Product Overview
The 35kV class oil-immersed power main transformer is a high-performance, reliable power conversion device designed for rated voltages up to 35kV in power transmission and distribution systems. It efficiently steps down high-voltage power from 35kV transmission lines to lower voltage levels suitable for distribution networks, industrial facilities, commercial complexes, and renewable energy projects.
The product complies with IEC 60076, GB 1094, and relevant international and national standards, featuring advanced design with low losses, high efficiency, and excellent overload capacity. The transformer is available in both ONAN and ONAF cooling configurations to meet diverse application requirements. The robust construction and high-quality materials ensure long-term reliable operation in various environmental conditions, making it an ideal solution for substation and power distribution applications.

Key Features
1. 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 and eddy current losses. 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 multi-layer cylindrical or interleaved winding structures to improve impulse voltage distribution. All fasteners are treated with special anti-loosening measures to ensure long-term operational stability.
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 offers reliable operation and long maintenance intervals.
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 optimal clearances and creepage distances to ensure reliable operation under various voltage and environmental conditions.
5. Advanced Cooling System
The transformer features ONAN or ONAF cooling systems for efficient heat dissipation. The cooling system ensures 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.
7. Comprehensive Monitoring and Protection
The transformer is equipped with oil temperature indicators, winding temperature indicators, pressure relief devices, and Buchholz relays for comprehensive monitoring and protection. All instruments provide local indication and remote transmission capabilities for integration with substation monitoring systems.
8. High Environmental Adaptability
The transformer is suitable for extreme ambient temperatures ranging from -35°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 and high humidity conditions.

Technical Specifications
Rated Power: 5MVA to 40MVA and above (customizable)
HV Voltage: 35kV, 38.5kV, 36.75kV (customizable)
LV Voltage: 10.5kV, 11kV, 6.3kV, 6.6kV, 0.4kV (customizable)
Vector Group: Yd11, Ynd11, Dyn11, Yyn0 (customizable)
Tapping Range: ±8 × 1.25% or ±2 × 2.5% or on-load tap changer (customizable)
Short-Circuit Impedance: 6.5% to 8% (depending on capacity rating)
Frequency: 50Hz or 60Hz
Cooling Method: ONAN or ONAF (customizable)
No-Load Losses: According to GB/IEC energy efficiency standards
Load Losses: According to GB/IEC energy efficiency standards (at 75°C, rated frequency)
No-Load Current: ≤ 0.8% to 1.5% (depending on capacity)
Insulation Level (HV): LI 200kV, AC 85kV (for 35kV class)
Insulation Level (LV): As per applicable standard based on voltage rating
Insulating Medium: Mineral insulating oil in accordance with IEC 60296
Winding Material: High-quality electrolytic copper
Oil Temperature Rise: ≤ 60K
Winding Temperature Rise: ≤ 65K
Operating Duration at 5% Overvoltage: Continuous
Operating Temperature: -35°C to +45°C
Altitude: Up to 1000m above sea level (customizable for higher altitudes)

Applications
The 35kV oil-immersed power main transformer is extensively used in primary and secondary substations of urban and regional power distribution networks. Industrial facilities including manufacturing plants, mining operations, petrochemical plants, and metallurgical facilities rely on this transformer for reliable power conversion. Commercial complexes and high-rise buildings utilize this transformer for main power supply. Renewable energy applications including photovoltaic plants, wind farms, and energy storage systems employ this transformer for grid interconnection and power collection. Infrastructure projects such as airports, railway stations, ports, and large-scale public facilities also rely on 35kV transformers for power supply. Rural electrification and township distribution networks benefit from its reliable performance and robust construction.

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, and relevant local and international standards for power transformers.

Why Choose Us
Our 35kV oil-immersed power main transformers feature 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 anti-corrosion treatment ensures reliable operation in harsh environments. We perform comprehensive quality control including core and winding assembly verification, dielectric withstand tests, and temperature rise tests before delivery. The on-load tap changer is available for flexible voltage regulation and stable output voltage under varying load conditions. 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 substations worldwide with proven reliability and customer satisfaction.