Safety technology of the hottest overhead line

Overhead line safety technology

1. Insulated conductors must be used for overhead lines

2. Overhead lines must be erected on special poles. It is strictly prohibited to erect on trees, scaffolds and other facilities

3. The selection of overhead line conductor section shall meet the following requirements:

1) the calculated load current in the conductor shall not be greater than its long-term continuous load allowable carrying capacity

2) the voltage offset at the end of the line shall not be greater than 5% of its rated voltage

3) the cross section of N line and PE line of three-phase four wire system line is not less than 50% of the phase line cross section, and the zero line cross section of single-phase line is the same as the phase line cross section

4) according to the mechanical strength requirements, the cross section of insulated copper wire is not less than 10mm2, and the cross section of insulated aluminum wire is not less than 16mm2

5) within the span of crossing railways, highways, rivers and power lines, the cross section of insulated copper wire shall not be less than 16mm2. The section of insulated aluminum wire shall not be less than 25mm2

4. Within a span of overhead line, the number of joints of each layer of conductor shall not exceed 50% of the number of conductors in that layer, and one conductor shall have only one joint

overhead lines shall not have joints within the span of crossing railways, highways, rivers and power lines

5. The phase sequence arrangement of overhead lines shall comply with the following provisions:

1) when the power and lighting lines are erected on the same cross arm, the conductor phase sequence arrangement is: facing the load, L1, N, L2, L3, PE from the left

2) when the power and lighting lines are respectively erected on the cross arm on the second floor, the conductor phase enters the painting preparation state when it needs to be painted. The sequence is: the upper cross arm faces the load and is L1, L2, L3 from the left; The lower cross arm faces the load and is L1 (L2, L3), N, PE from the left

6. The span of overhead lines shall not be greater than 35m

7. The distance between wires of overhead lines shall not be less than 0.3m, and the distance between two conductors close to the pole shall not be less than 0.5m

8. The minimum vertical distance between overhead line cross arms shall not be less than table 7.1 Values listed; The cross arm should be made of angle steel or square timber, and the low-voltage iron cross arm angle steel should be in accordance with table 7.1 Selection: the cross section of square timber cross arm shall be 80mm 80mm; The length of cross arm shall be in accordance with table 7.1 Selection

9. The distance between overhead lines and adjacent lines or fixtures shall comply with the provisions of table 7.1.9

10. Reinforced concrete poles or wooden poles should be used for the dead line. The reinforced concrete pole shall not have exposed reinforcement, cracks and distortions with a width greater than 0.4mm; The wooden pole shall not decay, and its tip diameter shall not be less than 140mm

11. The buried depth of the pole should be 1/10 of the pole length plus 0.6m, and the backfill soil should be compacted in layers. In the soft soil, it is better to increase the buried depth or adopt chuck for reinforcement

12, single cross arm and single insulator can be used for straight pole and corner pole below 15, but single cross arm and double insulator should be used when crossing the motorway; Angle poles from 15 to 45 shall adopt double cross arms and double insulators; Cross arms shall be used for corner rods above 45

13. The insulator of overhead line shall be selected according to the following principles:

1) the straight pole adopts pin insulator

2) the tension rod adopts the provisions of butterfly insulation "guidance"

14. At least three d4.0mm galvanized steel wires should be used for the stay wire of the pole. The included angle between the stay wire and the pole should be between 30 and 45. The buried depth of stay wire shall not be less than 1m. If the pole stay wire passes between conductors, stay insulator shall be installed 2.5m above the ground

5. The axle split control multifunctional experimental machine has a strong expansion capacity

15. When the stay wire cannot be installed due to the limitation of the surface environment, the stay rod can be used instead of the stay wire. The buried depth of the stay rod shall not be less than 0.8m, and its bottom shall be padded with chassis or stones. The included angle between the pole and the pole should be 30

16. There shall be no joint in the span of the household line, and the height from the ground at the incoming line shall not be less than 2.5m. The minimum cross section of the connecting line shall comply with table 7.1 regulations. The distance between the connecting lines and the hand paste process, which accounts for the largest proportion in the production of composite materials, and the adjacent lines should comply with table 7.1 Requirements

17. Overhead lines must have short-circuit protection

when a fuse is used for short-circuit protection, its melt rated current should not be greater than 1.5 times the allowable current carrying capacity of the long-term continuous load of the exposed insulated conductor

when the circuit breaker is used for short-circuit protection, the setting value of the instantaneous overcurrent release tripping current should be less than the single-phase short-circuit current at the end of the line

18. Overhead lines must have overload protection

when fuse or circuit breaker is used for overload protection, the allowable carrying capacity of long-term continuous load of insulated conductor shall not be less than 1.25 times of the rated current of fuse melt or the setting value of tripping current of long-time-delay overcurrent release of circuit breaker