Copper vs. Aluminum Windings: A Comprehensive Analysis of Material Selection for Distribution Transformers

Copper windings and aluminum windings of distribution transformers are the core differentiating factors that affect their performance, cost, and service life. There are significant differences between the two in terms of material properties, electrical performance, economy, and operation and maintenance requirements. This article will analyze from multiple perspectives to provide a comprehensive understanding of their distinctions.

Comparison of Electrical Performance

Losses and Efficiency

• Copper windings have high electrical conductivity, resulting in lower copper losses under the same current. For example, a 1000kVA transformer with copper windings has copper losses 15%-25% lower than one with aluminum windings when operating at full load. It saves electricity during long-term operation and meets energy-saving design requirements.

• Aluminum windings have low electrical conductivity, so their cross-sectional area needs to be increased to reduce resistance. However, copper losses are still slightly higher, and the efficiency is 1%-3% lower.

Overload Capacity

• Copper windings have a high melting point (1083℃) and excellent thermal stability. When overloaded, the temperature rises slowly, and the insulation is not easily damaged. They can withstand overload for 1-2 hours.

• Aluminum windings have a low melting point (660℃). When overloaded, the temperature rises rapidly, which easily leads to insulation aging or short circuits. They can only withstand overload for less than 30 minutes, so the load rate must be strictly controlled.

Temperature Rise and Heat Dissipation

• Copper windings have high thermal conductivity (401 W/(m·K)), enabling fast heat transfer and lower temperature rise (5-10K lower than that of aluminum windings).

• Aluminum windings have low thermal conductivity (237 W/(m·K)), which makes heat easy to accumulate. Larger radiators or enhanced structures need to be designed; otherwise, the service life of the insulation will be shortened.

Comparison of Economy

Initial Purchase Cost

For example, for a 2500kVA oil-immersed transformer, the material cost of the aluminum-core version is approximately 40%-60% lower than that of the copper-core version, and the overall price difference ranges from 30% to 50%. Using an aluminum-core transformer can significantly reduce the initial investment.

Long-term Operating Cost

• Copper windings have low copper losses, so the electricity cost saved during long-term operation can cover the initial price difference. Additionally, their maintenance cycle is longer, resulting in lower maintenance costs.

• Aluminum windings have high copper losses, leading to 5%-10% higher electricity costs. Moreover, their insulation ages faster, requiring frequent inspections and resulting in higher maintenance costs.

Service Life Difference

• Copper windings have good chemical stability and high-temperature resistance, with a designed service life of 25-30 years.

• Aluminum windings are prone to oxidation and have high temperature rise, with a designed service life of 15-20 years.

Market Analysis

In China, where the Huawei factory is located, the State Grid and the mainstream market mainly use copper-core transformers. The use of aluminum-core transformers in China's State Grid is regarded as a serious act of cutting corners by suppliers and will result in severe penalties. However, considering the return on investment, most new energy power plants use aluminum-core transformers in their packaged substations to reduce construction costs.

Globally, 80% of distribution transformers are aluminum-core. Countries such as those in the Middle East and Russia use aluminum-core transformers. The main reason is the significant cost advantage, which highly aligns with the core needs of large-scale infrastructure construction in the Middle East and the wide-area power grid coverage in Russia (especially in remote areas) for "low-cost and lightweight equipment". At the same time, it can also reduce reliance on imported copper resources, balancing economy and supply chain stability.

Selection Recommendations

Copper Windings are Suitable for:

1.Areas with long-term full load / frequent overload (e.g., urban core areas, industrial parks)

2.Projects with high energy-saving requirements and pursuit of long service life (e.g., municipal engineering, large enterprises)

3.Harsh environments such as high temperature and humidity (e.g., coastal areas)

Aluminum Windings are Suitable for:

1.Rural low-load areas (low load rate, small fluctuations)

2.Temporary infrastructure projects (e.g., construction sites, temporary housing quarters)

3.Scenarios sensitive to initial costs and accepting regular maintenance