[Report] The Heart of the Massive Ultra-High Voltage Transformer Is Made of Wood

LS Electric Busan: Ultra-High Voltage Transformer Production Site
Winding the "Heart" with Highly Insulating Wood
Vacuum Drying in the VPD is Key to Moisture Removal
Aiming for 1 Trillion KRW in Ultra-High Voltage Transformer Sales by 2030

On June 27, at the LS Electric Busan plant located in Hwajeon Industrial Complex, Gangseo-gu, Busan. After passing through the air shower and stepping into the factory, massive steel structures came into view. The ultra-high voltage transformer (HVTR), which stands nearly 4 meters tall, is surprisingly crafted through meticulous manual work. This is because each transformer must be customized to different specifications according to customer requirements, making mass production impossible.

This year alone, about 100 ultra-high voltage transformers are expected to be produced at Production Building 1. Most of these will be exported to the United States, which is experiencing a major boom in power infrastructure. Including Production Building 2, which will begin full-scale operations in October, it is projected that by 2027, up to 300 ultra-high voltage transformers will be produced annually at the Busan plant. In terms of revenue, this translates to over 600 billion KRW generated in Busan alone.

Hyungseok Choi, head of the HVTR manufacturing team at LS Electric, is explaining the ultra-high voltage transformer production process at the LS Electric Busan plant in Gangseo-gu, Busan. Photo by Heejun Jang

At the ultra-high voltage transformer factory at the Busan plant, completed in December 2009, a variety of products are manufactured, including oil-immersed transformers, high voltage direct current (HVDC) transformers, and flexible alternating current transmission systems (FACTS). The ultra-high voltage transformer production system is closer to "made-to-order" than simple "mass production." Because these are high-value products, costing up to 13 billion KRW, new designs must be applied each time to meet customer demands. It takes two months for design and another two months for production, so it takes a total of six months for a single ultra-high voltage transformer to be completed.

The manufacturing process for ultra-high voltage transformers is divided into six main stages: the "winding process," in which copper wires are wound to conduct current; the "core process," in which silicon steel plates are precisely processed and stacked according to design specifications; the "main assembly process," in which the windings are assembled onto the stacked core and the electrical circuit is configured; the "vacuum drying" process, in which moisture is removed from the main body; the "final assembly process," in which the dried main body is welded into a tank and filled with insulating oil; and finally, the "final testing," in which the transformer undergoes performance tests to ensure it meets customer requirements and standards.

A worker is manufacturing an ultra-high voltage transformer at the LS Electric Busan plant in Gangseo-gu, Busan. The brown material wrapping the coil, which is made by winding wire like a coil, is wood pulp, a key material ensuring the insulation of the oil-immersed transformer. LS Electric

The most striking feature of the Busan plant is the "brown" color that fills the factory. The key material in the process of creating these massive steel structures is none other than "wood." The "winding," made by winding wire like a coil, is considered the "heart" of the massive steel transformer, and it is wrapped in wood pulp. Wood is used as an insulating material to eliminate the risk of explosion in oil-immersed transformers.

Wood has excellent and stable insulating properties. However, due to its material characteristics, it tends to retain a lot of moisture, making thorough drying essential. This is achieved through the "vacuum drying" process, which uses a vacuum drying oven (VPD). Hyungseok Choi, head of the HVTR manufacturing team at the LS Electric Busan plant, said, "Moisture damages the insulation and is therefore fatal to transformers. Ultimately, transformer manufacturing can be seen as a battle against water."

A partially assembled extra-high voltage transformer is being moved to the air floating facility at the LS Electric Busan Plant in Gangseo-gu, Busan. It takes up to six months for an extra-high voltage transformer to be produced, from design to final testing. LS Electric

Once the main assembly is complete, the transformer is placed into the VPD equipment, which resembles a giant door. As the name suggests, the transformer is heated repeatedly over five days in a vacuum to remove moisture. For a 154kV transformer, as much as 100 liters of moisture is removed during vacuum drying. After vacuum drying, the transformer is placed in a tank, where it is re-dried, filled with insulating oil, and assembled to complete the transformer.

The VPD equipment, which enables this crucial process, is considered an indicator of ultra-high voltage transformer production capacity (CAPA). Seongyun Moon, head of production planning at the LS Electric Busan plant, explained, "The number of VPD units determines production capacity. Currently, there are two units in Production Building 1, and two more will be installed in the new Production Building 2." Each VPD unit costs between 100 billion and 200 billion KRW.

A bird's-eye view of the newly constructed Production Building 2 at the LS Electric Busan Plant in Gangseo-gu, Busan. Completion is scheduled for September, with full-scale mass production of ultra-high voltage transformers set to begin in October. LS Electric

Leaving the continuously operating Production Building 1 and walking for about five minutes, the framework of Production Building 2 comes into view. LS Electric decided to invest in expanding production last year to strengthen its position in the ultra-high voltage transformer market. Production Building 2, which is being built on a 13,223-square-meter site next to Production Building 1, will be equipped with assembly, testing, and welding facilities, covering the entire production process. Construction will be completed by September, with mass production starting immediately in October.

LS Electric is rapidly expanding its business portfolio, which previously focused on medium- and low-voltage transformers and switchgear, to ultra-high voltage transformers. This is due to the unprecedented boom in the power infrastructure market, driven by investments in artificial intelligence (AI) data centers in the United States and the demand for replacing aging power grids.

Last year, LS Electric generated sales of 203.1 billion KRW from ultra-high voltage transformers alone. In addition to supplying to Samsung Electronics' domestic and overseas sites, the company also delivered products to the data center of xAI, an AI development company founded by Tesla CEO Elon Musk. LS Electric aims to achieve sales of 1 trillion KRW by 2030.

An LS Electric official said, "Production Building 2 is currently 60% complete. This will enable us to establish production and management systems that match our scale and create the optimal working environment for manufacturing large-capacity transformers. We have already secured orders to meet our sales targets for 2026 and 2027."