Practical Guidance for Considering Reset Characteristics and Securing Coordination Over an Entire Reclose Sequence

Time-current coordination of electrical distribution network protection equipment is necessary to minimize the extent of customer outages. Reclosing devices, including relayed circuit breakers, help clear temporary faults but complicate the coordination process for faults that persist across several reclose attempts. Misoperations can occur if the reset characteristics of neighboring devices are not considered. These neighboring devices include other reclosers, fuses, and non-protective damageable equipment such as transformers and conductors. With the ongoing proliferation of lateral reclosers replacing previously deployed fuse links, avoiding damage to smalldiameter conductors are of particular concern. Previous publications were not sufficiently general to leverage the flexibility new digital reclosers provide and the variation in the cooling characteristic of different fuses. Other publications proposed processes that are not easily applied in modern coordination software. Most publications focus only on fuse-recloser coordination. The approach proposed here addresses fuse-recloser coordination, damageable-equipment-recloser coordination, and recloser-recloser coordination. It takes into account fuse preloading, ambient temperature, fast and slow responses, and varying open intervals. The detailed formulas included in this submission compute a single scaling factor that can be easily used in modern coordination software to modify TCC curves and verify coordination.