Lightning protection detection requirements for offline leads

General provisions of lightning protection downline Downline is a wire used to discharge lightning into the ground, and the quality of its construction directly affects whether the lightning current can be smoothly discharged into the ground and the discharge effect.

(1) Laying position of lightning protection lead line

Lead down the layout of the general use of Ming fu, dark fu or the use of the main reinforcement or other metal components in the building laying, specially set down the building can be more vulnerable to lightning corner wall Ming fu, high architectural art requirements can be used dark fu. Metal components such as fire ladders and steel columns of buildings should be used as part of the lead down line, and all the components should be connected into electrical channels. For example, copper zinc alloy welding, fusion welding, screw or bolt connection.

(2) Requirements for the average distance between special lead lines of lightning-proof buildings

A class of lightning protection buildings, spacing should be no more than 12 meters; The second type of lightning protection buildings, spacing should be no more than 18 meters; Category III lightning-proof buildings, the spacing should be no more than 25 meters.

(3) The number and laying requirements of all kinds of lightning-proof buildings

1. At least one lead line should be set at the independent lightning rod connecting tower, the end of overhead lightning wire connecting and each pillar of overhead lightning net of a type of lightning protection building. It is advisable to use towers and pillars made of metal or welded or tied to connect steel mesh as lead down line.

2. When a class of lightning-proof buildings are lightning-proof, every 18-24 meters around the metal roof should be grounded by the lead line. For the reinforced concrete roof made of on-site casting or prefabricated components, the steel bars should be bound or welded into a closed loop, and each 18-24 meters should be grounded by the lead line.

3. The second type of lightning protection building should have no less than 2 special leads, and should be evenly and symmetrically arranged around the building and the inner courtyard, the spacing along the perimeter should not be more than 18 meters. When the span of the building is large, leading lines cannot be set in the middle of the span, leading lines should be set at both ends of the span and the spacing of other leading lines should be reduced. The average spacing of the specially set leading lines should not be more than 18 meters. When only the steel column around the building or the reinforcement in the column is used as the lead line, the lead line can be set according to the span.

4. The special leads of the third type of lightning-proof building should not be less than 2, and they should be arranged symmetrically around the building and the inner courtyard, and the spacing should not be greater than 25 along the perimeter. When the span of a building is large, leading lines cannot be set in the middle of the span, leading lines should be set at both ends of the span and the spacing of other leading lines should be reduced. The average spacing of the specially set leading lines should not be greater than 25. When only the steel column around the building or the reinforcement in the column is used as the lead line, the lead line can be set according to the span.

5. The small distance between the lead line of open application and the laying of electrical and electronic lines should not be less than 1 meter in parallel laying, and not less than 0.3 meter in cross laying.

6. The distance between the lead line and the wall or wall insulation layer of flammable materials should not be greater than 0.1 meters. When less than 0.1 m, the cross-sectional area of the lead wire should not be less than 100mm2.

Ii. Precautions for the detection of lightning protection lead down line

(1) Test items

1. Check whether the position of the special lead down is correct;

2. Whether the fixed welding seam is full without omission, whether the rust prevention of the welding part of the brush is complete, and whether more than 1/3 of the specially set lead down interface is corroded;

3. Check whether the application lead line is straight and straight, without sharp bend, and whether the card nail is sectionally fixed;

4. The spacing of the leading line fixed support is uniform, whether it meets the requirements of 0.5-1m for the horizontal or vertical straight part and 0.3-0.5m for the bending part. Each fixed support should be able to withstand 49N vertical pulling force;

5. Check whether there is rust in the welding place of the specially set down lead, flash receiver and grounding device, whether the paint is missing and the protection facilities near the ground;

6. Test the electrical connection performance of each special lead-off and flash receiver, and its excessive resistance should not be greater than 0.2 ohms;

7. Check whether there is any electrical or electronic circuit attached to the special lead line. Measure the distance between the special lead line and the nearby electrical and electronic lines to meet the requirements of technical specifications;

8. Check whether the connection card for the special lead-off meets the requirements of the lightning protection technical specifications. Disconnect the connection card at least once a year when measuring the grounding resistance. The special lead line is connected with the ring earthing body. When measuring the earthing resistance, do not disconnect the connection card.

9. Check whether the protection of the special lead line near the ground vulnerable to mechanical damage meets the requirements of lightning protection technical specifications;

10. Use instruments to measure the electrical connection performance of the ground terminal and the ground body of the special lead down line, and the excessive resistance should not be greater than 0.2 ohms;

11. Check whether the anti-contact voltage measures meet the requirements of the lightning protection technical specifications.

12. In addition to the above test items, the first test should also check:

(1) Hidden engineering records of leading down line;

(2) Use a tape measure to measure the distance between two adjacent special lead lines, record the total number of special lead lines arranged, and each special lead line is a detection point, which is numbered and tested in sequence;

(3) Use vernier caliper to measure the size of each special lead line.