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400MVA 3 Phase Power Transformer

The 400 MVA 3‑Phase Power Transformer is a high‑capacity autotransformer engineered for outdoor transmission applications in temperate climates. Built to DSTU EN 60076‑1 and GOST standards, it steps down 330 kV to 165 kV with a Yna connection, delivering 400 MVA continuous through a three‑stage cooling system (ONAN → ONAF → OFAF). Its low‑loss core and optimized winding geometry yield a peak efficiency of 99.797 %, while robust construction—including a bell‑type tank with elastic membrane conservator—ensures a 30‑year service life. Rated for altitudes up to 1 000 m and ambient temperatures from –40 °C to +45 °C, this transformer features a ±8.4 %/ +7.2 % eight‑step on‑load tap changer, comprehensive safety relays, and galvanized control cabinets, making it ideal for critical power corridors.

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Product Accessories

On‑Load Tap Changer (OLTC): Vacuum‑type diverter switch rated 1 250 A with eight positions for ±8.4 % to +7.2 % voltage control.

Gas (Buchholz) Relay & Pressure‑Relief Valve: Dual‐float gas detection and overpressure trip with contact outputs.

Oil & Winding Temperature Sensors: PT100‑based devices with alarm/trip contacts and automatic fan control.

Conservator & Silica‑Gel Breather: Elastic membrane conservator with self‑regenerating desiccant to maintain oil dryness.

Porcelain HV/MV Bushings: Rated for 950 kV/550 kV full‑wave impulse, side‑mounted with cable entry ports.

Forced‑Air Radiators & Fans: Galvanized cooler banks with visual shut‑off valves and maintenance platforms.

Control Cabinet: IP55 stainless‑steel enclosure with automatic temperature maintenance, dual power feeds, lighting, and SCADA interface.

Surge Arresters: External station‑class arresters for both HV and MV sides.

Lifting Rails & Rollers: Integrated rail shoes and ribbed rollers for on‑site movement.

Nameplates & Wiring Schematics: Durable stainless‑steel plates and laminated diagrams.

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Product Specifications

Rated Power

400 MVA

High Voltage (HV)

330 kV nominal; 242 kV rated; 252 kV max

Medium Voltage (MV)

165 kV nominal; 190 kV rated; 198 kV max

Vector Group

Yna

Tap Changer Range

±8.4 % to +7.2 % (8 steps)

Cooling Method

ONAN / ONAF / OFAF

Efficiency (PEI)

99.797 %

Lightning Impulse Withstand (Full/Chopped)

HV: 950 / 1 050 kV; MV: 550 / 600 kV

Short-Duration Withstand (1 min)

HV Ph‑G: 395 kV; Ph‑Ph: 525 kV; MV Ph‑G: 230 kV

Temperature Rise (Oil/Windings)

65 °C / 65 °C

Product Applications

Economy is more affordable

Product Advantages

Three‑Stage Cooling Flexibility

Smooth transition from ONAN to ONAF and OFAF maximizes load capacity and thermal safety without manual intervention.

Ultra‑High Efficiency

Low‑loss magnetic core and advanced winding techniques achieve near‑99.8 % efficiency, reducing operating costs.

Built‑In Reliability

Rugged construction with high‑impulse BIL, comprehensive protective relays, and stainless‑steel control cabinets ensure decades of maintenance‑free operation.

WellDone Power Transformer Plan Drawing

FAQ

What range of transformer products do you offer and which standards do they meet?

We manufacture a diverse array of transformers including Oil-Immersed Distribution Transformers, Dry Type Transformers, Power Transformers, Three Phase Pad Mounted Transformers, Single Phase Pad Mounted Transformers, Substation Transformers, and Pole Mounted Transformers. Our technical team, with nearly 20 years of industry experience, ensures that our designs comply with international standards such as ANSI, IEEE, DOE, CSA, AS, AZS, GOST, IEC, and more. Additionally, many of our products have obtained UL, cUL, and CSA certifications, affirming their safety and performance in global markets.
How do you ensure the quality and reliability of your transformers?

Our transformers are produced under a rigorous quality management system covering every stage from material selection to final testing. Each product comes with a minimum 24-month warranty, ensuring long-term safety and reliability. This commitment to quality has earned the trust of global customers and leading industry players.
What are your production lead times, customization options, and global market reach?

For standard models, our production lead time is typically 10 to 25 days, and we offer flexible OEM/ODM services for customized projects. We also tailor packaging solutions to meet specific customer requirements. Our transformers are exported worldwide—including North America, Europe, South America, Australia, Asia, and Africa—with successful partnerships involving renowned companies. For more details or personalized support, please contact us via email or WhatsApp.