ARRANGEMENT OF PROTECTION IN AN ELECTRIC CIRCUIT

A direct (DC) or alternative (AC) electric circuit (1) needs to be efficiently protected both against excessive current and overvoltage, e.g. by lightning, wherein also selectivity of such protection would have to be assured, which means that by interruption of the electric circuit (1) one should be able to clarify, whether such interruption results from interruption of a fuse (4) within a primary conductor (11, 12) of the electric circuit (1), or from interruption of the switch (6) in an overvoltage protecting assembly (5). The invention proposes that a bridging electric conductor (13) of the overvoltage protecting assembly (5), by which primary electric conductors (11, 12) are bridged in the area between a voltage source (2) and a load (3), in addition to a varistor (50) with a belonging thermal sensor (50') also includes a three-point switch (6) with an interrupting member (60), which is in pre-determined conditions by means of a suitable triggering means (7) displaceable from its initial first position, in which a bridging conductor (13) of the overvoltage protecting assembly (5) is conductive, into its second terminal position, in which said bridging electric conductor (13) of the overvoltage protecting assembly (5) is interrupted, wherein the electric circuit through a parallel branch (13') and a belonging fuse (55) is established only upon interruption of the switch (6) in the bridging conductor (13), namely upon displacement of the interrupting member (60) of the switch (6) into its second terminal position and in contact with said parallel branch (13'). Une protection efficace d'un circuit électrique (1) continu (DC) ou alternatif (AC) doit être assurée à la fois contre un courant excessif et une surtension, par exemple par la foudre. La sélectivité d'une telle protection doit également être assurée, ce qui signifie qu'en cas d'interruption du circuit électrique (1), on doit pouvoir déterminer si cette interruption provient de l'interruption d'un fusible (4) dans un conducteur primaire (11, 12) du circuit électrique (1) ou de l'interruption de l'interrupteur (6) dans un ensemble de protection contre les surtensions (5). Selon l'invention, un conducteur électrique de pontage (13) de l'ensemble de protection contre les surtensions (5), par lequel des conducteurs électriques primaires (11, 12) sont pontés dans la zone entre une source de tension (2) et une charge (3), comprend, en plus d'une varistance (50) avec un capteur thermique correspondant (50