Analysis and Improvement of Last Circuit Breaker Logic in AC Filter

In HVDC converter station,the connection differential protection will be activated because of a trip of the last circuit breaker in AC Filter.In this paper,taking the UHVDC transmission project of Yunnan-Guangdong as an example,the software logic and related hardware circuit are analyzed of the last circuit breaker in AC Filter of the 6MD664 interval control unit,where the design defects and improvement are presented.