development of static detection of failure mechanisms of fuses

摘要

1364721 Protective arrangements COMPAGNIE DES COMPTEURS 29 Nov 1971 [2 Dec 1970] 55365/71 Heading H2K In a protective arrngement in which the incorrect operation of a fault sensing device M, e.g. an impedance relay or undervoltage relay, due to the blowing of a fuse FPa ... FPc is prevented by a first detector device P responsive to an open-circuit condition of a fuse, a second detector device DA is provided and responds to currents down circuit of the fuses to provide a signal in the period taken by a fuse to melt before the device P can become fully effective. The device P may be that of Fig. 4 of Specification 1,302,303 and with the device DA is connected to an OR-gate OU1 so that a signal from either device causes a relay R1 to open its contacts r11, r12 to prevent the device M causing the opening of a circuit-breaker D.