High-voltage transformers are key equipment in power systems, and their insulation performance directly affects the safety and reliability of the power grid. As the core material of high-voltage transformer windings, the quality of pinhole-free copper foil directly determines the transformer’s insulation class, service life, and operational reliability.
I. Technical Definition and Testing Standards of Non-Porous Copper Foil
1.1 Basic Concepts
Non-porous copper foil refers to high-purity copper foil material that has undergone special processing and has no defects such as pinholes, inclusions, or cracks on its surface. Pinholes are a common defect which can lead to:
- Insulation breakdown: Electric field concentration at pinholes can easily cause partial discharge
- Insulation aging: Accelerates deterioration of insulation materials
- Safety hazards: Serious risk of insulation failure
1.2 Pinhole Detection Methods
| Detection Method | Standard | Pinhole Size Range |
|---|---|---|
| Pinhole Detector | Custom | ≥0.01mm |
| Visual Inspection | ASTM B152 | ≥0.1mm |
| Eddy Current Testing | Custom | ≥0.05mm |
| Light Inspection | GB/T 5231 | ≥0.05mm |
1.3 Technical Requirements
- Pinhole Count: AATCC Class 100 (≤5 pinholes per square foot)
- Surface Roughness: Ra≤0.8μm
- Conductivity: IACS≥101%
- Tensile Strength: 200-280 MPa
II. High Voltage Transformer Requirements
2.1 Insulation Requirements
- High voltage level: Usually 110kV and above
- Strict insulation coordination: Various overvoltage conditions
- Partial discharge: Must be controlled ≤10pC
- Design life: ≥30 years
2.2 Core Selection Considerations
| Technical Points | Requirements |
|---|---|
| Pinhole Control | Zero pinholes or AATCC Class 100 |
| Surface Quality | Smooth, Ra≤0.8μm |
| Purity | Cu≥99.90% |
| Thickness Tolerance | Within ±3% |
III. Technical Specifications
3.1 Recommended Grades
| Grade | Purity | Conductivity | Tensile Strength | Elongation | Application |
|---|---|---|---|---|---|
| C11000 (ETP) | ≥99.90% | ≥101% IACS | 200-280 MPa | ≥15% | Standard HV |
| C10100 (OFC) | ≥99.99% | ≥101.5% IACS | 190-260 MPa | ≥20% | High-Performance |
| C10200 (TPA) | ≥99.95% | ≥101% IACS | 195-265 MPa | ≥18% | Precision |
3.2 Key Performance Parameters
Electrical: Conductivity IACS≥101%, Resistivity 0.01724 Ω·mm²/m
Dimensions: Thickness 0.05-3.0mm, Tolerance ±0.02mm, Width 10-600mm
Mechanical: Tensile strength 200-280 MPa, Elongation ≥15-25%, Hardness 35-65 HV
IV. Special Process Requirements
4.1 Insulation System Design
- Copper foil + Nomex paper + polyester film combination
- Oil channel width meets insulation and heat dissipation needs
- Electrical clearance: ≥5mm from edge to core
4.2 Partial Discharge Control
- Non-porous copper foil eliminates pinhole-based partial discharge sources
- Surface treatment reduces protrusions and sharp corners
- Welding quality avoids defect-induced discharge
4.3 Winding Parameters
| Parameter | Recommended Value |
|---|---|
| Winding Tension | 10-20 N/mm² |
| Winding Speed | 20-50 m/min |
| Annealing Temperature | 400-650°C |
| Insulation Class | Class E to H (120-180°C) |
V. Industry Standards and Certifications
Standards: IEC 60325, IEC 60076, GB/T 5231, ASTM B152, JIS H3100
Certifications: ISO 9001, UL, RoHS/REACH, SGS
VI. Quality Inspection
| Inspection | Method | Standard |
|---|---|---|
| Pinhole Detection | Pinhole Detector | AATCC Class 100 |
| Chemical Composition | Spectroscopy | Cu≥99.90% |
| Thickness Tolerance | Thickness Gauge | ±0.02mm |
| Conductivity | Eddy Current | IACS≥101% |
VII. Supplier Selection
- Full-process production line (melting → rolling → annealing → slitting)
- Professional pinhole detection capability
- Thickness control: ±0.02mm
- ISO 9001/14001/45001 certified
VIII. Product Specifications
| Grade | Thickness | Width | Temper | Conductivity |
|---|---|---|---|---|
| C11000 | 0.1-2.5mm | 20-500mm | O/H22/H24 | ≥101% IACS |
| C10100 | 0.05-2.0mm | 10-400mm | O/H22 | ≥101.5% IACS |
| C10200 | 0.1-3.0mm | 20-600mm | O/H24 | ≥101% IACS |
Non-Porous Grade: AATCC Class 100 or higher
Conclusion
The selection of pinhole-free copper foil for high voltage transformers requires focus on pinhole control accuracy, surface quality, and insulation compatibility.
Our company has 30 years of experience exporting electrical wire and metal foil. We provide C11000/C10100/C10200 series pinhole-free copper foil for high voltage transformers with customized sizes and global sample shipping.
Contact:
Email: office@cnlpzz.com
WhatsApp: 0086-19337889070
The technical parameters described are general reference values. Please consult our technical team for specific selections based on your high voltage transformer design requirements.