Installation sequence of distribution boxes and transformers

The installation of distribution transformers and boxes follows a structured sequence: site preparation, foundation setup, equipment positioning, wiring, grounding, and commissioning.1. Pre-Installation PreparationSite readiness: Ensure the installation area is clean, well-ventilated, and free from dust, moisture, or corrosive fumes. Indoor ceilings, walls, and finishes should be completed with no water leakage, and the ground leveling layer must be finished and inspected .Foundation inspection: Verify that the transformer and distribution box foundations are firm, level, dry, and capable of supporting the equipment. Embedded conduits, reserved holes for incoming/outgoing lines, and related embedded parts should be inspected and approved .Component check: Confirm that all transformer and distribution box components, including bushings, fuses, surge protective devices, and accessories, are present and undamaged .2. Transformer InstallationPositioning: Place the transformer in its permanent location, ensuring adequate clearance (typically 1.25 m on all sides for ventilation) and lock any rollers to prevent movement .Assembly: Reassemble any dismantled components, torque fasteners according to manufacturer specifications, and verify oil levels for oil-immersed transformers .Insulation and testing: Measure insulation resistance (IR) using a Megger, check oil breakdown voltage, and ensure all protective devices are correctly installed .Grounding: Connect the transformer neutral and body to separate earth electrodes, forming an interconnected earth bus with resistance not exceeding 2.5 ohms .3. Distribution Box InstallationMounting: For surface-mounted boxes, ensure walls and ceilings are finished; for flush-mounted boxes, verify reserved holes and conduits are ready .Connection: Connect the PE bar and ensure all components meet design specifications. Use copper core flexible wires (≥4 mm²) for protective connections .Wiring: Secondary circuits should follow design requirements, with proper insulation ratings (≥450/750V) and minimum conductor cross-sections (≥2.5 mm² for current circuits, ≥1.5 mm² for others). Separate AC, DC, and control lines with clear identification .Safety and fire protection: Ensure cabinets are fire-sealed if required, and all bolts and anti-loosening parts are complete .4. Commissioning and TestingPre-energization checks: Verify grounding, insulation, and component integrity. Confirm surge protective devices and wiring meet design requirements .Functional tests: Apply load (e.g., a three-phase motor) to check phase sequence and correct operation. Lubricate on-load tap changers and verify their positions match switch settings .Final inspection: Ensure all safety clearances, protective connections, and operational parameters comply with design and regulatory standards before energizing the system .5. Documentation and MaintenanceRecord baseline measurements, test results, and installation details for future maintenance and condition assessment .Schedule periodic inspections and maintenance to ensure long-term reliability and safety of transformers and distribution boxes . Following this sequence ensures safe, reliable, and compliant installation of distribution transformers and boxes, minimizing operational risks and extending equipment lifespan.