The world's first 800kV UHV converter transformer with 750kV AC-side interconnection has passed all model tests, signifying a great breakthrough in developing key equipment for Lingzhou-Shaoxing ±800kV UHV DC transmission project, and setting a new height for the development of UHV DC transmission technology.
The output-end Lingzhou converter station of Lingzhou-Shaoxing ±800kV UHV DC transmission project was directly interconnected to the 750kV AC system, which meant that the 750kV AC-side UHV converter transformer needed to be developed. The AC-side interconnection voltage of the converter transformer was 750kV and the AC-side and DC-side insulation design was more complex; the 750kV AC output facility was especially difficult. Meanwhile, rail transportation was the only option, which increased technological difficulty as the equipment length, width, height and weight was strictly limited.
In face of this enormous challenge, State Grid Corporation of China put the emphasis on the optimization of equipment technical parameters, design verification, test plan confirmation and whole-process quality control. Since the system design and technical standard formulation in 2013, the company organized experts and companies from home and abroad for joint research. A dozen special technical seminars were held to thoroughly discuss and study cargo transportation and identify technical solutions for impedance voltage, insulation level, and 750kV output method, which must be solved in developing the converter transformer. Based on the previous success in developing 500kV converter transformer interconnected to a UHV DC transmission project, SGCC finally selected the technical solutions for the impedance voltage, structure model, and insulation design of the converter transformer after repeated tests while optimizing its technical parameters and ensuring the system security.
In the development process, SGCC organized domestic and foreign experts to supervise the design, production quality control, test plan, and model test to ensure quality for multiple times. It successfully developed the UHV 800kV converter transformer with 750kV AC-side interconnection. It is SGCC’s effort in pursuit of excellence and innovative development with the goal to go beyond new technology and new height. It laid a solid foundation for the future development of UHV DC transmission technology with higher voltage level, larger transmission capacity and longer transmission distance.