On November 18th, at Zhoushan Converter Station of Zhoushan Soft-tolerance Project, after high-strength installation of engineers and technicians of Zhejiang Zhoushan Power Supply Company for half a month, the world's first set of high-voltage DC circuit breakers for engineering use was successfully installed. It will provide a strong guarantee for the stable operation of Zhoushan multi-end soft and straight system.

 

The high-voltage DC circuit breaker of Zhouding Converter Station adopts ±200 kV cascaded full-bridge hybrid DC circuit breaker. The DC circuit breaker solves the defect of high loss of the solid-state DC circuit breaker, effectively overcomes the limitation problem of the switching speed of the mechanical circuit breaker, and realizes the modular design of the electrical and mechanical structure. According to field experts, in the test, the DC circuit breaker can disconnect up to 15 kiloamps of fault current in 3 milliseconds, which is 100 times faster than the moment of human blink. In the current global circuit breaker, the voltage level is the highest, and the breaking capacity. The strongest is the "fighter" in the veritable circuit breaker.

 

It is understood that as the world's first five-terminal flexible DC transmission project, the Zhoushan multi-terminal flexible DC transmission project put into operation on July 4, 2014 has set up a DC interconnection grid for Zhoushan Island, which not only greatly improves the reliability of the island power grid. And it can better accommodate the access of new energy sources such as wind and solar energy. However, the flexible DC transmission system cannot achieve the rapid removal of DC faults, which makes the development and wide application of multi-terminal flexible DC transmission technology restricted and limited. To this end, State Grid Corporation launched the “Zhoushan Flexible System DC Circuit Breaker and Damping Recovery Technology Demonstration Project” in May this year to provide solutions for breaking the technical bottleneck faced by the flexible system.

 

"Because it is the world's first such high-profile DC circuit breaker, we don't have any ready-made installation experience to learn from, and the installation work is very difficult." The on-site installation commander said. In order to ensure the smooth completion of the installation work, as early as the first half of this year, Zhoushan Company dispatched a strong force, deployed circuit breaker installation planning in advance, and maintained close communication with manufacturers and provincial power design institutes, familiar with the working characteristics and installation conditions of DC circuit breakers. At the same time, combined with the actual installation work, bold innovation, design a new installation method and success, accumulated valuable experience for high-voltage DC circuit breaker installation technology.

 

Next, the technicians will perform various types of commissioning on the DC-DC circuit breakers to verify their functional operation and prepare for the final commissioning. At the same time, Zhoushan Company has done a good job in learning and training in advance, using type testing as a platform, mastering the principle of equipment characteristics, improving equipment operation and maintenance level, and ensuring good equipment operation and maintenance after commissioning.