Product Overview
The 330kV class three-phase oil-immersed power main transformer is a high-capacity, ultra-high-voltage power conversion device designed for rated voltages up to 330kV in backbone transmission and regional power grid systems. It efficiently steps down high-voltage power from 330kV transmission lines to lower voltage levels suitable for regional distribution networks, large-scale industrial facilities, and major infrastructure projects. This transformer is a critical component in extra-high-voltage transmission substations and grid interconnection systems.
The product complies with IEC 60076, GB 1094, GB/T 6451, and relevant international and national standards, featuring advanced design with ultra-low losses, high efficiency, and excellent overload capacity. The transformer is available in multiple cooling configurations including ONAF, OFAF, OFWF, and ODWF to meet diverse application requirements. The robust construction and high-quality materials ensure long-term reliable operation in various environmental conditions.

Key Features
1. Ultra-Low Loss and High Energy Efficiency
The core is made of high-quality cold-rolled grain-oriented silicon steel with advanced step-lap joint technology, significantly reducing no-load losses. The optimized winding design minimizes stray losses, eddy current losses, and additional losses in structural parts through advanced magnetic shielding and leakage flux control. The transformer meets or exceeds national and international energy efficiency standards.
2. Strong Short-Circuit Withstand Capability
The dynamic analysis method is applied for mechanical force calculation under short-circuit conditions. High-voltage windings adopt interleaved, shielded, or inner-shielded winding structures to improve impulse voltage distribution. The low-voltage windings use self-bonding transposed conductors to effectively enhance short-circuit resistance. All fasteners are treated with special anti-loosening measures and the clamping structure is reinforced with robust support systems to ensure long-term operational stability under severe fault conditions.
3. Reliable On-Load Tap Changer
The transformer is equipped with a high-quality on-load tap changer installed on the high-voltage side or neutral end. The tap changer provides automatic or manual voltage regulation to maintain stable output voltage under varying load and grid conditions. The tap changer features advanced vacuum switching technology with long maintenance intervals, remote control capability, and comprehensive monitoring functions.
4. Excellent Insulation and Dielectric Performance
The transformer uses high-quality mineral insulating oil in accordance with IEC 60296 standards, providing excellent electrical insulation and heat dissipation. The insulation system is designed with optimized clearances and creepage distances to ensure reliable operation under transient overvoltages and lightning impulse conditions. The 330kV class insulation level typically supports LI 950kV or LI 1175kV, and AC 395kV or AC 510kV withstand voltages depending on system requirements.
5. Advanced Cooling System
The transformer features multiple cooling options including ONAF, OFAF, OFWF, and ODWF for efficient heat dissipation. Forced oil directed flow cooling designs are available for large capacity units to ensure optimal operating temperatures under various load conditions. The cooling system extends transformer service life and maintains stable performance.
6. Low Partial Discharge and Long Service Life
The transformer is manufactured in air-conditioned, fully enclosed, dust-free workshops to effectively control foreign particle ingress into the core and windings. Advanced bonding techniques and vacuum oil filling prevent bubble formation in insulation components, significantly reducing partial discharge levels and extending service life.
7. Low Noise Operation
The transformer employs high-quality core materials with optimized flux density selection and step-lap joint technology to improve flux distribution at core joints. Soft connection between the core assembly and tank reduces noise transmission. The operating noise levels are well below international standard requirements.
8. Comprehensive Monitoring and Protection
The transformer is equipped with oil temperature indicators, winding temperature indicators, pressure relief devices, Buchholz relays, oil level indicators, moisture indicators, and partial discharge monitoring systems for comprehensive monitoring and protection. All instruments provide local indication and remote transmission capabilities for integration with substation SCADA and monitoring systems.

Technical Specifications
Rated Power: 50MVA to 360MVA and above (customizable)
HV Voltage: 330kV, 345kV, 363kV (customizable)
LV Voltage: 110kV, 121kV, 35kV, 38.5kV, 10.5kV, 13.8kV, 15.75kV, 20kV (customizable)
Vector Group: YNa0d11, YNd11, YNyn0 (customizable)
Tapping Range: ±8 × 1.25% or ±10% or ±12% (on-load tap changer) (customizable)
Short-Circuit Impedance: 10% to 18% for two-winding, 10% to 45% for three-winding auto-transformers (depending on configuration and capacity rating)
Frequency: 50Hz or 60Hz
Cooling Method: ONAF, OFAF, OFWF, ODWF (customizable)
No-Load Losses: According to applicable energy efficiency standards
Load Losses: According to applicable energy efficiency standards (at 75°C, rated frequency)
No-Load Current: ≤ 0.15% to 0.28% (depending on capacity)
Insulation Level (HV): LI 950kV or LI 1175kV, AC 395kV or AC 510kV (depending on system requirements)
Insulation Level (LV): As per applicable standard based on voltage rating
Insulating Medium: High-quality mineral insulating oil in accordance with IEC 60296
Winding Material: High-quality electrolytic copper
Oil Temperature Rise: ≤ 50K to 60K (depending on design)
Winding Temperature Rise: ≤ 60K to 65K (depending on design)
Operating Duration at 5% Overvoltage: Continuous
Operating Temperature: -35°C to +45°C
Altitude: Up to 1000m above sea level (customizable for higher altitudes up to 5000m)

Applications
The 330kV oil-immersed power main transformer is extensively used in backbone transmission substations of regional and national power grids. Large industrial facilities including heavy manufacturing plants, petrochemical complexes, steel mills, and mining operations rely on this transformer for high-capacity power conversion. Infrastructure projects including major airports, railway traction substations, ports, and large-scale public facilities utilize this transformer for main power supply. Renewable energy applications including large-scale photovoltaic plants, onshore wind farms, and utility-scale energy storage systems employ this transformer for grid interconnection and power collection. Utility companies and independent power producers use these transformers for transmission grid connections, bulk power distribution, and system interconnections.

Compliance Standards
IEC 60076 Power Transformers, GB 1094 Power Transformers, GB/T 6451 Technical Parameters and Requirements for Three-Phase Oil-Immersed Power Transformers, IEC 60296 Mineral Insulating Oils for Transformers, IEC 60529 Degrees of Protection Provided by Enclosures, and relevant local and international standards for extra-high-voltage power transformers.

Why Choose Us
Our 330kV oil-immersed power main transformers feature ultra-low loss design with high-quality silicon steel cores and optimized windings for exceptional energy efficiency. The robust construction with high-strength steel tank and advanced anti-corrosion treatment ensures reliable operation in harsh environments. The high-quality on-load tap changer provides reliable voltage regulation with remote control and long maintenance intervals. We perform comprehensive quality control including core and winding assembly verification, dielectric withstand tests, temperature rise tests, short-circuit impedance measurements, and partial discharge tests before delivery. Customization options are available for capacity, voltage levels, vector group, tapping range, and cooling methods to meet specific project requirements. Our engineering team provides professional technical support for system design, installation, and commissioning. Competitive pricing and efficient manufacturing processes ensure value for money. Comprehensive after-sales service includes installation guidance, commissioning assistance, spare parts supply, and technical support. Our 330kV power transformers have been installed in numerous backbone substations worldwide with proven reliability and customer satisfaction.