Beijing, China, May 9, 2016 – C-EPRI succeeded in winning an order to supply DC circuit breaker for the 200kV Zhoushan 5-Terminal VSC-HVDC Project on May 9, 2016. This is the first DC breaker application in an HVDC project of such scale worldwide.

Zhoushan project is the world’s first 5-terminal VSC-HVDC project. It was built to integrate wind power as well as to enable power connection between the five islands around Zhoushan. The capacity of each terminal is 400MW, 300MW, 100MW, 100MW and 100MW. The total transmission distance is 141km. The project was initially commissioned in 2014.

As a multi-terminal system with the most terminals in the world, Zhoushan project has to deal with some challenges that were never met before. For example, the DC side faults are unable to be isolated in a swift manner due to the absence of DC breaker; also, the trip of any one of the five converter stations would lead to the shutdown of the other four. There have occurred 9 forced outages since its operation from 2014.

To address these problems, SGCC decided to reinforce the whole system by installing 2 sets of DC breakers in Dinghai converter station as well as 5 sets of rapid damping restoration equipment in each of the 5 converter stations.

The introduction of DC breaker into the multi-terminal system will offer a higher degree of control flexibility. The failure or maintenance of any one of the 5 stations would leave the other 4 stations running unaffected. Moreover, the time required for DC fault clearance as well as the restart time for the healthy parts will be significantly shortened, therefore ensuring higher system stability and reliability.

What makes the breaker project more important is that it will also serve as a pilot project for the upcoming DC Grid ±500kV/7500MW Zhangbei Project between Beijing and Hebei Province. This project will offer valuable experience and guidance for the more challenging DC Grid project in terms of both technology and operation.