Assessment of arc current extinction time of transient faults in HVDC-VSC systems with hybrid DC breakers

The interest in half-bridge Voltage Source Converters (VSCs) with HVDC circuit breakers is a solution to manage transient faults when the link is fully or partially made with an overhead line. The role of the HVDC circuit breaker becomes of paramount importance since to clear transient faults its ability to operate multi reclosures helps to increase the availability of the link. On the other hand, the arc current extinction time on the fault point along the line plays a not negligible role since this time has an impact on the reclosure of the line. Unfortunately, very little can be found in the scientific literature about HVDC breakers. For such reason, in this paper with the aim to study the fault current transients and the stresses an intentionally simplified approach has been adopted with the goal to have a first access to the expected values. The estimation of the arc extinction time of transient pole-to-ground fault in overhead HVDC line, which impacts the minimum dead time for a successful reclosure, is in any case the main aim of this paper. This is a first and necessary step to understand if potential critical issues could be expected. A deeper analysis should be carried out once more details will be available about these technologies.