Main Power Transformer Solutions for Mining, Hydropower, and Renewable Energy
01 General
1.1 Project Description
Thanks to our South Africa customer for their continued trust. After the first order in 2019, they have once again chosen our 10MVA 33/33kV main power transformer for their mining substation project. This 10000 kVA main power transformer is used in the substation of a mining company. Due to the unstable 33kV line voltage of the local power grid, it often jumps from 26kV to 40kV, so we designed this 33kV to 33kV, ±8×2.5% (total ±20%) very wide voltage regulation range on-load tap-changer transformer to adjust the primary voltage to obtain a stable 33kV output voltage.
If you are dealing with grid voltage instability caused by an old grid, poor infrastructure, a large supply radius or poor grid regulation capabilities. An equal-voltage transformer, such as a 33/33kV, 22/22kV or 11/11kV model with a voltage fluctuation range of ±16% to ±20%, may be your ideal solution.
Equal-voltage transformers are primarily used for voltage regulation. It is ideal for applications such as mining operations, long-distance transmission of hydropower stations, oil and gas pipeline projects, cross-regional power supply, and renewable energy grid connection, where reliable power quality is critical.
1.2 Technical Specification
10MVA main power transformer specification and data sheet
| Delivered to | South Africa |
| Year | 2025 |
| Type | Oil immersed power transformer |
| Standard | IEC 60076 |
| Rated Power | 10MVA |
| Frequency | 50HZ |
| Phase | 3 |
| Cooling Type | ONAN |
| Primary Voltage | 33 KV |
| Secondary Voltage | 33 KV |
| Winding Material | copper |
| Angular displacement | YNyn0 |
| Impedance | 7% |
| Tap Changer | OLTC |
| Tapping Range | +8*2.5%, -8*2.5%@primary side |
| No Load Loss | 8.5 KW |
| On Load Loss | 72 KW |
1.3 Drawings
10MVA main power transformer dimensions and weight details
02 Manufacturing
2.1 Core
The main power transformer core is a key component in the power transformer, acting as a magnetic path to facilitate energy transfer between the primary winding and the secondary winding. This 10MVA-33/33kV power transformer core is usually constructed of high-quality grain oriented silicon steel sheet, with a no-load loss of only 8.5 kW, minimizing energy loss at maximum magnetic flux density. |  |
2.2 Winding
The continuous disc winding is a type of Disc winding, which is wound with a flat copper conductor and consists of several round pancake-shaped coils. Continuous winding avoids multiple joints and improves the long-term stability of the transformer. High-quality copper winding materials can effectively reduce the load loss of the winding and improve the efficiency of the transformer.
2.3 Tank
The transformer is equipped with an efficient ONAN cooling system, complemented by high-quality mineral oil and No PCB, thus ensuring safe and environmentally friendly operation. To enhance heat dissipation, four sets of plate-type radiators are installed on each side of the transformer. |  |
2.4 Final Assembly
 | 1. The active part of the main power transformer in the picture has been assembled, and the tester is performing routine electrical performance tests. 2. The active part is being lifted into the tank. 3. Install other parts: oil temperature indicator, pressure relief valve, oil level indicator, gas relay, breather, earthing terminal, terminal box, skid base (suitable for slideway type foundation or skid-mounted structure). 4. Pour insulating oil into the transformer tank to fill the internal space of the transformer and ensure that the oil level meets the requirements. 5. Due to the large area occupied by the radiator, it will be assembled before the test and then disassembled and packed for transportation after the test. |
03 Testing
Routine Test and 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
1. Measurement of dissolved gasses in dielectric liquid from each separate oil compartment except diverter switch compartment
2. Measurement of Voltage Ratio and Check of Phase Displacement
3. Measurement of Winding Resistance
4. Measurement of D.C Insulation Resistance Between Each Winding To Earth And Between Windings
5. Measurement of Core Insulation Resistance
6. Applied Voltage Test
7. Measurement of No-Load Loss and Current
8. Induced Voltage Test
9. Measurement of Short-circuit Impedance and Load Loss
10. Leak Testing with Pressure For Liquid-Immersed Transformers
04 Packing and Shipping
05 Site and Summary
Why choose Equal-Voltage Transformers?
We are proud to supply Equal-voltage transformers to our customers in South Africa again in 2025. Equal-voltage transformers are ideal for remote mining areas where voltage fluctuations and long power supply radius are common. Using equal-voltage transformers can keep equipment running stably and reduce downtime. Hydropower transmission, Oil & Gas Pipeline Projects, Renewable Energy Grid Integration, and many more are also suitable.
Scotech invests a lot of money in transformer research and development every year to improve product performance, efficiency and adaptability. We can customize a variety of different transformers according to your needs.
