Abstract: A method for determining the reclose time of a circuit breaker on a three-phase high-voltage electric network after separation of contacts 7A, 8A, 7B, 8B, 7C, 8C in the presence of a fault on one of the three phases A, B or C includes measuring voltages ULA0, ULBO and ULCO, measuring voltage USAO,determining the voltage USA0, USB0, and USCO, calculating the differences ULAB, ULAC and ULBC, calculating the differences USAB, USAC, and USBC. From these measurements and calculations, a determination of the reclose time is made on the basis of the voltage differences.

Abstract: The invention concerns a method for determining the reclose time of a circuit breaker on a three-phase high-voltage electric network after separation of contacts 7A, 8A, 7B, 8B, 7C, 8C in the presence of a fault on one of the three phases A, B or C, the determination of the reclose time comprising the following steps: measuring the voltages ULA0, ULBO and ULCO, measuring voltage USAO, determining the voltage USA0, USB0, and USCO, calculating the differences ULAB, ULAC and ULBC, calculating the differences USAB, USAC, and USBC, determining the reclose time on the basis of the voltage differences.

Abstract: This device for protecting a line (10, 12) of a network of supply lines comprises two protective relays (18, 20; 22, 24) furnished with means for detecting faults and a circuit breaker adapted so as to disconnect the line from the network of lines in the presence of a fault, each relay being adapted so as to monitor a first zone (Z1) of the line corresponding to a zone of certain detection of a fault (10, 12) and at least one second zone (Z2) juxtaposed with the first zone and corresponding to a zone of uncertain detection of a fault. At least one of the relays comprises means for detecting the opening of the circuit breaker associated with the other relay in response to a detection, by the latter, of a fault in the first zone in such a way as to cause the opening of the circuit breaker associated with the said at least one relay (18, 20; 22, 24).

Abstract: A preprocessing circuit receives signals representative of a current circulating in a primary winding and of a current circulating in a secondary winding of a transformer. The signals representative of currents are used to calculate the values of a through current and a differential current. The preprocessing circuit performs a spectral analysis and provides a neural network with signals representative of the fundamental component of the through current, of the fundamental component of the differential current, of the second harmonic and of the fifth harmonic of the differential current. The neural network identifies fault conditions and normal operation states, and supplies a triggering and/or alarm signal to an output when a fault condition is detected.

Abstract: The monitoring device comprises a measuring channel of the ground fault voltage, a measuring channel of the ground fault current, and a digital processing circuit whose role is to search for and indicate the presence of a ground fault. The processing circuit determines the fundamental parts of the ground fault current and voltage to compute the phase difference .phi. between the two parts and the cos .phi. value. The evolution of this phase difference is representative of a fault.