Conductors with voltage up to 35 kV. General requirements

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

Conductors with voltage up to 35 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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2.2.5. In networks of 6-35 kV industrial enterprises for the transmission in one direction of power more than 15-20 MVA at a voltage of 6 kV, more than 25-35 MVA at a voltage of 10 kV and more than 35 MVA at a voltage of 35 kV should be used, as a rule, flexible or rigid conductors are predominantly in front of lines made of a large number of cables laid in parallel.

Open laying of conductors should be used in all cases when it is possible under the terms of the general layout of the power supply facility and the environment.

2.2.6. In places where the air contains chemically active substances that have a destructive effect on current-carrying parts, supporting structures and insulators, current conductors must be of an appropriate design or other measures must be taken to protect them from these effects.

2.2.7. Calculation and selection of conductors, insulators, fittings, structures and devices of current conductors should be carried out both according to normal operating conditions (compliance with operating voltage and current), and according to operating conditions in case of short circuits (see Ch. 1.4).

2.2.8. Current-carrying parts must be marked and colored in accordance with the requirements of Ch. 1.1.

2.2.9. The current-carrying parts of conductors should be made, as a rule, from aluminum, steel-aluminum and steel wires, pipes and tires of a profile section.

2.2.10. For grounding of current-carrying parts of conductors, stationary grounding knives or portable grounding devices must be provided in accordance with the requirements of 4.2.25 (see also 2.2.30, clause 3).

2.2.11. Mechanical loads on conductors, as well as design ambient temperatures should be determined in accordance with the requirements given in 4.2.46-4.2.49.

2.2.12. The layout and design of current conductors should provide for the possibility of convenient and safe installation and repair work.

2.2.13. Conductors above 1 kV in the open air must be protected from lightning surges in accordance with the requirements of 4.2.167 and 4.2.168.

2.2.14. In AC conductors with a symmetrical load at a current of 1 kA or more, it is recommended, and at a current of 1,6 kA or more, measures should be taken to reduce power losses in busbar supports, fittings and structures from the effects of a magnetic field.

At currents of 2,5 kA or more, measures should also be taken to reduce and equalize the inductive resistance (for example, the arrangement of strips in packages on the sides of the square, the use of coupled phases, profile tires, round and square hollow pipes, transposition). For extended flexible conductors, it is also recommended to use intraphase transpositions, the number of which should be determined by calculation, depending on the length of the current conductor.

With unbalanced loads, the value of the current at which it is necessary to provide measures to reduce the loss of electricity from the effects of a magnetic field must be determined in each individual case by calculation.

2.2.15. In cases where temperature changes, vibration of transformers, uneven settlement of a building, etc. can lead to dangerous mechanical stresses in conductors, insulators or other elements of conductors, measures should be taken to eliminate these stresses (compensators or similar devices). On rigid conductors, compensators should also be installed at the intersections with temperature and sedimentary seams of buildings and structures.

2.2.16. Permanent connections of conductors are recommended to be made by welding. To connect branches with flexible conductors, the use of pressed clamps is allowed.

Connections of conductors of different materials must be made in such a way that corrosion of the contact surfaces is prevented.

2.2.17. The choice of cross-section of conductors above 1 kV for long-term permissible current in normal and post-emergency modes should be made taking into account the expected increase in loads, but not more than 25-30% higher than the calculated ones.

2.2.18. For conductors made using bare wires, long-term permissible currents should be determined according to Ch. 1.3 using a coefficient of 0,8 in the absence of intraphase transposition of wires, 0,98 in the presence of intraphase transposition of wires.

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

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