Study to improve operational reliability of 500kV Fixed Serial Compensator

500kV Sanpu Fixed Serial Compensator (FSC) is the first Serial Compensator in extra high voltage power systems in China. The paper introduced the research work of operational reliability improvement on the FSC. The research included defects analysis of protection logic and improvement study, for example bypass breaker failure protection and gap prolonged conducting protection. Electromagnetic compatibility (EMC) analysis of the secondary devices in this FSC and defects correcting were also introduced, which involved 500kV platform and Control cabin on the ground. The paper also proposed several effective measuring methods for EMC analysis on 500kV platform. After all the modification measures were applied on the field FSC, the operational reliability of Sanpu FSC was improved, meanwhile, the safety and stability of east China 500kV power systems was ensured.