Overhead power lines with voltage above 1 kV. General requirements

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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. General requirements

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

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2.5.8. All elements of the overhead line must comply with state standards, building codes and rules of the Russian Federation and this chapter of the Rules.

During the design, construction, reconstruction and operation of overhead lines, the requirements of the "Rules for the protection of electrical networks with voltages over 1000 V" and the current sanitary and epidemiological rules and regulations must be observed.

2.5.9. Mechanical calculation of wires and cables of overhead lines is carried out according to the method of permissible stresses, calculation of insulators and fittings - according to the method of breaking loads. For both methods, calculations are made for design loads.

The calculation of building structures of overhead lines (supports, foundations and bases) is carried out according to the method of limit states for design loads for two groups of limit states (2.5.137) in accordance with state standards and building codes and rules.

The use of other calculation methods in each individual case must be justified in the project.

2.5.10. Elements of overhead lines are calculated for combinations of loads acting in normal, emergency and installation modes.

Combinations of climatic and other factors in various modes of operation of overhead lines (the presence of wind, ice, temperature, the number of broken wires or cables, etc.) are determined in accordance with the requirements of 2.5.71 - 2.5.74, 2.5.141, 2.5.144 - 2.5.147 .XNUMX.

2.5.11. The main characteristics of loads are their normative values, which are established by these Rules, and for loads not regulated by them, in accordance with building codes and rules.

The design values of loads are determined as the product of their standard values by load safety factors γf, liability reliability γn, operating conditions γd, regional γp.

When calculating the elements of overhead lines, the calculated loads can be additionally multiplied by the combination coefficient.

The need to apply coefficients and their values are established by these Rules.

In the absence of instructions on the values of the coefficients, they are taken equal to one.

2.5.12. The normative values of loads from the weight of equipment, materials, from the tension of wires, lightning protection cables are taken on the basis of state standards or in accordance with the instructions of these Rules.

2.5.13. The main characteristic of the resistance of the material of the elements of overhead lines are:

breaking force (for wires and cables), mechanical (electromechanical) breaking load (for insulators), mechanical breaking load (for linear fittings) specified in the standards or specifications for these products;
regulatory and design resistance of the material of supports and foundations, established by the standards for the design of building structures.

2.5.14. On overhead lines of 110 kV and more with a length of more than 100 km, one complete transposition cycle must be performed to limit the asymmetry of currents and voltages.

Double-circuit overhead lines of 110 kV and above are recommended to be performed with the opposite phase sequence of the circuits (adjacent phases of different circuits must be of opposite names). The schemes of transposition of both chains are recommended to be the same.

It is allowed to increase the length of a non-transposed VL, perform incomplete transposition cycles, different lengths of segments in a cycle, and increase the number of cycles. The calculated asymmetry introduced at the same time by this overhead line, according to the conditions for ensuring the reliable operation of relay protection, should not exceed 0,5% for voltage and 2% for negative sequence current.

The step of transposition according to the condition of influence on the communication lines is not normalized.

For overhead lines with a horizontal arrangement of phases, a simplified transposition scheme is recommended (only two adjacent phases alternately change places at the place of transposition).

2.5.15. On overhead lines with a horizontal phase arrangement and two cables used for high-frequency communication, in order to reduce losses from currents in the cables in normal mode, it is recommended to cross (transpose) the cables. The number of crossings should be selected from the conditions of self-extinguishing of the arc of the accompanying current of industrial frequency during lightning flashes of spark gaps on the cable insulators.

The crossing scheme should be symmetrical with respect to each step of the phase transposition and grounding points of the cables, while the extreme sections are recommended to be taken equal to half the length of the remaining sections.

2.5.16. For overhead lines passing in areas with an ice wall thickness of 25 mm or more, as well as with frequent formations of ice or frost in combination with strong winds and in areas with frequent and intense dancing of wires, it is recommended to provide for melting ice on wires and cables.

For network enterprises with over 50% of overhead lines running in these areas, it is recommended to develop a general ice melting scheme.

When ensuring the melting of ice without interrupting the power supply to consumers, the thickness of the ice wall can be reduced by 15 mm, while the normative thickness of the ice wall must be at least 20 mm.

On overhead lines with ice melting, monitoring of ice should be organized, while it is preferable to use ice warning devices and devices for monitoring the end of ice melting.

The requirements of this paragraph do not apply to VLZ.

2.5.17. The intensity of the electrical and magnetic components of the electromagnetic field generated by overhead lines at maximum operating parameters (voltage and current) and at the absolute maximum air temperature for a populated area should not exceed the maximum allowable values established in the current sanitary and epidemiological rules and regulations.

For uninhabited and hard-to-reach areas, the air temperature at the maximum permissible electric field strength is assumed to be equal to the air temperature of the warm period with a security of 0,99.

2.5.18. Upon completion of the construction or reconstruction of the overhead line, it is necessary to perform:

earthing of lands allotted for permanent use;
reclamation of lands allotted for temporary use;
environmental protection measures aimed at minimal disturbance of natural landforms and the preservation of green spaces and the natural state of the soil;
anti-erosion measures.

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

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