Overhead power lines with voltage above 1 kV. Wires and lightning protection cables

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 2. Sewerage of electricity

Overhead power lines with voltage above 1 kV. Wires and lightning protection cables

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

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2.5.75. Overhead lines can be made with one or more wires in phase, in the second case the phase is called split.

The split phase wires can be insulated from each other.

The diameter of the wires, their cross section and the number in the phase, as well as the distance between the wires of the split phase are determined by calculation.

2.5.76. On the wires of the split phase in the spans and loops of the anchor supports, spacers must be installed. The distances between spacers or groups of spacers installed in a span on a split phase of two or three wires should not exceed 60 m, and when passing overhead lines through type A terrain (2.5.6) - 40 m. The distances between spacers or groups of spacers installed in span in a split phase of four or more wires, they should not exceed 40 m. When passing overhead lines through type C terrain, these distances can be increased to 60 m.

2.5.77. Multi-wire wires and cables should be used on overhead lines. The minimum allowable wire cross-sections are given in Table. 2.5.5.

Table 2.5.5. Minimum allowable cross-sections of wires according to the conditions of mechanical strength¹⁾

Overhead line characteristic	Wire section, mm²
Overhead line characteristic	aluminum and non-heat-treated aluminum alloy	made of heat treated aluminum alloy	steel-aluminum	steel
Overhead lines without crossings in areas on ice:
to II	70	50	35/6,2	35
in III-IV	95	50	50/8	35
in V or more	-	-	70/11	35
Crossings of overhead lines with navigable rivers and engineering structures in areas on ice:
to II	70	50	50/8	35
in III-IV	95	70	50/8	50
in V or more	-	-	70/11	50
Overhead lines constructed on double-circuit or multi-circuit supports:
up to 20 kV	-	-	70/11	-
35 kV and above	-	-	120/19	-

1. In spans of intersections with highways, trolleybus and tram lines, non-public railways, it is allowed to use wires of the same cross sections as on overhead lines without intersections.

2. In areas where the use of wires with anti-corrosion protection is required, the minimum allowable cross-sections of wires are taken to be the same as the sections of the corresponding grades without anti-corrosion protection.

2.5.78. To reduce power losses due to remagnetization of steel cores in steel-aluminum wires and in wires made of heat-treated aluminum alloy with a steel core, it is recommended to use wires with an even number of layers of aluminum wires.

2.5.79. As lightning protection cables, as a rule, steel ropes made of galvanized wire for especially harsh aggressive working conditions (OZH) and, according to the laying method, non-twisting (H) should be used with a cross section of at least:

35 mm2 - on 35 kV overhead lines without intersections;

35 mm2 - on 35 kV overhead lines in spans of intersections with public and electrified railways in areas on ice I-II;

50 mm2 - in other areas and on overhead lines built on double-circuit and multi-circuit supports;

50 mm2 - on 110-150 kV overhead lines;

70 mm2 - for overhead lines 220 kV and above.

Steel-aluminum wires or wires made of heat-treated aluminum alloy with a steel core are recommended to use as a lightning protection cable:

1) at especially important crossings through engineering structures (electrified railways, highways of category IA (2.5.256), navigable water barriers, etc.);

2) on sections of overhead lines passing in areas with increased atmospheric pollution (industrial zones with high chemical activity of entrainment, zones of intensive agriculture with saline soils and water bodies, sea coasts, etc.), as well as passing through populated and hard-to-reach areas;

3) on overhead lines with high currents of a single-phase short circuit according to the conditions of thermal stability and to reduce the influence of overhead lines on communication lines.

At the same time, for overhead lines constructed on double-circuit or multi-circuit supports, regardless of voltage, the total cross section of the aluminum (or aluminum alloy) and steel parts of the cable must be at least 120 mm2.

When using lightning protection cables for organizing multichannel high-frequency communication systems, if necessary, single or double cables isolated from each other or cables with an integrated optical communication cable (2.5.178 - 2.5.200) are used. Between the components of the double cable in the spans and loops of the anchor supports, distance insulating struts must be installed.

Distances between spacers in the span should not exceed 40 m.

2.5.80. For steel-aluminum wires with a cross-sectional area of aluminum wires A and steel wires C, the following applications are recommended:

1) areas with an ice wall thickness of 25 mm or less:

A up to 185 mm2 - with an A / C ratio of 6,0 to 6,25;
And from 240 mm2 and more - with an A / C ratio of more than 7,71;

2) areas with an ice wall thickness of more than 25 mm:

A up to 95 mm2 - at a ratio of A / C 6,0;
A from 120 to 400 mm2 - with an A / C ratio of 4,29 to 4,39;
A from 450 mm2 and more - with an A / C ratio of 7,71 to 8,04;

3) at large crossings with spans of more than 700 m - the A / C ratio is more than 1,46.

The choice of brands of wires from other materials is justified by calculations.

During the construction of overhead lines in places where operating experience has established the destruction of wires from corrosion (the coasts of the seas, salt lakes, industrial areas and areas of saline sands, adjacent areas with an air atmosphere of type II and III, as well as in places where, based on survey data such damage is possible, wires should be used that, in accordance with state standards and technical specifications, are designed for the specified conditions.

On flat terrain, in the absence of operational data, the width of the coastal strip to which the specified requirement applies should be taken equal to 5 km, and the strip from chemical enterprises - 1,5 km.

2.5.81. When choosing the design of the overhead line, the number of components and the cross-sectional area of the phase wires and their location, it is necessary to limit the electric field strength on the surface of the wires to levels that are permissible for the corona and radio interference (see Chap. 1.3).

According to the conditions of the corona and radio interference at elevations up to 1 m above sea level, it is recommended to use wires with a diameter of at least those indicated in Table 000 on overhead lines. 2.5.6.

At elevations of more than 1000 m above sea level for overhead lines of 500 kV and above, it is recommended to consider the feasibility of changing the design of the middle phase compared to the extreme phases.

2.5.82. The section of the lightning protection cable, selected by mechanical calculation, must be checked for thermal resistance in accordance with the instructions in Ch. 1.4 and 2.5.193, 2.5.195, 2.5.196.

Table 2.5.6. The minimum diameter of the wires of the overhead line under the conditions of the corona and radio interference, mm¹⁾

VL voltage, kV	Phase with wires
	solitary	two or more
110	11,4 (AC 70/11)	-
150	15,2 (AC 120/19)	-
220	21,6 (AC 240/32)	-
	24,0 (AC 300/39)	-
330	33,2 (AC 600/72)	2 x 21,6 (2 x AC 240/32)
		3 x 15,2 (3 x AC 120/19)
		3 x 17,1 (3 x AC 150/24)
500	-	2 x 36,2 (2 x AC 700/86)
		3 x 24,0 (3 x AC 300/39)
		4 x 18,8 (4 x AC 185/29)
750	-	4 x 29,1 (4 x AC 400/93)
		5 × 21,6 (5 × AC 240/32)

1. For 220 kV overhead lines, the minimum wire diameter of 21,6 mm refers to the horizontal arrangement of the phases, and in other cases it is permissible with a check for radio interference.

2. For 330 kV overhead lines, the minimum wire diameter of 15,2 mm (three wires per phase) refers to single-circuit supports.

2.5.83. Wires and cables must be calculated for the design loads of normal, emergency and installation modes of overhead lines for combinations of conditions specified in 2.5.71 - 2.5.74.

In this case, the voltages in the wires (cables) should not exceed the allowable values given in Table. 2.5.7.

Specified in table. 2.5.7 voltages should be referred to that point of the wire along the span at which the voltage is greatest. It is allowed to take the specified voltages for the lowest point of the wire, provided that the voltage at the suspension points is not more than 5%.

Table 2.5.7. Permissible mechanical stress in wires and cables of overhead lines with voltage above 1 kV

Wires and cables	Permissible stress, % tensile strength		Permissible stress, N/mm²
Wires and cables	at highest load and lowest temperature	at an average annual temperature	at highest load and lowest temperature	at an average annual temperature
Aluminum with a cross-sectional area, mm²:
70-95	35	30	56	48
120-240	40	30	64	51
300-750	45	30	72	51
From non-heat-treated aluminum alloy cross-sectional area, mm²:
50-95	40	30	83	62
120-185	45	30	94	62
From heat-treated aluminum alloy cross-sectional area, mm²:
50-95	40	30	114	85
120-185	45	30	128	85
Steel-aluminum cross-sectional area of the aluminum part of the wire, mm²:
400 and 500 at A / C 20,27 and 18,87	45	30	104	69
400, 500 and 1000 at A / C 17,91, 18,08 and 17,85	45	30	96	64
330 at A/C 11,51	45	30	117	78
150-800 at A / C from 7,8 to 8,04	45	30	126	84
35-95 at A / C from 5,99 to 6,02	40	30	120	90
185 and more with A / C from 6,14 to 6,28	45	30	135	90
120 and more with A / C from 4,29 to 4,38	45	30	153	102
500 at A/C 2,43	45	30	205	137
185, 300 and 500 at A/C 1,46	45	30	254	169
70 at A/C 0,95	45	30	272	204
95 at A/C 0,65	40	30	308	231
Heat treated aluminum alloy with steel core aluminum alloy cross-sectional area, mm²:
500 at A/C 1,46	45	30	292	195
70 at A/C 1,71	45	30	279	186
steel wires	50	35	310	216
steel ropes	50	35	According to standards and specifications
Protected wires	40	30	114	85

2.5.84. The calculation of mounting stresses and sag of wires (cables) must be carried out taking into account residual deformations (extraction).

In mechanical calculations of wires (cables), the physical and mechanical characteristics given in Table. 2.5.8.

Table 2.5.8. Physical and mechanical characteristics of wires and cables

Wires and cables	Modulus of elasticity, 10⁴ N / mm²	Temperature coefficient of linear elongation, 10^-6 town^-1	*Tensile strength δ_р^, N/mm², wire and cable in general**
aluminum	6,30	23,0	16
Steel-aluminum with a ratio of cross-sectional areas A / C:
20,27	7,04	21,5	210
16,87-17,82	7,04	21,2	220
11,51	7,45	21,0	240
8,04-7,67	7,70	19,8	270
6,28-5,99	8,25	19,2	290
4,36-4,28	8,90	18,3	340
2,43	10,3	16,8	460
1,46	11,4	15,5	565
0,95	13,4	14,5	690
0,65	13,4	14,5	780
Made from non-heat treated aluminum alloy	6,3	23,0	208
Made of heat treated aluminum alloy	6,3	23,0	285
Made of heat-treated aluminum alloy with a steel core with a ratio of cross-sectional areas A / C:
1,71	11,65	15,83	620
1,46	12,0	15,5	650
steel ropes	18,5	12,0	1200^**
steel wires	20,0	12,0	620
Protected wires	6,25	23,0	294

* Tensile strength δr is determined by the ratio of the breaking force of the wire (cable) Pr, normalized by the state standard or technical conditions, to the cross-sectional area sp, δr = Pr / sp For steel-aluminum wires sp = sA + sC.

** Accepted according to relevant standards, but not less than 1200 N/mm2

2.5.85. Vibration protection should be:

single wires and cables with span lengths exceeding the values \u2.5.9b\u2.5.10bgiven in table. XNUMX, and mechanical stresses at an average annual temperature exceeding those given in Table. XNUMX;
split wires and cables from two components with span lengths exceeding 150 m and mechanical stresses exceeding those given in Table. 2.5.11;
split-phase wires of three or more components with span lengths exceeding 700 m;
VLZ wires when passing the route on type A terrain, if the voltage in the wire at an average annual temperature exceeds 40 N / mm2.

In table. 2.5.9, 2.5.10 and 2.5.11 the terrain type is taken according to 2.5.6.

With span lengths less than those indicated in Table. 2.5.9 and in type C locations, vibration protection is not required.

Vibration protection is recommended:

aluminum wires and from non-heat-treated aluminum alloy with a cross-sectional area up to 95 mm2, from heat-treated aluminum alloy and steel-aluminum wires with a cross-sectional area of the aluminum part up to 70 mm2, steel cables with a cross-sectional area up to 35 mm2 - loop-type vibration dampers (damping loops) or reinforcing spiral bars, protectors , spiral knits;
wires (cables) of a larger cross section - vibration dampers such as Stockbridge;
VLZ wires at the points of their attachment to insulators - vibration dampers of a spiral type with a polymer coating.

Vibration dampers should be installed on both sides of the span.

For overhead lines passing under special conditions (regions of the Far North, orographically unprotected exits from mountain gorges, separate spans in type C areas, etc.), vibration protection should be carried out according to a special project.

Vibration protection for large walkways is provided in accordance with 2.5.163.

Table 2.5.9. Span lengths for single wires and cables requiring vibration protection

Wires, cables	*Cross-sectional area^, mm²**	Spans with a length of more than, m, in areas such as
Wires, cables	*Cross-sectional area^, mm²**	А	В
Steel-aluminum, heat-treated aluminum alloy with and without steel core^*	35-95	80	95
	120-240	100	120
	300 and more	120	145
Aluminum and non-heat-treated aluminum alloy	50-95	60	95
	120-240	100	120
	300 and more	120	145
Steel	25 and more	120	145

* The cross-sectional areas of the aluminum part are given.

Table 2.5.10. Mechanical stresses, N/mm2, of single wires and cables at an average annual temperature tсg requiring vibration protection

Wires, cables	Terrain type
Wires, cables	А	В
Steel-aluminum grades AC at A / C:
0,65-0,95	More 70	More 85
1,46	"60	"70
4,29-4,39	"45	"55
6,0-8,05	"40	"45
11,5 and more	"35	"40
Aluminum and non-heat-treated aluminum alloy of all grades	"35	"40
Heat treated aluminum alloy with and without steel core of all grades	"40	"45
Steel of all grades	"170	"195

Table 2.5.11. Mechanical stresses, N/mm2, of split wires and cables from two components, at an average annual temperature tсg, requiring vibration protection

Wires, cables	Terrain type
Wires, cables	А	В
Steel-aluminum grades AC at A/C:
0,65-0,95	More 75	More 85
1,46	"65	"70
4,29-4,39	"50	"55
6,0-8,05	"45	"50
11,5 and more	"40	"45
Aluminum and non-heat-treated aluminum alloy of all grades	"40	"45
Heat treated aluminum alloy with and without steel core of all grades	"45	"50
Steel of all grades	"195	"215

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

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