The Development of Dry-Type Transformers
Add time: 2025-07-31
Since 1964, when Germany's AEG company developed the first 400 kVA/20 kV epoxy-encapsulated dry-type transformer, dry-type transformers have entered a period of rapid growth. At the same time, the United States discovered Nomex insulation paper, which can be used as an insulating material for Class H dry-type transformers. As a result, today dry-type transformers fall into two main categories: one is the epoxy type, and the other is the Nomex-paper type.
Currently, in developed countries such as the United States, Germany, and Japan, dry-type transformers already account for more than 20% of distribution transformer production. In complete substation systems, dry-type transformers now make up 80–90%.
The "2013-2017 China Dry-Type Transformer Industry Market Demand Forecast and Investment Strategy Planning Analysis Report" reveals that China has now become the world's largest country in terms of both production and sales volume of dry-type transformers. Currently, various foreign high- and low-voltage electrical products still dominate several key domestic markets. However, dry-type transformers have been virtually free from foreign imports since the late 20th century, making it nearly impossible to spot imported models in China's major projects and critical infrastructure initiatives. Under China's existing organizational structure for the power transmission grid, the share of 10kV dry-type transformers has been steadily increasing year by year.
Currently, the pace of power grid construction in both urban and rural areas is accelerating, as China's electricity generation and consumption continue to grow steadily. Generally speaking, for every additional 1 kW of generating capacity, there is a corresponding need for an extra 11 kVA of transformer capacity. Among these transformers, Satons distribution transformers account for roughly one-third to one-half of the total transformer capacity. It’s estimated that dry-type distribution transformers make up about 1/5 to 1/4 of all distribution transformers. Driven by increased investment in grid infrastructure, the transformer industry is experiencing robust growth, with production expected to maintain an annual growth rate of around 20% since 2010. Based on historical trends and changes in the voltage-level structure of transformers, distribution transformers currently account for approximately 40% of the market. Applying this 40% ratio, China’s newly added output of dry-type distribution transformers could reach roughly 200 million kVA.
In China, in 1966, the Shenyang Transformer Factory successfully developed the ZSG-1800/10 directional air-cooled Class H dry-type transformer, while the Shanghai Transformer Factory pioneered the SG3-800/10/1.2/0.4 three-winding self-cooled Class H dry-type transformer. By the late 1970s, the Shanghai Transformer Factory had independently designed and introduced the SCL-630 epoxy-encapsulated dry-type transformer.
Over the past two decades, driven by global economic growth, dry-type transformers have experienced rapid expansion worldwide. Notably, their share in distribution transformers has steadily increased, particularly in developed countries like Europe and North America, where they now account for 40% to 50% of all distribution transformers. In China, dry-type transformers currently make up about 50% of the market.
In terms of production volume, following China’s second urban power grid renovation conference in 1989, the output of dry-type transformers saw a remarkable surge. Since the 1990s, annual production has grown at an impressive rate of roughly 20%, reaching nearly 10,000 MVA by 1999—far surpassing the earlier 10-year projection of 4,500 MVA. By 2002, total output had climbed to 20,000 MVA, and by 2004, it had already hit 32,000 MVA. Such rapid growth rates are truly unprecedented on a global scale.
As the data above shows, China has now become one of the world's largest producers and sellers of dry-type transformers, ranking among the global leaders in terms of factory scale, product capacity, voltage levels, and other key metrics.
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