The CU HVDC project life extension issues and examples

HVDC transmission systems using thyristor-based valves have been in service in some cases for over 20 years. Owners are looking at factors that determine the operating life. This contribution discusses this subject from the aspect of the CU HVDC transmission system, USA. This system is now over 20 years old. The continuing need for the project is presented as well as steps that have been taken or are contemplated to extend operating life. A description is given of experiences with a recent project to upgrade the valve control electronics.