Requirements for Completion Acceptance of Overhead Transmission Lines

Basic engineering acceptance requirements

As the foundation of the line, it is necessary to ensure structural stability and precise parameters. The surface of the concrete foundation should be smooth and compact, without defects such as exposed reinforcement, honeycomb, cracking, etc. The qualified rate of rebound testing strength should not be less than 95%; The deviation of the basic elevation cannot exceed ± 20mm of the design value, and the allowable deviation of the burial depth is+100mm and -50mm. The specifications of the anchor bolts should conform to the design, and the center of the anchor bolts in the same group should not deviate from the center of the column by more than 10mm. The height error of the exposed top surface of the foundation should be controlled between+10mm and -50mm. In addition, the stability of the upper and lower slopes of the foundation needs to meet the standard, and a 300-500mm high anti settling layer should be set up for backfill soil. Protective measures such as slope protection, retaining walls, and drainage ditches should be intact and have smooth drainage.

Acceptance requirements for tower engineering

The tower assembly must comply with structural strength and installation specifications. The specifications and quantity of tower materials should be consistent with the design, and the curvature of the main materials between adjacent nodes should not exceed 1/750; The allowable deviation of inclination for straight tower structures is 3 ‰, for high towers it is 1.5 ‰, and for terminal and corner towers it is 5 ‰. The installation of bolts should follow specific threading requirements, such as from inside out in the horizontal direction and from bottom to top in the vertical direction. The tightening torque should meet the standard, and the length of the screw exposed from the nut should not be less than two pitches for a single nut. The cable section should be in a straight line with the tower, and there should be no friction or collision at the intersection of the X-shaped cable. The allowable deviation of the angle with respect to the ground is 1 °, and the force on each combined cable should be balanced. At the same time, concrete poles shall not have longitudinal cracks, and the width of transverse cracks in ordinary reinforced concrete poles shall not exceed 0.1mm.

Acceptance requirements for grounding wires and connecting components

The grounding wire and related connectors directly affect the transmission efficiency and safety. The surface of the conductor and ground wire should have no obvious damage such as broken strands or twisting, and their relaxation should comply with the design and acceptance specifications, with a permissible deviation of ± 5%. Each level of grounding wire can only have one splicing tube and three repair tubes at most. The curvature of the splicing tube should not exceed 2%. After crimping, there must be a supervisor's on-site signature, and the distance between the crimping tube and the tension wire clamp should not be less than 15m. The minimum air gap between the grounding wire and other components should meet the design requirements, and the distance between the crossing and wind deviation should also comply with the specifications. The distance between the grounding wire and the conductor is usually not less than 3m.

Acceptance requirements for insulators and fittings

Insulators need to ensure insulation performance, and fittings need to ensure reliable connection. The number of insulator pieces, string numbers, and installation methods shall comply with the design, and the appearance shall be free of cracks, damage, and cleanliness standards. The withstand voltage of the dry flash test shall meet the corresponding voltage level requirements. The installation of metal fittings such as wire clamps and spacers must conform to the construction drawings, and the galvanized layer must be intact without deformation. Anti loosening washers should be installed at bolt connections to avoid loosening during operation. In addition, the series connection sequence of insulator strings should be correct, and the mechanical strength should be verified through bending tests to meet the design load requirements.

Acceptance requirements for grounding and lightning protection systems

The grounding system needs to ensure the grounding effect, and lightning protection facilities need to be installed in place. The burial depth and laying length of the grounding rays shall comply with the design. The grounding resistance of the tower grounding device shall be checked by remote sensing on a base by base basis. When the soil resistivity is ≤ 100 Ω· m, the grounding resistance usually does not exceed 4 Ω. The specifications of the grounding down conductor are consistent with the design, and there is no virtual welding or slag inclusion at the welding point with the tower. The anti-corrosion coating is intact. The installation position of the lightning rod is accurate, with a distance of not less than 1.5m from the conductor. The installation height error of the lightning arrester does not exceed 0.5m, and its grounding terminal is reliably connected to the down conductor.

Attachment and Identification Acceptance Requirements

All types of accessories and labels need to ensure line identification and safety. The bird proof facilities at the wire spacers, clamps, etc. are installed firmly and the density meets the design requirements. The tower should be clearly labeled with numbers and phase sequence identification, and the phase sequence colors should follow the specifications of A phase yellow, B phase green, and C phase red. At important intersections such as railways and highways, warning signs with a height of not less than 2 meters should be installed, including warning messages such as "high voltage danger", and the material should have good weather resistance.

Data and Compliance Acceptance Requirements

The completion documents must be complete, authentic, and valid, including factory certificates and inspection reports for main materials such as towers and conductors, construction logs for civil foundations and tower assembly, as well as acceptance records for concealed works such as grounding systems. When 110kV and above lines cross houses, an electromagnetic radiation environmental impact assessment report must be provided, and a cross house safety agreement must be signed with the homeowner. All acceptance data must be consistent with the completion documents, and all defects mentioned in the intermediate acceptance must be rectified. After acceptance, a complete set of materials such as acceptance forms and test reports must be organized and archived. At the same time, the line must pass a 72 hour live trial operation without any abnormalities to meet the acceptance requirements.

HZJY-15K 15kV High Voltage Insulation Resistance Tester