80 MVA Step Down Power Transformer-132/33 kV | South Africa 2024

A powerful core, stable output-our transformers keep your business running strong!

01 General

1.1 Project Description

Two units of 80/50MVA Power transformer were exported to South Africa in July, 2024. The rated power is 50 MVA with ONAN cooling method. The power is up to 80MVA when it is ONAF. The voltage is 132 to 33 kV, 132 kV primary, 33 kV secondary. The two transformers are used in photovoltaic power stations in South Africa.

The ambient temperature of the step down power transformer installation site is -5 ° C to +45 ° C, the degree of environmental pollution is severe, and the maximum humidity is 85%. This requires the transformer box to be able to adapt to a variety of harsh environments. The two medium power transformers we produced are equipped with a high-strength box, the surface of the box adopts anti-corrosion design and special spray paint treatment, the paint thickness is above 125mm, which can effectively prevent the erosion of sand and other harmful substances. The chip radiator of this transformer adopts a special process of hot dip galvanizing. In addition, the high and low pressure casing with galvanized arrester bracket. All control circuits of the transformer need to be shielded, and the high voltage neutral point needs to be grounded. Each oil pillow comes with a capsule oil pillow and a leak collector.

1.2 Technical Specification

80 MVA step down power transformer specification and data sheet

1.3 Drawings

80 MVA step down power transformer diagram drawing and size.

02 Manufacturing

2.1 Core

Each limb of the core supports the step down power transformer windings, with the size and shape of the limbs designed based on the rated power (80MVA) and voltage level. Horizontal sections of the core, called the yoke, connect the three limbs at the top and bottom, forming a closed magnetic circuit. The core is made of high-permeability, low-loss cold-rolled grain-oriented silicon steel sheets to minimize core losses (including hysteresis and eddy current losses). The core limbs and yoke form a closed magnetic circuit. Magnetic flux is distributed across the three limbs, with each phase’s flux passing through the yoke and linking with the other two phases, ensuring balanced three-phase flux.

2.2 Winding

The number of turns, cross-sectional area of the conductor, and spacing of each section are optimized based on the transformer’s voltage level, power capacity, and current requirements. Since the winding is continuous, the magnetic field is uniformly distributed across the winding, reducing the effects of leakage flux. The evenly spaced turns ensure a smooth voltage distribution, reducing inter-turn voltage stress and insulation strain. The tight arrangement of the winding parts makes the magnetic circuit more closed, minimizing leakage reactance and improving transformer efficiency.

2.3 Tank

When the thickness of the steel plate along the box is less than 12mm, the flat steel material of Q235 material is used, and the punching machine is used to cut off the mold. When the thickness of the steel plate along the box is > 12mm, the steel plate of Q235 material is used, and the material is cut by the CNC fire/plasma cutting machine. The bottom of the transformer tank is made of Q235 steel plate. When the thickness of the steel plate is less than 14mm, the cutting machine is used. When the thickness of the steel plate is > 16mm, use the CNC cutting machine to cut the material. After the box wall is assembled, chemical treatment is carried out according to OFL.140.5060 pickling phosphating process. The cover of the transformer tank is made of Q235 steel plate. When the thickness of the steel plate is less than 14mm, the cutting machine is used. When the thickness of the steel plate is > 16mm, use the CNC cutting machine to cut the material.

2.4 Final Assembly

03 Testing

04 Packing and Shipping

05 Site And Summary

Advantages of hot dip galvanizing

For chip radiators for 80 MVA step down power transformer, the hot dip galvanizing process offers several important advantages:

• Corrosion resistance: The hot dip galvanizing layer can effectively prevent the erosion of air and water on the metal and improve the service life of the radiator, especially in wet or corrosive environments.

• Wear resistance: The galvanized layer can also increase the wear resistance of the heat sink, making it less likely to be damaged in physical friction or collision.

• Simple maintenance: Hot dip galvanized radiators require almost no additional maintenance, reducing the need and cost of later maintenance.

• Improve heat dissipation efficiency: Although hot dip galvanizing is mainly for corrosion prevention, it can indirectly improve heat dissipation efficiency by keeping the surface of the radiator smooth and rust-free.