121kV Oil-Immersed High-Voltage Power Transformer
The 121kV Oil-Immersed High-Voltage Power Transformer is designed to provide stable, efficient, and long-term power transformation for transmission networks and high-voltage substations. Utilizing high-quality silicon steel cores and precision-wound copper conductors, the transformer achieves low no-load losses, strong short-circuit withstand capability, and excellent thermal stability. The oil-immersed insulation and cooling system ensures effective heat dissipation, supporting continuous operation under heavy-load and fluctuating grid conditions. Its reinforced tank structure, advanced insulation system, and outdoor-rated protection design enable reliable performance 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 infrastructure projects requiring high reliability, safety, and long service life.
- Primary Voltage Ratings 110kV, 115kV, 121kV 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 230kV
- Standards IEEE, ANSI, IEC
- Application high-voltage substations, regional transmission networks, power systems, and infrastructure projects
- Power Rating Up to 200 MVA
- 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
121kV Oil-Immersed High-Voltage Power Transformer
Technical Specifications
Accessories
| Rated Power | Up to 200 MVA |
| Rating Primary Voltage | 110kV, 115kV, 121kV |
| 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
121kV Oil-Immersed High-Voltage Power Transformer
The 121kV Oil-Immersed High-Voltage Power Transformer can be fully customized to meet specific grid requirements, operational conditions, and regional standards. Electrical customization includes tailored primary and secondary voltage ratings, selectable vector groups such as Dyn11, YNd1, or Yyn0, customized impedance values, and efficiency optimization to comply with local utility loss regulations. Customers may choose between no-load or on-load tap changers with flexible tap ranges to maintain stable voltage under varying load conditions. Winding materials are available in high-purity copper or aluminum, while insulation systems can be enhanced for high-altitude operation, extreme temperatures, or high-humidity environments. Optional low-loss core designs and environmentally friendly insulating oils are also available to support sustainability goals.
Mechanical and structural customization options include reinforced tank designs, corrosion-resistant coatings for coastal or industrial areas, and seismic-resistant structures for earthquake-prone regions. Cooling system configurations such as ONAN, ONAF, or OFAF can be selected based on thermal performance requirements. Advanced protection and monitoring devices—including Buchholz relays, digital temperature indicators, oil level sensors, pressure relief devices, and online condition monitoring systems—can be integrated for improved safety and predictive maintenance. Noise-reduction designs, compact footprints for space-limited substations, customized bushing arrangements, and project-specific accessory layouts are also supported. All customized solutions are engineered to comply with IEC, IEEE, or customer-defined technical specifications, ensuring reliable long-term performance.
Packing and Shipping
121kV Oil-Immersed High-Voltage Power Transformer
The packing and shipping process for the 121kV Oil-Immersed High-Voltage Power Transformer is carefully designed to ensure maximum protection during transportation and storage. Before packing, the transformer undergoes final inspection, oil handling procedures, and comprehensive surface treatment. External surfaces are coated with anti-corrosion paint, and all openings are sealed to prevent moisture ingress. Sensitive components such as bushings, radiators, conservators, and monitoring instruments are removed when required and packed separately in reinforced wooden crates with shock-absorbing materials.
The transformer's main body is securely mounted on a heavy-duty steel skid or export-grade wooden base to prevent movement during transit. Structural braces, vibration dampers, and impact-resistant padding are installed at critical points to minimize mechanical stress. The entire unit is wrapped in multiple protective layers, including moisture-proof films, UV-resistant covers, and rust-inhibiting materials. For long-distance or sea transportation, nitrogen filling or vacuum sealing may be applied to maintain insulation dryness and oil quality.
Depending on transformer size, weight, and destination, shipment is 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 shipping 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 installation site, 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 reliable long-term operation.
The transformer's main body is securely mounted on a heavy-duty steel skid or export-grade wooden base to prevent movement during transit. Structural braces, vibration dampers, and impact-resistant padding are installed at critical points to minimize mechanical stress. The entire unit is wrapped in multiple protective layers, including moisture-proof films, UV-resistant covers, and rust-inhibiting materials. For long-distance or sea transportation, nitrogen filling or vacuum sealing may be applied to maintain insulation dryness and oil quality.
Depending on transformer size, weight, and destination, shipment is 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 shipping 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 installation site, 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 reliable long-term operation.
32
32 years of industry experience
Manufacturer Test
121kV Oil-Immersed High-Voltage Power Transformer
Progress test
The Progress Test for the 121kV Oil-Immersed High-Voltage Power Transformer is conducted throughout the manufacturing process to ensure strict quality control and early fault detection. Incoming inspections verify the quality of silicon steel laminations, copper conductors, insulation materials, and transformer oil. During core stacking and winding operations, checks are performed on dimensional accuracy, insulation clearances, winding tension, and mechanical stability. Active parts undergo controlled drying and vacuum treatment, with temperature and moisture levels continuously monitored to ensure optimal insulation conditions.
Intermediate electrical tests include winding resistance measurement, insulation resistance testing, and turns ratio verification at key production stages. Fabrication of tanks and cooling components is inspected for welding quality, pressure resistance, and surface coating thickness. Vacuum leak tests and internal cleanliness inspections are completed before oil filling. All results are recorded in detailed progress reports to ensure traceability and manufacturing consistency prior to final assembly and 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 (FAT) for the 121kV Oil-Immersed High-Voltage Power Transformer is performed after final assembly in accordance with IEC and IEEE standards. Electrical routine tests include winding resistance measurement, verification of turns ratio and vector group, insulation resistance evaluation, and polarity checks. Dielectric tests such as applied AC voltage and induced overvoltage withstand tests, confirm insulation strength under rated operating conditions.
Performance tests measure no-load loss, load loss, impedance voltage, and temperature rise to verify efficiency and thermal stability. Partial discharge measurements assess insulation quality, while lightning impulse tests validate the transformer’s ability to withstand transient overvoltage events. Mechanical and functional inspections cover tank pressure testing, oil leakage checks, bushing installation accuracy, tap changer operation, cooling system performance, and oil quality analysis. All protection and monitoring devices are calibrated and verified. FAT documentation is reviewed and approved prior to shipment.
Routine Test - No Load Loss Test
Purpose of Testing
The purpose of No Load Loss Test is to measure the power loss of the equipment when it is not loaded to evaluate the iron loss and other core losses. This test can help understand the energy efficiency of the equipment and help determine the performance of the transformer or motor when it is running at no load.
Testing Equipment
No Load Loss tester (e.g. OMICRON, Megger, Schneider Electric, etc.)
Voltage source (usually 230V, 400V or customized according to customer requirements to adapt to different equipment)
Power analyzer (used to measure power loss and efficiency)
Ammeter and voltmeter
Temperature and humidity meter
Voltage source (usually 230V, 400V or customized according to customer requirements to adapt to different equipment)
Power analyzer (used to measure power loss and efficiency)
Ammeter and voltmeter
Temperature and humidity meter
Pre-Test Preparation
Disconnect the power supply of the device and ensure that the device is properly grounded and discharged to ensure safe operation.
Please ensure that the test is carried out in a suitable environment with a relative humidity of less than 75% and avoid rainy days or extreme weather (recommended temperature range: 20-30°C).
Please ensure that the test is carried out in a suitable environment with a relative humidity of less than 75% and avoid rainy days or extreme weather (recommended temperature range: 20-30°C).
Test Progress
Connect the Test Instrument:
Connect the test equipment to the high voltage side of the transformer, making sure the wiring is correct and the equipment is grounded.
Apply Test Voltage:
Usually it is 110% of the rated voltage, for example, if the rated voltage of the transformer is 33 KV, apply 36.3 KV (110%).
Connect the test equipment to the high voltage side of the transformer, making sure the wiring is correct and the equipment is grounded.
Apply Test Voltage:
Usually it is 110% of the rated voltage, for example, if the rated voltage of the transformer is 33 KV, apply 36.3 KV (110%).
Measure and Record
Connect the Test Instrument:
Connect the test equipment to the high voltage side of the transformer, making sure the wiring is correct and the equipment is grounded.
Apply Test Voltage:
Usually it is 110% of the rated voltage, for example, if the rated voltage of the transformer is 33 KV, apply 36.3 KV (110%).
Connect the test equipment to the high voltage side of the transformer, making sure the wiring is correct and the equipment is grounded.
Apply Test Voltage:
Usually it is 110% of the rated voltage, for example, if the rated voltage of the transformer is 33 KV, apply 36.3 KV (110%).
Temperature Correction
The power loss of the test results is corrected to a reference temperature (usually 20°C) to ensure an accurate evaluation.
Repeat Testing (if necessary)
Test at different rated voltages, especially when the transformer has multiple capacity levels, and perform no-load loss tests for each capacity level separately.
Evaluation Criteria (Reference)
No-load loss ≤ 0.2% rated power (excellent)
No-load loss < 0.2% ≤ 0.5% rated power (good)
No-load loss > 0.5% rated power (further inspection or corrective action required)
No-load loss < 0.2% ≤ 0.5% rated power (good)
No-load loss > 0.5% rated power (further inspection or corrective action required)
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
It provides stable voltage transformation, long-distance power transmission, and continuous heavy-load operation in environments requiring high reliability, safety, and extended service life.
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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