Fuses are used to protect distribution devices from damaging currents. A fuse is an intentionally weakened spot in the electric circuit that opens the circuit at a predetermined current that is maintained for a predetermined amount of time. Fuses are not dynamic in that they remain open and do not reclose. By automatically interrupting the flow of electricity, a fuse prevents or limits damage caused by an overload or short circuit.
Fuses are coordinated with reclosers to prevent fuses being damaged by temporary faults downstream. Time current characteristic (TCC) curves are used to rate fuses: the upper curve represents the total clearing time, and the lower curve represents the melting time. Coordination involves calculating the intersection of fuse curves with recloser curves to achieve desired results.
Fuse types include current limiting and expulsion fuses. At maximum interrupting current, the arc of limiting fuses actually melts sand to build up apparent resistance to reduce the fault current. Expulsion fuses create an arc during fault conditions that generates a gas that extinguishes fault current.
The DESIGNBANK model name is used by the Work Function tool in Designer. It designates a banked feature in the network.
The FDRMGRPROTECTIVE model name should be assigned to any feature class that can be considered a fuse or dynamic protective device (e.g. circuit breaker, recloser, sectionalizer) by Feeder Manager.
Electric Tracing uses the PROTECTIVE model name to identify the features that may be returned as protective devices. Structural Analysis (Designer) also uses the PROTECTIVE model name.
The Fuse class inherits attributes from the ElectricDevice and OvercurrentProtectiveDevice abstract classes. All model names assigned to these abstract classes should be assigned to the Fuse class as well.
Subtypes: Current Limiting, Overhead Expulsion, Underground Expulsion, Vacuum. The use of subtypes is optional. The Subtype attribute can be removed if subtypes aren't used in the model.
Model Names: DESIGNBANK, FDRMGRPROTECTIVE, PROTECTIVE