735kV 750kV 765kV Single-phase Oil-Immersed Autotransformer with Three Windings and No Excitation

Product Description：

As a pioneer in China's power transformer industry, we have specialized in the R&D and manufacturing of power transformer equipment for decades, and established industry standards with core technologies.

The 750kV Single-phase Oil-Immersed Autotransformer with Three Windings and No Excitation is a critical component designed for the highest tiers of power transmission systems. Its robust oil-immersed cooling technology ensures stable thermal performance and long-term reliability under heavy loads. The unique three-winding configuration provides exceptional operational flexibility, enabling efficient power transfer and system interconnection. As a "no excitation" design, it offers superior reliability and simplified maintenance by eliminating the need for on-load tap-changing mechanisms, making it an ideal and dependable solution for ultra-high voltage (UHV) grid applications that demand unwavering performance.

This power transformer is fully compliant with international standards including IEC 60076-1, IEEE C57.12.00, ANSI C57.12.90, AS/NZS 60076.5 and EN 61558-1. It meets quality requirements and is widely adaptable to the operational needs of power grids in multiple overseas regions.

Product Characteristics:

• Optimized Structural Design: Utilizes advanced computational analysis of electrical, magnetic, mechanical, and thermal behavior to ensure robust and reliable construction.

• Superior Electrical Performance: Complies with IEC standards while offering customized solutions, with partial discharge levels significantly lower than IEC 60076-3 limits.

• Enhanced Operational Reliability: Multi-physics field analysis optimizes insulation, amp-turns balance, and cooling, delivering strong resilience to overvoltage and short-circuit events while eliminating risks of local overheating.

• Premium Component Selection: Provides an exceptional user experience with a clean appearance, leak-free construction, and maintenance-free operation—no core disassembly required.

Technical Parameters

The voltage classes of some of these Power Transformer include 6kV, 6.3kV, 6.6kV, 6.9kV, 7.2kV, 10kV, 10.5kV, 11kV, 11.5kV, 12kV, 13.2kV, 13.8kV, 14.5kV, 14.4kV, 15kV, 15.5kV, 15.6kV, 17.5kV, 20kV, 21.9kV, 22kV, 24kV, 30kV, 33kV, 33.5kV, 34.5kV, 35kV, 36kV, 38kV, 38.5kV, 40.5kV, 44kV, 45kV, 46kV, 66kV  69kV.72.5kV 88kV 110kV 115kV 123kV 125kV 126kV 132kV 138kV 145kV 150kV 154kV 161kV 170kV  220kV 225kV 230kV 245kV 275kV 330kV 345kV 363kV 380kV 400kV 500kV Power transformers of voltage ，and aboveand customization is available.

Among these, some autotransformers cover non-standard voltage levels including 121kV, 132kV, 138kV, 200kV, 225kV, 230kV, 245kV, 275kV, 330kV, 345kV, 400kV and 756kV,  We also provide customization services.

Note: Transformers with various special parameters and performance can be manufactured according to customer requirements.

Normal Service Conditions

(1) Altitude:  ≤1000m;

(2) Ambient temperature:Maximum temperature: +40℃;Maximum monthly average temperature: +30℃;Maximum yearly average temperature: +20℃;Minimum temperature: -25℃.

(3) Power supply: approximate sinusoidal wave, three-phase symmetrical approximately

(4) Installation site: indoor or outdoor, without the obvious contamination.Note: The transformer used in special conditions should be specified when ordered.

Introduction to Structure and Performance:

Core:

• Adopting highest quality, non-aging, cold-rolled, grain-oriented, and high permeability silicon steel lamination silicon steel sheets.

• Processed on the GEORG length-cutting line from Germany.

• Fully mitred joint, step lapping and polyester tape binding structure making the transformer with low no-load losses and low noise level.

• Placing vibration isolation pads between the body and the tank to reduce vibration that transmits to the tank.

Winding:

• Winded by high-quality oxygen free copper with lower resistivity.

• Processed and manufactured on horizontal winding machines and large CNC vertical winding machines from both radial and axial directions.

• Reasonable transposition applied between paralleling wires, magnetic shielding used for guiding flux leakage when necessary to reduce the stray losses of the transformer.

• Reasonable design of insulation structure improving the ability of withstanding overvoltage.

• Optimizing the ampere turns distribution of the winding, increasing the radial support and axial compression of the winding, using the pre-densification of spacers, constant pressure drying, to resist the impulse current.

Tank:

• Bell type or cover bolted type tank.

• Carbon dioxide shielded welding process.

• High-quality gaskets and the limit groove.

• Strict leak detection test procedures.

Others:

• Cold-weld connection technology leads to improve the cleanliness of active part.

• The vacuum disassembly and the vacuum filling technology measures reduce the partial discharge level effectively and enhance the transformer operating reliability.

• The structure of "Six Direction Positioning" between the active part and the tank assures that the transformer has a strong ability of anti-transportation impact or anti-earthquake.

• Surface treatment and coating, fine processing to tank surface, 7 steps such as acid-washing and phosphating, etc. special anti-fouling paint, ensuring not falling off or rusting away.