UK National Grid Hams Hall BESS 400kV Transformer Project

Project Background

The UK National Grid Hams Hall BESS Substation Project is a key energy transition infrastructure for National Grid, located in the West Midlands. It is one of the largest battery energy storage system (BESS) transformer projects in the UK. The project has extremely stringent quality requirements, adhering to the UK G5/5-1 grid connection standard and relevant IEC standards.

Scope of Supervision

This supervision covers 2 × SFFZ-220000/400 large-scale BESS transformers (serial numbers: 202501020, 202501021). Supervision began with incoming material inspection, continued through all core manufacturing processes — including core manufacturing, winding, tank assembly, final assembly, drying and oil filling — and concluded with FAT witnessing and packing & shipping supervision.

Key Supervision Activities

Phase 1: Production Process Control

The supervision team conducted full-process on-site oversight of critical manufacturing stages, with key focus on:

• Personnel Qualification Review: Verified certificates for winding, welding, assembly, and testing operators
• Equipment Status Verification: Reviewed maintenance records for winding machines, vacuum drying equipment, and cranes
• Incoming Material Inspection: Witnessed acceptance procedures and verified material certificates against physical items
• Core Component Manufacturing Monitoring: Full on-site oversight of core manufacturing, winding, and tank assembly
• Final Assembly Supervision: Complete monitoring of tank filling, accessory installation, and lead connections

Phase 2: FAT Testing Witnessing

All 27 FAT test items were witnessed per IEC 60076 series standards and technical agreement requirements. Summary of results:

• Insulation performance: Dielectric dissipation factor, absorption ratio, and polarization index all meet specification requirements
• Withstand voltage tests: Applied power-frequency and induced voltage tests passed on first attempt
• Partial discharge: Full-process monitoring; PD level consistently below specification limit
• Impulse tests: Lightning impulse (full/chopped wave) and switching impulse waveform parameters comply with standards
• Temperature-rise test: Met design requirements under both ONAN and ONAF cooling modes
• Short-circuit impedance & load loss: Meets guaranteed values
• No-load performance: No-load loss measured below guaranteed value; core performance is excellent

Phase 3: Packing & Shipping Supervision

• Protective removal of precision accessories (bushings, tap changers, fiber optic thermometers, etc.)
• Installation of dry nitrogen protection system and micro-positive pressure setting
• Installation of mechanical/electronic impact indicators and initial state recording
• Comprehensive paint condition inspection and defect repair monitoring
• Packing plan review and on-site supervision
• Item-by-item verification of packing lists
• Final verification of land transport loading and port arrival

Supervision Conclusion

This project has been successfully completed. Through comprehensive on-site witnessing, inspection, and review, we confirm that the production process was under control, the manufacturer’s QA system operated effectively, all test results met requirements, documentation is complete and traceable, and packing and shipping were compliant. Approved for dispatch.