Associated Builders And Contractors (ABC) Year 1 Practice Test

Coordinating protection devices relies on adjusting the overload protection so the breaker trips in harmony with other devices in the system. The type that makes this possible is the adjustable trip breaker, because its thermal (long-time) trip setting can be tuned to a specific current level and time delay to achieve selective coordination with upstream or downstream protection. By setting the long-time trip, you control when the breaker will trip due to overload, which helps ensure the closest device to a fault clears first without nuisance trips elsewhere. The inverse-time characteristic describes how trip time changes with current but doesn’t imply adjusting the thermal setting for coordination. The instantaneous trip trips rapidly for severe faults, again not about coordinating via an adjustable thermal setting. So the adjustable trip option best fits the need to coordinate with other protection devices.