Power Transformers for Reliable Transmission and Distribution
Sieyuan power transformers keep electricity moving reliably from the power plant to the end user. Built on Toshiba core technology and a standardized design and manufacturing system, our liquid-immersed, gas-insulated and cast resin dry-type transformers cover voltages up to 765kV and capacities up to 1250MVA. Every unit is engineered to the customer's specification, designed and tested to IEC, IEEE/ANSI or national standards, and built for low losses, low noise and a long service life.
Lead times start from as short as 8 months, our average delivery time in 2025 was 10 months, and fast-track production is available when your project cannot wait.
Power and distribution transformers for every stage of the grid
Each Sieyuan transformer range is designed for a specific role in the network. Liquid-immersed power transformers form the backbone of high-voltage transmission and generation, gas-insulated power transformers bring fire-safe capacity into dense city centres, and cast resin dry-type transformers deliver clean, low-maintenance distribution inside buildings.
Liquid-immersed Power Transformer
Built for Long-Term Durability
Reliable Lead Times
Elevated Performance Standards
Customized Solutions
Gas-Insulated Power Transformers
Precision Quality and Proven Performance
Explosion-Proof and Non-Flammable
Compact and Durable Design
Cast Resin Dry-Type Transformer
Low Partial Discharge and Excellent Overvoltage Withstand Performance
Low Temperature Rise and High Overload Capability
Strong Short-Circuit Withstand Capacity
Efficient and Environmentally Responsible
Compare power transformer specifications
Selecting the right transformer starts with the network it will serve. Voltage level and rated capacity define the platform, while the insulation medium, cooling and arrangement decide where a unit can be installed, how it is maintained and how it behaves in a fault. The table summarizes the standard range of each technology; final ratings are engineered for every project.
| Liquid-immersed Power Transformer | Gas-Insulated Power Transformers | Cast Resin Dry-Type Transformer | |
|---|---|---|---|
| Voltage Level | Up to 765kV | 110kV, 220kV | ≤40.5kV |
| Capacity | Up to 1250MVA | Up to 75MVA | 100-20000kVA |
| Cooling Medium | Mineral oil, Ester oil | ||
| Insulated Gas | SF6 | ||
| Number of Phase | Single Phase, Three Phase | ||
| Cooling Mode | GNAN,GDAN,GDAF,GDWF | ||
| Transformer Arrangement | Integrated, Split | Integrated, Split | |
| Neutral Insulation Level | Full, Graded | Full, Graded | |
| Frequency | 50Hz/60 Hz | ||
| Winding Material | Copper/Aluminum | ||
| Lead Time | 8 Months |
Insulation and cooling options for safety and sustainability
The insulation medium shapes how a transformer performs, where it can be installed and how it affects its surroundings. Sieyuan offers four proven options, so every project can balance capacity, fire safety and environmental goals. For a deeper look at cooling methods, insulation liquids and ratings, read our power transformer selection guide.
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Mineral oil
The proven standard for liquid-immersed power transformers. Mineral oil combines high dielectric strength with efficient heat transfer and supports the highest voltage and capacity ratings, up to 765kV and 1250MVA.
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Ester oil
Ester oil has a higher fire point and better biodegradability than mineral oil. It is a strong choice for substations close to people, water or sensitive ecosystems, with the same liquid-immersed design.
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SF6 gas
In gas-insulated power transformers, SF6 replaces oil completely. An internal fault causes only a small rise in tank pressure, which removes the risk of tank rupture and fire in urban and indoor substations.
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Cast resin
Cast resin dry-type transformers encapsulate the windings in resin and use no liquid at all. Flame-retardant and self-extinguishing, they suit commercial buildings and sites with strict fire safety requirements.
Why choose Sieyuan power transformers
Utilities, developers and EPC contractors choose Sieyuan for proven technology, delivery they can plan around and a complete portfolio from one manufacturer.
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Toshiba core technology
Liquid-immersed power transformers are designed and manufactured with Toshiba core technology and strict quality control at every stage of production, for long-term stable operation.
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Delivery you can plan around
A standardized design and manufacturing system delivers lead times from as short as 8 months, a 10-month average in 2025 and fast-track production when schedules are tight.
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Built to your standard
Designs follow IEC, IEEE/ANSI or the national standard in your specification, with low losses, low noise, low partial discharge and high short-circuit withstand capability.
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One partner for the whole system
Shunt reactors, bushings, earthing transformers, protection relays and online monitoring from the same manufacturer simplify engineering, interfaces and after-sales support.
Power Transformer FAQ
Answers to the questions engineers and buyers ask most often when they specify and source a power transformer.
What types of power transformers does Sieyuan manufacture?
Sieyuan manufactures three transformer ranges. Liquid-immersed power transformers cover ratings up to 765kV and 1250MVA for transmission, generation and large industrial loads. Gas-insulated power transformers are available for 110kV and 220kV systems up to 75MVA, in single-phase and three-phase designs. SC(B) series cast resin dry-type transformers cover voltages up to 40.5kV and capacities from 100 to 20000kVA for distribution and building applications.
What is the lead time for a Sieyuan power transformer?
Sieyuan power transformers can be delivered in as little as 8 months, and our average delivery time across 2025 was 10 months. For time-critical projects, fast-track production is available. Every order runs through a standardized design and manufacturing system with strict quality control at each stage, so the delivery date we confirm with your quotation is one we can keep.
Which standards do your transformers comply with?
Liquid-immersed power transformers are designed to IEC and IEEE/ANSI standards. Gas-insulated power transformers follow IEC, and standard models meet GB 20052-2024 Class II energy efficiency, with Class I designs available on request. Cast resin dry-type transformers conform to IEC 60076, GB/T 1094, GB/T 10228 and GB 20052, with Class F or Class H thermal ratings. Tell us the standard in your specification and we design to it.
Can a liquid-immersed power transformer use ester oil instead of mineral oil?
Yes. Our liquid-immersed power transformers can be filled with either mineral oil or ester oil as the cooling and insulating medium. Ester oil has a higher fire point and better biodegradability than mineral oil, which makes it a good choice for sites with fire safety or environmental requirements. Arrangements with integrated or split radiators and full or graded neutral insulation are also available.
How do I choose between liquid-immersed, gas-insulated and cast resin dry-type transformers?
Choose a liquid-immersed power transformer for high voltages and large capacities, up to 765kV and 1250MVA. Choose a gas-insulated power transformer when fire risk, explosion risk or limited space matters most, such as in urban and indoor substations at 110kV or 220kV. Choose a cast resin dry-type transformer for distribution voltages up to 40.5kV inside buildings or other sites with strict fire safety rules.
Request a Power Transformer Quote
Share your voltage, capacity, applicable standard and delivery requirements, and a Sieyuan sales representative will get back to you.