I. Pre-construction Preparation Phase

1.1 Design Review and Briefing

• Drawing Review Focus on verifying the line routing (e.g., compliance with regulations for crossing railways and highways), the overall layout of substation sites (equipment spacing ≥ 2 m), and the lightning protection and grounding system (grounding resistance ≤ 4 Ω).
• Geological exploration review Conduct on-site re-inspection of the foundation bearing capacity (e.g., for transmission tower foundations, the requirement is ≥150 kPa) and the distribution of underground pipelines to avoid design deviations.
• Technical standard alignment Confirm that the design complies with the “Construction and Acceptance Specifications for Overhead Transmission Lines from 110kV to 750kV” (GB 50233-2014) and the “Construction and Acceptance Specifications for High-Voltage Electrical Equipment in Electrical Installation Engineering” (GB 50147-2010).

1.2 Construction Organization Design

• Resource allocation ：
  • Personnel: The certification rate for special operation personnel (high-voltage electricians and work-at-height operators) is 100%, and each work team is fully equipped with safety supervisors.
  • Equipment: Crane (rated load ≥ weight of tower materials + 10% safety margin), tensioner (tension control accuracy for cable laying ±5%).
• Construction Schedule Planning A three-level schedule is prepared using P6 software, with a 10% buffer time reserved for critical paths (e.g., foundation pouring → tower assembly → line stringing).

1.3 Materials and Equipment Management

• Acceptance of Materials Supplied by Party A ：
  • Conductor: Check the thickness of the galvanized layer (hot-dip galvanizing ≥85 μm) and tensile strength (steel-cored aluminum stranded wire ≥1270 MPa).
  • Insulators: Mechanical Breakdown Load Test (porcelain insulators ≥ 50 kN); Power Frequency Withstand Voltage Test (no breakdown within 1 minute).
• Control of Supplier-Provided Materials ：
  • Concrete: Mix Design (C25 concrete, water-cement ratio ≤ 0.55; slump: 180 ± 20 mm).
  • Reinforcing bars: Mechanical property testing (yield strength ≥ 335 MPa); weld joint inspection (100% pass rate in ultrasonic testing).

II. Key Control Points in the Construction Process

2.1 Foundation Construction

• Earth excavation ：
  • Excavation dimension deviation (length/width/height ≤ ±50mm); slope control (slope coefficient: 1:0.5 to 1:1).
  • Puddle pits shall be provided (with a depth ≥ 0.5 m), and a backup drainage pump shall be installed to prevent the trench from becoming flooded.
• Formwork Engineering ：
  • Template stiffness verification (deflection ≤ 1/400 of the span); joint sealing (leak-proof grouting measures).
  • Pre-embedded component positioning (center deviation of anchor bolts ≤ 2 mm, elevation deviation ≤ 5 mm).
• Concrete pouring ：
  • Layered vibration (each layer thickness ≤ 300 mm, vibration time 15–30 s).
  • Maintenance covering (plastic film + straw bags; maintenance period ≥ 14 days).

2.2 Tower Assembly

• Ground assembly ：
  • The bolts are threaded in a uniform manner (vertically from bottom to top, and horizontally from inside to outside).
  • Tower material bending control (main members ≤ 1/1000, secondary members ≤ 1/750).
• Overall tower erection ：
  • Pole selection (lattice-type poles shall have a permissible load ≥ 1.2 times the tower weight, accounting for a safety factor).
  • Verticality adjustment (tower tilt rate ≤ 0.3%).
• Bolt tightening ：
  • Torque re-inspection (torque for M24 bolts ≥ 250 N·m, with a sampling rate ≥ 10%).

2.3 Overhead Line Construction

• Conductor and ground wire stringing ：
  • Tension control (conductor tension ≤ 25% RTS, ground wire tension ≤ 20% RTS).
  • Crossing construction (erecting protective sheds over highways and railways; using insulated cable bridges for energized lines).
• Attachment installation ：
  • Metal fittings connected (bolts aligned in the same direction, split pins doubled and bent).
  • Jumper wire fabrication (sag deviation ≤ ±2%, equipotential wires securely tied).
• Parameter measurement ：
  • Conductor-to-ground clearance (for 500kV lines ≥ 8.5 m, measured at crossing and overpass points).
  • Sag observation (parallelogram method, error ≤ ±2%).

2.4 Substation Equipment Installation

• Main transformer installation ：
  • Body inspection (core insulation resistance ≥ 1000 MΩ, winding DC resistance difference ≤ 2%).
  • Oil filling and nitrogen purging (vacuum level ≤133 Pa, holding time ≥8 hours).
• GIS installation ：
  • Cleanliness control (particle count ≤ ISO 4406 Class 18/16).
  • Flange connection (bolt tightening torque complies with the manufacturer’s requirements; sealing groove is clean and free of scratches).
• Secondary wiring ：
  • Cable laying (bending radius ≥ 10 times the cable’s outer diameter; reliable grounding of the shielding layer).
  • Circuit verification (insulation resistance ≥ 10 MΩ, withstand voltage test: 2 kV/1 min).

III. Special Measures for Safety and Environmental Protection

3.1 Safety Management

• Hazard Identification ：
  • High-altitude fall (tower assembly/line stringing operations, with dual-hook safety belt and fall-arrest device installed).
  • Electric shock risk (when working near energized equipment, maintain a safe distance: 10 kV ≥ 1.0 m, 500 kV ≥ 6.0 m).
  • Lifting injuries (the “Ten No-Lift” rules for lifting operations, with clear command signals).
• Emergency Management ：
  • Emergency plan preparation (specialized plans for electric shock, fire, and collapse).
  • Emergency supplies reserve (fire extinguishers, first-aid kits, stretchers—checked monthly).

3.2 Environmental Management

• Pollution Prevention and Control ：
  • Noise control: Pile-driving operations shall be conducted between 6:00 and 22:00, with noise levels not exceeding 70 dB.
  • Dust control (enclosure of concrete mixing stations, with water spraying for dust suppression at a frequency of ≥2 times/hour).
• Resource Circulation ：
  • Recycling of scrap steel (recycling rate ≥95%, stored separately by type).
  • Construction wastewater treatment (settling ponds installed; discharge after pH adjustment to 6–9).
• Ecological conservation ：
  • Vegetation restoration (temporary land reclamation, planting native species).
  • Animal passage installation (routing paths avoid protected areas, and animal bridges are constructed at crossing points).

IV. Integration of Acceptance and Operations & Maintenance

4.1 Acceptance of Concealed Works

• Basic acceptance ：
  • Reinforcement work (deviation in cover thickness ≤ ±5 mm, deviation in rebar spacing ≤ ±10 mm).
  • Concrete strength (tested by rebound method; the strength of test cubes cured under the same conditions ≥ 90% of the design value).
• Grounding acceptance ：
  • Grounding electrode burial depth (≥0.8 m; if soil resistivity is high, replace with a resistance-reducing agent).
  • Contact voltage test (contact potential ≤ 50V, step voltage ≤ 10V).

4.2 System Debugging

• Unit debugging ：
  • Transformer partial discharge test (≤100 pC, 500 kV equipment).
  • Circuit breaker closing and opening characteristics (synchronism ≤ 5 ms; speed conforms to the manufacturer’s curve).
• Joint commissioning test ：
  • Protection setting verification (differential protection ratio restraint coefficient: 0.3–0.5; operating time ≤ 30 ms).
  • Integrated commissioning of the automation system (remote control accuracy: 100%; telemetry accuracy ≤ 1%).

4.3 Operations and Maintenance Handover

• Document handover ：
  • As-built drawings (electronic version + paper version, with clear markings for any changes).
  • Equipment manual (operating procedures, maintenance schedule, list of wear parts).
• Training Services ：
  • Practical Training for Operations and Maintenance Personnel (Key Points for Equipment Inspection, Abnormality Handling Procedures).
  • Digital platform integration (data connection with online monitoring systems, threshold alert settings).

V. Application of Innovative Technologies

5.1 Intelligent Construction

• BIM application ：
  • 3D modeling (route optimization and collision detection to reduce design changes).
  • Construction simulation (tower assembly process animation, early identification of operational risks).
• Drone Inspection ：
  • Line re-survey (aerial survey-generated DEM, accuracy ≤ 0.1 m).
  • Construction monitoring (real-time video transmission, AI-based identification of quality hazards).

5.2 Green Building Materials

• Low-carbon concrete ：
  • Fly ash content ≥ 30%, carbon emission reduction benefit ≥ 20%.
  • Use of recycled aggregates (crushed stone replacement rate ≥50%, strength grade ≥C25).
• Environmentally friendly insulating material ：
  • Plant-oil transformer (biodegradable, flash point ≥300℃).
  • Composite insulator (silicone rubber sheds, with a 30% improvement in pollution flashover resistance).

VI. Summary

Transmission and transformation project construction approved. Refined preliminary planning, standardized process control, and intelligent technological innovation. To achieve high-quality, efficient, and environmentally friendly project delivery, the following aspects require particular attention during the process: Quality of foundation construction, safety of high-altitude operations, accuracy of equipment installation, and implementation of environmental protection measures. And closely follow industry trends by actively adopting new technologies such as BIM, drones, and low-carbon materials to enhance the overall efficiency of projects.