Although developing the UHVDC transmission technology can save transmission corridor and enhance electric power industry technology based on the successful EHVDC technology

the reliability is more and more important due to its bulk capacity.The more reliable wiring of converter transformer and valve are recommended according to the detail analysis

on the other hand

the operation of some typical ±500 kV converter stations is reviewed and an overall analysis of fault cases is given.Based on the research on the features of ultra high voltage direct current system

the reliability of a practical ±800 kV project is evaluated in order to find the key factors that affect the system reliability significantly

and then some measures and methods are presented to enhance the reliability of UHVDC system.