120kV High-Voltage Three-Phase Oil-Immersed Power Transformer
The 120kV High-Voltage Three-Phase Oil-Immersed Power Transformer is engineered for reliable and efficient operation in transmission networks and high-voltage substations. Designed with high-permeability silicon steel cores and precision-wound copper conductors, it delivers low losses, excellent thermal performance, and strong short-circuit withstand capability. The oil-immersed cooling system ensures effective heat dissipation, supporting continuous operation under heavy-load and fluctuating grid conditions. A robust tank structure, advanced insulation system, and outdoor-rated protection allow stable operation in harsh climates and demanding environments. Manufactured in accordance with IEC, IEEE, and ANSI standards, this transformer is widely applied in utility grids, industrial power systems, and large-scale infrastructure projects where high reliability, long service life, and stable voltage transformation are essential.
- Primary Voltage Ratings 110kV, 115kV or others
- Secondary Voltage Ratings 11/10.5/6.6/6.3kV or customized
- H.V. Tap Range ± 8×2.5% HV taps or others
- Type Oil-immersed power transformer
- BIL up to 350kV
- Standards IEEE, ANSI, IEC
- Application high-voltage substations, regional transmission networks, power systems, and infrastructure projects
- Power Rating 35MVA 50MVA
- Certificate UL , CESI , CE
- Cooling Method ONAN/ ONAF
- Opeartion Step Down & Step Up
Technical Specifications
Customization Optional
Packing and Shipping
Manufacturer Test
Routine Testing
Application
Technical Specifications
120kV High-Voltage Three-Phase Oil-Immersed Power Transformer
Technical Specifications
Accessories
| Rated Power | 35MVA 50MVA |
| Rating Primary Voltage | 110kV, 115kV |
| Secondary Voltage |
6.3 kV 6.6 kV 10.5 kV 11 kV Customized |
| Frequency | 50/60Hz |
| Vector Group | Dyn11, YD11, YNd11 |
| 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
120kV High-Voltage Three-Phase Oil-Immersed Power Transformer
The 120kV High-Voltage Three-Phase Oil-Immersed Power Transformer can be fully customized to meet specific grid requirements, environmental conditions, and project standards. Electrical customization includes flexible primary and secondary voltage ratings, vector group configurations such as Dyn11, YNd1, or Yyn0, impedance optimization, and efficiency tuning to comply with regional utility regulations. Customers may select no-load or on-load tap changers with customized tap ranges for accurate voltage regulation. Winding materials are available in high-purity copper or aluminum, while insulation systems can be enhanced for high-altitude, high-temperature, or high-humidity applications. Optional low-loss core designs and environmentally friendly insulating oils are also available to improve operational efficiency and sustainability.
Mechanical and structural customization options include reinforced tank designs, corrosion-resistant coatings for coastal or industrial environments, seismic-resistant structures, and customized cooling systems such as ONAN, ONAF, or OFAF. Advanced monitoring and protection devices—such as Buchholz relays, digital temperature indicators, oil level sensors, pressure relief devices, and online condition monitoring systems—can be integrated to support predictive maintenance and operational safety. Noise-reduction solutions, compact footprints for space-limited substations, customized bushing arrangements, and project-specific accessory configurations are also supported. All customized designs comply with IEC, IEEE, or customer-specified technical standards, ensuring reliable long-term performance.
Packing and Shipping
120kV High-Voltage Three-Phase Oil-Immersed Power Transformer
The packing and shipping process for the 120kV High-Voltage Three-Phase Oil-Immersed Power Transformer is designed to ensure maximum protection during transportation and storage. Prior to packing, the transformer undergoes final inspection, surface anti-corrosion treatment, and oil handling in accordance with transport requirements. All openings are sealed to prevent moisture ingress, and exposed metal surfaces are protected against corrosion. Sensitive components such as bushings, radiators, conservators, and monitoring devices are removed when required and packed separately in reinforced wooden crates with shock-absorbing padding.
The transformer's main body is mounted securely on a heavy-duty steel skid or export-grade wooden base to prevent movement during transit. Structural braces, vibration dampers, and impact-resistant materials are installed at critical points to minimize mechanical stress. The unit is wrapped in multiple protective layers, including moisture-proof films, UV-resistant covers, and rust-inhibiting materials. For long-distance sea transport, nitrogen filling or vacuum sealing may be applied to maintain insulation dryness and oil quality.
Depending on the transformer’s size, weight, and destination, shipment can be arranged using flat-rack containers, open-top containers, or break-bulk cargo methods. All packaging materials comply with international shipping standards, including ISPM-15 requirements. Clear lifting instructions, center-of-gravity markings, and handling labels are applied to ensure safe loading and unloading. Complete documentation—including packing lists, test reports, quality certificates, drawings, and operation manuals—is provided in waterproof packaging attached to the transformer.
Upon arrival at the destination, detailed unpacking, storage, and installation guidelines are supplied. Optional on-site services include unloading supervision, accessory reassembly, oil filling, filtration, and commissioning support. This comprehensive packing and shipping process ensures the transformer arrives in optimal condition, ready for safe installation and long-term operation.
The transformer's main body is mounted securely on a heavy-duty steel skid or export-grade wooden base to prevent movement during transit. Structural braces, vibration dampers, and impact-resistant materials are installed at critical points to minimize mechanical stress. The unit is wrapped in multiple protective layers, including moisture-proof films, UV-resistant covers, and rust-inhibiting materials. For long-distance sea transport, nitrogen filling or vacuum sealing may be applied to maintain insulation dryness and oil quality.
Depending on the transformer’s size, weight, and destination, shipment can be arranged using flat-rack containers, open-top containers, or break-bulk cargo methods. All packaging materials comply with international shipping standards, including ISPM-15 requirements. Clear lifting instructions, center-of-gravity markings, and handling labels are applied to ensure safe loading and unloading. Complete documentation—including packing lists, test reports, quality certificates, drawings, and operation manuals—is provided in waterproof packaging attached to the transformer.
Upon arrival at the destination, detailed unpacking, storage, and installation guidelines are supplied. Optional on-site services include unloading supervision, accessory reassembly, oil filling, filtration, and commissioning support. This comprehensive packing and shipping process ensures the transformer arrives in optimal condition, ready for safe installation and long-term operation.
32
32 years of industry experience
Manufacturer Test
120kV High-Voltage Three-Phase Oil-Immersed Power Transformer
Progress test
The Progress Test for the 120kV High-Voltage Three-Phase Oil-Immersed Power Transformer is implemented as a staged quality assurance program throughout the entire manufacturing cycle. Incoming material inspections are first conducted on core laminations, copper conductors, insulation materials, structural steel, and insulating oil to ensure conformity with approved specifications. During core stacking and coil winding, process inspections verify dimensional tolerances, insulation clearances, winding compression, and mechanical stability. Active parts undergo controlled drying and vacuum treatment, with temperature and moisture levels continuously monitored to ensure optimal insulation condition.
Intermediate electrical examinations include winding resistance measurement, insulation resistance testing, and turns ratio verification to confirm electrical integrity before final assembly. Fabrication of the transformer tank and radiators is inspected for welding quality, pressure endurance, and surface coating thickness. Prior to oil filling, vacuum leak tests and internal cleanliness checks are performed. All findings are recorded in detailed progress reports, ensuring traceability and early detection of deviations before the transformer proceeds to final acceptance testing.
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 (FAT) for the 120kV High-Voltage Three-Phase Oil-Immersed Power Transformer is carried out after complete assembly to confirm full compliance with contractual and international standards. Electrical routine tests include measurement of winding resistance, verification of turns ratio and vector group, insulation resistance evaluation, and polarity confirmation. Dielectric testing consists of applied AC voltage and conducting overvoltage withstand tests to validate insulation strength under rated conditions.
Performance tests measure no-load loss, load loss, impedance voltage, and temperature rise to ensure operational efficiency and thermal stability. Partial discharge measurements assess insulation quality, while lightning impulse tests verify the transformer’s ability to withstand transient overvoltage events. Mechanical and functional inspections cover oil tank pressure testing, bushing installation accuracy, tap changer operation, cooling system functionality, and oil quality analysis. All protection devices and monitoring instruments are checked for correct calibration. FAT results are formally documented and reviewed with the customer prior to shipment approval.
Routine Test - DC Insulation Resistance Test
Purpose of Testing
The purpose of DC insulation resistance testing is to measure the insulation resistance of a device by applying a DC voltage, thereby evaluating the health of the insulation material and the voltage withstand capability of the electrical device. This test helps detect potential insulation aging, moisture or damage, preventing electrical failures in the device.
Testing Equipment
Insulation resistance tester (e.g. Megger, Fluke, Hioki, Klein Tools, etc.)
Voltage source (usually 500V, 1000V, 2500V, or customized according to customer requirements)
Temperature and humidity meter (used to record the ambient temperature and humidity during the test to ensure that the test conditions meet the standard requirements.)
Voltage source (usually 500V, 1000V, 2500V, or customized according to customer requirements)
Temperature and humidity meter (used to record the ambient temperature and humidity during the test to ensure that the test conditions meet the standard requirements.)
Pre-Test Preparation
Make sure the device is properly grounded and fully discharged to prevent residual charge in the device from affecting the test results.
Perform the test under suitable environmental conditions. It is recommended to have a relative humidity below 75%, no rain, and a temperature range of 20-30°C to avoid moisture or temperature fluctuations affecting the test results.
Perform the test under suitable environmental conditions. It is recommended to have a relative humidity below 75%, no rain, and a temperature range of 20-30°C to avoid moisture or temperature fluctuations affecting the test results.
Test Progress
Connect the Test Instrument:
Connect an insulation resistance tester to the high voltage terminal of the device under test and to ground.
Apply Test Voltage:
Select an appropriate test voltage based on the rated voltage of the equipment .
Connect an insulation resistance tester to the high voltage terminal of the device under test and to ground.
Apply Test Voltage:
Select an appropriate test voltage based on the rated voltage of the equipment .
Measure and Record
Start the test and record the following parameters:
Insulation resistance value (MΩ)
Applied voltage
Ambient temperature and humidity during testing
Insulation resistance value (MΩ)
Applied voltage
Ambient temperature and humidity during testing
Temperature Correction
The measured insulation resistance values are corrected to a reference temperature (usually 20°C) for accurate evaluation.
Repeat Testing (if necessary)
Measure different windings (high voltage, medium voltage, low voltage) or each bushing separately, and conduct comparative analysis to ensure the insulation status of all parts.
Evaluation Criteria (Reference)
Insulation resistance ≥ 1000 MΩ (excellent)
500 MΩ ≤ Insulation resistance < 1000 MΩ (good)
100 MΩ ≤ Insulation resistance < 500 MΩ
Insulation resistance < 100 MΩ
500 MΩ ≤ Insulation resistance < 1000 MΩ (good)
100 MΩ ≤ Insulation resistance < 500 MΩ
Insulation resistance < 100 MΩ
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
It supports stable voltage transformation, long-distance power transmission, and continuous heavy-load operation in environments requiring high reliability, safety, and long service life.
Technical Advantages
● 30+ years of manufacturing experience
● ISO and UL certified production
● Customized cable and transformer solutions
Product Packaging
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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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