370MVA 750kV Oil-Immersed High-Voltage Transformer for Power Transmission
The 370 MVA 750 kV Oil-Immersed High-Voltage Transformer is designed for ultra-high-voltage (UHV) power transmission systems requiring exceptional reliability, stability, and long-distance energy delivery. With a robust oil-immersed insulation structure and high-grade copper windings, this transformer offers outstanding dielectric strength, low partial discharge, and excellent thermal performance. Engineered for 750kV grid networks, it effectively reduces transmission losses, enhances voltage regulation, and ensures safe operation under demanding load variations. Its precision-built core, advanced cooling system, and reinforced tank construction enable superior efficiency, extended service life, and high short-circuit resistance. Ideal for national power grid projects, long-distance transmission corridors, high-capacity substations, and UHV interconnection systems, this transformer delivers consistent and secure performance in critical large-scale power infrastructures.
- 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 750kV
- Standards IEEE, ANSI, NEMA, IEC, CE
- Application power plants, renewable energy transmission
- Power Rating 350MVA
- 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
370MVA 750kV Oil-Immersed High-Voltage Transformer for Power Transmission
Technical Specifications
Accessories
| Rated Power | 350 MVA | |
| Rating Primary Voltage | 750kV | |
| Secondary Voltage | 480/277V 400/230V 380/220V Customized |
|
| Frequency | 50/60Hz | |
| Vector Group | Dyn11, Yyn0, Dyn5 | |
| Winding Material | Aluminum/Copper | |
| 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
370MVA 750kV Oil-Immersed High-Voltage Transformer for Power Transmission
The 370 MVA 750 kV Oil-Immersed High-Voltage Transformer can be fully customized to meet the technical needs of UHV transmission projects. Customers may select specific voltage ratios, impedance levels, vector groups, and advanced insulation configurations to align with national grid standards. Cooling systems such as ONAN, ONAF, OFAF, or hybrid cooling can be customized based on ambient temperature, load characteristics, and installation environment. Reinforced tank structures, noise-reduction designs, and enhanced shock resistance are available for harsh operating conditions.
Additional optional features include digital smart monitoring systems capable of real-time temperature tracking, dissolved gas analysis (DGA), moisture detection, OLTC monitoring, and remote IoT communication. High-strength bushings, special insulation materials, and eco-friendly ester oil can be selected based on project requirements. These customizable options ensure that the 370MVA 750kV transformer delivers maximum efficiency, reliability, and operational safety in ultra-high-voltage networks.
Packing and Shipping
370MVA 750kV Oil-Immersed High-Voltage Transformer for Power Transmission
The 370 MVA 750 kV Oil-Immersed High-Voltage Transformer is packaged and shipped using advanced protection and handling procedures to ensure its safety throughout transportation. Before packaging, the transformer undergoes a thorough cleaning, drying, and sealing process. All bushings, valves, radiators, and accessories are protected with shock-absorbing materials, sealed covers, and moisture-proof layers to prevent contamination or mechanical impact. A corrosion-resistant coating is applied to the tank exterior, and desiccants are added to internal compartments to maintain dryness during long-distance shipping.
The main transformer body is mounted onto a reinforced steel skid designed to support extreme weight and prevent movement during transportation. Multiple layers of protective wrapping—waterproof sheets, anti-slip pads, and heavy-duty straps—are applied to safeguard the unit from vibration, weather exposure, and accidental impact. Sensitive components such as OLTC controllers, gauges, and sensors are either removed for separate packing or secured in protective housings.
For domestic delivery, the transformer is transported using heavy-duty trucks with hydraulic suspension systems to reduce vibration. International shipments are arranged using flat-rack or open-top containers, lifted by certified cranes and secured following IEC, ISO, and maritime safety standards. Vibration, tilt, and shock recorders may be installed for real-time monitoring during transit.
Upon arrival, unloading is supervised by trained engineers to ensure safe handling. Only after a final inspection is the protective packaging removed. These meticulous packing and shipping procedures ensure the 370MVA 750kV transformer arrives on site safely, intact, and ready for installation.
The main transformer body is mounted onto a reinforced steel skid designed to support extreme weight and prevent movement during transportation. Multiple layers of protective wrapping—waterproof sheets, anti-slip pads, and heavy-duty straps—are applied to safeguard the unit from vibration, weather exposure, and accidental impact. Sensitive components such as OLTC controllers, gauges, and sensors are either removed for separate packing or secured in protective housings.
For domestic delivery, the transformer is transported using heavy-duty trucks with hydraulic suspension systems to reduce vibration. International shipments are arranged using flat-rack or open-top containers, lifted by certified cranes and secured following IEC, ISO, and maritime safety standards. Vibration, tilt, and shock recorders may be installed for real-time monitoring during transit.
Upon arrival, unloading is supervised by trained engineers to ensure safe handling. Only after a final inspection is the protective packaging removed. These meticulous packing and shipping procedures ensure the 370MVA 750kV transformer arrives on site safely, intact, and ready for installation.
32
32 years of industry experience
Manufacturer Test
370MVA 750kV Oil-Immersed High-Voltage Transformer for Power Transmission
Progress Test
During the manufacturing of the 370 MVA 750 kV Oil-Immersed High-Voltage Transformer, multiple progress tests are performed to ensure quality and consistency. These include core assembly inspection, lamination measurement, winding tension checks, and insulation drying validation. Intermediate electrical tests—such as partial discharge checks, turn ratio verification, and insulation resistance measurement—are conducted at key production stages. Pressure tightness tests, vacuum oil filling control, and mechanical strength assessments confirm structural reliability. These continuous progress tests guarantee that each component meets ultra-high-voltage performance requirements.
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 370MVA 750kV Oil-Immersed High-Voltage Transformer ensures full compliance with IEC, IEEE, and national UHV standards before delivery. FAT includes visual inspection, winding resistance measurement, ratio testing, and insulation resistance checks. High-voltage dielectric tests—induced voltage, AC withstand, and partial discharge tests—verify superior insulation performance. Functional tests on OLTC, cooling equipment, control panels, and protection devices ensure operational accuracy. Additional tests include oil dielectric strength, temperature-rise simulation, and noise-level assessment. These comprehensive procedures guarantee safe, stable, and long-term performance for UHV power transmission.
Routine Test - Insulation Power Factor
Purpose of Testing
The purpose of testing the insulation power factor is to evaluate the dielectric loss of the insulation system in electrical equipment, and to determine whether issues such as moisture ingress, aging, or contamination are present. A high power factor value usually indicates insulation deterioration.
Testing Equipment
Insulation power factor tester (e.g., brands like Doble, Megger) Voltage source (typically 1 kV, 2.5 kV, or 10 kV or as the customer request standard) Temperature and humidity meter (for recording environmental conditions)
Pre-Test Preparation
De-energize tap changer the equipment and ensure it has been properly grounded and discharged. Make sure the bushings and terminal connections to prevent surface contamination from affecting test results. Perform the test under suitable environmental conditions: relative humidity below 75% and no rain (recommended temperature: 20–30°C). Calibrate and inspect the test instruments to ensure they are in good working condition.
Test Progress
Connect the Test Instrument: Connect the test equipment to the bushings or terminals of the equipment under test and ensure proper grounding. Apply Test Voltage: Select the appropriate test voltage according to the rated voltage of the equipment (e.g., 25 kV for high-voltage windings or as the request of the pad mounted transformer).
Measure and Record
Start the test and record the following parameters: Capacitive current (IC) Power current (IW) Power factor (PF) or dissipation factor (Tanδ) Capacitance Ambient temperature and humidity at the time of testing
Temperature Correction
Correct the measured power factor to the reference temperature (typically 20°C) for accurate evaluation.
Repeat Testing (if necessary)
Measure different windings (high-voltage, medium-voltage, low-voltage) and bushings separately for comparative analysis.
Evaluation Criteria (Reference)
Insulation power factor ≤ 0.5% (Excellent) 0.5% < Power factor ≤ 1% (Good) 1% (Further inspection or corrective action required) Test standard:IEEE C57.12.00 & IEEE C57.12.90 (Liquid-Immersed)
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
The 370MVA 750kV High-Voltage Transformer is ideal for ultra-high-voltage transmission corridors, long-distance power delivery systems, national grid backbone networks, large substations, and interconnection projects. It is also widely used in power plants, renewable energy transmission, and large-scale energy distribution networks requiring maximum reliability and efficiency.
Technical Advantages
● 30+ years of manufacturing experience
● ISO and UL certified production
● Customized cable and transformer solutions
Product Packaging
Transformers Packaging (1)
Transformers Packaging (2)
Transformers Packaging (3)
Transformers Packaging (4)
Transformers Packaging (5)
Transformers Packaging (6)
Transformers Packaging (7)
Transformers Packaging (8)
Related Products
100kVA Conventional Type Single Phase Pole Mounted Transformer
NPC ELECTRIC has been specialized in manufacturing 100kVA Conventional Type Single Phase pole Mounted transformer for more than 20 years, which complies with international standards such as ANSI/IEEE C57, IEC60076 and other standards. Its main function is to convert high voltage electricity (such as 11kV, 13.8kV, etc.) into low voltage electricity (such as 120V/240V), providing stable and reliable power supply to end users. It is suitable for residential, commercial, agricultural and small industrial loads.
10kVA Single Phase Pad Mounted Transformer
The 10 kVA pad-mounted transformer meets ANSI, CSA, NEMA, IEEE, and DOE standards. NPC Electric's 10 kVA pad-mounted transformers comply with DOE efficiency values and are UL listed. Based on specific technical requirements, the incoming line can be designed as either a loop feed or radial feed, and it also supports customized dual voltage.
5000kVA Dry Type Transformer
The NPC ELECTRIC 5000kVA Dry Type Transformer is a high-capacity, reliable power solution designed for large-scale industrial and commercial operations. With a robust 5000kVA rating, it features advanced dry-type insulation technology for enhanced safety, low maintenance, and long-lasting performance. Engineered for demanding environments, this transformer ensures stable, efficient, and quiet operation while minimizing environmental impact.
150kVA Three Phase Pad Mounted Transformer
150kVA Three-Phase Pad Mounted Transformer is an efficient and reliable power transformer designed for applications in commercial, industrial, and residential areas. This transformer features a robust enclosure and protective design, enabling stable operation in outdoor environments and making it suitable for power systems with high load demands. With a high power capacity of 150kVA and three-phase power output, it ensures a stable voltage and smooth power supply for the equipment.
80kVA Oil Immersed Transformer
NPC ELECTRIC 80kva Oil Immersed Transformer boasts a robust design that incorporates high-quality materials and advanced manufacturing techniques. The transformer's core is made from premium cold-rolled silicon steel sheets, ensuring low loss and high efficiency. The windings are constructed using high-grade copper wire, which is carefully insulated to prevent short circuits and ensure long-term reliability. The oil-immersed design of the NPC ELECTRIC 80kVA transformer provides effective cooling and insulation, ensuring that the transformer operates within safe temperature limits and maintains optimal performance. The oil also acts as a dielectric medium, enhancing the transformer's electrical properties and protecting it from environmental factors.
11kV Three-Phase Oil-Immersed Power Transformer
The 11kV Three-Phase Oil-Immersed Power Transformer is engineered for stable and efficient distribution across medium-voltage networks. Designed with high-grade silicon steel, advanced insulation systems, and premium mineral oil, this transformer ensures superior dielectric strength, excellent heat dissipation, and long service life. Its oil-immersed configuration delivers reliable cooling performance, enabling continuous operation under varying load conditions. The three-phase design ensures balanced power delivery, reduced energy losses, and improved grid stability. With enhanced short-circuit strength, low noise levels, and robust mechanical structure, it is suitable for industrial facilities, commercial complexes, substations, and utility distribution networks. Custom voltage ratios, tap changers, protection devices, and enclosure options are available to meet regional standards and project-specific requirements.FAQ From Customers
-
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.
-
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.
-
Do you have UL listed?Yes, our transformer has UL listed. We have exported to America many pad mounted transformer,substation transformer and HV.
Welcome your inquiry
Honesty, Integrity, Frugality, Activeness and Passion