500kV Oil-Immersed Power Transformer For Ultra-High Voltage Grid Solutions
NPC Electric 500kV Oil-Immersed Power Transformer is a critical component for national ultra-high voltage (UHV) backbones, engineered to transmit massive blocks of power with industry-leading efficiency. Utilizing premium, laser-scribed CRGO silicon steel in a multi-step lap core construction, this transformer minimizes magnetizing current and core noise. The active part is submerged in high-grade inhibited mineral oil, processed through advanced vacuum degasification to ensure maximum dielectric strength. Its robust, shield-type winding structure provides exceptional resistance against lightning surges and short-circuit mechanical stresses. Designed to meet IEC 60076 and IEEE standards, this 500kV unit is the definitive solution for long-distance energy dispatch, connecting remote generation hubs to major load centers while maintaining grid frequency and voltage stability.
- Primary Voltage Ratings 220kV 230kV 500 kV
- Secondary Voltage Ratings 69/35/37/34.5/26.4./11/10.5/6.6/13.2 kV or others
- H.V. Tap Range ± 8×1.25% HV taps or others
- Type Oil-immersed power transformer
- BIL 900kV
- Standards IEEE, ANSI, IEC, GB
- Application ultra-high voltage substations, Renewable Energy Integration
- Power Rating 250MVA-1000MVA
- Certificate UL, ISO, CESI
- Cooling Method ONAN/ ONAF
- Oil Mineral Oil or FR3
- Opeartion Step Down & Step Up
Technical Specifications
Customization Optional
Packing and Shipping
Manufacturer Test
Routine Testing
Application
Technical Specifications
500kV Oil-Immersed Power Transformer For Ultra-High Voltage Grid Solutions
Technical Specifications
Accessories
| Rated Power | 250MVA-1000MVA |
| Rating Primary Voltage | 220kV 230kV 500kV |
| Secondary Voltage |
69/35/37/34.5/26.4/11/10.5/6.6/13.2 kV Customized |
| Frequency | 50/60Hz |
| Vector Group | Dyn11, YD11, YNd11 or anothers |
| 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
500kV Oil-Immersed Power Transformer For Ultra-High Voltage Grid Solutions
NPC Electric 500kV units offer bespoke cooling and structural engineering to match specific environmental demands. For regions with extreme ambient heat, we provide ODAF (Oil Directed Air Forced) or ODWF (Oil Directed Water Forced) cooling systems that use high-speed pumps to circulate oil through the windings, significantly increasing the power-to-weight ratio. We also offer customization of the transformer tank into "Bell-type" or "Tank-type" configurations to meet transport weight restrictions or site assembly preferences. Bushings can be specified as OIP (Oil Impregnated Paper) or RIS (Resin Impregnated Synthetic) to ensure optimal performance in high-altitude or coastal environments.
Beyond physical specs, we offer Digital Twin integration and advanced monitoring. This includes the installation of smart sensors for Online Dissolved Gas Analysis (DGA), fiber-optic probes for direct winding hotspot measurement, and electronic pressure relief devices. We can also customize the On-Load Tap Changer (OLTC) with vacuum-type switching technology, reducing maintenance intervals and extending the life of the transformer oil. For noise-sensitive areas, we offer external acoustic shielding and low-decibel cooling fans to ensure compliance with strict local environmental regulations without sacrificing power output.
Packing and Shipping
500kV Oil-Immersed Power Transformer For Ultra-High Voltage Grid Solutions
Shipping a 500kV transformer—often weighing over 250 tons—is a logistical feat requiring military-grade precision. The main tank is shipped dry-filled with high-purity nitrogen to maintain an internal pressure of 0.02-0.03 MPa, preventing any moisture ingress into the delicate insulation during the journey. All external accessories, including the 500kV capacitive bushings, radiator banks, and the oil conservator, are packed in heavy-duty, seaworthy steel-framed crates. These crates are lined with VCI (Volatile Corrosion Inhibitor) materials to protect electrical contacts from salt-air degradation during international sea freight.
The transformer body is transported using Schnabel cars (rail) or multi-axle self-propelled modular trailers (SPMT) to ensure the weight is distributed safely across road and rail infrastructure. Prior to dispatch, a detailed route survey is mandatory to verify clearances under bridges and the load-bearing capacity of all transit surfaces. The transformer is secured using 20mm+ high-tensile steel chains and turnbuckles, with rubber friction mats placed under the base to prevent any micro-movements during the high-inertia forces encountered during sea or rail transport.
To guarantee the unit arrives in factory-calibrated condition, we install multiple 3D Digital Impact Recorders. These devices provide real-time, time-stamped logs of any shocks in the X, Y, and Z axes. GPS tracking allows the client to monitor the location and transit speed in real-time. Upon arrival at the port of entry or the substation site, a joint inspection is performed by our engineers and the logistics team to verify the nitrogen pressure and analyze the impact recorder data before any unloading begins, ensuring total transparency in the supply chain.
The final "last mile" delivery involves positioning the unit on its foundation using hydraulic jacks and sliders. Once the transformer is anchored, the nitrogen is purged using a vacuum pump (reaching <50 Pa) before the unit is refilled with hot, filtered oil. This vacuum-filling process is critical for 500kV units to ensure there are no air bubbles (voids) in the insulation system. Our end-to-end shipping strategy ensures that your high-value asset is protected from the factory floor to the final energization at the substation.
The transformer body is transported using Schnabel cars (rail) or multi-axle self-propelled modular trailers (SPMT) to ensure the weight is distributed safely across road and rail infrastructure. Prior to dispatch, a detailed route survey is mandatory to verify clearances under bridges and the load-bearing capacity of all transit surfaces. The transformer is secured using 20mm+ high-tensile steel chains and turnbuckles, with rubber friction mats placed under the base to prevent any micro-movements during the high-inertia forces encountered during sea or rail transport.
To guarantee the unit arrives in factory-calibrated condition, we install multiple 3D Digital Impact Recorders. These devices provide real-time, time-stamped logs of any shocks in the X, Y, and Z axes. GPS tracking allows the client to monitor the location and transit speed in real-time. Upon arrival at the port of entry or the substation site, a joint inspection is performed by our engineers and the logistics team to verify the nitrogen pressure and analyze the impact recorder data before any unloading begins, ensuring total transparency in the supply chain.
The final "last mile" delivery involves positioning the unit on its foundation using hydraulic jacks and sliders. Once the transformer is anchored, the nitrogen is purged using a vacuum pump (reaching <50 Pa) before the unit is refilled with hot, filtered oil. This vacuum-filling process is critical for 500kV units to ensure there are no air bubbles (voids) in the insulation system. Our end-to-end shipping strategy ensures that your high-value asset is protected from the factory floor to the final energization at the substation.
32
32 years of industry experience
Manufacturer Test
500kV Oil-Immersed Power Transformer For Ultra-High Voltage Grid Solutions
Progress test
After the windings are pressed and dried, we perform Winding Resistance and Turns Ratio Tests across all tap positions to ensure high-precision voltage regulation. A critical Frequency Response Analysis (SFRA) is conducted at the pre-tanking stage to establish a mechanical baseline of the coil structure. Finally, we perform an Insulation Power Factor (Tan Delta) Test on the main insulation to verify that the Vapor Phase Drying (VPD) process has successfully removed all traces of moisture from the cellulose materials.
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 FAT for our 500kV units is dominated by high-voltage endurance testing. This includes Lightning Impulse Tests (BIL) at 1550kV and Switching Impulse (SIL) tests to simulate extreme grid transients. We then perform a Long-duration Induced Overvoltage (ACLD) Test combined with Partial Discharge (PD) monitoring. For 500kV reliability, we guarantee PD levels below 50pC at 1.58Ur, ensuring the unit is free from internal voids or manufacturing defects that could cause long-term insulation failure.
Routine Test - Induced Voltage
Purpose of Testing
The purpose of the Induced Voltage test is to simulate the electrical stress that the equipment may encounter under actual working conditions by applying an induced voltage, thereby evaluating the tolerance and stability of the equipment's insulation system. This test helps to detect the insulation performance of the equipment under high voltage conditions and ensure its safety and reliability in operation.
Testing Equipment
Induced Voltage Tester (e.g. OMICRON, Megger, HioKI, etc.)
AC voltage source, commonly 2 kV, 5 kV, 10 kV, or customized according to test requirements.
Environmental thermometer and hygrometer, used to record the temperature and humidity of the environment for appropriate test evaluation.
AC voltage source, commonly 2 kV, 5 kV, 10 kV, or customized according to test requirements.
Environmental thermometer and hygrometer, used to record the temperature and humidity of the environment for appropriate test evaluation.
Pre-Test Preparation
Disconnect all relevant power supplies and ensure that the equipment is properly grounded and discharged.
Check the connection wires and terminals to ensure they are secure and free of contamination.
Test under suitable environmental conditions: relative humidity below 75%, no rain (recommended temperature: 20-30°C).
Check the connection wires and terminals to ensure they are secure and free of contamination.
Test under suitable environmental conditions: relative humidity below 75%, no rain (recommended temperature: 20-30°C).
Test Progress
Connect the Test Instrument:
Connect the test equipment to the appropriate terminals or bushings of the device under test, ensuring that the connections are secure and properly grounded.
Apply Test Voltage:
Select the appropriate induction voltage according to the rated voltage and standard of the equipment.
Connect the test equipment to the appropriate terminals or bushings of the device under test, ensuring that the connections are secure and properly grounded.
Apply Test Voltage:
Select the appropriate induction voltage according to the rated voltage and standard of the equipment.
Test Standard
IEC 60076 Oil-immersed power transformers
Measure and Record
Start the test and record the following parameters:
Induced Voltage
Applied Current
Voltage peak, stability and waveform (waveform analysis)
Any abnormal current or voltage changes during the measurement process.
Induced Voltage
Applied Current
Voltage peak, stability and waveform (waveform analysis)
Any abnormal current or voltage changes during the measurement process.
Temperature Correction
The measured induced voltage data is corrected to the reference temperature (usually 20°C) to ensure the accuracy of the test results.
Repeat Testing (if necessary)
If necessary, test different windings (HV, MV, LV) and bushings separately and compare the results at different test points.
Evaluation Criteria (Reference)
Inductive voltage ≤ 1% (Excellent): normally and meets safety standards.
1% < Inductive voltage ≤ 3% (Good): still within acceptable range.
Inductive voltage > 3% : faulty or not meet safety requirements and requires further analysis and repair.
1% < Inductive voltage ≤ 3% (Good): still within acceptable range.
Inductive voltage > 3% : faulty or not meet safety requirements and requires further analysis and repair.
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
Strategically deployed as a primary transformer in 500kV ultra-high voltage substations, this unit facilitates the bulk transfer of power across thousands of kilometers, connecting the national grid to regional energy pools with extremely low transmission losses.
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
110kV 115kV Power Transformer
NPC ELECTRIC's 110kV and 115kV power transformers are designed with advanced low-loss silicon steel sheets and efficient cooling systems, complying with international standards such as IEC 60076 and GB 1094, ensuring stable and reliable operation in high-voltage transmission systems. They are widely used in large power plants, substations, and industrial parks, providing safe and efficient power conversion and transmission solutions for power grids.
800kVA Dry Type Transformer
NPC ELECTRIC 800kVA Dry-Type Transformer provides reliable, oil-free power distribution with a compact design. Featuring advanced insulation and cooling systems, it ensures safe, low-maintenance operation for industrial and commercial use. With 800kVA capacity, it delivers efficient and environmentally friendly performance.
50kVA Conventional Type Single Phase Pole Mounted Transformer
The 50kVA Conventional Type Single Phase pole Mounted transformer produced by NPC ELECTRIC has a rated capacity ranging from 10kVA to 333kVA, meeting the standards of ANSI/IEEE C57, IEC60076, etc. Its main function is to convert high-voltage power (such as 10kV, 11kV, etc.) into low-voltage power (such as 220V, 240V) through the transformer for use in homes, shops, industrial equipment, etc. It is suitable for residential areas, commercial areas, rural power grids, agricultural facilities and small industrial power supply.
115kV 35MVA Three-Phase Oil-Immersed Power Transformer
The 115kV 35MVA Three-Phase Oil-Immersed Power Transformer is designed for reliable and efficient operation in high-voltage transmission and substation applications. Built with high-permeability silicon steel cores and precision-wound copper conductors, it delivers low losses, strong short-circuit withstand capability, and excellent thermal stability. The oil-immersed cooling system ensures effective heat dissipation, enabling continuous operation under heavy-load conditions. A robust tank structure, advanced insulation system, and outdoor-rated protection make the transformer suitable for harsh environmental conditions. Manufactured in accordance with IEC, IEEE, and ANSI standards, this transformer is widely used in utility substations, industrial power systems, and regional transmission networks where long service life, stable voltage regulation, and high operational reliability are critical.
66kV 69kV Power Transformer
66 69kV power transformer uses high-performance silicon steel sheets and a fully sealed structure design, with excellent insulation performance and thermal stability. The product complies with international and national standards, such as 1 . IEC 60076 Power Transformers; 2. AS NZS 60076 Power Transformers CSAC88-16 Power Transformers 3.ANSI/IEEE C57.12.00 IEEE Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers; 4. GOST R 52719 Power Transformers - General Specifications; 5. EN60076 Poer Transformer;8. Local After-Sales Services In North America South
5kVA Completely self-protected(CSP) Single Phase Pole Mounted Transformer
NPC ELECTRIC the production of the 5kVA Completely self-protected(CSP) Single Phase pole Mounted transformer is designed for reliable and efficient distribution of electrical power in residential and light commercial applications. Built to withstand harsh outdoor conditions, this transformer is equipped with a self-protection system that eliminates the need for external protection devices, offering enhanced safety and durability. The CSP feature ensures that the transformer can handle internal faults such as short circuits or overloads without causing damage to the system. This compact, oil-immersed transformer is easy to install on poles, making it ideal for overhead distribution in areas with limited space. It is designed to meet international standards, including ANSI, IEEE, and CSA, ensuring high-quality performance and long-lasting operation. The 5kVA CSP transformer is energy-efficient, providing stable voltage regulation and minimizing maintenance requirements, making it an excellent choice for both utility and commercial applications.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