Efficient and reliable 6 MVA oil-immersed transformers for inverter systems, delivering safe voltage, low losses, and durable performance in South Africa's outdoor environments
01 General
1.1 Project Description
This 6MVA oil-immersed power transformer was delivered to South Africa in 2024 for use in inverter systems. The 6 MVA electrical power transformer has a rated capacity of 6000 kVA, a primary voltage of 33 kV, and a secondary voltage of 2.2 kV. It strictly adheres to IEC 60076 standards
Although inverters can convert DC power into AC power, the grid voltage is often higher than the inverter can withstand. To ensure safe system operation, our transformer steps down the grid’s high voltage (33 kV) to the 2.2 kV acceptable to the inverter. The transformer also provides electrical isolation, harmonic suppression, and system protection, ensuring safe and stable operation between the inverter and the grid.
It boasts high operating efficiency. No-load losses are as low as 6.2 kW, and loaded losses are as low as 39 kW, reducing energy consumption and operating costs. A 7% impedance ensures stable voltage in short-circuit conditions, and the copper windings offer excellent conductivity, protecting both the inverter and the grid.
The 6 MVA electrical power transformers are filled with PCB-free mineral insulating oil, enhancing environmental safety. The cooling system utilizes natural air cooling and features a hot-dip galvanized radiator. This ensures efficient heat dissipation and strong weather resistance, making them ideal for South Africa’s outdoor environment.
Standard accessories include an oil level gauge, pressure relief valve, oil and winding temperature monitoring devices, a Buchholz relay, and a respirator, ensuring safe and stable operation and extending the service life of the equipment. With its high efficiency, low losses, and robust design, this 6MVA oil-immersed power transformer is not only an ideal choice for inverter grid-connected systems, but also a reliable core component for new energy power projects.
1.2 Technical Specification
6MVA electrical power transformers specification and data sheet
| Delivered to | South Africa |
| Year | 2024 |
| Type | Oil Immersed Power Transformer |
| Standard | IEC 60076 |
| Rated Power | 6MVA |
| Frequency | 50HZ |
| Phase | Three |
| Cooling Type | ONAN |
| Primary Voltage | 33KV |
| Secondary Voltage | 2.2 KV |
| Winding Material | Copper |
| Coolant Material | PCB free transformer mineral oil |
| Vector Group | Dyn11 |
| Impedance | 7 % |
| Tap Changer | NLTC |
| Tapping Range | ±2*3% @ Primary side |
| No Load Loss | 6.2KW |
| On Load Loss | 39KW |
| Accessories | Standard Configuration |
1.3 Drawings
6MVA electrical power transformers dimensions and weight details
02 Manufacturing
2.1 Core
We rigorously follow design drawings, standards, and manufacturing procedures for every step, ensuring precise core assembly, secure interconnection of live parts, and reliable grounding. Through this strict control, our iron cores achieve low losses, reduced noise, high insulation strength, and strong short-circuit resistance, ensuring long-term reliable transformer operation. |  |
2.2 Winding
 | Coil winding is a critical process. We use high-quality copper, ensuring excellent conductivity and mechanical strength. During winding, we maintain uniform insulation, consistent spacing, and tight, neat layers to prevent hotspots and insulation failure. After winding, coils are shaped, secured, and insulated, with strict quality checks, ensuring stability under short-circuit, thermal, and electrical stresses while meeting Dyn11 connection requirements. |
2.3 Tank
The plate-type radiator is hot-dip galvanized and painted in C12 avocado green. During the power transformer oil tank and radiator production, all welds are carefully executed to ensure no leaks, verified by an air pressure test at 30 kPa for 8 hours. The inner and outer surfaces are treated to prevent corrosion, guaranteeing long-term durability and reliable heat dissipation in service.
2.4 Final Assembly
| After the transformer core and windings are assembled, the unit is placed in the drying chamber. Once dried, it is lifted and installed into the oil tank. This transformer is equipped with a full set of accessories, including a plate-type radiator, oil level indicator, pressure relief valve, oil temperature indicator, Buchholz relay, oil conservator, breather, no-load tap changer, and winding temperature indicator. All accessories are installed according to our strict production requirements, with neat and organized wiring. After accessory installation, the assembly process is completed with oil filling and sealing, electrical connections and tests, and inspection of appearance and markings. |  |
03 Testing
Testing Standard
IEC 60076-1-2011, Power transformers – Part 1: General
IEC 60076-3-2013, Power Transformers-Part 3: Insulation levels, dielectric
tests and external clearances in air
IEC 60076-7-2018, Power transformers- Part 7 Loading guide for mineral-oil-immersed power transformers
Routine Test
- Measurement of dissolved gasses in dielectric liquid from each separate oil compartment except diverter switch compartment
- Measurement of Voltage Ratio and Check of Phase Displacement
- Measurement of Winding Resistance
- Measurement Of D.C Insulation Resistance Between Each Winding To Earth And Between Windings
- Applied Voltage Test
- Measurement of No-Load Loss and Current
- Induced Voltage Test
- Measurement of Short-circuit Impedance and Load Loss
- Leak Testing with Pressure For Liquid-Immersed Transformers
After Routine Test of this product comply with the requirements of IEC 60076-1-2011, IEC 60076-3-2013, IEC 60076-7-2018 standard and the product is qualified. Conclusion: Qualified, permit to leave factory.
04 Packing and Shipping
4.1 Packing
1. After factory testing, drain oil (or leave a small amount), dry the interior, fill with dry air or nitrogen, and maintain a slight positive pressure.
2. Install a pressure gauge and relief valve to prevent overpressure.
3. Remove accessories (radiators, oil conservator, gas relay, pipes) and pack separately.
4. Seal all flanges with secondary gaskets and tighten bolts.
5. Add corner protectors and wrap the unit with protective film.
6. Pack disassembled accessories with angle iron and plywood; keep the main body bare.
7. Place the transformer in a steel-frame wooden crate; attach shock monitors if required.
8. Mark the crate with forklift and center-of-gravity symbols.
9. Cover the crate with a moisture-proof tarp.
4.2 Shipping
Before loading, measure the transformer’s size and weight, and plan a route that avoids height, width, and weight restrictions. Use low-bed or specialized trucks with adequate capacity.
Align the transformer’s center of gravity with the vehicle. Use channel steel and proper fastening methods to secure the base to the truck, if permitted. Secure the transformer with slings or chains through designated transport holes, avoiding fragile components such as radiators and bushings. Lock internal components and seal all doors.
Keep speed ≤60 km/h and tilt ≤15° during transport. Avoid sudden moves and strong vibrations. Assign escorts to check binding and stop transport in severe weather.
When lifting, keep rope angles ≤60°. Use spreader bars if needed. Always lift upright, and for units without top lugs, use bottom lifting rods.
05 Site and Summary
With precise manufacturing, high-quality materials, and strict assembly standards, this 6MVA oil-immersed power transformer delivers reliable, efficient, and long-lasting performance. Every detail, from the core and windings to the tank and accessories, is designed to ensure safe and stable operation in inverter grid-connected systems across South Africa.
