China has successfully developed the world's first ±408 kV DC transfer switch.

Recently, China’s switchgear manufacturer independently developed the world’s first ±408 kV DC transfer switch, which has successfully passed the full set of type tests. This marks the official successful development of the product and represents the first breakthrough in DC transfer switches applied on the 400 kV pole line side.

The Jinshang–Hubei UHV project is currently the world’s highest-altitude ±800 kV ultra-high-voltage (UHV) DC transmission project. It adopts China’s independently developed multi-terminal cascaded UHV DC technology and was the first to propose the application requirement for a 408 kV DC transfer switch. Facing the stringent demands imposed by the complex environment of the Sichuan-Tibet region—characterized by high altitude and high seismic intensity—the manufacturer’s project team remained undaunted, focusing on core technology breakthroughs and innovative structural design. 

Through coupled analysis of the DC arc electromagnetic field, flow field, temperature field, and external auxiliary circuits, the team achieved rapid self-excited oscillation of DC current, enabling a maximum transfer current of 6,400 amperes. Additionally, research on corona prevention at high altitudes led to the design of a complete shielding system for the equipment, achieving a DC withstand voltage of 975 kV, meeting requirements for operation at 4,000-meter altitude.

This product features high current-carrying capacity, with an overload current rating of 8,000 A; strong DC current transfer capability, supporting a DC transfer current of 6,400 A; high insulation withstand strength, satisfying insulation performance requirements at 4,000-meter altitude; and robust seismic resistance, rated at AG5 seismic level. The successful development of this product fills a global gap in the switchgear industry for 408 kV-class DC transfer switches and meets the special requirements of the Jinshang–Hubei ±800 kV UHV DC transmission project for geographically separated cascaded configurations.

 It can be applied to large-scale, long-distance transmission of renewable energy under the “West-to-East Power Transmission” initiative and is suitable for high-altitude, high-seismic-intensity, and heavily polluted regions, effectively enhancing the efficiency and reliability of DC transmission systems. Its development holds significant importance for ensuring safe and reliable power supply, accelerating the clean and low-carbon energy transition, supporting the planning and construction of a new-type energy system, and expediting the formation of a new development paradigm.

In recent years, China’s switchgear manufacturer has aimed to build a world-class enterprise-level scientific and technological innovation platform, adhering to an innovation-driven development strategy, firmly grasping the lifeline of key power grid equipment technologies, strengthening its scientific and technological innovation system, promoting high-level self-reliance and self-strengthening in science and technology, and gradually establishing a leading core competitive advantage in the industry.