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

Product Description：

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.

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

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.