System Application of Low-Voltage Power Circuit Breakers with Solid-State Trip Devices

The protection provided by low-voltage power circuit breakers for circuit conductors and connected load devices, and the degree to which breakers can be coordinated with other protective devices in the power distribution system, depend to a large extent on the characteristics of overcurrent trip devices on these breakers. Trip devices using solid-state circuitry, with characteristics established to meet requirements for both protection and coordination, offer distinct advantages over electromechanical types of trip devices to application engineers and system designers. The extent to which inherent advantages of solid-state circuitry are realized in the design of a recently introduced trip device' is illustrated by a number of examples of system application of low-voltage power circuit breakers for both phase-overcurrent and ground fault protection.