Overhead power lines with voltage up to 1 kV. Wires. Linear reinforcement

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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 up to 1 kV. Wires. Linear reinforcement

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

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2.4.13. As a rule, self-supporting insulated wires (SIP) should be used on overhead lines.

The SIP must be classified as protected and have insulation made of fire-resistant, light-stabilized synthetic material that is resistant to ultraviolet radiation and ozone.

2.4.14. According to the conditions of mechanical strength, wires with the minimum cross-sections specified in Tables 2.4.1 and 2.4.2 should be used on the main lines of the overhead line, on the linear branch from the overhead line and on the branches to the inputs.

Table 2.4.1. Minimum permissible cross-sections of insulated wires

Normative ice wall thickness b_э, mm	Cross-section of the carrier core, mm², on the VLI main line, on a linear branch from the VLI	Cross-section of the core on the branches from the VLI and from the VL to the inputs, mm²
10	35 (25)^*	16
15 and more	50 (25)^*	16

* The cross-section of the core of self-supporting insulated wires, twisted into a bundle, without a supporting wire, is given in parentheses.

Table 2.4.2. Minimum permissible cross-sections of bare and insulated wires

Normative ice wall thickness b_э, mm	Wire material	Wire cross-section on the main and linear branch, mm
10	Aluminum (A), non heat treated aluminum alloy (AH)	25
	Steel-aluminum (AS), heat-treated aluminum alloy (AJ)	25
	Copper (M)	16
15 and more	A, AN	35
	AS, AZ	25
	М	16

2.4.15. When constructing overhead lines in places where operating experience has established the destruction of wires from corrosion (sea coasts, salt lakes, industrial areas and areas of saline sand), as well as in places where, based on research data, it is possible, self-supporting insulated wires with an insulated core should be used .

2.4.16. The overhead line, as a rule, should be made with wires of a constant cross-section.

The cross section of the phase wires of the HP main is recommended to be at least 50 mm2.

2.4.17. Mechanical calculation of wires must be carried out using the permissible stress method for the conditions specified in 2.5.38 - 2.5.74. In this case, the voltage in the wires should not exceed the permissible voltages given in table. 2.4.3, and the distances from the wires to the ground surface, intersecting structures and grounded elements of the supports must meet the requirements of this chapter.

The calculation uses the parameters of the wires given in Table. 2.5.8.

Table 2.4.3. Permissible mechanical stress in overhead line wires up to 1 kV

The wire	Permissible stress, % tensile strength
The wire	at maximum load and lowest temperature t_г=t_-	at an average annual temperature t_cr
SIP with a section of 25-120 mm²	40	30
Aluminum section, mm²:
25-95	35	30
120	40	30
From heat-treated and non-heat-treated aluminum alloy with cross-section, mm²:
25-95	40	30
120	45	30
Steel-aluminum section, mm²:
25	35	30
35-95	40	30

2.4.18. All types of mechanical loads and impacts on a self-supporting insulated wire with a load-bearing wire must be absorbed by this core, and on a self-supporting insulated wire without a support wire - all cores of the twisted bundle must be absorbed.

2.4.19. The span length of the branch from the overhead line to the input must be determined by calculation depending on the strength of the support on which the branch is made, the height of the suspension of the branch wires on the support and at the input, the number and cross-section of the cores of the branch wires.

When distances from the overhead line main to the building exceed the calculated values of the branch span, the required number of additional supports is installed.

2.4.20. The selection of the cross-section of current-carrying conductors according to the long-term permissible current should be carried out taking into account the requirements of Chapter. 1.3.

The cross-section of current-carrying conductors must be checked for heating conditions during short circuits (short circuits) and for thermal resistance.

2.4.21. Fastening, connecting SIP and connecting to SIP should be done as follows:

1) fastening the VLI main wire to intermediate and corner intermediate supports - using supporting clamps;

2) fastening of the VLI main wire on anchor-type supports, as well as end fastening of the branch wires on the VLI support and at the input - using tension clamps;

3) connection of the VLI wire in the span - using special connecting clamps; in the loops of anchor-type supports, it is allowed to connect an uninsulated support wire using a die clamp. Connecting clamps intended for connecting the supporting wire in a span must have a mechanical strength of at least 90% of the breaking force of the wire;

4) connection of phase wires of the VLI main line - using connecting clamps having an insulating coating or a protective insulating shell;

5) connection of wires in the span of a branch to the input is not allowed;

6) connection of grounding conductors - using flat clamps;

7) branch clamps should be used in the following cases:

branches from phase conductors, with the exception of self-supporting insulated wires with all supporting conductors of the bundle;

branches from the carrier core.

2.4.22. Fastening of support and tension clamps to overhead line supports, walls of buildings and structures should be done using hooks and brackets.

2.4.23. The design forces in supporting and tension clamps, fastening units and brackets in normal mode should not exceed 40% of their mechanical breaking load.

2.4.24. Connections of wires in overhead line spans should be made using connecting clamps that provide mechanical strength of at least 90% of the breaking force of the wire.

In one span of overhead lines, no more than one connection is allowed for each wire.

In the spans of intersection of overhead lines with engineering structures, the connection of overhead line wires is not allowed.

The connection of wires in the loops of anchor supports must be made using clamps or welding.

Wires of different brands or sections should be connected only in the loops of anchor supports.

2.4.25. It is recommended to fasten bare wires to insulators and insulating cross-arms on overhead line supports, with the exception of supports for intersections, in a single manner.

Fastening of bare wires to pin insulators on intermediate supports should be done, as a rule, on the neck of the insulator on its inner side in relation to the support post.

2.4.26. Hooks and pins must be calculated in normal operation of overhead lines using the destructive load method.

In this case, the forces shall not exceed the values given in 2.5.101.

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

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