Product Overview
The 220kV class three-phase oil-immersed power main transformer is a high-capacity, high-performance power conversion device designed for rated voltages up to 220kV in power transmission and distribution systems. It efficiently steps down high-voltage power from 220kV transmission lines to lower voltage levels suitable for regional distribution networks, large industrial facilities, and major infrastructure projects. This transformer is a critical component in backbone transmission substations.
The product complies with IEC 60076, GB 1094, 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. The transformer meets or exceeds national and international energy efficiency standards including GB 20052-2020 Energy Efficiency Grade 1, 2, or 3 requirements.
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. 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. 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 220kV class insulation level supports LI 950kV, AC 395kV withstand voltages.
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, extending transformer service life and maintaining stable performance.
6. Robust Construction and Long Service Life
The transformer tank is constructed from high-strength steel plates with advanced welding and anti-corrosion treatment for enhanced durability. The sealed tank structure prevents oil contamination and slows insulation aging. The transformer is designed for continuous operation under adverse weather conditions with direct solar radiation, high humidity, and extreme temperatures.
7. 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.
8. High Environmental Adaptability
The transformer is suitable for extreme ambient temperatures ranging from -40°C to +45°C and altitudes up to 1000m above sea level. The robust construction ensures reliable operation in outdoor installations with direct solar radiation, high humidity, salt-spray, and other harsh environmental conditions.

Technical Specifications
Rated Power: 50MVA to 240MVA and above (customizable)
HV Voltage: 220kV, 230kV, 242kV (customizable)
LV Voltage: 110kV, 115kV, 121kV, 35kV, 38.5kV (customizable)
Vector Group: YNyn0, YNd11, YNa0d11 (customizable)
Tapping Range: ±8 × 1.25% or ±10% or ±12% (on-load tap changer) (customizable)
Short-Circuit Impedance: 12% to 15% (depending on capacity rating)
Frequency: 50Hz or 60Hz
Cooling Method: ONAF, OFAF, OFWF, ODWF (customizable)
No-Load Losses: According to GB 20052-2020 Energy Efficiency Grade 1, 2, or 3 standards
Load Losses: According to GB 20052-2020 Energy Efficiency Grade 1, 2, or 3 standards (at 75°C, rated frequency)
No-Load Current: ≤ 0.15% to 0.6% (depending on capacity)
Insulation Level (HV): LI 950kV, AC 395kV (for 220kV class)
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: ≤ 55K or 60K (depending on design)
Winding Temperature Rise: ≤ 60K or 65K (depending on design)
Operating Duration at 5% Overvoltage: Continuous
Operating Temperature: -40°C to +45°C
Altitude: Up to 1000m above sea level (customizable for higher altitudes up to 3000m)

Applications
The 220kV 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 large airports, railway traction substations, ports, and major public facilities utilize this transformer for main power supply. Renewable energy applications including large-scale photovoltaic plants, onshore and offshore 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, GB 20052-2020 Energy Efficiency Limits and Energy Efficiency Grades for Power Transformers, IEC 60296 Mineral Insulating Oils for Transformers, IEC 60529 Degrees of Protection Provided by Enclosures, and relevant local and international standards for high-voltage power transformers.

Why Choose Us
Our 220kV oil-immersed power main transformers feature ultra-low loss design with high-quality silicon steel cores and optimized windings for exceptional energy efficiency meeting GB 20052-2020 Energy Efficiency Grade 1, 2, or 3 requirements. 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 power transformers have been installed in numerous backbone substations worldwide with proven reliability and customer satisfaction.