Device for protection against short circuits for AC networks and current limiting circuit breaker appropriate for such a device

Claim 1

A device for protecting an AC distribution network against short circuit currents, the network comprising at least one upstream current limiting circuit breaker and at least one downstream current limiting circuit breaker, these current limiting circuit breakers being placed in series in an upstream branch and respectively in at least one dependent downstream branch of the network and each including a main power circuit with separable contacts, a magnetic tripping means and a current limiter capable of cutting off the corresponding branch when the current reaches respectively a tripping threshold (I D ) and a limitation threshold (I R ), characterized by the fact that: the downstream branch having the downstream current limiting circuit breaker (D1) is provided with a current sensor (13) connected to a threshold processing circuit (14) which generates a neutralization signal (S) for opening the contacts for the upstream current limiting circuit breaker (D2) when the current in the downstream branch exceeds a given neutralization threshold (I A1 ) less than the tripping threshold (I D ) and/or than the limitation threshold (I R ) of the upstream current limiting circuit breaker (I D2 ), a pair of head to tail thyristors (TH1, TH2) is disposed in parallel with the main power circuit of the upstream current limiting circuit breaker (D2), while a circuit (16) for controlling the gates of said thyristors is adapted and controlled by the neutralization signal (S) coming from the downstream current limiting circuit breaker (D1) for enabling one at least of the thyristors and inhibiting the main power circuit of the upstream current limiting circuit breaker (D2) for a time at most equal to a half wave.

Claim 2

A device for protecting an AC distribution network against short circuit currents, the network comprising at least one upstream current limiting circuit breaker and at least one downstream current limiting circuit breaker, these current limiting circuit breakers being placed in series in an upstream branch and respectively in at least one dependent downstream branch of the network and each including a main power circuit with separable contacts, a magnetic tripping means and a current limiter capable of cutting off the corresponding branch when the current reaches respectively a tripping threshold (I D ) and a limitation threshold (I R ), characterized by the fact that: the downstream branch having the downstream current limiting circuit breaker (D1) is provided with a current sensor (13) connected to a threshold processing circuit (14) which generates a neutralization signal (S) for opening the contacts for the upstream current limiting circuit breaker (D2) when the current in the downstream branch exceeds a given neutralization threshold (I A1 ) less than the tripping threshold (I D ) and/or than the limitation threshold (I R ) of the upstream current limiting circuit breaker (I D2 ), a pair of head to tail thyristors (TH1, TH2) is disposed in parallel with the main power circuit of the upstream current limiting circuit breaker (D2), while a circuit (16) for controlling the gates of said thyristors is adapted and controlled by the neutralization signal (S) coming from the downstream current limiting circuit breaker (D1) for enabling one at least of the thyristors and inhibiting the main power circuit of the upstream current limiting circuit breaker (D2) for a time at most equal to a half wave.