Design of Modular Fault Current Limiter to Avoid Reliability Degradation

With the short circuit level increase in power grids, thereis a need to increase rating of switch type fault currentlimiters (STFCLs), therefore, modularization of STFCLsis inevitable. This paper presents a comparativereliability analysis between the modular and non-modularSTFCL topologies. It is demonstrated that modulardesign causes a considerable reduction in reliability. Theaim of the presented study is to increase the reliability ofmodular fault current limiters using thermal management.The failure rate of STFCL module and junctiontemperature calculation is developed. The mean time tofailure (MTTF) is used as the reliability metric. MTTFsof two topologies are calculated and compared. It isdemonstrated that reliability of STFCL depends on thejunction temperature of the semiconductor switches inthe steady state, that it can be controlled by the thermalresistance of the heat sink. Ranges of the junctiontemperature and thermal resistance in which the modularconfiguration is more reliable are formulated. Thennumerical studies are presented to verify the efficacy ofthe proposed approach.

Keywords:

Fault Current Limiter , Reliability , Junction Temperature