Fibre=optic transmission for circuit-breaker triggering - uses magnetic deflection of mass in path between fibre ends and photodetector system

摘要

Overcurrent is detected rapidly by the effect of its magnetic field on a ferromagnetic mass in close proximity to the conductor. The movement of the mass interrupts the light path between the ends of two fibre-optic cables. The output fibre is coupled to a photodetector which responds by triggering an electromagnetic or electronic relay to open the circuit-breaker. Alternatively the mass is attracted indirectly by an induction winding connected to a sensing winding which surrounds the conductor, and/or the light path is influenced by the displacement of a small mirror integral with the ferromagnetic mass.