20kV Three-Phase Oil-Immersed Power Transformer 50-2500kVA Copper
The 20kV Three-Phase Oil-Immersed Power Transformer 50-2500kVA Copper adopts high-purity electrolytic copper windings, Class A insulation, and advanced ONAN cooling design. Available in energy-saving S11/S13/S20 series with no-load loss reduced by up to 40%. Fully sealed corrugated tank or conservator type effectively prevents oil aging and moisture ingress. It complies with IEC 60076, GB/T 1094, and can be equipped with ±5% or ±2×2.5% off-circuit tap changer. Low noise (<55 dB), strong short-circuit withstand capability, and overload capacity make it ideal for industrial parks, commercial buildings, and renewable energy projects. Vacuum oil filling and nitrogen sealing ensure insulation performance for over 30 years. Factory supports full third-party inspection (SGS/BV) and provides type test reports.
- Primary Voltage Ratings 35kV, 34.5kV, 33kV, 46kV or others
- Secondary Voltage Ratings 13.8kV 6kV 10kV or others
- H.V. Tap Range ±8×1.25% or others
- Type Oil-immersed power transformer
- BIL 20kV
- Standards IEEE, ANSI, NEMA, IEC, CE
- Application industrial distribution networks, large factories
- Power Rating 50-2500kVA
- Certificate UL, CESI, IEEE
- 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
20kV Three-Phase Oil-Immersed Power Transformer 50-2500kVA Copper
Technical Specifications
Accessories
| Rated Power | 50-2500kVA | |
| Rating Primary Voltage | 20 kV | |
| Secondary Voltage |
6.6kV 10kV 13.8kV 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
20kV Three-Phase Oil-Immersed Power Transformer 50-2500kVA Copper
Clients can freely select capacity 50-2500kVA, copper or aluminum windings, S11/S13/S20 low-loss series, voltage ratios 20±5%/0.4kV, 20/0.69kV, 20/10.5kV or special dual-voltage. Tap changer options include off-circuit ±2×2.5%, ±5% or on-load ±8×1.25%. Vector group Dyn11, Yyn0, or custom. Cooling methods: ONAN or ONAF with auto fan control. Tank types: corrugated fins, detachable radiator, or fully sealed conservator.
Additional options include built-in protection (gas relay, pressure relief valve, oil temperature/winding temperature gauge with 4-20mA output), IP54 protective enclosure, anti-corrosion C5-M painting, high-altitude (>3000 m) design, low-noise version (<50 dB), online oil filtration interface, and smart monitoring terminal for SCADA. All customizations fully comply with IEC standards and support type/special test reports.
Packing and Shipping
20kV Three-Phase Oil-Immersed Power Transformer 50-2500kVA Copper
The 20kV three-phase oil-immersed power transformer (50–2500 kVA) is packaged with the highest attention to transport safety and product integrity. The core-coil assembly is vacuum-dried and oil-impregnated under controlled conditions before final tank sealing to eliminate moisture and maintain dielectric strength. All bushings, conservator, Buchholz relay, gauges, valves and accessories are factory-mounted where possible; sensitive components are separately crated with foam padding and shock-absorbing material to prevent transit damage.
The transformer is securely mounted on a reinforced wooden pallet or heavy-duty steel skid suitable for forklift and crane handling. The entire unit is wrapped in volatile corrosion inhibitor (VCI) paper, followed by multi-layer heavy polyethylene sheeting and strong steel banding. Desiccant bags are placed inside the packaging to control humidity during long-distance transport. For oil-immersed units, the transformer is shipped either fully filled with nitrogen blanketing to maintain positive pressure or partially filled with separate sealed drums to comply with hazardous goods regulations and reduce shipping weight.
Export crating uses ISPM-15 certified heat-treated lumber, reinforced with steel strapping, corner protectors and impact-resistant bracing. Each crate is clearly marked with gross/net weight, center of gravity, lifting points, dimensions, “Fragile – High Voltage Equipment” warnings and handling instructions. Tamper-evident seals are applied to all access points; weatherproof covers protect bushings, terminals and control cabinets.
Domestic shipments utilize flatbed or lowboy trailers with secure blocking and strapping; oversize permits are arranged when necessary. International transport typically involves 20ft/40ft open-top containers or flat-rack loading, with professional lashing using chains, turnbuckles and timber dunnage to withstand sea and road forces. Real-time GPS tracking and full-value cargo insurance are standard. Upon delivery, detailed handling and installation manuals are provided, including lifting procedures, foundation alignment, oil top-up (if partial fill), grounding, bushing connections and pre-energization checks.
The transformer is securely mounted on a reinforced wooden pallet or heavy-duty steel skid suitable for forklift and crane handling. The entire unit is wrapped in volatile corrosion inhibitor (VCI) paper, followed by multi-layer heavy polyethylene sheeting and strong steel banding. Desiccant bags are placed inside the packaging to control humidity during long-distance transport. For oil-immersed units, the transformer is shipped either fully filled with nitrogen blanketing to maintain positive pressure or partially filled with separate sealed drums to comply with hazardous goods regulations and reduce shipping weight.
Export crating uses ISPM-15 certified heat-treated lumber, reinforced with steel strapping, corner protectors and impact-resistant bracing. Each crate is clearly marked with gross/net weight, center of gravity, lifting points, dimensions, “Fragile – High Voltage Equipment” warnings and handling instructions. Tamper-evident seals are applied to all access points; weatherproof covers protect bushings, terminals and control cabinets.
Domestic shipments utilize flatbed or lowboy trailers with secure blocking and strapping; oversize permits are arranged when necessary. International transport typically involves 20ft/40ft open-top containers or flat-rack loading, with professional lashing using chains, turnbuckles and timber dunnage to withstand sea and road forces. Real-time GPS tracking and full-value cargo insurance are standard. Upon delivery, detailed handling and installation manuals are provided, including lifting procedures, foundation alignment, oil top-up (if partial fill), grounding, bushing connections and pre-energization checks.
32
32 years of industry experience
Manufacturer Test
20kV Three-Phase Oil-Immersed Power Transformer 50-2500kVA Copper
Progress Test
During production, the 20kV Three-Phase Oil-Immersed Power Transformer undergoes strict staged Progress Tests:
- Core-coil: winding DC resistance at all taps, insulation resistance (PI ≥ 2.0), core grounding current <50 mA.
- Pre-tanking: ratio at all taps (deviation ≤ ±0.5%), vector group Dyn11/Yyn0 verification.
- After vapor-phase drying & vacuum oil-filling: final insulation resistance, tanδ ≤ 0.004, PD <5 pC at 1.5Um/√3, oil BDV >60 kV.
- Tank sealing: 24 h leakage test + 0.3 bar pressure/vacuum test. All records are submitted for client approval before FAT.
These incremental checks enable early identification and correction of nonconformities, ensuring the finished transformer meets efficiency, impedance and reliability targets.
Design Tests
All transformers will be tested after finishing the production, test items as follows:
♦ 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)
♦ Applied Voltage
♦ Induced Voltage
♦ Lightning Impulse
♦ Insulation Resistance (Rated Voltage)
♦ Temperature Rise
♦ Dielectric Withstand (Hipot)
Transformer Factory Acceptance Test
The Factory Acceptance Test is performed strictly in accordance with IEC 60076-1/3/5/11, GB/T 1094, and customer technical specifications, fully witnessed by the client or third-party inspection agency (SGS, BV, TÜV, etc.).
- Winding resistance measurement at all tap positions (ambient temperature, corrected to 75 °C)
- Voltage ratio and polarity test at rated tap and all off-circuit/on-load tap positions (tolerance ≤ ±0.5 %)
- Vector group and magnetic balance verification (typically Dyn11 or Yyn0)
- No-load loss and no-load current at 90 %, 100 %, and 110 % rated voltage on principal tap
All raw data, oscillograms, and calibration certificates are recorded in the official FAT protocol. The transformer is released for shipment only after client signature, ensuring every 20kV Three-Phase Oil-Immersed Power Transformer 50-2500kVA Copper is 100 % qualified for immediate energization and long-term reliable service.
Routine Test - Applied Voltage
Purpose of Testing
The purpose of testing the applied voltage is to verify the insulation strength of the transformer by applying a voltage higher than its normal operating level, ensuring it can withstand potential electrical stresses. This test helps identify any weaknesses or defects in the insulation system before the transformer is put into service.
Testing Equipment
Test equipment: High voltage tester (e.g. TTR, Hipot, etc.)
Voltage source: usually 1 kV, 5 kV, 10 kV, or customized according to customer needs
Temperature and humidity meter: used to record environmental conditions
Voltage source: usually 1 kV, 5 kV, 10 kV, or customized according to customer needs
Temperature and humidity meter: used to record environmental conditions
Pre-Test Preparation
Disconnect the device from the power supply and make sure it is properly grounded and discharged.
Check the connection terminals and wiring to ensure that they are not loose or contaminated.
Test under suitable environmental conditions: relative humidity below 75% and no rain (recommended temperature: 20-30°C).
Check the connection terminals and wiring to ensure that they are not loose or contaminated.
Test under suitable environmental conditions: relative humidity below 75% and no rain (recommended temperature: 20-30°C).
Test Progress
Connect the Test Instrument:
Properly connect the test equipment to the bushings or terminals of the device under test and ensure that all connection points are properly grounded.
Selecting the test voltage:
Select the appropriate applied voltage based on the rated voltage of the equipment.
Properly connect the test equipment to the bushings or terminals of the device under test and ensure that all connection points are properly grounded.
Selecting the test voltage:
Select the appropriate applied voltage based on the rated voltage of the equipment.
Measure and Record
Start the test and record the following parameters:
Measuring leakage current
Applied voltage
Current stability
Any possible voltage fluctuations
Measuring leakage current
Applied voltage
Current stability
Any possible voltage fluctuations
Temperature Correction
If necessary, the measured data is temperature corrected to ensure that it corresponds to standard temperature conditions (usually 20°C).
Repeat Testing (if necessary)
Multiple tests were conducted on different windings (high voltage, medium voltage, low voltage) and bushings, and comparative analysis was performed.
Evaluation Criteria (Reference)
The test was normal and the equipment performed well (qualified)
The current value exceeded the allowable range and the equipment needs to be inspected or maintained (pending repair)
There was a serious fault or instability and the equipment could not continue to operate (unqualified)
The current value exceeded the allowable range and the equipment needs to be inspected or maintained (pending repair)
There was a serious fault or instability and the equipment could not continue to operate (unqualified)
Observing electrical behavior
Observe the electrical behavior of the device under test to ensure that there are no abnormal currents, arcing, noise, or electrical faults.
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
Widely used in 20kV industrial distribution networks, large factories (chemical, steel, paper), commercial complexes, data centers, hospitals, urban compact substations, wind/solar farm step-up stations, port & railway 20kV power supply systems, and rural 35kV/20kV transformation projects.
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
200kVA Oil Immersed Transformer
The 200kVA oil-immersed transformer produced by our company adopts a new insulation structure to improve the short-circuit resistance; the iron core is made of high-quality cold-rolled silicon steel sheet; the high-voltage winding is made of high-quality oxygen-free copper wire and adopts a multi-layer cylindrical structure; all fasteners are treated with special anti-loosening treatment. Standard configuration includes mineral oil or FR3 natural ester fluid, ONAN cooling, aluminum or copper windings, high-voltage 34.5kV / 24.94kV / 13.8kV / 12.47kV / 4.16kV.
400kVA Oil Immersed Transformer
The 400kVA Oil Immersed Transformer produced by our company adopts a new insulation structure to improve the short-circuit resistance; the iron core is made of high-quality cold-rolled silicon steel sheet; the high-voltage winding is made of high-quality oxygen-free copper wire and adopts a multi-layer cylindrical structure; all fasteners are treated with special anti-loosening treatment. ONAN cooling, aluminum or copper windings, high-voltage 34.5kV / 24.94kV / 13.8kV / 12.47kV / 4.16kV (delta or wye), low-voltage 480Y/277V, 208Y/120V, 600Y/347V or custom, ±2×2.5% HV taps.
260 kV 20MVA 28 MVA Substation Power Transformer
The robust 260 kV 20/28 MVA substation power transformer, engineered for high-voltage applications in modern electrical grids. This oil-immersed unit features dual capacity ratings for flexible operation under varying loads, ensuring efficient power distribution and voltage step-down in utility substations. With advanced insulation systems and low-loss core materials, it minimizes energy dissipation while handling peak demands reliably. Ideal for integrating renewable energy sources or industrial power systems, this transformer complies with IEC 60076 standards, offering superior performance in harsh environments. Its compact design facilitates easy installation, making it a top choice for upgrading aging infrastructure or expanding grid capacity.
750kVA 3-Phase Oil-Immersed Outdoor Substation Transformer
A 750kVA 3-phase oil-immersed outdoor substation transformer is designed for stable and efficient power distribution in industrial, commercial, and utility applications. Built with high-quality insulation and premium transformer oil, it provides excellent cooling performance and long-term reliability. The transformer ensures accurate current measurement and voltage conversion, making it ideal for outdoor substations operating under demanding conditions.
25000kVA Oil-Immersed Copper Transformer For Substation
The 25,000kVA oil-immersed copper transformer is engineered for high-standard power distribution in large industrial facilities, utility networks, and high-voltage substations. Built with premium pure copper windings, it delivers exceptional electrical conductivity, reduced losses, and long-term operational stability. The oil-immersed cooling system ensures efficient heat dissipation, allowing the transformer to perform reliably under continuous heavy load conditions.
630kVA Three-Phase Oil-Immersed Outdoor Substation Transformer | 220V to 380V Step-Up Transformer
This 630kVA three-phase oil-immersed transformer is designed for outdoor substations, providing reliable voltage conversion from 220V to 380V. With a robust oil-immersed cooling system, it ensures excellent heat dissipation, stable performance, and long service life. Ideal for industrial facilities, commercial power distribution, and utility applications, this step-up transformer delivers consistent efficiency even under heavy load conditions.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