Interpretation of key technologies for escaping UHV DC transmission

On June 9th, a significant conference of two academicians was held in Beijing. During the opening ceremony, President Xi Jinping emphasized that mastering key technologies domestically is crucial for securing the initiative in both competition and development. This statement highlighted the importance of technological self-reliance in driving national progress. This summer marks an important milestone as the two major DC power transmission projects—Xiluodu to Guangdong and Nuozhadu to Guangdong—will be fully operational. These green energy initiatives, which deliver clean hydropower from the western regions to the eastern provinces, rely heavily on the continuous advancement and application of critical technologies. The research and application of high-voltage ±800 kV UHVDC external insulation properties conducted by the China Southern Power Grid Science Institute played a pivotal role in the world's first UHV DC transmission project. The technology has since been widely adopted in subsequent UHV projects and was recognized with the 2012 National Energy Technology Progress Award. One of the most notable breakthroughs in UHV technology came with the Yunguang UHV project. In recent years, debates over UHV AC/DC systems have largely subsided. However, just a few years ago, the concept of UHV construction was still relatively unknown. At that time, even the use of 800 kV was uncharted territory. Li Ruihai, director of the China Southern Power Grid Production Technical Support Center, recalls that the Yunguang project was the world’s first UHV DC transmission line, with no prior experience to reference. The Yunguang-Guangdong UHVDC transmission line stretches from Chuxiong Prefecture in Yunnan Province to Guangzhou City in Guangdong, passing through the Guangxi Zhuang Autonomous Region. It crosses rugged terrain, including a plateau at approximately 2,000 meters above sea level. One of the major challenges was ensuring the insulation performance of converter stations at such high altitudes, which directly impacted the safety and success of the project. The Chuxiong Converter Station, located on the Yunnan-Guizhou Plateau at 1,850 meters above sea level, is the second highest converter station in the world. To address the issue of reduced air density affecting insulation, the China Southern Power Grid developed the world’s first ±800 kV UHV DC composite insulator. This innovation stemmed from collaborative research between the South China Research Institute and Tsinghua University on high-voltage ±800 kV external insulation properties. At the time, foreign technologies were primarily based on low-altitude testing. However, after five years of dedicated research, the team utilized the UHV Engineering Technology (Kunming) National Engineering Laboratory, situated at 2,100 meters above sea level. This allowed them to study the elevation correction of external insulation for UHVDC transmission projects and develop a comprehensive solution for designing external insulation in high-altitude areas. This breakthrough significantly advanced the feasibility and safety of UHVDC projects in challenging environments.

Lighting Accessories

Lamp accessories are various parts and accessories used to install, secure and connect lighting fixture. They play an important role, not only to ensure the normal operation of the lamp, but also to improve the use effect and aesthetics of the light.

There are many materials for making lamp accessories, generally speaking, there are metal, plastic, glass, ceramics, etc. Metal generally has a long service life, corrosion resistance, and should not be aged, such as iron product lamps, which have a long service life; Plastic lighting product have a short use time, a faster aging speed, and are easy to deform when heated; The service life of glass and ceramic lighting is long as well.

Nowadays, the lighting and lighting accessories industry uses metal materials as the most widely used base, generally used materials are zinc alloy, aluminum alloy, steel, stainless steel, etc. The use of technology is mainly electroplating, painting, oxidation and electrophoretic coating. With the current people to lighting accessories product performance requirements and environmental awareness improved, electrophoretic coating process has gradually become the preferred process for surface treatment of lighting accessories.

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