Safe and reliable, enduring quality, Power Transformer empowers electricity with limitless vitality.
01 General
1.1 Project Description
A 30 MVA power transformer was delivered to South Africa in April 2025. The rated power of the transformer is 30 MVA with ONAN cooling. The primary voltage is 33 kV with +4(-12) *1.25% tapping range (OLTC), the secondary voltage is 6.6 kV, and they formed a vector group of Dyn11.
The transformer for power combines advanced technology with outstanding performance, providing strong support for modern power systems. It is equipped with an on-load tap changer (OLTC), gas relay, winding temperature indicator, and shock recorder, forming a comprehensive system for performance and safety assurance.
The on-load tap changer (OLTC) enables precise voltage adjustment without affecting the load, ensuring the stability of power transmission to meet the ever-changing power demands. The gas relay is responsible for real-time internal monitoring, quickly detecting abnormalities and issuing alerts, effectively preventing equipment damage and downtime risks. To maintain the long-term stability of the equipment, the winding temperature indicator monitors the temperature of the transformer windings, preventing overheating from damaging insulation materials and thus extending the service life of the equipment. Meanwhile, the shock recorder records and analyzes mechanical shocks received during transportation or operation, assisting maintenance personnel in promptly identifying and addressing potential issues.
1.2 Technical Specification
30 MVA transformer for power specification and data sheet
| Delivered to | South Africa |
| Year | 2025 |
| Type | Oil immersed power transformer |
| Standard | IEC60076 |
| Rated Power | 30 MVA |
| Frequency | 50HZ |
| Phase | 3 |
| Cooling Type | ONAN |
| Primary Voltage | 33 kV |
| Secondary Voltage | 6.6 kV |
| Winding Material | Copper |
| Angular displacement | Dyn11 |
| Impedance | 10% |
| Tap Changer | OLTC |
| Tapping Range | +4(-12) *1.25% |
| No Load Loss | 21.8kW |
| On Load Loss | 160kW |
| Accessories | Standard Configuration |
1.3 Drawings
30 MVA transformer for power diagram drawing and size.
02 Manufacturing
2.1 Core
| The iron core is a vital component in every power transformer, acting as the center of its magnetic circuit. Made from high-quality, cold-rolled silicon steel sheets with a thickness of 0.3 mm or less, the core is precision-cut using advanced laser technology to meet strict quality standards. The sheets are assembled using a “step-lap” technique, which minimizes flux leakage at the joints, reducing energy losses and operational noise. This process ensures a robust structure capable of withstanding mechanical stresses. |  |
2.2 Winding
 | Coil windings are crucial components in transformer design, ensuring operational efficiency and mechanical resilience. High-voltage (HV) windings feature a continuous entangled structure with inner screened phase insulation, significantly enhancing insulating strength and minimizing breakdown risks. Low-voltage (LV) windings utilize high-strength or transposed conductors to optimize conductivity and reduce resistance. They incorporate forced cooling methods to effectively manage heat and improve short-circuit withstand capability, ensuring reliable performance under fluctuating loads. |
2.3 Tank
| The manufacturing process of transformer oil tanks involves selecting high-quality, high-strength steel, which is cut and bent into shape. Advanced welding techniques are used to ensure structural integrity and sealing. The tank is then assembled to enhance strength, with added fins to improve heat dissipation. Surface treatment involves coating with anti-corrosion paint, and the tank undergoes sealing and pressure tests to ensure no leakage. |  |
2.4 Final Assembly
 | Winding Installation: Install the high-voltage and low-voltage windings on the core, using insulation materials to prevent short circuits. Tank Assembly: Place the core and windings into the treated oil tank, ensuring proper sealing to prevent leaks. Cooling System Installation: Install radiators to facilitate effective cooling. Accessory Installation: Install the On-Load Tap Changer (OLTC), gas relay, winding temperature indicator, and current transformer (CT), ensuring reliable connections. Filling and Vacuum Processing: Fill the oil tank with insulating oil and perform vacuum treatment to remove air. |
03 Testing
1. Measurement Of Dissolved Gasses In Dielectric Liquid From Each Separate Oil Compartment Except Diverter Switch
2. Measurement Of Voltage Ratio And Check Of Phase Displacement
3. Measurement Of Winding Resistance
4. Check Of Core And Frame Insulation For Liquid Immersed Transformers With Core Or Frame Insulation
5. Measurement Of D.C Insulation Resistance Between Each Winding To Earth And Between Windings
6. Determination of capacitances windings to earth and between windings
7. Applied Voltage Test (AV)
8. Measurement Of No-Load Loss And Current
9. Induced Voltage Withstand Test
10. Measurement of Short-circuit Impedance and Load Loss
11. Measurement of dissolved gasses in dielectric liquid from each separate oil compartment except diverter switch compartment
12. Leak Testing With Pressure For Liquid-Immersed Transformers (Tightness Test)
04 Packing and Shipping
05 Site And Summary
In conclusion, our power transformers are engineered to deliver exceptional performance, reliability, and efficiency for a wide range of applications. With advanced technology and robust construction, they are designed to meet the demanding requirements of modern energy systems while ensuring optimal safety and minimal environmental impact. By choosing our power transformers, you are investing in a crucial component that will enhance your energy infrastructure and contribute to a sustainable future. We invite you to explore our range of products and discover how our solutions can meet your energy needs effectively and efficiently. Thank you for considering our transformers as a vital part of your operations.
