Oil-Immersed Transformer Winding Process Whitepaper

Chapter 1: Fundamental Theory

1.1 Oil-immersed transformer electromagnetic design

• Ampere-turn balance calculation (±2% tolerance)
• Leakage flux optimization (axial component <15%)
• Eddy current loss control (coefficient ≤1.1)

1.2 Oil-immersed transformer thermal characteristics

• Hotspot gradient (ΔT <15K)
• Oil duct design (flow velocity 0.3-0.5m/s)
• Cooling area calculation (≥0.12㎡/kW)

Chapter 2: Conductor Processing

2.1 Copper material for oil-immersed transformers

• Oxygen-free copper (O₂ ≤5ppm)
• Annealing process (550±10℃)
• Surface treatment (Ra≤0.6μm)

2.2 Conductor forming

• Flat wire rolling (±0.02mm)
• Transposed conductor (pitch ≤50mm)
• Composite conductor (fill factor >0.9)

Chapter 3: Winding Process

3.1 Layer winding for oil-immersed transformers

• Electrostatic ring configuration (radius ≥5×width)
• Interlayer oil duct (±0.5mm)
• Axial pressure (15-20N/cm²)

3.2 Disc winding for oil-immersed transformers

• Radial spacer positioning (±1mm)
• Inter-disc insulation (0.5-1.5mm)
• Pre-stress pressure (30-50MPa)

Chapter 4: Insulation Treatment

4.1 Drying process

• Gradual heating (≤10℃/h)
• Final moisture content (<0.5%)
• Vacuum level (≤10Pa)

4.2 Impregnation

• Oil temperature (60±5℃)
• Gas content (<0.5%)
• Oil circulation (viscosity ≤9mm²/s)