ice wall thickness be should be taken 5 mm more than for adjacent sections of overhead lines, and for areas with the lowest temperature of minus 45º and below - by 10 mm.

2.5.48. The normative wind load in ice conditions on the wire (cable) is determined according to 2.5.52, taking into account the conditional ice wall thickness bу, which is adopted according to the regional zoning of wind loads in ice conditions or is calculated according to the guidelines for calculating climatic loads. In the absence of regional maps and observational data, bu = be.

2.5.49. The thickness of the ice wall (be, bу) on the wires of the overhead line is determined at the height of the reduced center of gravity of all wires, on the cables - at the height of the center of gravity of the cables. The height of the reduced center of gravity of wires and cables is determined in accordance with 2.5.44.

The wall thickness of ice on wires (cables) at a height of their reduced center of gravity of more than 25 m is determined by multiplying its value by the coefficients Ki and Kd, taken according to Table. 2.5.4. In this case, the initial ice wall thickness (for a height of 10 m and a diameter of 10 mm) should be taken without the increase provided for in 2.5.47. The obtained values ​​of the ice wall thickness are rounded up to 1 mm.

When the height of the reduced center of gravity of the wires or cables is up to 25 m, no corrections for the thickness of the ice wall on the wires and cables, depending on the height and diameter of the wires and cables, are introduced.

Table 2.5.4. Coefficients Ki and Kd taking into account changes in ice wall thickness*

* For intermediate heights and diameters, the values ​​of the coefficients Ki and Kd are determined by linear interpolation.

2.5.50. For sections of overhead lines constructed in mountainous areas along orographically protected winding and narrow sloping valleys and gorges, regardless of the height of the area above sea level, it is recommended to take the normative thickness of the ice wall be no more than 15 mm. In this case, the Ki coefficient should not be taken into account.

2.5.51. Air temperatures - the average annual, the lowest, which is taken as the absolute minimum, the highest, which is taken as the absolute maximum - are determined by building codes and regulations and from observational data, rounded to multiples of five.

The air temperature at standard wind pressure W0 should be taken equal to minus 5 ºС, except for areas with an average annual temperature of minus 5 ºС and below, for which it should be taken equal to minus 10 ºС.

The air temperature during icy conditions for areas with elevations up to 1000 m above sea level should be taken equal to minus 5 ºС, while for areas with an average annual temperature of minus 5 ºС and lower, the air temperature during icy conditions should be taken equal to minus 10 ºС. For mountainous areas with altitudes above 1000 m and up to 2000 m, the temperature should be taken equal to minus 10 ºС, more than 2000 m - minus 15 ºС. In areas where the temperature is below minus 15 ºС during ice, it should be taken according to the actual data.

2.5.52. The normative wind load on wires and cables PHW, N, acting perpendicular to the wire (cable), for each calculated condition is determined by the formula

P^H_W = a_wK_lK_wC_xWFsin²φ

where αw is the coefficient taking into account the non-uniformity of wind pressure along the overhead line span, taken equal to:

Intermediate values ​​of αw are determined by linear interpolation;

Kl - coefficient taking into account the influence of the span length on the wind load, equal to 1,2 with a span length of up to 50 m, 1,1 - at 100 m, 1,05 - at 150 m, 1,0 - at 250 m or more (intermediate Kl values ​​are determined by interpolation);

Kw - coefficient taking into account the change in wind pressure along the height depending on the type of terrain, determined from Table. 2.5.2;

Cx - coefficient of drag, taken equal to: 1,1 - for wires and cables free of ice, with a diameter of 20 mm or more; 1,2 - for all wires and cables covered with ice, and for all wires and cables free of ice, with a diameter of less than 20 mm;

W - standard wind pressure, Pa, in the considered mode:

W = W0 - determined according to the table. 2.5.1 depending on the wind region;

W = Wg - determined according to 2.5.43;

F is the area of ​​the longitudinal diametrical section of the wire, m2 (with ice, taking into account the conditional thickness of the ice wall bу);

φ is the angle between the wind direction and the axis of the overhead line.

The area of ​​the longitudinal diametrical section of the wire (cable) F is determined by the formula, m2

F = (d + 2K_iK_db_у)l 10^-3

where d - wire diameter, mm;

Ki and Kd - coefficients that take into account the change in the thickness of the ice wall along the height and depending on the diameter of the wire and are determined from Table. 2.5.4;

bu - conditional ice wall thickness, mm, is taken in accordance with 2.5.48;

l is the length of the wind span, m.

2.5.53. Normative linear ice load per 1 m of wire and cable PHG is determined by the formula, N/m

P^H_Г = πK_iK_d b_э(d+K_iK_db_э)ρg 10^-3

where Ki, Kd are coefficients that take into account the change in the thickness of the ice wall along the height and depending on the diameter of the wire and are taken according to Table. 2.5.4;

be - ice wall thickness, mm, according to 2.5.46;

d - wire diameter, mm;

ρ - ice density, taken equal to 0,9 g/cm3;

g is the free fall acceleration, assumed to be 9,8 m/s2.

2.5.54. The design wind load on the wires (cables) PWp in the mechanical calculation of wires and cables according to the method of permissible stresses is determined by the formula, N

P_Wп = P^H_Wγ_nwγ_pγ_f

where PHW is the standard wind load according to 2.5.52;

γnw - liability reliability factor taken equal to: 1,0 - for overhead lines up to 220 kV; 1,1 - for 330-750 kV overhead lines and overhead lines constructed on double-circuit and multi-circuit supports, regardless of voltage, as well as for individual especially critical single-circuit overhead lines up to 220 kV, if justified;

γp - regional coefficient, taken from 1 to 1,3. The value of the coefficient is taken on the basis of operating experience and is indicated in the assignment for the design of overhead lines;

γf - safety factor for wind load, equal to 1,1.

2.5.55. Estimated linear ice load per 1 m of wire (cable) Pg.p in the mechanical calculation of wires and cables according to the method of permissible stresses is determined by the formula, N/m

P_g.p. = P^H_Гγ_nwγ_pγ_fγ_d

where PHG - normative linear ice load, taken according to 2.5.53;

γnw - liability reliability factor taken equal to: 1,0 - for overhead lines up to 220 kV; 1,3 - for 330-750 kV overhead lines and overhead lines constructed on double-circuit and multi-circuit supports, regardless of voltage, as well as for individual especially critical single-circuit overhead lines up to 220 kV, if justified;

γp - regional coefficient, taken equal to from 1 to 1,5. The value of the coefficient is taken on the basis of operating experience and is indicated in the assignment for the design of overhead lines;

γf - reliability coefficient for ice load, equal to 1,3 for areas of ice I and II; 1,6 - for areas on ice III and above;

γd - coefficient of working conditions, equal to 0,5.

2.5.56. When calculating the approximations of current-carrying parts to structures, plantings and support elements, the calculated wind load on wires (cables) is determined according to 2.5.54.

2.5.57. When determining the distances from wires to the ground surface and to intersected objects and plantings, the calculated linear ice load on wires is taken according to 2.5.55.

2.5.58. The normative wind load on the support structure is defined as the sum of the average and pulsation components.

2.5.59. The normative average component of the wind load on the support Qns is determined by the formula, N

Q^н_с =K_wWC_xА

where Kw - is taken according to 2.5.44;

W - accepted according to 2.5.52;

Cx - aerodynamic coefficient, determined depending on the type of structure, in accordance with building codes and regulations;

A - projection area limited by the contour of the structure, its part or element from the windward side onto a plane perpendicular to the wind flow, calculated from the outer dimension, m2.

For pole structures made of rolled steel covered with ice, when determining A, icing of the structure with ice wall thickness bу at a pole height of more than 50 m is taken into account, as well as for regions with ice V and above, regardless of the height of the poles.

For reinforced concrete and wooden poles, as well as steel poles with pipe elements, icing of structures is not taken into account when determining the load Qns.

2.5.60. The normative pulsating component of the wind load Qnp for supports up to 50 m high is taken:

for free-standing single-column steel poles:

Q^н_п = 0,5Q^н_с;

for free-standing portal steel supports:

Q^н_п = 0,6Q^н_с;

for free-standing reinforced concrete supports (gantry and single-column) on centrifuged racks:

Q^н_п = 0,5Q^н_с;

for free-standing single-column reinforced concrete poles of overhead lines up to 35 kV:

Q^н_п = 0,8Q^н_с;

for steel and reinforced concrete supports with braces when hinged to foundations:

Q^н_п = 0,6Q^н_с.

The normative value of the pulsating component of the wind load for free-standing supports with a height of more than 50 m, as well as for other types of supports not listed above, regardless of their height, is determined in accordance with building codes and rules for loads and impacts.

In the calculations of wooden supports, the pulsating component of the wind load is not taken into account.

2.5.61. The normative ice load on the structures of metal supports Jn is determined by the formula, N

J^н =K_ib_эμ_гρgA₀

where Ki, be, ρ, g - are taken according to 2.5.53;

μg - coefficient taking into account the ratio of the surface area of ​​the element subject to icing to the total surface of the element and is taken equal to: 0,6 - for areas on ice up to IV with a height of supports more than 50 m and for areas on ice V and above, regardless of the height of the supports ;

A0 is the total surface area of ​​the element, m2.

For ice areas up to IV, with a support height of less than 50 m, ice deposits on the supports are not taken into account.

For reinforced concrete and wooden poles, as well as steel poles with pipe elements, ice deposits are not taken into account.

Icing deposits on traverses are recommended to be determined according to the above formula with the replacement of the total surface area of ​​the element by the area of ​​the horizontal projection of the traverse console.

2.5.62. The design wind load on the wires (cables), perceived by the supports Pw0, is determined by the formula, N

P_w0 = P^н_wγ_nwγ_pγ_f

where Pnw - standard wind load according to 2.5.52;

γnw, γp - taken according to 2.5.54;

γf - safety factor for wind load, equal for wires (cables) covered with ice and free from ice:

1,3 - when calculating for the first group of limit states;

1,1 - when calculating for the second group of limit states.

2.5.63. The design wind load on the support structure Q, N, is determined by the formula

Q = (Q^н_с + Q^н_п) γ_nwγ_pγ_f

where Qns is the normative average component of the wind load, adopted according to 2.5.59;

Qnp - standard pulsation component of the wind load, taken according to 2.5.60;

γnw, γp are accepted according to 2.5.54;

γf - safety factor for wind load, equal to:

1,3 - when calculating for the first group of limit states;

1,1 - when calculating for the second group of limit states.

2.5.64. The design wind load on the string of insulators Pi, N, is determined by the formula

P_и = c_nwγ_p K_w C_x F_и W₀γ_f

where γnw, γp are taken according to 2.5.54;

Kw - accepted according to 2.5.44;

Cx - drag coefficient of the insulator circuit, taken equal to 1,2;

γf - safety factor for wind load, equal to 1,3;

W0 - standard wind pressure (see 2.5.41);

Fi - area of ​​the diametrical section of the insulator string chain, m2, is determined by the formula

F_и = 0,7D_иH_иnN 10^-6

where Di is the diameter of the plate of insulators, mm;

Hi - building height of the insulator, mm;

n is the number of insulators in the circuit;

N is the number of insulator circuits in the string.

2.5.65. Estimated linear ice load per 1 m of wire (cable) Pr.o, N/m, perceived by the supports, is determined by the formula

Р_g.o = P^н_гγ_pgγ_pγ_fγ_d

where Png - normative linear ice load, taken according to 2.5.53;

γпг, γp - are accepted according to 2.5.55;

γf - reliability coefficient for ice load in the calculation for the first and second groups of limit states, is taken equal to 1,3 for areas of ice I and II; 1,6 for ice regions III and above;

γd - coefficient of working conditions, equal to:

1,0 - when calculating for the first group of limit states;

0,5 - when calculating for the second group of limit states.

2.5.66. The ice load from wires and cables applied to their attachment points on the supports is determined by multiplying the corresponding linear ice load (2.5.53, 2.5.55, 2.5.65) by the length of the weight span.

2.5.67. The design ice load on the support structures J, N, is determined by the formula

J=J^нγ_pgγ_pγ_fγ_d

where Jn - normative ice load, accepted according to 2.5.61;

γпг, γp - are accepted according to 2.5.55;

γf, γd are accepted according to 2.5.65.

2.5.68. In ice regions III and above, icing of insulator strings is taken into account by increasing their weight by 50%. Icing is not taken into account in areas with ice II and less.

The impact of wind pressure on the strings of insulators during ice is not taken into account.

2.5.69. The calculated load on the overhead line supports from the weight of wires, cables, strings of insulators, structures of supports for the first and second groups of limit states is determined in the calculations as the product of the standard load by the safety factor for the weight load γf, taken equal to 1,05 for wires, cables and strings of insulators , for support structures - with indications of building codes and rules for loads and impacts.

2.5.70. The normative loads on the overhead line supports from the tension of wires and cables are determined at the calculated wind and ice loads according to 2.5.54 and 2.5.55.

The design horizontal load from the tension of wires and cables, Tmax, free from ice or covered with ice, when calculating the structures of supports, foundations and bases, is determined as the product of the standard load from the tension of wires and cables and the safety factor for the load from tension γf, equal to:

• 1,3 - when calculating for the first group of limit states;
• 1,0 - when calculating for the second group of limit states.

2.5.71. Calculation of overhead lines for normal operation must be carried out for a combination of the following conditions:

1. The highest temperature is t+, there is no wind and ice.

2. The lowest temperature t-, wind and ice are absent.

3. Average annual temperature tsg, wind and ice are absent.

4. Wires and cables are covered with ice according to 2.5.55, the temperature during ice is according to 2.5.51, there is no wind.

5. Wind as of 2.5.54, temperature at W0 as of 2.5.51, no ice.

6. Wires and cables are covered with ice according to 2.5.55, wind during ice on wires and cables according to 2.5.54, temperature during ice according to 2.5.51.

7. Estimated load from wire tension according to 2.5.70.

2.5.72. Calculation of overhead lines for emergency operation must be carried out for a combination of the following conditions:

1. Average annual temperature tcg, wind and ice are absent.

2. The lowest temperature t-, wind and ice are absent.

3. Wires and cables are covered with ice according to 2.5.55, the temperature during ice is according to 2.5.51, there is no wind.

4. Estimated load from wire tension according to 2.5.70.

2.5.73. When calculating the approach of current-carrying parts to tree crowns, elements of overhead lines supports and structures, the following combinations of climatic conditions must be taken:

1) at operating voltage: calculated wind load according to 2.5.54, temperature at W0 according to 2.5.51, no ice;

2) during lightning and internal overvoltages: temperature +15 ºС, wind pressure equal to 0,06 W0, but not less than 50 Pa;

3) to ensure safe climbing to the support in the presence of voltage on the line: for overhead lines of 500 kV and below - the temperature is minus 15 ºС, there is no ice and wind; for 750 kV overhead lines - temperature is minus 15 ºС, wind pressure is 50 Pa, there is no ice.

When calculating approximations, the angle of deviation of the supporting string of insulators from the vertical is determined by the formula

tan γ = (K_gR + R_и± R_о)/(G_etc. + 0,5G_г)

where P is the calculated wind load on the phase wires, directed across the axis of the overhead line (or along the bisector of the angle of rotation of the overhead line), N;

Kg - coefficient of inertia of the system "garland - wire in the span", with deviations under wind pressure is taken equal to:

Intermediate values ​​are determined by linear interpolation;

Ro - the horizontal component of the tension of the wires on the supporting garland of the intermediate-angle support (taken with a plus sign if its direction coincides with the direction of the wind, and with a minus sign if it is directed to the windward side), N;

Gpr - design load from the weight of the wire, perceived by the garland of insulators, N;

Gg - design load from the weight of the string of insulators, N;

Pi - design wind load on insulator strings, N, taken according to 2.5.64.

2.5.74. Checking the overhead line supports according to the installation conditions must be carried out according to the first group of limit states for design loads under the following climatic conditions: temperature minus 15 ºС, wind pressure at a height of 15 m above the ground 50 Pa, no ice.

See other articles Section Rules for the installation of electrical installations (PUE).

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