90kV Three-Phase Oil-Immersed Power Transformer
The 90kV Three-Phase Oil-Immersed Power Transformer for High-Voltage Distribution is engineered to deliver reliable and efficient performance across utility grids, industrial substations, and high-voltage transmission systems. Designed with high-grade silicon steel cores and 100% copper windings, the transformer ensures low losses, strong short-circuit resistance, and stable thermal performance. Its oil-immersed cooling structure provides superior heat dissipation, supporting continuous and heavy-duty operation. The robust tank, high-performance insulation system, and outdoor-ready protection structure enable safe operation in harsh climate conditions. Compliant with IEC, IEEE, and GB standards, the transformer offers excellent voltage stability, long service life, and high operational reliability. It is widely used in power utilities, infrastructure projects, renewable energy integration, and industrial distribution networks requiring dependable high-voltage transformation.
- Primary Voltage Ratings 69kV 66kV 90kV or others
- Secondary Voltage Ratings 33/13.8/11 kV or customized
- H.V. Tap Range ±8×1.25% or others
- Type Oil-immersed power transformer
- BIL Up to 350kV
- Standards IEEE, ANSI, IEC, CSA
- Application regional substations, large industrial parks, wind/solar farm step-up stations
- Power Rating 75-4000kVA
- Certificate UL ,CESI ,ISO
- Cooling Method ONAN/ ONAF
- Opeartion Step Down & Step Up
Technical Specifications
Customization Optional
Packing and Shipping
Manufacturer Test
Routine Testing
Application
Technical Specifications
90kV Three-Phase Oil-Immersed Power Transformer
Technical Specifications
Accessories
| Rated Power | 75-4000kVA |
| Rating Primary Voltage | 69kV 66kV 90kV or others |
| Secondary Voltage |
33kV 13.8kV 11kV Customized |
| Frequency | 50/60Hz |
| Vector Group | Dyn11, YNd1, Dyn1, YNd11 or others |
| Winding Material | Aluminum/Copper |
| Efficiency | As IEEE, CAS Std or Customized |
| Impedance Voltage | As IEC |
| Altitude | ≤1,000m or Customized |
| Enclosure material | Mid Steel |
| HV Bushing |
| LV Bushing |
| OLTC/NLTC |
| Lifting hook for complete transformer |
| Name plate |
| Oil temperature |
| Winding temperature |
| Radiators |
| Oil level |
| Pressure relief valve |
| CT |
Customization Optional
90kV Three-Phase Oil-Immersed Power Transformer
Customization for the 90kV Three-Phase Oil-Immersed Power Transformer covers all electrical, mechanical, and protection aspects to meet diverse application requirements. Electrical parameters such as primary and secondary voltage ratings, vector group configurations (Dyn11, YNd1, Yyn0), impedance values, and tap changer specifications can be fully tailored. Customers may choose between no-load and on-load tap changers with customized tap ranges to support precise voltage regulation. Additional electrical customization includes low-loss core options, alternative copper/aluminum winding materials, enhanced insulation levels, and special dielectric oils such as FR3 or low-temperature fluids for extreme environments. Transformers can be designed for high altitude, coastal conditions, or heavy industrial zones with increased pollution and humidity.
Mechanical customization includes reinforced tank designs, corrugated or radiator cooling options, explosion-proof features, and anti-corrosion coatings suitable for corrosive or coastal installations. Intelligent monitoring systems—such as digital temperature controllers, SCADA communication modules, Buchholz relays, pressure relief devices, and online DGA sensors—can be integrated for advanced condition monitoring. Custom accessories, cable boxes, surge arresters, seismic-resistant structures, low-noise designs, and compact footprints can also be implemented. Every customized configuration is engineered to comply with IEC, IEEE, and national standards, ensuring optimized performance, reliability, and compatibility with project-specific requirements.
Packing and Shipping
90kV Three-Phase Oil-Immersed Power Transformer
The packing and shipping process for the 90kV Three-Phase Oil-Immersed Power Transformer is designed to ensure maximum protection and reliability throughout domestic or international transport. Before packaging, the transformer undergoes final inspection, oil filling or nitrogen-sealing, and anti-corrosion treatment. External components are coated, sealed, and cleaned to prevent oxidation or moisture absorption. All accessories—including bushings, radiators, sensors, control units, and hardware—are removed when required and individually packed in reinforced wooden crates with carefully fitted shock-absorbing materials.
The transformer body is mounted securely onto a heavy-duty steel base or export-grade wooden pallet. This frame prevents shifting, vibration, and impact damage during transport. Shock absorbers, braces, and structural protectors are placed at all vulnerable points. Multiple protective layers—including moisture-proof barriers, UV-resistant films, rust-preventive coatings, and reinforced corner guards—are applied to ensure full protection in extreme weather or long-distance transportation. Nitrogen-filled sealing can be applied to maintain insulation dryness during sea shipment.
Depending on size and destination, the transformer may be shipped via flat-rack containers, open-top containers, or break-bulk shipment. All packing materials adhere to global ISPM-15 and export regulations. The logistics team coordinates loading, transportation mode selection, customs clearance, and required documentation—including packing lists, test certificates, manuals, quality reports, and installation guides—provided in waterproof envelopes attached to the transformer tank.
Upon arrival on-site, engineering support can be provided for unloading, inspection, reassembly of accessories, oil filling, vacuum filtration, and commissioning. The complete packing and shipping process ensures the transformer reaches the site in perfect mechanical and electrical condition, ready for safe installation and long-term service.
The transformer body is mounted securely onto a heavy-duty steel base or export-grade wooden pallet. This frame prevents shifting, vibration, and impact damage during transport. Shock absorbers, braces, and structural protectors are placed at all vulnerable points. Multiple protective layers—including moisture-proof barriers, UV-resistant films, rust-preventive coatings, and reinforced corner guards—are applied to ensure full protection in extreme weather or long-distance transportation. Nitrogen-filled sealing can be applied to maintain insulation dryness during sea shipment.
Depending on size and destination, the transformer may be shipped via flat-rack containers, open-top containers, or break-bulk shipment. All packing materials adhere to global ISPM-15 and export regulations. The logistics team coordinates loading, transportation mode selection, customs clearance, and required documentation—including packing lists, test certificates, manuals, quality reports, and installation guides—provided in waterproof envelopes attached to the transformer tank.
Upon arrival on-site, engineering support can be provided for unloading, inspection, reassembly of accessories, oil filling, vacuum filtration, and commissioning. The complete packing and shipping process ensures the transformer reaches the site in perfect mechanical and electrical condition, ready for safe installation and long-term service.
32
32 years of industry experience
Manufacturer Test
90kV Three-Phase Oil-Immersed Power Transformer
Progress test
The Progress Test for the 90kV Three-Phase Oil-Immersed Power Transformer is conducted throughout the production process to ensure strict quality control and early detection of defects. Raw materials—including copper conductors, silicon steel, insulation paper, and transformer oil—are tested for compliance with technical specifications. During coil winding, inspections verify winding tightness, dimensional accuracy, insulation layering, and conductor integrity. Core assembly is checked for geometric alignment, clamping pressure, and minimal air gaps. Intermediate electrical tests—such as winding resistance, insulation resistance, and partial discharge checks—confirm stability before final assembly. Mechanical components, including the tank and radiators, undergo pressure, leak, and weld integrity tests. Each stage ensures manufacturing consistency and readiness for the final FAT.
Design Tests
All transformers will be tested after finishing the production test items as below:
♦ Leak testing with pressure for liquid-immersed transformers
♦ Test of transformer oil
♦ Measurement of voltage ratio and check of phase displacement
♦ Measurement of winding DC resistance
♦ Measurement of d. c. Insulation resistance between each winding to earth, and check of the core and frame insulation
♦ Capacitive bushing test
♦ Measurement of dissipation factor (tan δ) of the insulation system capacitances, and determination of capacitances windings-to-earth
♦ Measurement of no-load loss and current at 90%,100%,110% of rated voltage
♦ Operation test on on-load tap-changer
♦ Measurement of short-circuit impedance and load loss
♦ Lightning impulse test
♦ Induced-voltage test with partial discharge measurement
♦ Auxiliary wiring check
♦ Current transformer test
♦ Frequency response analysis test
Transformer Factory Acceptance Test
The Factory Acceptance Test for the 90kV Three-Phase Oil-Immersed Power Transformer validates full compliance with international standards and project specifications. Routine electrical tests include winding resistance, turns ratio verification, vector group check, insulation resistance measurement, and polarity confirmation. High-voltage tests—such as applied AC withstand, induced voltage withstand, and partial discharge—ensure dielectric strength. Performance evaluations include no-load loss, load loss, impedance measurement, and temperature-rise testing. Lightning impulse tests verify insulation resilience against overvoltage surges. Mechanical inspections confirm tank tightness, bushing alignment, cooling system function, tap changer operation, and transformer oil quality. All protection devices, including Buchholz relays and temperature controllers, are calibrated and tested. FAT reports are reviewed with the customer before shipment.
Routine Test - Excitation & No-Load Loss (Rated Voltage)
Purpose of Testing
The purpose of testing Excitation & No-Load Loss at rated voltage is to assess the transformer's core loss and magnetizing current under normal operating conditions, ensuring efficient performance and identifying any potential issues in the core or windings. This test helps verify that the transformer operates within specified parameters and meets its design requirements.
Testing Equipment
Test equipment: Excitation Test instrument (such as OMICRON, Megger, etc.)
Voltage source: usually rated voltage (such as 230V, 400V, 660V, customized according to equipment requirements)
Temperature and humidity meter: used to record ambient temperature and humidity conditions
Voltage source: usually rated voltage (such as 230V, 400V, 660V, customized according to equipment requirements)
Temperature and humidity meter: used to record ambient temperature and humidity conditions
Pre-Test Preparation
Disconnect and make sure the device is powered off and properly grounded and discharged.
Check the device terminals and wiring to ensure that the connection is secure and not loose or contaminated.
Ensure the test environment is suitable: relative humidity below 75%, no rain, and recommended temperature is 20-30°C.
Check the device terminals and wiring to ensure that the connection is secure and not loose or contaminated.
Ensure the test environment is suitable: relative humidity below 75%, no rain, and recommended temperature is 20-30°C.
Test Progress
Connect the Test Instrument:
Connect the test equipment to the appropriate terminals of the device under test and ensure that all connection points are properly grounded to avoid current leakage during the test.
Apply Test Voltage:
Select a suitable test voltage according to the rated voltage of the equipment (for example, the rated voltage is 11kV, 33kV or others), and ensure that the applied voltage is stable.
Connect the test equipment to the appropriate terminals of the device under test and ensure that all connection points are properly grounded to avoid current leakage during the test.
Apply Test Voltage:
Select a suitable test voltage according to the rated voltage of the equipment (for example, the rated voltage is 11kV, 33kV or others), and ensure that the applied voltage is stable.
Measure and Record
No-load current
No-load loss
Excitation loss
Power factor
Voltage
Current
Ambient temperature and humidity during testing
No-load loss
Excitation loss
Power factor
Voltage
Current
Ambient temperature and humidity during testing
Temperature Correction
The measured loss values and currents are corrected to a reference temperature (typically 20°C) for an accurate evaluation.
Repeat Testing (if necessary)
If necessary, measure the no-load loss and excitation loss of different windings (high voltage, medium voltage, low voltage) and at different voltage levels for comparative analysis.
Evaluation Criteria (Reference)
No-load loss ≤ rated loss (meets specifications)
No-load loss > rated loss (further inspection or corrective action required)
No-load loss > rated loss (further inspection or corrective action required)
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
90kV three-phase oil-immersed power transformers are mainly used in regional substations, large industrial parks, wind/solar farm step-up stations, urban distribution hubs, and 110kV/35kV primary transformation, providing efficient voltage conversion, reactive power compensation, and reliable power support for high-load, long-distance transmission scenarios.
Technical Advantages
● 30+ years of manufacturing experience
● ISO and UL certified production
● Customized cable and transformer solutions
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What is a Transformer?A transformer is an electrical device used to change the voltage of alternating current (AC). It works on the principle of electromagnetic induction, converting high-voltage current into low-voltage current or low-voltage current into high-voltage current. Transformers are widely used in power transmission, distribution systems, and various electronic devices.
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What are the main uses of a transformer?The main use of a transformer is voltage conversion. Transformers are used in power transmission systems to help transfer electricity from power plants to consumers. In addition, transformers are also used in electronic devices such as chargers, televisions, power adapters, etc., to adjust the voltage to meet the requirements of different devices.
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Do you have UL listed?Yes, our transformer has UL listed. We have exported to America many pad mounted transformer,substation transformer and HV.
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