Selectivity (circuit breakers)

Selectivity, also known as circuit breaker discrimination, is the coordination of overcurrent protection devices so that a fault in the installation is cleared by the protection device located immediately upstream of the fault. The purpose of selectivity is to minimize the impact of a failure on the network. Faults in an installation are, for example, overload and short circuit.^[1][2]

There are four ways in which selectivity is achieved:^[3]

• Current selectivity: different breaking capacities
• Time selectivity: time delay before tripping of a breaker
• Energy based selectivity: analysis of the current waves
• Zone selective interlocking: communication between the breakers, forwarding a time delay instruction

References

1. "Selectivity, Cascading and Coordination Guide" (pdf). Schneider Electric. 2021. p. A-2. from the original on 17 September 2021. Retrieved 18 September 2021.
2. National Fire Protection Association (2017). "Article 100 Definitions". NFPA 70 National Electrical Code. 1 Batterymarch Park, Quincy, Massachusetts 02169: NFPA. Retrieved October 9, 2023. Coordination, selective (selective coordination): localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcurrent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the maxiumum available fault current, and for the full range of overcurrent protective device opening times associated with those overcurrents.{{cite book}}: CS1 maint: location (link)
3. Jean-Pierre Nereau (April 2001). "Discrimination with LV power circuit-breakers" (PDF). Schneider Electric. p. 6. (PDF) from the original on 17 September 2021. Retrieved 18 September 2021.