Safety system for protecting cables and devices from fire producing faults through the use of a guard lead causing the tripping of highly sensitive differential circuit breakers.

摘要

To reduce fire hazards which can occur when, owing to wear, at least one of the leads (42, 44) of a supply cable losts continuity, allowing just a problematic current conduction, causing repeated electric arcs (60) tending to set on fire electrically insulating but flammable materials, is provided a guard lead (66), surrounding the leads (42, 44) and connectable to a ground tap (32) compulsory for every electric system causing the intervention of a differential circuit breaker (14) of highly sensitive kind for protection from electric shocks. Specifically, the guard lead (66) is wound around the conductor pair forming the supply cable and is in the form of a flat ribbon or a wire gauze (preferably a copper gauze) to lower the temperature of insulating parts starting a fire and contain this fire in the immediate neighbourhood of the fault having caused that. Further, the guard lead (66) is ground connected through current limiting means (70) to limit the ground fault currents to a magnitude sufficient to cause tripping of the differential circuit breaker but not cause fire beginnings. <IMAGE>