Design of DC System Protection

A modified Z-source breaker topology is introduced to minimize the reflected fault current drawn from a source while retaining a common return ground path. A conventional Z-source breaker does not provide steady-state overload protection and can only guard against extremely large transient faults. The Z-source breaker can be designed for considerations affecting both rate of fault current rise and absolute fault current level, analogous in some respects to a "thermal-magnetic" breaker. The proposed manual tripping mechanism enables protection against both instantaneous current surges and longer-term over-current conditions. The fault operation intervals of the proposed Z-source breaker topologies are demonstrated in SPICE simulation.