20 MVA substation power transformer-33/6.65 kV | South Africa 2025
Delivery Country: South Africa 2025
Capacity: 20MVA
Voltage: 33/6.65 kV
Feature: four wheels (10-ton)
01 General
Project Description
A South African customer ordered a 20MVA-33/6.65kV step down power transformer in May 2025. Our customer is supplying transformers, small substations and power cables to local and international mines. This transformer is also one of the main transformers customized for mine substations. South Africa is one of the most developed mining countries in the world, and there is a large demand for transformers for mines.
This step down power transformer adopts IEC 60076-1:2011 standard. It adopts the ONAN cooling method. Wiring group: YNyn0, suitable for a complex grounding environment. The winding material is copper, and the copper loss is lower. It is rated at 33kV on the primary side and 6.65kV on the secondary side. Equipped with an on-load tap changer (OLTC) with a ±10 × 1% regulation range, it allows flexible voltage adjustment under load, ensuring a stable power supply to mining equipment. The substation power transformer achieves excellent energy performance, with a no-load loss of 13.65 kW, load loss at 75°C of 132.8 kW, and a total loss limited to 72 kW. To improve mobility, especially at remote mining sites, the transformer is designed with heavy-duty wheels, a feature that significantly simplifies on-site operations.
Why It’s Ideal for Mining Applications
In mining operations, a reliable and efficient power supply is essential to ensure both safety and productivity. This substation power transformer is perfectly suited to typical mining power distribution scenarios:
Surface Substations: Steps down 33kV from the utility grid or captive power stations to 6.6kV, the standard voltage for mining equipment.
Underground Power Delivery: Transmits 6.6kV power through cables to underground systems – an ideal voltage for long-distance transmission with low losses.
High-Power Equipment Operation: Powers essential heavy-duty mining machinery such as ball mills, hoists, ventilation fans, and dewatering pumps.
- Outline Drawing
02 Manufacturing
2.1 Core
The substation power transformer features a three-phase three-limb core, shown in the image as a technician removes the upper yoke. The core is made of cold-rolled grain-oriented silicon steel, which offers excellent magnetic properties along the rolling direction-ideal for transformer applications. To further reduce no-load loss, fully mitered (step-lap) joints are used to align the magnetic flux with the steel’s rolling direction, enhancing overall efficiency.
2.2 Winding
The YNyn0 power transformer adopts a continuous disc winding structure for both high-voltage and low-voltage windings. The continuous disc winding offers superior axial cooling performance and is especially suitable for high-current, high-capacity applications. Each winding undergoes strict insulation treatment, layer-by-layer drying, and dimensional control to ensure consistency and insulation strength.
