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The development of high-voltage AC isolation switchgear has been significantly accelerated
In recent years, the commencement of AC and DC ultra-high voltage (UHV) projects has intensified the pressure on the power transmission industry, pushing forward the development of new technologies in the high-voltage switch sector. The progress in high-voltage AC isolating switchgear has accelerated significantly, marking a major leap from ultra-high voltage to UHV. While the overall industry environment has improved, enhancing R&D capabilities and reducing production costs remain key challenges for continued growth.
China’s UHV and EHV AC isolating switchgear development is often seen as a model of independent innovation in power transmission equipment. Companies have focused on improving product quality and technical standards. According to the latest industry data, by the end of 2006, more than 300 500 kV substations were equipped with 550 kV isolating switches. Since the 1960s, China has been developing 363 kV and 550 kV isolating switches, and after 40 years of innovation, it has successfully entered the UHV era, reaching the peak of global power technology.
The first 330 kV transmission line in China used domestically produced equipment. To address the power transmission needs of the Liujiaxia Hydropower Station, Xi'an High-Voltage Switchgear Factory and Shenyang High-Voltage Switchgear Factory developed the country’s first 330 kV switchgear, launching the GW7-330/1500 three-column disconnector. This project was entirely built using domestic equipment and achieved great success. In addition, to meet the special requirements of the hydropower station for compact and space-saving design, they also introduced the ZH1-330 open-type combination appliance, which optimized layout and reduced costs. This unique structure became a hallmark of Chinese engineering.
The first generation of 550 kV isolating switches broke the foreign technology monopoly, marking a significant breakthrough in China's high-voltage switch industry. Initially, China relied heavily on imported equipment, but the development of these domestic products changed the landscape. For example, on the Jinliao test line, Shengao developed the GW6-550 scissor disconnector and JW2-550 earthing switch, while Xikai launched the GW7-550 three-column isolating switch. Though only 20 sets were produced, these achievements laid the foundation for future independent designs.
These developments were based on independent innovation, overcoming various technical challenges such as aluminum alloy conductor design, insulation testing, radio interference testing, and small capacitor current switching. These efforts accumulated valuable experience for the industry's long-term growth.
With the construction of major UHV DC projects like the Three Gorges Project and the West-East Power Transmission, the power transmission and transformation equipment industry has experienced rapid growth. Key enterprises have accelerated their product upgrades, introducing new innovations to enhance market competitiveness.
For instance, Pinggao developed the GW27-550 isolating switch and JW8-550 earthing switch with independent intellectual property rights, while also creating the GW28-550 and GW29-550 models. Shengao upgraded its GW6-550 to GW6A-550 and GW12-550 to GW12A-550, both featuring enhanced reliability and corrosion resistance. Changsha High Voltage Switch Co., Ltd. also made notable progress, developing GW16A-550, GW17A-550, and other models that positioned it among top UHV manufacturers.
As the industry continues to evolve, the 750 kV transmission project in the northwest marked a new phase in UHV development. Xikai introduced the GW45-800 isolating switch, while Pinggao and Shengao launched their own 800 kV models, all passing rigorous technical evaluations. These advancements set the stage for the upcoming 1,000 kV UHV projects.
The Jindongnan-Nanyang-Jingmen 1,000 kV AC demonstration project provided a rare opportunity for companies with strong technical backgrounds. Xikai, Pinggao, and Shengao quickly developed 1,000 kV isolating switches, showcasing their technological capabilities. These products have passed critical tests and are now being used in the State Grid Corporation's UHV test base.
Currently, over 6,000 750 kV and 800 kV isolating switches are in operation across China, with some systems running safely for nearly two years. Looking ahead, the expansion of the power grid will create new opportunities for the high-voltage switch industry. At the same time, the development of UHV DC transmission will drive research into new technologies and open up new markets.
Despite the progress, challenges remain. There is still a gap between China’s product quality and that of multinational companies, particularly in areas like appearance, reliability, stability, and material quality. To address this, the industry must focus on increasing innovation, improving product levels, and adopting advanced manufacturing techniques. This will help reduce costs and strengthen market competitiveness.