On November 27, at the west-to-west converter station at the receiving end of the Xiluodu Right Bank Power Station, a key project of the China Southern Power Grid’s power transmission project, Guangdong’s ±500 kV double-circuit DC transmission project on the same tower, along with the release of operating instructions for on-site operators , The knife switch of the AC field of the west converter station is slowly closed, and the current flows from the west thousands of miles away to the east in an instant. It marks that the first converter transformer independently developed by my country using domestic on-load tap-changers has been successfully put into operation.
Experts in the industry pointed out that this is a major achievement in the research and development of high-end power equipment in my country. In the field of large-capacity on-load tap-changers, my country has achieved a leap-forward breakthrough from “from scratch, from righteousness to excellence”. The “gearbox” of the system realizes “Made in China”, which is of great significance to promote the technological upgrading of related industries.
The east-west span of our country is thousands of kilometers, and most of the west-to-east power transmission uses long-distance, large-capacity, high-voltage DC projects for power transmission. Both the project sending end and the receiving end site need to use a converter transformer weighing more than 300 tons. hub device. A key component of the converter transformer is the on-load tap changer, which is the core component of the voltage regulation and stabilization of the DC transmission system, and is also a very precise electromechanical device.
“The on-load tap-changer of the converter transformer is like the automatic ‘gearbox’ of a car. The voltage is adjusted up and down, the load is adjusted up and down, and the current is adjusted up and down. It is adjusted through its gear position.” China Southern Power Grid Supervision Feng Dong, deputy general manager of the Biotechnology Department of High Voltage Company, said.
According to reports, the on-load tap changer of the converter transformer has more than 1,000 parts, and the switching times are very frequent, as high as more than 6,000 times a year. One switching includes 9 processes, and each action involves the precise coordination of more than 400 parts. , and the timing of each process is on the millisecond level, and the action process involves the coupling of multiple fields of electricity, heat, and force. The accuracy of this timing coordination is comparable to that of a mechanical watch.
“Due to extremely high reliability requirements and extremely difficult manufacturing, this technology has always been in the hands of a few foreign manufacturers. Equipment maintenance is also limited to foreign manufacturers. Once a failure occurs, only imported products of the same model can be replaced, and the cycle takes three to three months.” Four months.” Said Wang Yang, deputy general manager of the Guangzhou Bureau of China Southern Power Grid EHV Corporation, “In recent years, the imported converter transformer on-load tap-changer has exposed major problems such as mechanical cracking and insulation degradation during operation, which seriously threatens the power grid. safe operation.”
In order to overcome this problem, China Southern Power Grid EHV Co., Ltd. has established a “production-university-research-application” research team to jointly carry out localization research on the key technology of “6000kVA on-load tap-changer for large-capacity converter transformers” in conjunction with upstream and downstream enterprises in the industrial chain.
According to Deng Jun, a senior technical expert of China Southern Power Grid EHV Company, in view of the problems of insufficient insulation margin, unreasonable material selection, and imperfect electrical design exposed by imported equipment, the research team independently carried out refined modeling and simulation and real-type prototype testing. Verify and overcome the problems one by one.
For example, in terms of equipment structure and reliability, the team selected 36 types from over 2 million possible structures, selected the best among the best, and avoided international property rights disputes, and finally selected the most concise and balanced on-load tap-changer topology .
The development of core components is the key, and the most difficult is the development of vacuum interrupters, which are also the core components of medium and high voltage power switches. “At the beginning of the research and development, we planned to use imported vacuum interrupters. After in-depth research and analysis, we decided to cooperate with domestic leading companies to independently develop vacuum interrupters, although this road will be very difficult.” Deng Jun said.
After calculation, simulation, and comparison, the research team carried out 3,000 times of performance testing, 370,000 times of load switching, 1.6 million times of mechanical life, 9 million times of bellows fatigue and other tests, and finally developed a vacuum interrupter.
It is understood that after two years of unremitting efforts, the research team broke through a series of key technologies in design, manufacturing, testing and reliable application, and successfully developed my country’s first large-capacity motor with a rated capacity of 6000kVA, a maximum voltage of 6000V, and a maximum rated current of 1300A. The rheological transformer on-load tap-changer has realized the domestic manufacturing of the whole chain of “raw materials-components-complete machine”.
Chen Huan, deputy general manager of the Innovation Department of China Southern Power Grid EHV Company, said, “Compared with similar imported products, the domestic converter transformer on-load tap-changer has a more reasonable structure, better material selection, and better indicators. It has achieved international leading evaluation, broken the technology monopoly of western companies, not only achieved localization, but also achieved better performance.”
According to reports, the successful development of the domestic converter transformer on-load tap-changer will greatly reduce the investment in engineering construction. Only in terms of equipment costs, the construction of a new UHV DC transmission project can save nearly 40 million yuan, which will greatly improve the construction of Western Electric Power Co., Ltd. The independent and controllable level of Dongsong’s main grid equipment is of great significance to promote the upgrading of my country’s high-end electrical equipment industry chain and ensure the safety and stability of my country’s energy and power supply.
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