125kV Three-Phase Power Distribution Transformer
The 125kV Three-Phase Power Distribution Transformer is engineered to deliver reliable, efficient, and stable voltage transformation for high-voltage distribution networks and utility substations. Designed with a high-permeability silicon steel core and precision-wound conductors, it achieves low no-load loss, reduced operating noise, and excellent short-circuit withstand capability. The robust insulation system and optimized thermal design ensure long-term performance under continuous load and fluctuating grid conditions. Its reinforced tank structure and outdoor-rated configuration allow safe operation in demanding environments, including high temperature, humidity, and industrial pollution areas. Manufactured in compliance with IEC, IEEE, and ANSI standards, this transformer is suitable for modern power distribution systems requiring high reliability, operational safety, and extended service life.
- Primary Voltage Ratings 110kV, 115kV,125kV 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 350kV
- Standards IEEE, ANSI, IEC
- Application Power transmission and transformation systems, large industrial parks, energy infrastructure projects etc
- 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
125kV Three-Phase Power Distribution Transformer
Technical Specifications
Accessories
| Rated Power | Up to 200 MVA |
| Rating Primary Voltage | 110kV, 115kV, 125kV |
| 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
125kV Three-Phase Power Distribution Transformer
The 125kV Three-Phase Power Distribution Transformer supports extensive customization to match diverse grid requirements and project specifications. Electrical parameters such as rated voltage, capacity, frequency, impedance, and vector group (Dyn11, YNd1, Yyn0, or customized configurations) can be tailored to meet local utility standards. On-load or off-load tap changers with adjustable tap ranges are available to ensure precise voltage regulation under variable load conditions. Customers may select high-purity copper or aluminum windings, enhanced insulation classes, and optimized core designs to meet efficiency targets and loss regulations. Special designs for high-altitude operation, wide temperature ranges, or high-humidity environments are also supported.
Mechanical and system-level customization includes corrosion-resistant tanks, reinforced structures for seismic regions, and customized cooling methods such as ONAN, ONAF, or OFAF. Noise-reduction designs, compact layouts for space-limited substations, and special bushing arrangements can be provided. Advanced protection and monitoring options—such as Buchholz relays, oil and winding temperature indicators, pressure relief devices, oil level gauges, and online condition monitoring systems—enhance operational safety and maintenance efficiency. Fire-resistant insulating oil, eco-friendly materials, and customer-specific painting schemes are available upon request. All customized solutions are engineered and tested to comply with international standards and project-specific technical requirements.
Packing and Shipping
125kV Three-Phase Power Distribution Transformer
The packing and shipping process for the 125kV Three-Phase Power Distribution Transformer is carefully planned to ensure safe transportation and equipment integrity. Prior to packing, the transformer undergoes final inspection, oil processing, surface cleaning, and anti-corrosion treatment. All exposed metal parts are coated with protective paint, and openings are securely sealed to prevent moisture and dust ingress. Sensitive components such as bushings, radiators, conservators, and control accessories are dismantled when necessary and packed separately in reinforced wooden crates with shock-absorbing padding.
The transformer's main body is firmly mounted on a heavy-duty steel skid or export-grade wooden base to prevent movement during transit. Vibration dampers, structural supports, and impact-resistant materials are applied at critical points to minimize mechanical stress. Moisture-proof films, desiccants, and rust-inhibiting layers are used to protect the insulation system and metal surfaces. For long-distance or sea transportation, vacuum sealing or nitrogen filling may be applied to maintain internal dryness and oil quality.
Shipment methods are selected based on transformer size, weight, and destination, including flat-rack containers, open-top containers, or break-bulk cargo. All packing materials comply with international export regulations and ISPM-15 standards. Clear handling instructions, lifting points, center-of-gravity markings, and safety labels are displayed to ensure proper loading and unloading. Complete documentation—such as packing lists, test certificates, quality reports, drawings, and operation manuals—is provided in waterproof packaging.
Upon arrival at the installation site, detailed guidance for unpacking, storage, and installation is supplied. Optional services include on-site supervision, accessory reassembly, oil filtration, testing, and commissioning support. This comprehensive packing and shipping approach ensures the transformer arrives safely and is ready for reliable operation.
The transformer's main body is firmly mounted on a heavy-duty steel skid or export-grade wooden base to prevent movement during transit. Vibration dampers, structural supports, and impact-resistant materials are applied at critical points to minimize mechanical stress. Moisture-proof films, desiccants, and rust-inhibiting layers are used to protect the insulation system and metal surfaces. For long-distance or sea transportation, vacuum sealing or nitrogen filling may be applied to maintain internal dryness and oil quality.
Shipment methods are selected based on transformer size, weight, and destination, including flat-rack containers, open-top containers, or break-bulk cargo. All packing materials comply with international export regulations and ISPM-15 standards. Clear handling instructions, lifting points, center-of-gravity markings, and safety labels are displayed to ensure proper loading and unloading. Complete documentation—such as packing lists, test certificates, quality reports, drawings, and operation manuals—is provided in waterproof packaging.
Upon arrival at the installation site, detailed guidance for unpacking, storage, and installation is supplied. Optional services include on-site supervision, accessory reassembly, oil filtration, testing, and commissioning support. This comprehensive packing and shipping approach ensures the transformer arrives safely and is ready for reliable operation.
32
32 years of industry experience
Manufacturer Test
125kV Three-Phase Power Distribution Transformer
Progress test
Progress testing is conducted throughout the manufacturing process of the 125kV Three-Phase Power Distribution Transformer to ensure consistent quality and process control. Incoming inspections verify the compliance of core steel, winding conductors, insulation materials, and transformer oil with technical specifications. During core stacking and winding, dimensional accuracy, insulation spacing, and mechanical stability are closely monitored. The active part undergoes controlled drying and vacuum treatment, with continuous monitoring of temperature and moisture content.
Intermediate electrical tests include winding resistance measurement, insulation resistance testing, and turns ratio verification at key production stages. Tank fabrication is inspected for welding quality, dimensional accuracy, and coating thickness. Pressure and leak tests are conducted to confirm tank integrity before oil filling. All progress test data are recorded and reviewed to ensure traceability and early detection of potential issues 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 125kV Three-Phase Power Distribution Transformer is performed after final assembly in accordance with IEC and IEEE standards. Routine tests include winding resistance measurement, voltage ratio and vector group verification, polarity checks, and insulation resistance testing. Dielectric tests such as applied AC withstand voltage and induced overvoltage tests confirm insulation reliability.
Performance tests evaluate no-load loss, load loss, impedance voltage, and temperature rise to verify efficiency and thermal performance. Partial discharge measurement assesses insulation condition, while lightning impulse tests validate overvoltage withstand capability. Mechanical and functional inspections include tank pressure testing, oil leakage inspection, tap changer operation, cooling system performance, and oil quality analysis. All protective and monitoring devices are checked for accuracy and functionality. FAT reports are reviewed and approved prior to shipment.
Routine Test - On load Loss Test
Purpose of Testing
The purpose of On-load Loss Test is to measure the active power loss of the transformer under rated voltage and rated load, evaluate its energy efficiency level and design compliance, and provide a basis for energy consumption calculation and performance optimization during operation.
Testing Equipment
Power transformer test system (e.g. OMICRON, ISA, Tettex, Vanguard, etc.)
Voltage source and current source (usually rated voltage, or adjusted according to the test standard, such as 10 KV, 20 KV, 35 KV, etc.)
Temperature and humidity meter (used to record ambient temperature and humidity for correction of test data)
Voltage source and current source (usually rated voltage, or adjusted according to the test standard, such as 10 KV, 20 KV, 35 KV, etc.)
Temperature and humidity meter (used to record ambient temperature and humidity for correction of test data)
Pre-Test Preparation
Disconnect the transformer high voltage, low voltage and neutral power supply to ensure that the equipment is properly grounded and safely discharged.
The test environment should be dry and rainless, with a relative humidity of less than 75% and a recommended temperature range of 20–30°C.
The test environment should be dry and rainless, with a relative humidity of less than 75% and a recommended temperature range of 20–30°C.
Test Progress
Connect the Test Instrument:
Connect the test equipment to the appropriate terminals of the device under test and ensure that all wiring is correct and the device is well grounded.
Apply Test Voltage:
Apply the specified test voltage at the rated frequency and adjust the low voltage side to maintain the rated current (or specified current).
Connect the test equipment to the appropriate terminals of the device under test and ensure that all wiring is correct and the device is well grounded.
Apply Test Voltage:
Apply the specified test voltage at the rated frequency and adjust the low voltage side to maintain the rated current (or specified current).
Measure and Record
Start the test and record the following parameters:
On-Load Loss Power
Input Power and Output Power
Current
Voltage
Temperature (temperature rise or winding temperature)
Ambient temperature and humidity during the test
On-Load Loss Power
Input Power and Output Power
Current
Voltage
Temperature (temperature rise or winding temperature)
Ambient temperature and humidity during the test
Temperature Correction
The measured loss data is corrected based on a reference temperature (usually 20°C) to ensure the accuracy of the results.
Repeat Testing (if necessary)
Test different tap positions (Tap Changer) and record and compare the load loss data of each tap point.
Evaluation Criteria (Reference)
Evaluate the test results based on the equipment type and manufacturer requirements. If the load losses are low and the efficiency is high, it is considered "normal". If the load losses are too high or the efficiency is low, further inspection or corrective action is required.
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
It provides reliable voltage transformation, stable power delivery, and long-term operation for applications requiring high efficiency, safety, and dependable performance in high-voltage distribution environments.
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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