250MVA 330kV High-Voltage Oil-Immersed Distribution Transformer for Grid & Substation
The 250MVA 330kV High-Voltage Oil-Immersed Distribution Transformer is engineered for reliable and efficient power transmission in large utility grids and high-demand substations. Designed with advanced insulation and a durable oil-immersed cooling system, it ensures excellent thermal stability and long service life. The high-voltage 330kV configuration provides exceptional performance in long-distance power delivery, minimizing losses and improving grid stability. Its precision-wound copper coils, high-strength core materials, and robust tank structure guarantee safe operation under fluctuating load conditions. With strong short-circuit resistance, high dielectric strength, and low noise operation, this transformer meets stringent international standards. It is widely used in national grid projects, power plants, and heavy-industry energy networks, supporting continuous, stable, and efficient power distribution.
- Primary Voltage Ratings 34.5-19.92/13.8-7.957/13.2-7.62/12.47-7.2, 33 or others
- Secondary Voltage Ratings 480/277V, 400/230V, 380/220V or customized
- H.V. Tap Range ± 2×2.5% HV taps or others
- Type Oil immersed transformer
- BIL 330kV
- Standards IEEE, ANSI, NEMA, IEC, CE
- Application Power Substations, Industrial Power Supply
- Power Rating 250MVA
- Certificate UL, CESI, IEEE
- Cooling Method ONAN, ONAN/ONAF, KNAN, KNAN/KNAF
- Oil Mineral Oil or FR3
- Opeartion Step Down & Step Up
Technical Specifications
Customization Optional
Packing and Shipping
Manufacturer Test
Routine Testing
Application
Technical Specifications
250MVA 330kV High-Voltage Oil-Immersed Distribution Transformer for Grid & Substation
Technical Specifications
Accessories
| Rated Power | 250 MVA | |
| Rating Primary Voltage | 330kV | |
| Secondary Voltage | 480/277V 400/230V 380/220V Customized |
|
| Frequency | 50/60Hz | |
| Vector Group | YNd11 / YNyn0 / Dyn11 / Custom on request | |
| Winding Material | High-conductivity copper (aluminum optional) | |
| Efficiency | As IEEE, Doe 2016, CAS Std or Customized | |
| Impedance Voltage | Nominal 2% or Customized 1.1 - 5.75% | |
| Altitude | ≤1,000m or Customized | |
| Color | ANSI 70 Light gray/Munsell 7GY3.29/1.5 or customized, etc | |
| Tank material | Mild Steel, 304 Stainless Steel | |
| HV Bushing |
| LV Bushing |
| Tap changer |
| Oil level gauge |
| Oil temperature indicator |
| Pressure relief device |
| Pressure vacuum gauge |
| Lifting hook for complete transformer |
| Name plate |
| Radiators |
| Oil upper filtering valve |
| Oil drain valve with 3/8" sampler |
Customization Optional
250MVA 330kV High-Voltage Oil-Immersed Distribution Transformer for Grid & Substation
The 250MVA 330kV High-Voltage Oil-Immersed Distribution Transformer offers a wide range of customisation options to meet different grid, substation, and industrial requirements. Customers can select specific voltage ratios, impedance levels, vector groups, and copper winding configurations to ensure compatibility with regional electrical systems. Cooling methods such as ONAN, ONAF, or OFAF can also be customised for varying load conditions and climate environments. Additional options include high-strength bushings, enhanced insulation systems, and special tap-changing mechanisms for improved voltage regulation.
Further customization includes smart monitoring features such as online DGA sensors, temperature monitoring, IoT communication modules, or digital control panels for advanced performance tracking. Structural enhancements, such as seismic-resistant bases, corrosion-proof coatings, noise-reduction designs, and reinforced tank construction, can be applied for harsh outdoor conditions. With these configurable options, the 250MVA 330kV transformer can be engineered to provide optimal safety, efficiency, and reliability for any high-voltage power transmission application.
Packing and Shipping
250MVA 330kV High-Voltage Oil-Immersed Distribution Transformer for Grid & Substation
The 250MVA 330kV High-Voltage Oil-Immersed Distribution Transformer is packed and shipped following strict international safety standards to ensure the unit arrives in perfect working condition. Before packing, the transformer undergoes a full inspection, tank sealing, and moisture removal process. All bushings, valves, radiators, and accessories are securely protected with shock-absorbing materials and protective caps. The external surface receives a corrosion-resistant coating, while moisture-proof desiccants are placed inside necessary compartments to maintain dryness during long-distance transport.
The main body of the transformer is mounted onto a reinforced steel skid or wooden base designed to support its heavy weight and prevent movement during handling. Multi-layer wrapping, waterproof covers, and high-strength tension straps are applied to safeguard the unit from impact, vibration, and weather exposure. Sensitive components such as OLTC control panels, gauges, and sensors are either removed for separate packaging or reinforced with dedicated protective housings.
For domestic transport, heavy-duty trucks equipped with air-suspension systems are used to minimise vibration. For international shipping, the transformer is loaded onto flat-rack or open-top containers using certified lifting points and cranes to avoid structural stress. All loading operations follow IEC, ISO, and marine transport regulations. Shock and tilt sensors may be installed to monitor transport conditions in real time.
Upon delivery, the unloading process is coordinated with the receiving team to ensure safe handling. A final inspection is performed before removing the protective packaging. This comprehensive packing and shipping procedure guarantees that the 250MVA 330kV oil-immersed transformer arrives safely, intact, and ready for installation.
The main body of the transformer is mounted onto a reinforced steel skid or wooden base designed to support its heavy weight and prevent movement during handling. Multi-layer wrapping, waterproof covers, and high-strength tension straps are applied to safeguard the unit from impact, vibration, and weather exposure. Sensitive components such as OLTC control panels, gauges, and sensors are either removed for separate packaging or reinforced with dedicated protective housings.
For domestic transport, heavy-duty trucks equipped with air-suspension systems are used to minimise vibration. For international shipping, the transformer is loaded onto flat-rack or open-top containers using certified lifting points and cranes to avoid structural stress. All loading operations follow IEC, ISO, and marine transport regulations. Shock and tilt sensors may be installed to monitor transport conditions in real time.
Upon delivery, the unloading process is coordinated with the receiving team to ensure safe handling. A final inspection is performed before removing the protective packaging. This comprehensive packing and shipping procedure guarantees that the 250MVA 330kV oil-immersed transformer arrives safely, intact, and ready for installation.
32
32 years of industry experience
Manufacturer Test
250MVA 330kV High-Voltage Oil-Immersed Distribution Transformer for Grid & Substation
Progress Test
During the production of the 250MVA 330kV Oil-Immersed Distribution Transformer, several progress tests are conducted to ensure manufacturing accuracy and performance consistency. These include core lamination inspection, coil winding tension checks, and insulation drying verification. Each stage undergoes dimensional measurements, vacuum oil-filling control, and partial discharge assessments. Pressure tightness tests, intermediate electrical tests, and mechanical strength evaluations ensure that assembly quality meets design requirements. Through continuous monitoring, the transformer’s components are guaranteed to meet high-voltage performance and long-term operational reliability.
Design Tests
All transformer will be test after finished the production, test items as below:
♦ Insulation Power Factor
♦ Ratio, Polarity, and Phase Relation
♦ Winding Resistance
♦ Impulse Tests
♦ On load Loss Test
♦ No Load Loss Test
♦ Leak Test
♦ DC Insulation Resistance Test
♦ Transformer Turns Ratio/TTR (All Tap Voltages)
♦ Impedance Voltage & Load Loss (Rated Voltage)
♦ Polarity, 1-Ph / Phase Relation, 3-Ph (Rated Voltage)
♦ Excitation & No-Load Loss (Rated Voltage)
♦ Applied Voltage
♦ Induced Voltage
♦ Lightning Impulse
♦ Insulation Resistance (Rated Voltage)
♦ Temperature Rise
♦ Dielectric Withstand (Hipot)
Transformer Factory Acceptance Test
The Factory Acceptance Test (FAT) for the 250MVA 330kV High-Voltage Oil-Immersed Distribution Transformer verifies compliance with international standards before shipment. FAT includes detailed visual examination, ratio testing, insulation resistance measurement, winding resistance checks, and dielectric tests such as induced voltage and AC withstand. Functional tests on OLTC, cooling systems, protection relays, and monitoring devices ensure proper operation. Additional assessments—such as oil dielectric strength, temperature-rise simulation, and noise level measurement—confirm the transformer’s durability, safety, and performance. These comprehensive FAT procedures guarantee reliable service in grid and substation applications.
Routine Test - Lightning Impulse
Purpose of Testing
The purpose of the lightning impulse test is to simulate the performance of the equipment when it is subjected to lightning or high voltage transient pulses, so as to evaluate its lightning resistance and insulation performance.
Testing Equipment
Lightning Impulse Tester. Usually a high voltage DC power supply, used to simulate lightning impulse waves. The voltage range can be adjusted according to the test standards and equipment requirements. Common voltages are 200 kV, 500 kV or higher. The specific voltage is customized according to customer requirements.
Pre-Test Preparation
Disconnect the device from the power supply and ensure that the device is properly grounded and discharged.
Check all terminals and connections to ensure they are secure and free of contamination.
Perform the test under suitable environmental conditions: relative humidity less than 75%, temperature between 20-30°C, no rain.
Check all terminals and connections to ensure they are secure and free of contamination.
Perform the test under suitable environmental conditions: relative humidity less than 75%, temperature between 20-30°C, no rain.
Test Progress
Connect the Test Instrument: Connect the lightning impulse test equipment to the high-voltage terminal or bushing of the device under test. Apply Test Voltage: According to the rated voltage of the equipment and the test standard, select the appropriate test voltage.
Measure and Record
Start the test and record the following parameters: Applied impulse voltage (kV)
Current waveform Impedance
Reaction voltage waveform
Ambient temperature and humidity during testing
Current waveform Impedance
Reaction voltage waveform
Ambient temperature and humidity during testing
Temperature Correction
The measured test data is temperature corrected according to the ambient temperature during the test, usually with a reference temperature of 20°C, to ensure the accuracy of the test results.
Repeat Testing (if necessary)
Repeated testing of different windings (high voltage, medium voltage, low voltage) or bushings under different test conditions ensures that the insulation performance of each part meets the standards.
Evaluation Criteria (Reference)
The lightning impulse test did not produce breakdown or irreversible damage: qualified
The voltage waveform meets the standard requirements, and the equipment does not have abnormal discharge or local breakdown: good
Obvious damage or non-standard waveform during the test: Further inspection or corrective measures are required
The voltage waveform meets the standard requirements, and the equipment does not have abnormal discharge or local breakdown: good
Obvious damage or non-standard waveform during the test: Further inspection or corrective measures are required
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
The transformer is also suitable for large-scale power plants, including thermal, hydro, wind, and solar generation stations, offering reliable step-up or step-down performance.
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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