Three Phase Level 1 1250kVA 35kV Fully Sealed Oil-Immersed Transformer Price & Supplier

Time：2026-03-11    Auther：ZTelec-www.ztelectransformer.com

The three phase 1250kVA 35kV fully sealed oil-immersed transformer is a core piece of electrical equipment widely used in industrial power distribution systems, renewable energy power plants, and urban grid infrastructure. Its main function is to convert 35kV medium voltage into 0.4kV low voltage, ensuring stable power supply for factories, commercial buildings, and infrastructure projects. For engineering procurement managers and EPC contractors, understanding the transformer price range, technical specifications, and reliable supplier information is essential for completing an efficient procurement process. This article provides a comprehensive overview including market pricing, key technical parameters, and selection guidelines for a 1250kVA 35kV oil-filled transformer.

Overview of Three Phase 1250kVA 35kV Fully Sealed Oil-Immersed Transformer

The three-phase 1250kVA 35kV transformer adopts the standard three-phase power supply structure commonly used in industrial power systems. This configuration provides stable voltage output and balanced load distribution, making it suitable for factories, commercial complexes, mining operations, and renewable energy grid connection projects.

The transformer is designed with Level 1 energy efficiency, meeting requirements defined by standards such as GB 20052-2020 and international transformer efficiency regulations. Compared with lower efficiency transformers, Level 1 models significantly reduce both no-load and load losses, helping enterprises lower long-term electricity consumption and operating costs.

The rated capacity of 1250kVA allows the transformer to supply electricity to medium-scale electrical loads such as industrial equipment, shopping malls, residential complexes, and infrastructure facilities. Under normal operating conditions, this capacity level provides a stable and efficient power distribution solution.

The 35kV voltage class is commonly used in regional substations and medium-voltage distribution networks. The transformer connects the high-voltage grid to the low-voltage power system, ensuring reliable voltage conversion and safe power transmission.

The fully sealed structure is one of the most important design features. The transformer tank is isolated from external air, and oil expansion is compensated through corrugated cooling fins. This design prevents moisture from entering the insulating oil, slows down oil aging, and significantly reduces maintenance requirements.

Price of a Three Phase 1250kVA 35kV Fully Sealed Oil-Immersed Transformer

The market price of a 1250kVA 35kV fully sealed oil-immersed transformer typically ranges from approximately RMB 300,000 to RMB 450,000 in the Chinese manufacturing market. However, the final quotation may vary depending on technical specifications, materials, efficiency level, and additional configuration requirements. Buyers should always request a detailed quotation from the manufacturer based on project specifications.

Several key factors influence the final transformer price. Raw material costs play an important role, as the prices of copper windings, silicon steel sheets, transformer oil, and insulation materials can fluctuate significantly in the global market.

The energy efficiency level also affects pricing. Level 1 efficiency transformers usually cost more than Level 2 models due to improved core materials and optimized manufacturing processes. However, energy savings during long-term operation can offset the initial price difference.

Manufacturing standards also impact costs. Transformers designed according to IEC standards for international projects may require different testing procedures and configurations compared with those designed under domestic standards.

Transportation and installation expenses should also be considered in the procurement budget. Because transformers are heavy electrical equipment, logistics costs, on-site installation, and commissioning services can contribute significantly to the overall project investment.

Key Parameters When Purchasing a 1250kVA 35kV Fully Sealed Oil-Immersed Transformer

Capacity and Load Matching: When selecting a transformer, engineers should calculate the required capacity based on the total electrical load and power factor, which typically ranges between 0.8 and 0.9. For stable operation and longer equipment lifespan, it is recommended that the transformer operates at approximately 85% to 90% load rate.

Voltage Regulation Method: Transformers can use either off-circuit tap changers or on-load tap changers. Off-circuit tap changers are suitable for systems with relatively stable grid voltage, offering adjustment ranges such as ±2×2.5%. On-load tap changers allow voltage regulation during operation and are widely used in renewable energy projects or power systems with frequent voltage fluctuations.

Insulation and Protection Design: High-voltage transformers should include reliable insulation structures and protective devices such as gas relays, oil level indicators, and pressure relief valves. These components help detect internal faults early and protect the transformer from severe damage.

Loss Performance Indicators: No-load loss and load loss are key parameters affecting energy consumption during long-term operation. Lower losses indicate higher energy efficiency and lower operational costs.

Installation and Maintenance Considerations: Buyers should also review tank structure design, cooling methods, and maintenance accessibility to ensure the transformer can operate reliably throughout its service life.

Four Key Inspection Points When Buying a 1250kVA 35kV Oil-Immersed Transformer

Type Test Report: The supplier should provide an official type test report confirming that the transformer meets Level 1 energy efficiency requirements and complies with the 35kV voltage class technical standards.

Corrugated Fin Thickness: Corrugated fins serve as the primary heat dissipation structure in fully sealed transformers. Their thickness and manufacturing quality directly affect the transformer’s cooling performance and long-term reliability.

Vacuum Oil Filling Process: High-quality transformers are manufactured using vacuum oil filling technology. This process removes moisture and air from the insulation system, improving dielectric strength and operational stability.

After-Sales Support: Buyers should confirm the manufacturer’s warranty terms and after-sales service coverage. Typical warranty periods include 18 months after shipment or 12 months after commissioning.

Reliable Supplier for 1250kVA 35kV Oil-Immersed Transformers

ZTelec is a professional transformer manufacturer specializing in the production of three-phase Level 1 1250kVA 35kV fully sealed oil-immersed transformers for industrial power distribution and grid infrastructure projects.

The company operates its own manufacturing facility, allowing it to supply transformers directly from the factory and provide competitive pricing for international engineering projects. Its S20 and S22 series transformers are designed to meet Level 1 energy efficiency standards and are manufactured using high-permeability silicon steel cores and full copper windings.

Advanced production processes such as vacuum drying and vacuum oil filling improve insulation strength and reliability. Each transformer undergoes comprehensive routine testing before leaving the factory to ensure stable performance.

The company also provides export packaging, logistics coordination, and technical documentation for international customers. Customized transformer designs can be offered according to project requirements, including voltage ratios, tap changer configurations, and structural dimensions.

Get Detailed Quotation and Technical Support

If you are searching for a reliable 1250kVA 35kV oil-immersed transformer supplier, professional manufacturers can provide detailed technical specifications, competitive pricing, and engineering support to ensure successful project implementation.