Importance

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Abstract

A protective device against fault currents includes a triggering arrangement for performing at least the functions of detecting a fault current and/or triggering power-down of the network to be protected. The triggering arrangement, outside the most strict quartic curve (A), corresponds to the protection of persons in case of indirect contact, and below the triggering quartic curve (B), corresponds to protection against fire. The triggering quartic curve (B) satisfies the relationship: I.sub.Limit (f)/I.sub..DELTA.n =F(f)=B=const., wherein I.sub.Limit (f)=W.sub.Fire /U.sub.Network. In the relationships, I.sub.Limit (f) represents the limit fault current permissible for the corresponding frequency, where there is still no risk of fire; I.sub..DELTA.n represents the nominal triggering fault current at the frequency of the network taking into consideration the protection of persons; W.sub.Fire represents the power limit in watt required for protection against fire; U.sub.Network represents the network voltage to be protected and F(f) represents what is called the frequency factor.

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First Claim