35kV high-voltage transformer from core principles to intelligent selection

35kV oil immersed high voltage transformers are the core heart of modern power transmission and distribution systems, widely applied in power grids, new energy stations and industrial plants. This comprehensive guide elaborates on the working principle, internal structure, technical strengths, selection criteria and applicable scenarios of 35kV transformers. Supported by 56 national patents and 19 years of manufacturing experience, Kechang Electric supplies high-efficiency, reliable oil-immersed transformers for global power projects.

High voltage transformers are based on the law of electromagnetic induction. When alternating current passes through the primary coil (high voltage side) of the transformer, an alternating magnetic field is generated in the core, which in turn induces an electromotive force in the secondary coil (low voltage side), thereby effecting a transformation of the voltage. Under the condition of conservation of energy (ignoring the tiny losses of the transformer itself), its primary input power is substantially equal to its secondary output power, that is, it achieves almost lossless transfer of electrical energy.

A complete 35kV oil-immersed transformer is a sophisticated system composed mainly of the following core components:

• Iron core: The main magnetic circuit and the mechanical skeleton of the transformer, usually made of high magnetic permeability cold rolled oriented silicon steel sheet superimposed by laser processing, the quality of which directly determines the no-load loss and noise level.
• Winding: The circuit part of the transformer, made of copper or aluminum wires, isolated between high and low voltage windings by insulating materials, is responsible for the task of transmitting electrical energy.
• Fuel Tank: Sealed container to hold transformer and insulating oil, usually with fully sealed corrugated sheet structure, not only beautiful, but also moisture-proof, dust-proof and corrosion-proof.
• Insulating oil: As the insulation and cooling medium, Kechang Electric adopts high quality insulating oil with ignition point ≥140℃, which has insulation strength more than 3 times that of air.
• Protective device: including gas relay (action accuracy ≤0.5 m/s oil flow), pressure release valve (opening pressure 35 kPa to achieve directional injection), moisture absorber, etc. to ensure safe operation.
• Cooling system: For oil-immersed transformers, oil-immersed self-cooling (ONAN) or oil-immersed air-cooling (ONAF) is usually used, by natural circulation of oil or forced air-cooling for heat dissipation.
• Insulated Sleeve: Lead the high and low voltage leads of the inner winding safely out to the outside of the fuel tank and keep it insulated to the ground.

Kechang Electric continues to make breakthroughs in 35kV transformer technology and has formed significant technical advantages:

• Structural innovation technology: High and low pressure clamps are tightened with steel pull straps or upper and side beams to form a solid frame, which greatly enhances resistance to short circuit and resistance to transport impact. Longitudinal oil passages are provided in high and low voltage coils, which effectively reduces the temperature difference between copper and oil and the temperature rise of the hottest spot inside the coil.
• Efficient and energy-saving technology: Using high magnetic permeability oriented silicon steel sheet and optimized iron core laminating process, the no-load loss of the product is reduced by more than 30% on average compared to traditional S11 type products. Taking the S22-31500/35 model as an example, the no-load loss is only 11460W and the load loss is 80640W, reaching the national first-level energy efficiency standard.
• Advanced noise control technology: The core burr is controlled within 0.03 mm, combined with the five-step lamination process, so that the product noise is 20% lower than the average level of the international standard JB/T10088-2004, and the 20000 kVA transformer noise can be as low as 52dB (A).
• Fully sealed and environmentally friendly technology: The fully sealed fuel tank structure makes the oil age slowly, and the silicone replacement cycle of the moisture absorber is more than 5 years, which greatly reduces maintenance costs. Transformer oil is recyclable and has a significantly lower carbon footprint than dry-type transformers.

1. High reliability and long life: The design life is more than 30 years, passed GB/T1094.5 short circuit test verification, strong resistance to short circuit.

2. Excellent energy efficiency with low operating costs: Level 1 energy efficiency standards mean lower no-load loss and load loss, which can save huge electricity bills throughout the life cycle.

3. Strong environmental adaptability: The fully sealed structure can operate stably in the temperature range of -25 ℃to +40℃, the altitude can be customized up to 3000 meters, suitable for high humidity, high altitude, chemical and other harsh environment.

4. Comprehensive improvement of safety performance: perfect protection device and explosion-proof design to ensure the safety of equipment and personnel.

5. Low-noise operation: especially suitable for residential areas, hospitals, data centers and other noise-sensitive areas.

• Complete qualification documents: Type test report and certification certificate for inspection products.
• Verification of technical parameters: Check key parameters such as no-load loss, load loss and short-circuit impedance
• Process and material: Focus on iron core silicon steel sheet brand (such as Shougang, Baowu Steel), winding material (copper or aluminum), etc., these directly affect product performance and life.
• Traceability: Choose an enterprise like Kechang that implements automated production, where every component and every process of its products is systematically recorded, and any details can be traced, providing a solid guarantee for quality.

35kV high-voltage transformer has been successfully used in many national key projects and fields

Choose the plan that suits you best.

Power grid construction and transformation

The urban and rural power grid transformation project of the State Grid serves as the core equipment of the hub substation.

 

Industrial sector

Total drop substations of large industrial enterprises such as petrochemicals, metallurgy and mining, and rail transit.

Access to new energy sources

Boost stations in wind farms and photovoltaic power stations to efficiently connect clean energy sources to the main grid.

 

 

Commercial & Public Facilities

Dedicated Substations for Large Parks, Hospitals, Data Centers.

Choosing a qualified, energy-saving 35kV oil immersed transformer determines the long-term safe operation of your power infrastructure. As a professional manufacturer with rich project experience, Kechang Electric can customize parameters according to your ambient temperature, altitude and load demands. If you need technical parameters, quotation and exclusive selection suggestions for 35kV high voltage transformers, please contact our engineering team to get the free technical whitepaper now.