Design of Intelligent Fault Isolation Device to Prevent Wide-Area Power Outage in Radial-Type ± 35 kV MVDC Distribution System

When a fault in secondary feeder is occurred in MVDC distribution system, the operation method of protection devices is being required to achieve better protection coordination in order to minimize interruption region in primary feeder, considering the operation time interval of the protection devices in primary and secondary feeder before the shut-down of the main converter. Therefore, this paper presents an intelligent fault isolation device(IFID) to instantaneously clamp and consume the fault current in order to prevent shut-down of main converter in radial-type MVDC distribution system. And also, the proposed device is installed in both main converter and section converter, its operation mechanism is categorized as 4 modes such as initial operation mode, auxiliary operation mode, main operation mode and restoration mode. From the simulation results based on modeling of the IFID using PSCAD/EMTDC, it is confirmed that the proposed device is a useful tool to isolate fault section by preventing shut-down of main converter and securing operation time interval for protection coordination in MVDC and LVDC feeders. And also, it is founded that the main converter can be continuously operated and then unfaulted sections in primary feeder can be supplied as the faulted section is isolated by section converter.