Potential Use of Fault Current Limiter in VSC Based DC Transmission Systems

DC transmission systems are playing a more important role today. While HVDC transmission technology wins on key aspects over AC transmissions, there are still problems which make it difficult to handle and expand to grids. Among these problems is the most undesirable one: interruption of dc currents. Using DC breakers based on various principles has proved to be effective. However, the function of DC breakers is still limited due to their capacities: most of them in use now do not play like breaker which can handle fault currents. In fact, in HVDC transmission systems, DC breakers cannot handle fault currents. To interrupt fault current in orders of 10kA or above is quite demanding for currently used DC breakers. IGBT breakers might be possible solutions; however their loss cannot be ignored. Implementing fault current limiters (FCL) could be very promising if possible. The problem is that most FCL is for AC use. Currently there are more than dozens kinds of FCL technologies, varies from traditional reactors one to novel ones like high temperature superconducting (HTS) or solid state FCL. They are originally invented to reduce fault currents in AC systems, thus these FCL for DC use still calls for investigation. This paper focuses on the current FCL technologies, discusses the possibility of implementing them in DC applications, especially in DC transmission systems whose currents are considerably larger.