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Power Transformer

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Power Transformer (11kV to 220kV Liquid-Immersed Step-Up and Step-Down Transformers)

 

Liquid-immersed power transformers step up voltage for long-distance power transmission or step down voltage for regional distribution substations. Designed in compliance with IEC 60076 and IEEE C57 standards, these transformers integrate high-permeability grain-oriented silicon steel cores, copper windings, and active cooling radiators to maintain stable continuous operation under heavy electrical loads.

 
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Product Types

Substation Step-Down Power Transformer

Reduces high-voltage transmission levels to medium-voltage distribution circuits for municipal grids and industrial complexes. Features On-Load Tap Changers (OLTC) for real-time voltage regulation under varying grid loads.

Renewable Energy Step-Up Transformer (GSU)

Step-up power transformer installed at wind farms and solar PV plants to boost inverter output voltage (e.g., 0.69kV/33kV or 33kV/138kV) to grid interconnect levels. Engineered to handle high harmonic contents and frequent load fluctuations.

Industrial Dedicated Power Transformer

Heavy-duty transformers configured for arc furnaces, chemical electrolysis plants, and mining sites. Built with reinforced mechanical bracing to withstand high current surges and repetitive short-circuit stresses.

 

Technical Specifications

 

Parameter

33kV Class Power Transformer

110kV Class Power Transformer

220kV Class Power Transformer

Rated Capacity (MVA)

2.5 MVA - 31.5 MVA

10 MVA - 100 MVA

31.5 MVA - 250 MVA

Primary Voltage (kV)

33 / 34.5

110 / 115 / 138

220 / 230

Secondary Voltage (kV)

6.6 / 11 / 22

11 / 22 / 33

33 / 66 / 110

Vector Group

Dyn11 / Ynd11

YNd11 / YNyn0d11

YNautod11 / YNd11

Cooling Method

ONAN / ONAF

ONAN / ONAF

ONAN / ONAF / OFAF

Tap Changer Type

Off-Circuit (NLTC) / On-Load (OLTC)

On-Load Tap Changer (OLTC)

On-Load Tap Changer (OLTC)

Impedance Voltage (%)

7.5% - 10% (IEC 60076)

10% - 14% (IEC 60076)

12% - 18% (IEC 60076)

Partial Discharge Level

< 10 pC at 1.2 Um

< 10 pC at 1.2 Um

< 5 pC at 1.2 Um

Insulation Class and Liquid

Class A / Mineral Oil / Synthetic Ester

Class A / High-grade Mineral Oil

Class A / Inhibited Transformer Oil

 

Residential Distribution Transformer

 

Applications

Utility Transmission and Distribution: Serves as the core voltage conversion equipment in primary grid substations, switching regional high-voltage loops.

 

Solar and Wind Generation Hubs: Steps up cumulative generation voltage from central inverters and turbine transformers for utility-scale grid tie-in.

 

Heavy Manufacturing Facilities: Supplies continuous power to steel mills, paper factories, and manufacturing complexes requiring dedicated high-capacity transformers.

 

 
Customization Options
 
01/

Voltage and Tapping Range: Customized primary/secondary voltage ratings with +/-8 x 1.25% or +/-10 x 1.0% OLTC tapping steps from MR or ABB tap changers.

02/

Insulating Fluid Options: Standard naphthenic mineral oil, or biodegradable synthetic ester fluid (K-class, flash point > 300 degrees C) for fire-sensitive urban or indoor installations.

03/

On-Line Monitoring Systems (DGA): Integrated Dissolved Gas Analysis (DGA) sensors, fiber-optic real-time winding temperature monitoring, and oil moisture transmitters compatible with SCADA protocols (IEC 61850, Modbus).

04/

Corrosion Control Coatings: C4 or C5-M industrial paint systems applied via multi-layer shot blasting and epoxy-polyurethane coating for coastal or high-salinity offshore environments.

 

 

Quality and Compliance

Standards Compliance: Designed, manufactured, and tested per IEC 60076-1 through 60076-5, IEEE C57.12.00, and ISO 9001/14001 quality management systems.

 

Short-Circuit Withstand Capability: Core and winding assemblies feature high-density pressboard spacers and rigid radial clamping systems verified by short-circuit testing reports from independent laboratories.

 

Core and Winding Quality: Utilizes high-grade cold-rolled grain-oriented (CRGO) silicon steel sheets with step-lap miter joints to reduce no-load loss and audible noise levels.

 

Routine and Factory Acceptance Testing (FAT): 100% of manufactured units undergo routine testing prior to dispatch, including insulation resistance, winding resistance, voltage ratio, vector group verification, power frequency withstand voltage, applied voltage, and partial discharge measurement (< 10 pC).

Underground Distribution Transformer

 

Manufacturing and Delivery

 

1

Winding and Assembly Facilities

Dust-free, climate-controlled winding clean rooms ensure low moisture absorption during conductor processing.

2

Vacuum Drying and Oil Filling

Transformer active parts undergo Vacuum Pressure Impregnation (VPI) and long-cycle low-pressure vapor-phase drying (VPD) before vacuum oil filling under < 1 mbar pressure.

3

Production Lead Tim

12 to 16 weeks for standard substation transformers; 20 to 24 weeks for high-capacity 110kV/220kV custom units.

4

Heavy Freight Logistics

Main transformer tanks are shipped nitrogen-filled or oil-filled with impact recorders attached to log triple-axis g-force acceleration during transport. Radiators, conservator tanks, and bushings are disassembled and packaged in fumigated wooden crates.

 

FAQ

 

Q: What routine tests are performed on each power transformer before leaving the factory?

A: Every unit undergoes full routine testing according to IEC 60076-1. This includes winding resistance measurements, voltage ratio and phase displacement checks, short-circuit impedance and load loss measurement, no-load loss and current measurement, separate-source AC withstand voltage testing, induced overvoltage withstand testing, and partial discharge measurement.

Q: What tap changer brands and configurations can you integrate into the transformer?

A: We integrate both On-Load Tap Changers (OLTC) and Off-Circuit Tap Changers (NLTC). Standard OLTC options include vacuum and oil switch tap changers sourced from Maschinenfabrik Reinhausen (MR) or reputable domestic equivalents, depending on project technical specifications.

Q: How do you prevent oil leakage during long-term outdoor operation?

A: Tank covers utilize seamless CNC-machined flange sealing surfaces fitted with high-grade nitrile butadiene rubber (NBR) or fluoroelastomer (FKM) O-rings. All radiator connections use machined flat flanges with recessed rubber gaskets to eliminate stress relaxation and oil weeping.

Q: Can you supply transformers filled with biodegradable synthetic ester fluid instead of mineral oil?

A: Yes. We manufacture transformers compatible with synthetic ester fluids (such as MIDEL 7131). Synthetic esters offer high fire points (> 300 degrees C) and full biodegradability, making them suitable for environmentally sensitive sites or installations close to residential zones.

Q: Do you provide 2D General Arrangement drawings and 3D CAD models for engineering design review?

A: Yes. Upon receiving project voltage and capacity specifications, our design department generates 2D General Arrangement (GA) drawings, foundation layouts, terminal connection details, and 3D STEP models within 3 to 5 working days for customer review.

Q: How is the transformer prepared and protected for international ocean shipping?

A: For large power transformers, the active part is transported inside its fully welded main steel tank under nitrogen pressure to keep the insulation dry. Triple-axis impact recorders are mounted on the tank wall to monitor shock forces during transit. Detachable accessories (bushings, conservator, radiators, and piping) are packed separately in heavy-duty fumigated wooden cases.

As one of the most experienced power transformer manufacturers and suppliers in China, we also support customized service. We warmly welcome you to buy high quality power transformer from our factory. If you have any enquiry about pricelist, please feel free to email us.

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